/*
 * Just-In-Time compiler for eBPF filters on MIPS
 *
 * Copyright (c) 2017 Cavium, Inc.
 *
 * Based on code from:
 *
 * Copyright (c) 2014 Imagination Technologies Ltd.
 * Author: Markos Chandras <markos.chandras@imgtec.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; version 2 of the License.
 */

#include <linux/bitops.h>
#include <linux/errno.h>
#include <linux/filter.h>
#include <linux/bpf.h>
#include <linux/slab.h>
#include <asm/bitops.h>
#include <asm/byteorder.h>
#include <asm/cacheflush.h>
#include <asm/cpu-features.h>
#include <asm/uasm.h>

/* Registers used by JIT */
#define MIPS_R_ZERO     0
#define MIPS_R_AT       1
#define MIPS_R_V0       2       /* BPF_R0 */
#define MIPS_R_V1       3
#define MIPS_R_A0       4       /* BPF_R1 */
#define MIPS_R_A1       5       /* BPF_R2 */
#define MIPS_R_A2       6       /* BPF_R3 */
#define MIPS_R_A3       7       /* BPF_R4 */
#define MIPS_R_A4       8       /* BPF_R5 */
#define MIPS_R_T4       12      /* BPF_AX */
#define MIPS_R_T5       13
#define MIPS_R_T6       14
#define MIPS_R_T7       15
#define MIPS_R_S0       16      /* BPF_R6 */
#define MIPS_R_S1       17      /* BPF_R7 */
#define MIPS_R_S2       18      /* BPF_R8 */
#define MIPS_R_S3       19      /* BPF_R9 */
#define MIPS_R_S4       20      /* BPF_TCC */
#define MIPS_R_S5       21
#define MIPS_R_S6       22
#define MIPS_R_S7       23
#define MIPS_R_T8       24
#define MIPS_R_T9       25
#define MIPS_R_SP       29
#define MIPS_R_RA       31

/* eBPF flags */
#define EBPF_SAVE_S0    BIT(0)
#define EBPF_SAVE_S1    BIT(1)
#define EBPF_SAVE_S2    BIT(2)
#define EBPF_SAVE_S3    BIT(3)
#define EBPF_SAVE_S4    BIT(4)
#define EBPF_SAVE_RA    BIT(5)
#define EBPF_SEEN_FP    BIT(6)
#define EBPF_SEEN_TC    BIT(7)
#define EBPF_TCC_IN_V1  BIT(8)

/*
 * For the mips64 ISA, we need to track the value range or type for
 * each JIT register.  The BPF machine requires zero extended 32-bit
 * values, but the mips64 ISA requires sign extended 32-bit values.
 * At each point in the BPF program we track the state of every
 * register so that we can zero extend or sign extend as the BPF
 * semantics require.
 */
enum reg_val_type {
        /* uninitialized */
        REG_UNKNOWN,
        /* not known to be 32-bit compatible. */
        REG_64BIT,
        /* 32-bit compatible, no truncation needed for 64-bit ops. */
        REG_64BIT_32BIT,
        /* 32-bit compatible, need truncation for 64-bit ops. */
        REG_32BIT,
        /* 32-bit zero extended. */
        REG_32BIT_ZERO_EX,
        /* 32-bit no sign/zero extension needed. */
        REG_32BIT_POS
};

/*
 * high bit of offsets indicates if long branch conversion done at
 * this insn.
 */
#define OFFSETS_B_CONV  BIT(31)

/**
 * struct jit_ctx - JIT context
 * @skf:                The sk_filter
 * @stack_size:         eBPF stack size
 * @tmp_offset:         eBPF $sp offset to 8-byte temporary memory
 * @idx:                Instruction index
 * @flags:              JIT flags
 * @offsets:            Instruction offsets
 * @target:             Memory location for the compiled filter
 * @reg_val_types       Packed enum reg_val_type for each register.
 */
struct jit_ctx {
        const struct bpf_prog *skf;
        int stack_size;
        int tmp_offset;
        u32 idx;
        u32 flags;
        u32 *offsets;
        u32 *target;
        u64 *reg_val_types;
        unsigned int long_b_conversion:1;
        unsigned int gen_b_offsets:1;
        unsigned int use_bbit_insns:1;
};

static void set_reg_val_type(u64 *rvt, int reg, enum reg_val_type type)
{
        *rvt &= ~(7ull << (reg * 3));
        *rvt |= ((u64)type << (reg * 3));
}

static enum reg_val_type get_reg_val_type(const struct jit_ctx *ctx,
                                          int index, int reg)
{
        return (ctx->reg_val_types[index] >> (reg * 3)) & 7;
}

/* Simply emit the instruction if the JIT memory space has been allocated */
#define emit_instr(ctx, func, ...)                      \
do {                                                    \
        if ((ctx)->target != NULL) {                    \
                u32 *p = &(ctx)->target[ctx->idx];      \
                uasm_i_##func(&p, ##__VA_ARGS__);       \
        }                                               \
        (ctx)->idx++;                                   \
} while (0)

static unsigned int j_target(struct jit_ctx *ctx, int target_idx)
{
        unsigned long target_va, base_va;
        unsigned int r;

        if (!ctx->target)
                return 0;

        base_va = (unsigned long)ctx->target;
        target_va = base_va + (ctx->offsets[target_idx] & ~OFFSETS_B_CONV);

        if ((base_va & ~0x0ffffffful) != (target_va & ~0x0ffffffful))
                return (unsigned int)-1;
        r = target_va & 0x0ffffffful;
        return r;
}

/* Compute the immediate value for PC-relative branches. */
static u32 b_imm(unsigned int tgt, struct jit_ctx *ctx)
{
        if (!ctx->gen_b_offsets)
                return 0;

        /*
         * We want a pc-relative branch.  tgt is the instruction offset
         * we want to jump to.

         * Branch on MIPS:
         * I: target_offset <- sign_extend(offset)
         * I+1: PC += target_offset (delay slot)
         *
         * ctx->idx currently points to the branch instruction
         * but the offset is added to the delay slot so we need
         * to subtract 4.
         */
        return (ctx->offsets[tgt] & ~OFFSETS_B_CONV) -
                (ctx->idx * 4) - 4;
}

enum which_ebpf_reg {
        src_reg,
        src_reg_no_fp,
        dst_reg,
        dst_reg_fp_ok
};

/*
 * For eBPF, the register mapping naturally falls out of the
 * requirements of eBPF and the MIPS n64 ABI.  We don't maintain a
 * separate frame pointer, so BPF_REG_10 relative accesses are
 * adjusted to be $sp relative.
 */
int ebpf_to_mips_reg(struct jit_ctx *ctx, const struct bpf_insn *insn,
                     enum which_ebpf_reg w)
{
        int ebpf_reg = (w == src_reg || w == src_reg_no_fp) ?
                insn->src_reg : insn->dst_reg;

        switch (ebpf_reg) {
        case BPF_REG_0:
                return MIPS_R_V0;
        case BPF_REG_1:
                return MIPS_R_A0;
        case BPF_REG_2:
                return MIPS_R_A1;
        case BPF_REG_3:
                return MIPS_R_A2;
        case BPF_REG_4:
                return MIPS_R_A3;
        case BPF_REG_5:
                return MIPS_R_A4;
        case BPF_REG_6:
                ctx->flags |= EBPF_SAVE_S0;
                return MIPS_R_S0;
        case BPF_REG_7:
                ctx->flags |= EBPF_SAVE_S1;
                return MIPS_R_S1;
        case BPF_REG_8:
                ctx->flags |= EBPF_SAVE_S2;
                return MIPS_R_S2;
        case BPF_REG_9:
                ctx->flags |= EBPF_SAVE_S3;
                return MIPS_R_S3;
        case BPF_REG_10:
                if (w == dst_reg || w == src_reg_no_fp)
                        goto bad_reg;
                ctx->flags |= EBPF_SEEN_FP;
                /*
                 * Needs special handling, return something that
                 * cannot be clobbered just in case.
                 */
                return MIPS_R_ZERO;
        case BPF_REG_AX:
                return MIPS_R_T4;
        default:
bad_reg:
                WARN(1, "Illegal bpf reg: %d\n", ebpf_reg);
                return -EINVAL;
        }
}
/*
 * eBPF stack frame will be something like:
 *
 *  Entry $sp ------>   +--------------------------------+
 *                      |   $ra  (optional)              |
 *                      +--------------------------------+
 *                      |   $s0  (optional)              |
 *                      +--------------------------------+
 *                      |   $s1  (optional)              |
 *                      +--------------------------------+
 *                      |   $s2  (optional)              |
 *                      +--------------------------------+
 *                      |   $s3  (optional)              |
 *                      +--------------------------------+
 *                      |   $s4  (optional)              |
 *                      +--------------------------------+
 *                      |   tmp-storage  (if $ra saved)  |
 * $sp + tmp_offset --> +--------------------------------+ <--BPF_REG_10
 *                      |   BPF_REG_10 relative storage  |
 *                      |    MAX_BPF_STACK (optional)    |
 *                      |      .                         |
 *                      |      .                         |
 *                      |      .                         |
 *     $sp -------->    +--------------------------------+
 *
 * If BPF_REG_10 is never referenced, then the MAX_BPF_STACK sized
 * area is not allocated.
 */
static int gen_int_prologue(struct jit_ctx *ctx)
{
        int stack_adjust = 0;
        int store_offset;
        int locals_size;

        if (ctx->flags & EBPF_SAVE_RA)
                /*
                 * If RA we are doing a function call and may need
                 * extra 8-byte tmp area.
                 */
                stack_adjust += 16;
        if (ctx->flags & EBPF_SAVE_S0)
                stack_adjust += 8;
        if (ctx->flags & EBPF_SAVE_S1)
                stack_adjust += 8;
        if (ctx->flags & EBPF_SAVE_S2)
                stack_adjust += 8;
        if (ctx->flags & EBPF_SAVE_S3)
                stack_adjust += 8;
        if (ctx->flags & EBPF_SAVE_S4)
                stack_adjust += 8;

        BUILD_BUG_ON(MAX_BPF_STACK & 7);
        locals_size = (ctx->flags & EBPF_SEEN_FP) ? MAX_BPF_STACK : 0;

        stack_adjust += locals_size;
        ctx->tmp_offset = locals_size;

        ctx->stack_size = stack_adjust;

        /*
         * First instruction initializes the tail call count (TCC).
         * On tail call we skip this instruction, and the TCC is
         * passed in $v1 from the caller.
         */
        emit_instr(ctx, daddiu, MIPS_R_V1, MIPS_R_ZERO, MAX_TAIL_CALL_CNT);
        if (stack_adjust)
                emit_instr(ctx, daddiu, MIPS_R_SP, MIPS_R_SP, -stack_adjust);
        else
                return 0;

        store_offset = stack_adjust - 8;

        if (ctx->flags & EBPF_SAVE_RA) {
                emit_instr(ctx, sd, MIPS_R_RA, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }
        if (ctx->flags & EBPF_SAVE_S0) {
                emit_instr(ctx, sd, MIPS_R_S0, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }
        if (ctx->flags & EBPF_SAVE_S1) {
                emit_instr(ctx, sd, MIPS_R_S1, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }
        if (ctx->flags & EBPF_SAVE_S2) {
                emit_instr(ctx, sd, MIPS_R_S2, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }
        if (ctx->flags & EBPF_SAVE_S3) {
                emit_instr(ctx, sd, MIPS_R_S3, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }
        if (ctx->flags & EBPF_SAVE_S4) {
                emit_instr(ctx, sd, MIPS_R_S4, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }

        if ((ctx->flags & EBPF_SEEN_TC) && !(ctx->flags & EBPF_TCC_IN_V1))
                emit_instr(ctx, daddu, MIPS_R_S4, MIPS_R_V1, MIPS_R_ZERO);

        return 0;
}

static int build_int_epilogue(struct jit_ctx *ctx, int dest_reg)
{
        const struct bpf_prog *prog = ctx->skf;
        int stack_adjust = ctx->stack_size;
        int store_offset = stack_adjust - 8;
        int r0 = MIPS_R_V0;

        if (dest_reg == MIPS_R_RA &&
            get_reg_val_type(ctx, prog->len, BPF_REG_0) == REG_32BIT_ZERO_EX)
                /* Don't let zero extended value escape. */
                emit_instr(ctx, sll, r0, r0, 0);

        if (ctx->flags & EBPF_SAVE_RA) {
                emit_instr(ctx, ld, MIPS_R_RA, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }
        if (ctx->flags & EBPF_SAVE_S0) {
                emit_instr(ctx, ld, MIPS_R_S0, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }
        if (ctx->flags & EBPF_SAVE_S1) {
                emit_instr(ctx, ld, MIPS_R_S1, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }
        if (ctx->flags & EBPF_SAVE_S2) {
                emit_instr(ctx, ld, MIPS_R_S2, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }
        if (ctx->flags & EBPF_SAVE_S3) {
                emit_instr(ctx, ld, MIPS_R_S3, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }
        if (ctx->flags & EBPF_SAVE_S4) {
                emit_instr(ctx, ld, MIPS_R_S4, store_offset, MIPS_R_SP);
                store_offset -= 8;
        }
        emit_instr(ctx, jr, dest_reg);

        if (stack_adjust)
                emit_instr(ctx, daddiu, MIPS_R_SP, MIPS_R_SP, stack_adjust);
        else
                emit_instr(ctx, nop);

        return 0;
}

static void gen_imm_to_reg(const struct bpf_insn *insn, int reg,
                           struct jit_ctx *ctx)
{
        if (insn->imm >= S16_MIN && insn->imm <= S16_MAX) {
                emit_instr(ctx, addiu, reg, MIPS_R_ZERO, insn->imm);
        } else {
                int lower = (s16)(insn->imm & 0xffff);
                int upper = insn->imm - lower;

                emit_instr(ctx, lui, reg, upper >> 16);
                emit_instr(ctx, addiu, reg, reg, lower);
        }

}

static int gen_imm_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
                        int idx)
{
        int upper_bound, lower_bound;
        int dst = ebpf_to_mips_reg(ctx, insn, dst_reg);

        if (dst < 0)
                return dst;

        switch (BPF_OP(insn->code)) {
        case BPF_MOV:
        case BPF_ADD:
                upper_bound = S16_MAX;
                lower_bound = S16_MIN;
                break;
        case BPF_SUB:
                upper_bound = -(int)S16_MIN;
                lower_bound = -(int)S16_MAX;
                break;
        case BPF_AND:
        case BPF_OR:
        case BPF_XOR:
                upper_bound = 0xffff;
                lower_bound = 0;
                break;
        case BPF_RSH:
        case BPF_LSH:
        case BPF_ARSH:
                /* Shift amounts are truncated, no need for bounds */
                upper_bound = S32_MAX;
                lower_bound = S32_MIN;
                break;
        default:
                return -EINVAL;
        }

        /*
         * Immediate move clobbers the register, so no sign/zero
         * extension needed.
         */
        if (BPF_CLASS(insn->code) == BPF_ALU64 &&
            BPF_OP(insn->code) != BPF_MOV &&
            get_reg_val_type(ctx, idx, insn->dst_reg) == REG_32BIT)
                emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);
        /* BPF_ALU | BPF_LSH doesn't need separate sign extension */
        if (BPF_CLASS(insn->code) == BPF_ALU &&
            BPF_OP(insn->code) != BPF_LSH &&
            BPF_OP(insn->code) != BPF_MOV &&
            get_reg_val_type(ctx, idx, insn->dst_reg) != REG_32BIT)
                emit_instr(ctx, sll, dst, dst, 0);

        if (insn->imm >= lower_bound && insn->imm <= upper_bound) {
                /* single insn immediate case */
                switch (BPF_OP(insn->code) | BPF_CLASS(insn->code)) {
                case BPF_ALU64 | BPF_MOV:
                        emit_instr(ctx, daddiu, dst, MIPS_R_ZERO, insn->imm);
                        break;
                case BPF_ALU64 | BPF_AND:
                case BPF_ALU | BPF_AND:
                        emit_instr(ctx, andi, dst, dst, insn->imm);
                        break;
                case BPF_ALU64 | BPF_OR:
                case BPF_ALU | BPF_OR:
                        emit_instr(ctx, ori, dst, dst, insn->imm);
                        break;
                case BPF_ALU64 | BPF_XOR:
                case BPF_ALU | BPF_XOR:
                        emit_instr(ctx, xori, dst, dst, insn->imm);
                        break;
                case BPF_ALU64 | BPF_ADD:
                        emit_instr(ctx, daddiu, dst, dst, insn->imm);
                        break;
                case BPF_ALU64 | BPF_SUB:
                        emit_instr(ctx, daddiu, dst, dst, -insn->imm);
                        break;
                case BPF_ALU64 | BPF_RSH:
                        emit_instr(ctx, dsrl_safe, dst, dst, insn->imm & 0x3f);
                        break;
                case BPF_ALU | BPF_RSH:
                        emit_instr(ctx, srl, dst, dst, insn->imm & 0x1f);
                        break;
                case BPF_ALU64 | BPF_LSH:
                        emit_instr(ctx, dsll_safe, dst, dst, insn->imm & 0x3f);
                        break;
                case BPF_ALU | BPF_LSH:
                        emit_instr(ctx, sll, dst, dst, insn->imm & 0x1f);
                        break;
                case BPF_ALU64 | BPF_ARSH:
                        emit_instr(ctx, dsra_safe, dst, dst, insn->imm & 0x3f);
                        break;
                case BPF_ALU | BPF_ARSH:
                        emit_instr(ctx, sra, dst, dst, insn->imm & 0x1f);
                        break;
                case BPF_ALU | BPF_MOV:
                        emit_instr(ctx, addiu, dst, MIPS_R_ZERO, insn->imm);
                        break;
                case BPF_ALU | BPF_ADD:
                        emit_instr(ctx, addiu, dst, dst, insn->imm);
                        break;
                case BPF_ALU | BPF_SUB:
                        emit_instr(ctx, addiu, dst, dst, -insn->imm);
                        break;
                default:
                        return -EINVAL;
                }
        } else {
                /* multi insn immediate case */
                if (BPF_OP(insn->code) == BPF_MOV) {
                        gen_imm_to_reg(insn, dst, ctx);
                } else {
                        gen_imm_to_reg(insn, MIPS_R_AT, ctx);
                        switch (BPF_OP(insn->code) | BPF_CLASS(insn->code)) {
                        case BPF_ALU64 | BPF_AND:
                        case BPF_ALU | BPF_AND:
                                emit_instr(ctx, and, dst, dst, MIPS_R_AT);
                                break;
                        case BPF_ALU64 | BPF_OR:
                        case BPF_ALU | BPF_OR:
                                emit_instr(ctx, or, dst, dst, MIPS_R_AT);
                                break;
                        case BPF_ALU64 | BPF_XOR:
                        case BPF_ALU | BPF_XOR:
                                emit_instr(ctx, xor, dst, dst, MIPS_R_AT);
                                break;
                        case BPF_ALU64 | BPF_ADD:
                                emit_instr(ctx, daddu, dst, dst, MIPS_R_AT);
                                break;
                        case BPF_ALU64 | BPF_SUB:
                                emit_instr(ctx, dsubu, dst, dst, MIPS_R_AT);
                                break;
                        case BPF_ALU | BPF_ADD:
                                emit_instr(ctx, addu, dst, dst, MIPS_R_AT);
                                break;
                        case BPF_ALU | BPF_SUB:
                                emit_instr(ctx, subu, dst, dst, MIPS_R_AT);
                                break;
                        default:
                                return -EINVAL;
                        }
                }
        }

        return 0;
}

static void * __must_check
ool_skb_header_pointer(const struct sk_buff *skb, int offset,
                       int len, void *buffer)
{
        return skb_header_pointer(skb, offset, len, buffer);
}

static int size_to_len(const struct bpf_insn *insn)
{
        switch (BPF_SIZE(insn->code)) {
        case BPF_B:
                return 1;
        case BPF_H:
                return 2;
        case BPF_W:
                return 4;
        case BPF_DW:
                return 8;
        }
        return 0;
}

static void emit_const_to_reg(struct jit_ctx *ctx, int dst, u64 value)
{
        if (value >= 0xffffffffffff8000ull || value < 0x8000ull) {
                emit_instr(ctx, daddiu, dst, MIPS_R_ZERO, (int)value);
        } else if (value >= 0xffffffff80000000ull ||
                   (value < 0x80000000 && value > 0xffff)) {
                emit_instr(ctx, lui, dst, (s32)(s16)(value >> 16));
                emit_instr(ctx, ori, dst, dst, (unsigned int)(value & 0xffff));
        } else {
                int i;
                bool seen_part = false;
                int needed_shift = 0;

                for (i = 0; i < 4; i++) {
                        u64 part = (value >> (16 * (3 - i))) & 0xffff;

                        if (seen_part && needed_shift > 0 && (part || i == 3)) {
                                emit_instr(ctx, dsll_safe, dst, dst, needed_shift);
                                needed_shift = 0;
                        }
                        if (part) {
                                if (i == 0 || (!seen_part && i < 3 && part < 0x8000)) {
                                        emit_instr(ctx, lui, dst, (s32)(s16)part);
                                        needed_shift = -16;
                                } else {
                                        emit_instr(ctx, ori, dst,
                                                   seen_part ? dst : MIPS_R_ZERO,
                                                   (unsigned int)part);
                                }
                                seen_part = true;
                        }
                        if (seen_part)
                                needed_shift += 16;
                }
        }
}

static int emit_bpf_tail_call(struct jit_ctx *ctx, int this_idx)
{
        int off, b_off;

        ctx->flags |= EBPF_SEEN_TC;
        /*
         * if (index >= array->map.max_entries)
         *     goto out;
         */
        off = offsetof(struct bpf_array, map.max_entries);
        emit_instr(ctx, lwu, MIPS_R_T5, off, MIPS_R_A1);
        emit_instr(ctx, sltu, MIPS_R_AT, MIPS_R_T5, MIPS_R_A2);
        b_off = b_imm(this_idx + 1, ctx);
        emit_instr(ctx, bne, MIPS_R_AT, MIPS_R_ZERO, b_off);
        /*
         * if (--TCC < 0)
         *     goto out;
         */
        /* Delay slot */
        emit_instr(ctx, daddiu, MIPS_R_T5,
                   (ctx->flags & EBPF_TCC_IN_V1) ? MIPS_R_V1 : MIPS_R_S4, -1);
        b_off = b_imm(this_idx + 1, ctx);
        emit_instr(ctx, bltz, MIPS_R_T5, b_off);
        /*
         * prog = array->ptrs[index];
         * if (prog == NULL)
         *     goto out;
         */
        /* Delay slot */
        emit_instr(ctx, dsll, MIPS_R_T8, MIPS_R_A2, 3);
        emit_instr(ctx, daddu, MIPS_R_T8, MIPS_R_T8, MIPS_R_A1);
        off = offsetof(struct bpf_array, ptrs);
        emit_instr(ctx, ld, MIPS_R_AT, off, MIPS_R_T8);
        b_off = b_imm(this_idx + 1, ctx);
        emit_instr(ctx, beq, MIPS_R_AT, MIPS_R_ZERO, b_off);
        /* Delay slot */
        emit_instr(ctx, nop);

        /* goto *(prog->bpf_func + 4); */
        off = offsetof(struct bpf_prog, bpf_func);
        emit_instr(ctx, ld, MIPS_R_T9, off, MIPS_R_AT);
        /* All systems are go... propagate TCC */
        emit_instr(ctx, daddu, MIPS_R_V1, MIPS_R_T5, MIPS_R_ZERO);
        /* Skip first instruction (TCC initialization) */
        emit_instr(ctx, daddiu, MIPS_R_T9, MIPS_R_T9, 4);
        return build_int_epilogue(ctx, MIPS_R_T9);
}

static bool is_bad_offset(int b_off)
{
        return b_off > 0x1ffff || b_off < -0x20000;
}

/* Returns the number of insn slots consumed. */
static int build_one_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
                          int this_idx, int exit_idx)
{
        int src, dst, r, td, ts, mem_off, b_off;
        bool need_swap, did_move, cmp_eq;
        unsigned int target = 0;
        u64 t64;
        s64 t64s;
        int bpf_op = BPF_OP(insn->code);

        switch (insn->code) {
        case BPF_ALU64 | BPF_ADD | BPF_K: /* ALU64_IMM */
        case BPF_ALU64 | BPF_SUB | BPF_K: /* ALU64_IMM */
        case BPF_ALU64 | BPF_OR | BPF_K: /* ALU64_IMM */
        case BPF_ALU64 | BPF_AND | BPF_K: /* ALU64_IMM */
        case BPF_ALU64 | BPF_LSH | BPF_K: /* ALU64_IMM */
        case BPF_ALU64 | BPF_RSH | BPF_K: /* ALU64_IMM */
        case BPF_ALU64 | BPF_XOR | BPF_K: /* ALU64_IMM */
        case BPF_ALU64 | BPF_ARSH | BPF_K: /* ALU64_IMM */
        case BPF_ALU64 | BPF_MOV | BPF_K: /* ALU64_IMM */
        case BPF_ALU | BPF_MOV | BPF_K: /* ALU32_IMM */
        case BPF_ALU | BPF_ADD | BPF_K: /* ALU32_IMM */
        case BPF_ALU | BPF_SUB | BPF_K: /* ALU32_IMM */
        case BPF_ALU | BPF_OR | BPF_K: /* ALU64_IMM */
        case BPF_ALU | BPF_AND | BPF_K: /* ALU64_IMM */
        case BPF_ALU | BPF_LSH | BPF_K: /* ALU64_IMM */
        case BPF_ALU | BPF_RSH | BPF_K: /* ALU64_IMM */
        case BPF_ALU | BPF_XOR | BPF_K: /* ALU64_IMM */
        case BPF_ALU | BPF_ARSH | BPF_K: /* ALU64_IMM */
                r = gen_imm_insn(insn, ctx, this_idx);
                if (r < 0)
                        return r;
                break;
        case BPF_ALU64 | BPF_MUL | BPF_K: /* ALU64_IMM */
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (dst < 0)
                        return dst;
                if (get_reg_val_type(ctx, this_idx, insn->dst_reg) == REG_32BIT)
                        emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);
                if (insn->imm == 1) /* Mult by 1 is a nop */
                        break;
                gen_imm_to_reg(insn, MIPS_R_AT, ctx);
                emit_instr(ctx, dmultu, MIPS_R_AT, dst);
                emit_instr(ctx, mflo, dst);
                break;
        case BPF_ALU64 | BPF_NEG | BPF_K: /* ALU64_IMM */
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (dst < 0)
                        return dst;
                if (get_reg_val_type(ctx, this_idx, insn->dst_reg) == REG_32BIT)
                        emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);
                emit_instr(ctx, dsubu, dst, MIPS_R_ZERO, dst);
                break;
        case BPF_ALU | BPF_MUL | BPF_K: /* ALU_IMM */
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (dst < 0)
                        return dst;
                td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
                if (td == REG_64BIT || td == REG_32BIT_ZERO_EX) {
                        /* sign extend */
                        emit_instr(ctx, sll, dst, dst, 0);
                }
                if (insn->imm == 1) /* Mult by 1 is a nop */
                        break;
                gen_imm_to_reg(insn, MIPS_R_AT, ctx);
                emit_instr(ctx, multu, dst, MIPS_R_AT);
                emit_instr(ctx, mflo, dst);
                break;
        case BPF_ALU | BPF_NEG | BPF_K: /* ALU_IMM */
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (dst < 0)
                        return dst;
                td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
                if (td == REG_64BIT || td == REG_32BIT_ZERO_EX) {
                        /* sign extend */
                        emit_instr(ctx, sll, dst, dst, 0);
                }
                emit_instr(ctx, subu, dst, MIPS_R_ZERO, dst);
                break;
        case BPF_ALU | BPF_DIV | BPF_K: /* ALU_IMM */
        case BPF_ALU | BPF_MOD | BPF_K: /* ALU_IMM */
                if (insn->imm == 0)
                        return -EINVAL;
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (dst < 0)
                        return dst;
                td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
                if (td == REG_64BIT || td == REG_32BIT_ZERO_EX)
                        /* sign extend */
                        emit_instr(ctx, sll, dst, dst, 0);
                if (insn->imm == 1) {
                        /* div by 1 is a nop, mod by 1 is zero */
                        if (bpf_op == BPF_MOD)
                                emit_instr(ctx, addu, dst, MIPS_R_ZERO, MIPS_R_ZERO);
                        break;
                }
                gen_imm_to_reg(insn, MIPS_R_AT, ctx);
                emit_instr(ctx, divu, dst, MIPS_R_AT);
                if (bpf_op == BPF_DIV)
                        emit_instr(ctx, mflo, dst);
                else
                        emit_instr(ctx, mfhi, dst);
                break;
        case BPF_ALU64 | BPF_DIV | BPF_K: /* ALU_IMM */
        case BPF_ALU64 | BPF_MOD | BPF_K: /* ALU_IMM */
                if (insn->imm == 0)
                        return -EINVAL;
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (dst < 0)
                        return dst;
                if (get_reg_val_type(ctx, this_idx, insn->dst_reg) == REG_32BIT)
                        emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);
                if (insn->imm == 1) {
                        /* div by 1 is a nop, mod by 1 is zero */
                        if (bpf_op == BPF_MOD)
                                emit_instr(ctx, addu, dst, MIPS_R_ZERO, MIPS_R_ZERO);
                        break;
                }
                gen_imm_to_reg(insn, MIPS_R_AT, ctx);
                emit_instr(ctx, ddivu, dst, MIPS_R_AT);
                if (bpf_op == BPF_DIV)
                        emit_instr(ctx, mflo, dst);
                else
                        emit_instr(ctx, mfhi, dst);
                break;
        case BPF_ALU64 | BPF_MOV | BPF_X: /* ALU64_REG */
        case BPF_ALU64 | BPF_ADD | BPF_X: /* ALU64_REG */
        case BPF_ALU64 | BPF_SUB | BPF_X: /* ALU64_REG */
        case BPF_ALU64 | BPF_XOR | BPF_X: /* ALU64_REG */
        case BPF_ALU64 | BPF_OR | BPF_X: /* ALU64_REG */
        case BPF_ALU64 | BPF_AND | BPF_X: /* ALU64_REG */
        case BPF_ALU64 | BPF_MUL | BPF_X: /* ALU64_REG */
        case BPF_ALU64 | BPF_DIV | BPF_X: /* ALU64_REG */
        case BPF_ALU64 | BPF_MOD | BPF_X: /* ALU64_REG */
        case BPF_ALU64 | BPF_LSH | BPF_X: /* ALU64_REG */
        case BPF_ALU64 | BPF_RSH | BPF_X: /* ALU64_REG */
        case BPF_ALU64 | BPF_ARSH | BPF_X: /* ALU64_REG */
                src = ebpf_to_mips_reg(ctx, insn, src_reg);
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (src < 0 || dst < 0)
                        return -EINVAL;
                if (get_reg_val_type(ctx, this_idx, insn->dst_reg) == REG_32BIT)
                        emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);
                did_move = false;
                if (insn->src_reg == BPF_REG_10) {
                        if (bpf_op == BPF_MOV) {
                                emit_instr(ctx, daddiu, dst, MIPS_R_SP, MAX_BPF_STACK);
                                did_move = true;
                        } else {
                                emit_instr(ctx, daddiu, MIPS_R_AT, MIPS_R_SP, MAX_BPF_STACK);
                                src = MIPS_R_AT;
                        }
                } else if (get_reg_val_type(ctx, this_idx, insn->src_reg) == REG_32BIT) {
                        int tmp_reg = MIPS_R_AT;

                        if (bpf_op == BPF_MOV) {
                                tmp_reg = dst;
                                did_move = true;
                        }
                        emit_instr(ctx, daddu, tmp_reg, src, MIPS_R_ZERO);
                        emit_instr(ctx, dinsu, tmp_reg, MIPS_R_ZERO, 32, 32);
                        src = MIPS_R_AT;
                }
                switch (bpf_op) {
                case BPF_MOV:
                        if (!did_move)
                                emit_instr(ctx, daddu, dst, src, MIPS_R_ZERO);
                        break;
                case BPF_ADD:
                        emit_instr(ctx, daddu, dst, dst, src);
                        break;
                case BPF_SUB:
                        emit_instr(ctx, dsubu, dst, dst, src);
                        break;
                case BPF_XOR:
                        emit_instr(ctx, xor, dst, dst, src);
                        break;
                case BPF_OR:
                        emit_instr(ctx, or, dst, dst, src);
                        break;
                case BPF_AND:
                        emit_instr(ctx, and, dst, dst, src);
                        break;
                case BPF_MUL:
                        emit_instr(ctx, dmultu, dst, src);
                        emit_instr(ctx, mflo, dst);
                        break;
                case BPF_DIV:
                case BPF_MOD:
                        emit_instr(ctx, ddivu, dst, src);
                        if (bpf_op == BPF_DIV)
                                emit_instr(ctx, mflo, dst);
                        else
                                emit_instr(ctx, mfhi, dst);
                        break;
                case BPF_LSH:
                        emit_instr(ctx, dsllv, dst, dst, src);
                        break;
                case BPF_RSH:
                        emit_instr(ctx, dsrlv, dst, dst, src);
                        break;
                case BPF_ARSH:
                        emit_instr(ctx, dsrav, dst, dst, src);
                        break;
                default:
                        pr_err("ALU64_REG NOT HANDLED\n");
                        return -EINVAL;
                }
                break;
        case BPF_ALU | BPF_MOV | BPF_X: /* ALU_REG */
        case BPF_ALU | BPF_ADD | BPF_X: /* ALU_REG */
        case BPF_ALU | BPF_SUB | BPF_X: /* ALU_REG */
        case BPF_ALU | BPF_XOR | BPF_X: /* ALU_REG */
        case BPF_ALU | BPF_OR | BPF_X: /* ALU_REG */
        case BPF_ALU | BPF_AND | BPF_X: /* ALU_REG */
        case BPF_ALU | BPF_MUL | BPF_X: /* ALU_REG */
        case BPF_ALU | BPF_DIV | BPF_X: /* ALU_REG */
        case BPF_ALU | BPF_MOD | BPF_X: /* ALU_REG */
        case BPF_ALU | BPF_LSH | BPF_X: /* ALU_REG */
        case BPF_ALU | BPF_RSH | BPF_X: /* ALU_REG */
                src = ebpf_to_mips_reg(ctx, insn, src_reg_no_fp);
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (src < 0 || dst < 0)
                        return -EINVAL;
                td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
                if (td == REG_64BIT || td == REG_32BIT_ZERO_EX) {
                        /* sign extend */
                        emit_instr(ctx, sll, dst, dst, 0);
                }
                did_move = false;
                ts = get_reg_val_type(ctx, this_idx, insn->src_reg);
                if (ts == REG_64BIT || ts == REG_32BIT_ZERO_EX) {
                        int tmp_reg = MIPS_R_AT;

                        if (bpf_op == BPF_MOV) {
                                tmp_reg = dst;
                                did_move = true;
                        }
                        /* sign extend */
                        emit_instr(ctx, sll, tmp_reg, src, 0);
                        src = MIPS_R_AT;
                }
                switch (bpf_op) {
                case BPF_MOV:
                        if (!did_move)
                                emit_instr(ctx, addu, dst, src, MIPS_R_ZERO);
                        break;
                case BPF_ADD:
                        emit_instr(ctx, addu, dst, dst, src);
                        break;
                case BPF_SUB:
                        emit_instr(ctx, subu, dst, dst, src);
                        break;
                case BPF_XOR:
                        emit_instr(ctx, xor, dst, dst, src);
                        break;
                case BPF_OR:
                        emit_instr(ctx, or, dst, dst, src);
                        break;
                case BPF_AND:
                        emit_instr(ctx, and, dst, dst, src);
                        break;
                case BPF_MUL:
                        emit_instr(ctx, mul, dst, dst, src);
                        break;
                case BPF_DIV:
                case BPF_MOD:
                        emit_instr(ctx, divu, dst, src);
                        if (bpf_op == BPF_DIV)
                                emit_instr(ctx, mflo, dst);
                        else
                                emit_instr(ctx, mfhi, dst);
                        break;
                case BPF_LSH:
                        emit_instr(ctx, sllv, dst, dst, src);
                        break;
                case BPF_RSH:
                        emit_instr(ctx, srlv, dst, dst, src);
                        break;
                default:
                        pr_err("ALU_REG NOT HANDLED\n");
                        return -EINVAL;
                }
                break;
        case BPF_JMP | BPF_EXIT:
                if (this_idx + 1 < exit_idx) {
                        b_off = b_imm(exit_idx, ctx);
                        if (is_bad_offset(b_off))
                                return -E2BIG;
                        emit_instr(ctx, beq, MIPS_R_ZERO, MIPS_R_ZERO, b_off);
                        emit_instr(ctx, nop);
                }
                break;
        case BPF_JMP | BPF_JEQ | BPF_K: /* JMP_IMM */
        case BPF_JMP | BPF_JNE | BPF_K: /* JMP_IMM */
                cmp_eq = (bpf_op == BPF_JEQ);
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg_fp_ok);
                if (dst < 0)
                        return dst;
                if (insn->imm == 0) {
                        src = MIPS_R_ZERO;
                } else {
                        gen_imm_to_reg(insn, MIPS_R_AT, ctx);
                        src = MIPS_R_AT;
                }
                goto jeq_common;
        case BPF_JMP | BPF_JEQ | BPF_X: /* JMP_REG */
        case BPF_JMP | BPF_JNE | BPF_X:
        case BPF_JMP | BPF_JSLT | BPF_X:
        case BPF_JMP | BPF_JSLE | BPF_X:
        case BPF_JMP | BPF_JSGT | BPF_X:
        case BPF_JMP | BPF_JSGE | BPF_X:
        case BPF_JMP | BPF_JLT | BPF_X:
        case BPF_JMP | BPF_JLE | BPF_X:
        case BPF_JMP | BPF_JGT | BPF_X:
        case BPF_JMP | BPF_JGE | BPF_X:
        case BPF_JMP | BPF_JSET | BPF_X:
                src = ebpf_to_mips_reg(ctx, insn, src_reg_no_fp);
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (src < 0 || dst < 0)
                        return -EINVAL;
                td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
                ts = get_reg_val_type(ctx, this_idx, insn->src_reg);
                if (td == REG_32BIT && ts != REG_32BIT) {
                        emit_instr(ctx, sll, MIPS_R_AT, src, 0);
                        src = MIPS_R_AT;
                } else if (ts == REG_32BIT && td != REG_32BIT) {
                        emit_instr(ctx, sll, MIPS_R_AT, dst, 0);
                        dst = MIPS_R_AT;
                }
                if (bpf_op == BPF_JSET) {
                        emit_instr(ctx, and, MIPS_R_AT, dst, src);
                        cmp_eq = false;
                        dst = MIPS_R_AT;
                        src = MIPS_R_ZERO;
                } else if (bpf_op == BPF_JSGT || bpf_op == BPF_JSLE) {
                        emit_instr(ctx, dsubu, MIPS_R_AT, dst, src);
                        if ((insn + 1)->code == (BPF_JMP | BPF_EXIT) && insn->off == 1) {

                                b_off = b_imm(exit_idx, ctx);
                                if (is_bad_offset(b_off))
                                        return -E2BIG;
                                if (bpf_op == BPF_JSGT)
                                        emit_instr(ctx, blez, MIPS_R_AT, b_off);
                                else
                                        emit_instr(ctx, bgtz, MIPS_R_AT, b_off);
                                emit_instr(ctx, nop);
                                return 2; /* We consumed the exit. */
                        }
                        b_off = b_imm(this_idx + insn->off + 1, ctx);
                        if (is_bad_offset(b_off))
                                return -E2BIG;
                        if (bpf_op == BPF_JSGT)
                                emit_instr(ctx, bgtz, MIPS_R_AT, b_off);
                        else
                                emit_instr(ctx, blez, MIPS_R_AT, b_off);
                        emit_instr(ctx, nop);
                        break;
                } else if (bpf_op == BPF_JSGE || bpf_op == BPF_JSLT) {
                        emit_instr(ctx, slt, MIPS_R_AT, dst, src);
                        cmp_eq = bpf_op == BPF_JSGE;
                        dst = MIPS_R_AT;
                        src = MIPS_R_ZERO;
                } else if (bpf_op == BPF_JGT || bpf_op == BPF_JLE) {
                        /* dst or src could be AT */
                        emit_instr(ctx, dsubu, MIPS_R_T8, dst, src);
                        emit_instr(ctx, sltu, MIPS_R_AT, dst, src);
                        /* SP known to be non-zero, movz becomes boolean not */
                        emit_instr(ctx, movz, MIPS_R_T9, MIPS_R_SP, MIPS_R_T8);
                        emit_instr(ctx, movn, MIPS_R_T9, MIPS_R_ZERO, MIPS_R_T8);
                        emit_instr(ctx, or, MIPS_R_AT, MIPS_R_T9, MIPS_R_AT);
                        cmp_eq = bpf_op == BPF_JGT;
                        dst = MIPS_R_AT;
                        src = MIPS_R_ZERO;
                } else if (bpf_op == BPF_JGE || bpf_op == BPF_JLT) {
                        emit_instr(ctx, sltu, MIPS_R_AT, dst, src);
                        cmp_eq = bpf_op == BPF_JGE;
                        dst = MIPS_R_AT;
                        src = MIPS_R_ZERO;
                } else { /* JNE/JEQ case */
                        cmp_eq = (bpf_op == BPF_JEQ);
                }
jeq_common:
                /*
                 * If the next insn is EXIT and we are jumping arround
                 * only it, invert the sense of the compare and
                 * conditionally jump to the exit.  Poor man's branch
                 * chaining.
                 */
                if ((insn + 1)->code == (BPF_JMP | BPF_EXIT) && insn->off == 1) {
                        b_off = b_imm(exit_idx, ctx);
                        if (is_bad_offset(b_off)) {
                                target = j_target(ctx, exit_idx);
                                if (target == (unsigned int)-1)
                                        return -E2BIG;
                                cmp_eq = !cmp_eq;
                                b_off = 4 * 3;
                                if (!(ctx->offsets[this_idx] & OFFSETS_B_CONV)) {
                                        ctx->offsets[this_idx] |= OFFSETS_B_CONV;
                                        ctx->long_b_conversion = 1;
                                }
                        }

                        if (cmp_eq)
                                emit_instr(ctx, bne, dst, src, b_off);
                        else
                                emit_instr(ctx, beq, dst, src, b_off);
                        emit_instr(ctx, nop);
                        if (ctx->offsets[this_idx] & OFFSETS_B_CONV) {
                                emit_instr(ctx, j, target);
                                emit_instr(ctx, nop);
                        }
                        return 2; /* We consumed the exit. */
                }
                b_off = b_imm(this_idx + insn->off + 1, ctx);
                if (is_bad_offset(b_off)) {
                        target = j_target(ctx, this_idx + insn->off + 1);
                        if (target == (unsigned int)-1)
                                return -E2BIG;
                        cmp_eq = !cmp_eq;
                        b_off = 4 * 3;
                        if (!(ctx->offsets[this_idx] & OFFSETS_B_CONV)) {
                                ctx->offsets[this_idx] |= OFFSETS_B_CONV;
                                ctx->long_b_conversion = 1;
                        }
                }

                if (cmp_eq)
                        emit_instr(ctx, beq, dst, src, b_off);
                else
                        emit_instr(ctx, bne, dst, src, b_off);
                emit_instr(ctx, nop);
                if (ctx->offsets[this_idx] & OFFSETS_B_CONV) {
                        emit_instr(ctx, j, target);
                        emit_instr(ctx, nop);
                }
                break;
        case BPF_JMP | BPF_JSGT | BPF_K: /* JMP_IMM */
        case BPF_JMP | BPF_JSGE | BPF_K: /* JMP_IMM */
        case BPF_JMP | BPF_JSLT | BPF_K: /* JMP_IMM */
        case BPF_JMP | BPF_JSLE | BPF_K: /* JMP_IMM */
                cmp_eq = (bpf_op == BPF_JSGE);
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg_fp_ok);
                if (dst < 0)
                        return dst;

                if (insn->imm == 0) {
                        if ((insn + 1)->code == (BPF_JMP | BPF_EXIT) && insn->off == 1) {
                                b_off = b_imm(exit_idx, ctx);
                                if (is_bad_offset(b_off))
                                        return -E2BIG;
                                switch (bpf_op) {
                                case BPF_JSGT:
                                        emit_instr(ctx, blez, dst, b_off);
                                        break;
                                case BPF_JSGE:
                                        emit_instr(ctx, bltz, dst, b_off);
                                        break;
                                case BPF_JSLT:
                                        emit_instr(ctx, bgez, dst, b_off);
                                        break;
                                case BPF_JSLE:
                                        emit_instr(ctx, bgtz, dst, b_off);
                                        break;
                                }
                                emit_instr(ctx, nop);
                                return 2; /* We consumed the exit. */
                        }
                        b_off = b_imm(this_idx + insn->off + 1, ctx);
                        if (is_bad_offset(b_off))
                                return -E2BIG;
                        switch (bpf_op) {
                        case BPF_JSGT:
                                emit_instr(ctx, bgtz, dst, b_off);
                                break;
                        case BPF_JSGE:
                                emit_instr(ctx, bgez, dst, b_off);
                                break;
                        case BPF_JSLT:
                                emit_instr(ctx, bltz, dst, b_off);
                                break;
                        case BPF_JSLE:
                                emit_instr(ctx, blez, dst, b_off);
                                break;
                        }
                        emit_instr(ctx, nop);
                        break;
                }
                /*
                 * only "LT" compare available, so we must use imm + 1
                 * to generate "GT" and imm -1 to generate LE
                 */
                if (bpf_op == BPF_JSGT)
                        t64s = insn->imm + 1;
                else if (bpf_op == BPF_JSLE)
                        t64s = insn->imm + 1;
                else
                        t64s = insn->imm;

                cmp_eq = bpf_op == BPF_JSGT || bpf_op == BPF_JSGE;
                if (t64s >= S16_MIN && t64s <= S16_MAX) {
                        emit_instr(ctx, slti, MIPS_R_AT, dst, (int)t64s);
                        src = MIPS_R_AT;
                        dst = MIPS_R_ZERO;
                        goto jeq_common;
                }
                emit_const_to_reg(ctx, MIPS_R_AT, (u64)t64s);
                emit_instr(ctx, slt, MIPS_R_AT, dst, MIPS_R_AT);
                src = MIPS_R_AT;
                dst = MIPS_R_ZERO;
                goto jeq_common;

        case BPF_JMP | BPF_JGT | BPF_K:
        case BPF_JMP | BPF_JGE | BPF_K:
        case BPF_JMP | BPF_JLT | BPF_K:
        case BPF_JMP | BPF_JLE | BPF_K:
                cmp_eq = (bpf_op == BPF_JGE);
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg_fp_ok);
                if (dst < 0)
                        return dst;
                /*
                 * only "LT" compare available, so we must use imm + 1
                 * to generate "GT" and imm -1 to generate LE
                 */
                if (bpf_op == BPF_JGT)
                        t64s = (u64)(u32)(insn->imm) + 1;
                else if (bpf_op == BPF_JLE)
                        t64s = (u64)(u32)(insn->imm) + 1;
                else
                        t64s = (u64)(u32)(insn->imm);

                cmp_eq = bpf_op == BPF_JGT || bpf_op == BPF_JGE;

                emit_const_to_reg(ctx, MIPS_R_AT, (u64)t64s);
                emit_instr(ctx, sltu, MIPS_R_AT, dst, MIPS_R_AT);
                src = MIPS_R_AT;
                dst = MIPS_R_ZERO;
                goto jeq_common;

        case BPF_JMP | BPF_JSET | BPF_K: /* JMP_IMM */
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg_fp_ok);
                if (dst < 0)
                        return dst;

                if (ctx->use_bbit_insns && hweight32((u32)insn->imm) == 1) {
                        if ((insn + 1)->code == (BPF_JMP | BPF_EXIT) && insn->off == 1) {
                                b_off = b_imm(exit_idx, ctx);
                                if (is_bad_offset(b_off))
                                        return -E2BIG;
                                emit_instr(ctx, bbit0, dst, ffs((u32)insn->imm) - 1, b_off);
                                emit_instr(ctx, nop);
                                return 2; /* We consumed the exit. */
                        }
                        b_off = b_imm(this_idx + insn->off + 1, ctx);
                        if (is_bad_offset(b_off))
                                return -E2BIG;
                        emit_instr(ctx, bbit1, dst, ffs((u32)insn->imm) - 1, b_off);
                        emit_instr(ctx, nop);
                        break;
                }
                t64 = (u32)insn->imm;
                emit_const_to_reg(ctx, MIPS_R_AT, t64);
                emit_instr(ctx, and, MIPS_R_AT, dst, MIPS_R_AT);
                src = MIPS_R_AT;
                dst = MIPS_R_ZERO;
                cmp_eq = false;
                goto jeq_common;

        case BPF_JMP | BPF_JA:
                /*
                 * Prefer relative branch for easier debugging, but
                 * fall back if needed.
                 */
                b_off = b_imm(this_idx + insn->off + 1, ctx);
                if (is_bad_offset(b_off)) {
                        target = j_target(ctx, this_idx + insn->off + 1);
                        if (target == (unsigned int)-1)
                                return -E2BIG;
                        emit_instr(ctx, j, target);
                } else {
                        emit_instr(ctx, b, b_off);
                }
                emit_instr(ctx, nop);
                break;
        case BPF_LD | BPF_DW | BPF_IMM:
                if (insn->src_reg != 0)
                        return -EINVAL;
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (dst < 0)
                        return dst;
                t64 = ((u64)(u32)insn->imm) | ((u64)(insn + 1)->imm << 32);
                emit_const_to_reg(ctx, dst, t64);
                return 2; /* Double slot insn */

        case BPF_JMP | BPF_CALL:
                ctx->flags |= EBPF_SAVE_RA;
                t64s = (s64)insn->imm + (s64)__bpf_call_base;
                emit_const_to_reg(ctx, MIPS_R_T9, (u64)t64s);
                emit_instr(ctx, jalr, MIPS_R_RA, MIPS_R_T9);
                /* delay slot */
                emit_instr(ctx, nop);
                break;

        case BPF_JMP | BPF_TAIL_CALL:
                if (emit_bpf_tail_call(ctx, this_idx))
                        return -EINVAL;
                break;

        case BPF_LD | BPF_B | BPF_ABS:
        case BPF_LD | BPF_H | BPF_ABS:
        case BPF_LD | BPF_W | BPF_ABS:
        case BPF_LD | BPF_DW | BPF_ABS:
                ctx->flags |= EBPF_SAVE_RA;

                gen_imm_to_reg(insn, MIPS_R_A1, ctx);
                emit_instr(ctx, addiu, MIPS_R_A2, MIPS_R_ZERO, size_to_len(insn));

                if (insn->imm < 0) {
                        emit_const_to_reg(ctx, MIPS_R_T9, (u64)bpf_internal_load_pointer_neg_helper);
                } else {
                        emit_const_to_reg(ctx, MIPS_R_T9, (u64)ool_skb_header_pointer);
                        emit_instr(ctx, daddiu, MIPS_R_A3, MIPS_R_SP, ctx->tmp_offset);
                }
                goto ld_skb_common;

        case BPF_LD | BPF_B | BPF_IND:
        case BPF_LD | BPF_H | BPF_IND:
        case BPF_LD | BPF_W | BPF_IND:
        case BPF_LD | BPF_DW | BPF_IND:
                ctx->flags |= EBPF_SAVE_RA;
                src = ebpf_to_mips_reg(ctx, insn, src_reg_no_fp);
                if (src < 0)
                        return src;
                ts = get_reg_val_type(ctx, this_idx, insn->src_reg);
                if (ts == REG_32BIT_ZERO_EX) {
                        /* sign extend */
                        emit_instr(ctx, sll, MIPS_R_A1, src, 0);
                        src = MIPS_R_A1;
                }
                if (insn->imm >= S16_MIN && insn->imm <= S16_MAX) {
                        emit_instr(ctx, daddiu, MIPS_R_A1, src, insn->imm);
                } else {
                        gen_imm_to_reg(insn, MIPS_R_AT, ctx);
                        emit_instr(ctx, daddu, MIPS_R_A1, MIPS_R_AT, src);
                }
                /* truncate to 32-bit int */
                emit_instr(ctx, sll, MIPS_R_A1, MIPS_R_A1, 0);
                emit_instr(ctx, daddiu, MIPS_R_A3, MIPS_R_SP, ctx->tmp_offset);
                emit_instr(ctx, slt, MIPS_R_AT, MIPS_R_A1, MIPS_R_ZERO);

                emit_const_to_reg(ctx, MIPS_R_T8, (u64)bpf_internal_load_pointer_neg_helper);
                emit_const_to_reg(ctx, MIPS_R_T9, (u64)ool_skb_header_pointer);
                emit_instr(ctx, addiu, MIPS_R_A2, MIPS_R_ZERO, size_to_len(insn));
                emit_instr(ctx, movn, MIPS_R_T9, MIPS_R_T8, MIPS_R_AT);

ld_skb_common:
                emit_instr(ctx, jalr, MIPS_R_RA, MIPS_R_T9);
                /* delay slot move */
                emit_instr(ctx, daddu, MIPS_R_A0, MIPS_R_S0, MIPS_R_ZERO);

                /* Check the error value */
                b_off = b_imm(exit_idx, ctx);
                if (is_bad_offset(b_off)) {
                        target = j_target(ctx, exit_idx);
                        if (target == (unsigned int)-1)
                                return -E2BIG;

                        if (!(ctx->offsets[this_idx] & OFFSETS_B_CONV)) {
                                ctx->offsets[this_idx] |= OFFSETS_B_CONV;
                                ctx->long_b_conversion = 1;
                        }
                        emit_instr(ctx, bne, MIPS_R_V0, MIPS_R_ZERO, 4 * 3);
                        emit_instr(ctx, nop);
                        emit_instr(ctx, j, target);
                        emit_instr(ctx, nop);
                } else {
                        emit_instr(ctx, beq, MIPS_R_V0, MIPS_R_ZERO, b_off);
                        emit_instr(ctx, nop);
                }

#ifdef __BIG_ENDIAN
                need_swap = false;
#else
                need_swap = true;
#endif
                dst = MIPS_R_V0;
                switch (BPF_SIZE(insn->code)) {
                case BPF_B:
                        emit_instr(ctx, lbu, dst, 0, MIPS_R_V0);
                        break;
                case BPF_H:
                        emit_instr(ctx, lhu, dst, 0, MIPS_R_V0);
                        if (need_swap)
                                emit_instr(ctx, wsbh, dst, dst);
                        break;
                case BPF_W:
                        emit_instr(ctx, lw, dst, 0, MIPS_R_V0);
                        if (need_swap) {
                                emit_instr(ctx, wsbh, dst, dst);
                                emit_instr(ctx, rotr, dst, dst, 16);
                        }
                        break;
                case BPF_DW:
                        emit_instr(ctx, ld, dst, 0, MIPS_R_V0);
                        if (need_swap) {
                                emit_instr(ctx, dsbh, dst, dst);
                                emit_instr(ctx, dshd, dst, dst);
                        }
                        break;
                }

                break;
        case BPF_ALU | BPF_END | BPF_FROM_BE:
        case BPF_ALU | BPF_END | BPF_FROM_LE:
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (dst < 0)
                        return dst;
                td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
                if (insn->imm == 64 && td == REG_32BIT)
                        emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);

                if (insn->imm != 64 &&
                    (td == REG_64BIT || td == REG_32BIT_ZERO_EX)) {
                        /* sign extend */
                        emit_instr(ctx, sll, dst, dst, 0);
                }

#ifdef __BIG_ENDIAN
                need_swap = (BPF_SRC(insn->code) == BPF_FROM_LE);
#else
                need_swap = (BPF_SRC(insn->code) == BPF_FROM_BE);
#endif
                if (insn->imm == 16) {
                        if (need_swap)
                                emit_instr(ctx, wsbh, dst, dst);
                        emit_instr(ctx, andi, dst, dst, 0xffff);
                } else if (insn->imm == 32) {
                        if (need_swap) {
                                emit_instr(ctx, wsbh, dst, dst);
                                emit_instr(ctx, rotr, dst, dst, 16);
                        }
                } else { /* 64-bit*/
                        if (need_swap) {
                                emit_instr(ctx, dsbh, dst, dst);
                                emit_instr(ctx, dshd, dst, dst);
                        }
                }
                break;

        case BPF_ST | BPF_B | BPF_MEM:
        case BPF_ST | BPF_H | BPF_MEM:
        case BPF_ST | BPF_W | BPF_MEM:
        case BPF_ST | BPF_DW | BPF_MEM:
                if (insn->dst_reg == BPF_REG_10) {
                        ctx->flags |= EBPF_SEEN_FP;
                        dst = MIPS_R_SP;
                        mem_off = insn->off + MAX_BPF_STACK;
                } else {
                        dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                        if (dst < 0)
                                return dst;
                        mem_off = insn->off;
                }
                gen_imm_to_reg(insn, MIPS_R_AT, ctx);
                switch (BPF_SIZE(insn->code)) {
                case BPF_B:
                        emit_instr(ctx, sb, MIPS_R_AT, mem_off, dst);
                        break;
                case BPF_H:
                        emit_instr(ctx, sh, MIPS_R_AT, mem_off, dst);
                        break;
                case BPF_W:
                        emit_instr(ctx, sw, MIPS_R_AT, mem_off, dst);
                        break;
                case BPF_DW:
                        emit_instr(ctx, sd, MIPS_R_AT, mem_off, dst);
                        break;
                }
                break;

        case BPF_LDX | BPF_B | BPF_MEM:
        case BPF_LDX | BPF_H | BPF_MEM:
        case BPF_LDX | BPF_W | BPF_MEM:
        case BPF_LDX | BPF_DW | BPF_MEM:
                if (insn->src_reg == BPF_REG_10) {
                        ctx->flags |= EBPF_SEEN_FP;
                        src = MIPS_R_SP;
                        mem_off = insn->off + MAX_BPF_STACK;
                } else {
                        src = ebpf_to_mips_reg(ctx, insn, src_reg_no_fp);
                        if (src < 0)
                                return src;
                        mem_off = insn->off;
                }
                dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                if (dst < 0)
                        return dst;
                switch (BPF_SIZE(insn->code)) {
                case BPF_B:
                        emit_instr(ctx, lbu, dst, mem_off, src);
                        break;
                case BPF_H:
                        emit_instr(ctx, lhu, dst, mem_off, src);
                        break;
                case BPF_W:
                        emit_instr(ctx, lw, dst, mem_off, src);
                        break;
                case BPF_DW:
                        emit_instr(ctx, ld, dst, mem_off, src);
                        break;
                }
                break;

        case BPF_STX | BPF_B | BPF_MEM:
        case BPF_STX | BPF_H | BPF_MEM:
        case BPF_STX | BPF_W | BPF_MEM:
        case BPF_STX | BPF_DW | BPF_MEM:
        case BPF_STX | BPF_W | BPF_XADD:
        case BPF_STX | BPF_DW | BPF_XADD:
                if (insn->dst_reg == BPF_REG_10) {
                        ctx->flags |= EBPF_SEEN_FP;
                        dst = MIPS_R_SP;
                        mem_off = insn->off + MAX_BPF_STACK;
                } else {
                        dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
                        if (dst < 0)
                                return dst;
                        mem_off = insn->off;
                }
                src = ebpf_to_mips_reg(ctx, insn, src_reg_no_fp);
                if (src < 0)
                        return src;
                if (BPF_MODE(insn->code) == BPF_XADD) {
                        switch (BPF_SIZE(insn->code)) {
                        case BPF_W:
                                if (get_reg_val_type(ctx, this_idx, insn->src_reg) == REG_32BIT) {
                                        emit_instr(ctx, sll, MIPS_R_AT, src, 0);
                                        src = MIPS_R_AT;
                                }
                                emit_instr(ctx, ll, MIPS_R_T8, mem_off, dst);
                                emit_instr(ctx, addu, MIPS_R_T8, MIPS_R_T8, src);
                                emit_instr(ctx, sc, MIPS_R_T8, mem_off, dst);
                                /*
                                 * On failure back up to LL (-4
                                 * instructions of 4 bytes each
                                 */
                                emit_instr(ctx, beq, MIPS_R_T8, MIPS_R_ZERO, -4 * 4);
                                emit_instr(ctx, nop);
                                break;
                        case BPF_DW:
                                if (get_reg_val_type(ctx, this_idx, insn->src_reg) == REG_32BIT) {
                                        emit_instr(ctx, daddu, MIPS_R_AT, src, MIPS_R_ZERO);
                                        emit_instr(ctx, dinsu, MIPS_R_AT, MIPS_R_ZERO, 32, 32);
                                        src = MIPS_R_AT;
                                }
                                emit_instr(ctx, lld, MIPS_R_T8, mem_off, dst);
                                emit_instr(ctx, daddu, MIPS_R_T8, MIPS_R_T8, src);
                                emit_instr(ctx, scd, MIPS_R_T8, mem_off, dst);
                                emit_instr(ctx, beq, MIPS_R_T8, MIPS_R_ZERO, -4 * 4);
                                emit_instr(ctx, nop);
                                break;
                        }
                } else { /* BPF_MEM */
                        switch (BPF_SIZE(insn->code)) {
                        case BPF_B:
                                emit_instr(ctx, sb, src, mem_off, dst);
                                break;
                        case BPF_H:
                                emit_instr(ctx, sh, src, mem_off, dst);
                                break;
                        case BPF_W:
                                emit_instr(ctx, sw, src, mem_off, dst);
                                break;
                        case BPF_DW:
                                if (get_reg_val_type(ctx, this_idx, insn->src_reg) == REG_32BIT) {
                                        emit_instr(ctx, daddu, MIPS_R_AT, src, MIPS_R_ZERO);
                                        emit_instr(ctx, dinsu, MIPS_R_AT, MIPS_R_ZERO, 32, 32);
                                        src = MIPS_R_AT;
                                }
                                emit_instr(ctx, sd, src, mem_off, dst);
                                break;
                        }
                }
                break;

        default:
                pr_err("NOT HANDLED %d - (%02x)\n",
                       this_idx, (unsigned int)insn->code);
                return -EINVAL;
        }
        return 1;
}

#define RVT_VISITED_MASK 0xc000000000000000ull
#define RVT_FALL_THROUGH 0x4000000000000000ull
#define RVT_BRANCH_TAKEN 0x8000000000000000ull
#define RVT_DONE (RVT_FALL_THROUGH | RVT_BRANCH_TAKEN)

static int build_int_body(struct jit_ctx *ctx)
{
        const struct bpf_prog *prog = ctx->skf;
        const struct bpf_insn *insn;
        int i, r;

        for (i = 0; i < prog->len; ) {
                insn = prog->insnsi + i;
                if ((ctx->reg_val_types[i] & RVT_VISITED_MASK) == 0) {
                        /* dead instruction, don't emit it. */
                        i++;
                        continue;
                }

                if (ctx->target == NULL)
                        ctx->offsets[i] = (ctx->offsets[i] & OFFSETS_B_CONV) | (ctx->idx * 4);

                r = build_one_insn(insn, ctx, i, prog->len);
                if (r < 0)
                        return r;
                i += r;
        }
        /* epilogue offset */
        if (ctx->target == NULL)
                ctx->offsets[i] = ctx->idx * 4;

        /*
         * All exits have an offset of the epilogue, some offsets may
         * not have been set due to banch-around threading, so set
         * them now.
         */
        if (ctx->target == NULL)
                for (i = 0; i < prog->len; i++) {
                        insn = prog->insnsi + i;
                        if (insn->code == (BPF_JMP | BPF_EXIT))
                                ctx->offsets[i] = ctx->idx * 4;
                }
        return 0;
}

/* return the last idx processed, or negative for error */
static int reg_val_propagate_range(struct jit_ctx *ctx, u64 initial_rvt,
                                   int start_idx, bool follow_taken)
{
        const struct bpf_prog *prog = ctx->skf;
        const struct bpf_insn *insn;
        u64 exit_rvt = initial_rvt;
        u64 *rvt = ctx->reg_val_types;
        int idx;
        int reg;

        for (idx = start_idx; idx < prog->len; idx++) {
                rvt[idx] = (rvt[idx] & RVT_VISITED_MASK) | exit_rvt;
                insn = prog->insnsi + idx;
                switch (BPF_CLASS(insn->code)) {
                case BPF_ALU:
                        switch (BPF_OP(insn->code)) {
                        case BPF_ADD:
                        case BPF_SUB:
                        case BPF_MUL:
                        case BPF_DIV:
                        case BPF_OR:
                        case BPF_AND:
                        case BPF_LSH:
                        case BPF_RSH:
                        case BPF_NEG:
                        case BPF_MOD:
                        case BPF_XOR:
                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
                                break;
                        case BPF_MOV:
                                if (BPF_SRC(insn->code)) {
                                        set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
                                } else {
                                        /* IMM to REG move*/
                                        if (insn->imm >= 0)
                                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
                                        else
                                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
                                }
                                break;
                        case BPF_END:
                                if (insn->imm == 64)
                                        set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
                                else if (insn->imm == 32)
                                        set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
                                else /* insn->imm == 16 */
                                        set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
                                break;
                        }
                        rvt[idx] |= RVT_DONE;
                        break;
                case BPF_ALU64:
                        switch (BPF_OP(insn->code)) {
                        case BPF_MOV:
                                if (BPF_SRC(insn->code)) {
                                        /* REG to REG move*/
                                        set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
                                } else {
                                        /* IMM to REG move*/
                                        if (insn->imm >= 0)
                                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
                                        else
                                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT_32BIT);
                                }
                                break;
                        default:
                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
                        }
                        rvt[idx] |= RVT_DONE;
                        break;
                case BPF_LD:
                        switch (BPF_SIZE(insn->code)) {
                        case BPF_DW:
                                if (BPF_MODE(insn->code) == BPF_IMM) {
                                        s64 val;

                                        val = (s64)((u32)insn->imm | ((u64)(insn + 1)->imm << 32));
                                        if (val > 0 && val <= S32_MAX)
                                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
                                        else if (val >= S32_MIN && val <= S32_MAX)
                                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT_32BIT);
                                        else
                                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
                                        rvt[idx] |= RVT_DONE;
                                        idx++;
                                } else {
                                        set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
                                }
                                break;
                        case BPF_B:
                        case BPF_H:
                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
                                break;
                        case BPF_W:
                                if (BPF_MODE(insn->code) == BPF_IMM)
                                        set_reg_val_type(&exit_rvt, insn->dst_reg,
                                                         insn->imm >= 0 ? REG_32BIT_POS : REG_32BIT);
                                else
                                        set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
                                break;
                        }
                        rvt[idx] |= RVT_DONE;
                        break;
                case BPF_LDX:
                        switch (BPF_SIZE(insn->code)) {
                        case BPF_DW:
                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
                                break;
                        case BPF_B:
                        case BPF_H:
                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
                                break;
                        case BPF_W:
                                set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
                                break;
                        }
                        rvt[idx] |= RVT_DONE;
                        break;
                case BPF_JMP:
                        switch (BPF_OP(insn->code)) {
                        case BPF_EXIT:
                                rvt[idx] = RVT_DONE | exit_rvt;
                                rvt[prog->len] = exit_rvt;
                                return idx;
                        case BPF_JA:
                                rvt[idx] |= RVT_DONE;
                                idx += insn->off;
                                break;
                        case BPF_JEQ:
                        case BPF_JGT:
                        case BPF_JGE:
                        case BPF_JLT:
                        case BPF_JLE:
                        case BPF_JSET:
                        case BPF_JNE:
                        case BPF_JSGT:
                        case BPF_JSGE:
                        case BPF_JSLT:
                        case BPF_JSLE:
                                if (follow_taken) {
                                        rvt[idx] |= RVT_BRANCH_TAKEN;
                                        idx += insn->off;
                                        follow_taken = false;
                                } else {
                                        rvt[idx] |= RVT_FALL_THROUGH;
                                }
                                break;
                        case BPF_CALL:
                                set_reg_val_type(&exit_rvt, BPF_REG_0, REG_64BIT);
                                /* Upon call return, argument registers are clobbered. */
                                for (reg = BPF_REG_0; reg <= BPF_REG_5; reg++)
                                        set_reg_val_type(&exit_rvt, reg, REG_64BIT);

                                rvt[idx] |= RVT_DONE;
                                break;
                        default:
                                WARN(1, "Unhandled BPF_JMP case.\n");
                                rvt[idx] |= RVT_DONE;
                                break;
                        }
                        break;
                default:
                        rvt[idx] |= RVT_DONE;
                        break;
                }
        }
        return idx;
}

/*
 * Track the value range (i.e. 32-bit vs. 64-bit) of each register at
 * each eBPF insn.  This allows unneeded sign and zero extension
 * operations to be omitted.
 *
 * Doesn't handle yet confluence of control paths with conflicting
 * ranges, but it is good enough for most sane code.
 */
static int reg_val_propagate(struct jit_ctx *ctx)
{
        const struct bpf_prog *prog = ctx->skf;
        u64 exit_rvt;
        int reg;
        int i;

        /*
         * 11 registers * 3 bits/reg leaves top bits free for other
         * uses.  Bit-62..63 used to see if we have visited an insn.
         */
        exit_rvt = 0;

        /* Upon entry, argument registers are 64-bit. */
        for (reg = BPF_REG_1; reg <= BPF_REG_5; reg++)
                set_reg_val_type(&exit_rvt, reg, REG_64BIT);

        /*
         * First follow all conditional branches on the fall-through
         * edge of control flow..
         */
        reg_val_propagate_range(ctx, exit_rvt, 0, false);
restart_search:
        /*
         * Then repeatedly find the first conditional branch where
         * both edges of control flow have not been taken, and follow
         * the branch taken edge.  We will end up restarting the
         * search once per conditional branch insn.
         */
        for (i = 0; i < prog->len; i++) {
                u64 rvt = ctx->reg_val_types[i];

                if ((rvt & RVT_VISITED_MASK) == RVT_DONE ||
                    (rvt & RVT_VISITED_MASK) == 0)
                        continue;
                if ((rvt & RVT_VISITED_MASK) == RVT_FALL_THROUGH) {
                        reg_val_propagate_range(ctx, rvt & ~RVT_VISITED_MASK, i, true);
                } else { /* RVT_BRANCH_TAKEN */
                        WARN(1, "Unexpected RVT_BRANCH_TAKEN case.\n");
                        reg_val_propagate_range(ctx, rvt & ~RVT_VISITED_MASK, i, false);
                }
                goto restart_search;
        }
        /*
         * Eventually all conditional branches have been followed on
         * both branches and we are done.  Any insn that has not been
         * visited at this point is dead.
         */

        return 0;
}

static void jit_fill_hole(void *area, unsigned int size)
{
        u32 *p;

        /* We are guaranteed to have aligned memory. */
        for (p = area; size >= sizeof(u32); size -= sizeof(u32))
                uasm_i_break(&p, BRK_BUG); /* Increments p */
}

struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
{
        struct bpf_prog *orig_prog = prog;
        bool tmp_blinded = false;
        struct bpf_prog *tmp;
        struct bpf_binary_header *header = NULL;
        struct jit_ctx ctx;
        unsigned int image_size;
        u8 *image_ptr;

        if (!prog->jit_requested || !cpu_has_mips64r2)
                return prog;

        tmp = bpf_jit_blind_constants(prog);
        /* If blinding was requested and we failed during blinding,
         * we must fall back to the interpreter.
         */
        if (IS_ERR(tmp))
                return orig_prog;
        if (tmp != prog) {
                tmp_blinded = true;
                prog = tmp;
        }

        memset(&ctx, 0, sizeof(ctx));

        preempt_disable();
        switch (current_cpu_type()) {
        case CPU_CAVIUM_OCTEON:
        case CPU_CAVIUM_OCTEON_PLUS:
        case CPU_CAVIUM_OCTEON2:
        case CPU_CAVIUM_OCTEON3:
                ctx.use_bbit_insns = 1;
                break;
        default:
                ctx.use_bbit_insns = 0;
        }
        preempt_enable();

        ctx.offsets = kcalloc(prog->len + 1, sizeof(*ctx.offsets), GFP_KERNEL);
        if (ctx.offsets == NULL)
                goto out_err;

        ctx.reg_val_types = kcalloc(prog->len + 1, sizeof(*ctx.reg_val_types), GFP_KERNEL);
        if (ctx.reg_val_types == NULL)
                goto out_err;

        ctx.skf = prog;

        if (reg_val_propagate(&ctx))
                goto out_err;

        /*
         * First pass discovers used resources and instruction offsets
         * assuming short branches are used.
         */
        if (build_int_body(&ctx))
                goto out_err;

        /*
         * If no calls are made (EBPF_SAVE_RA), then tail call count
         * in $v1, else we must save in n$s4.
         */
        if (ctx.flags & EBPF_SEEN_TC) {
                if (ctx.flags & EBPF_SAVE_RA)
                        ctx.flags |= EBPF_SAVE_S4;
                else
                        ctx.flags |= EBPF_TCC_IN_V1;
        }

        /*
         * Second pass generates offsets, if any branches are out of
         * range a jump-around long sequence is generated, and we have
         * to try again from the beginning to generate the new
         * offsets.  This is done until no additional conversions are
         * necessary.
         */
        do {
                ctx.idx = 0;
                ctx.gen_b_offsets = 1;
                ctx.long_b_conversion = 0;
                if (gen_int_prologue(&ctx))
                        goto out_err;
                if (build_int_body(&ctx))
                        goto out_err;
                if (build_int_epilogue(&ctx, MIPS_R_RA))
                        goto out_err;
        } while (ctx.long_b_conversion);

        image_size = 4 * ctx.idx;

        header = bpf_jit_binary_alloc(image_size, &image_ptr,
                                      sizeof(u32), jit_fill_hole);
        if (header == NULL)
                goto out_err;

        ctx.target = (u32 *)image_ptr;

        /* Third pass generates the code */
        ctx.idx = 0;
        if (gen_int_prologue(&ctx))
                goto out_err;
        if (build_int_body(&ctx))
                goto out_err;
        if (build_int_epilogue(&ctx, MIPS_R_RA))
                goto out_err;

        /* Update the icache */
        flush_icache_range((unsigned long)ctx.target,
                           (unsigned long)(ctx.target + ctx.idx * sizeof(u32)));

        if (bpf_jit_enable > 1)
                /* Dump JIT code */
                bpf_jit_dump(prog->len, image_size, 2, ctx.target);

        bpf_jit_binary_lock_ro(header);
        prog->bpf_func = (void *)ctx.target;
        prog->jited = 1;
        prog->jited_len = image_size;
out_normal:
        if (tmp_blinded)
                bpf_jit_prog_release_other(prog, prog == orig_prog ?
                                           tmp : orig_prog);
        kfree(ctx.offsets);
        kfree(ctx.reg_val_types);

        return prog;

out_err:
        prog = orig_prog;
        if (header)
                bpf_jit_binary_free(header);
        goto out_normal;
}