/*
 * BPF JIT compiler for ARM64
 *
 * Copyright (C) 2014-2016 Zi Shen Lim <zlim.lnx@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#define pr_fmt(fmt) "bpf_jit: " fmt

#include <linux/filter.h>
#include <linux/printk.h>
#include <linux/skbuff.h>
#include <linux/slab.h>

#include <asm/byteorder.h>
#include <asm/cacheflush.h>
#include <asm/debug-monitors.h>

#include "bpf_jit.h"

int bpf_jit_enable __read_mostly;

#define TMP_REG_1 (MAX_BPF_REG + 0)
#define TMP_REG_2 (MAX_BPF_REG + 1)

/* Map BPF registers to A64 registers */
static const int bpf2a64[] = {
        /* return value from in-kernel function, and exit value from eBPF */
        [BPF_REG_0] = A64_R(7),
        /* arguments from eBPF program to in-kernel function */
        [BPF_REG_1] = A64_R(0),
        [BPF_REG_2] = A64_R(1),
        [BPF_REG_3] = A64_R(2),
        [BPF_REG_4] = A64_R(3),
        [BPF_REG_5] = A64_R(4),
        /* callee saved registers that in-kernel function will preserve */
        [BPF_REG_6] = A64_R(19),
        [BPF_REG_7] = A64_R(20),
        [BPF_REG_8] = A64_R(21),
        [BPF_REG_9] = A64_R(22),
        /* read-only frame pointer to access stack */
        [BPF_REG_FP] = A64_R(25),
        /* temporary register for internal BPF JIT */
        [TMP_REG_1] = A64_R(23),
        [TMP_REG_2] = A64_R(24),
};

struct jit_ctx {
        const struct bpf_prog *prog;
        int idx;
        int tmp_used;
        int epilogue_offset;
        int *offset;
        u32 *image;
};

static inline void emit(const u32 insn, struct jit_ctx *ctx)
{
        if (ctx->image != NULL)
                ctx->image[ctx->idx] = cpu_to_le32(insn);

        ctx->idx++;
}

static inline void emit_a64_mov_i64(const int reg, const u64 val,
                                    struct jit_ctx *ctx)
{
        u64 tmp = val;
        int shift = 0;

        emit(A64_MOVZ(1, reg, tmp & 0xffff, shift), ctx);
        tmp >>= 16;
        shift += 16;
        while (tmp) {
                if (tmp & 0xffff)
                        emit(A64_MOVK(1, reg, tmp & 0xffff, shift), ctx);
                tmp >>= 16;
                shift += 16;
        }
}

static inline void emit_a64_mov_i(const int is64, const int reg,
                                  const s32 val, struct jit_ctx *ctx)
{
        u16 hi = val >> 16;
        u16 lo = val & 0xffff;

        if (hi & 0x8000) {
                if (hi == 0xffff) {
                        emit(A64_MOVN(is64, reg, (u16)~lo, 0), ctx);
                } else {
                        emit(A64_MOVN(is64, reg, (u16)~hi, 16), ctx);
                        emit(A64_MOVK(is64, reg, lo, 0), ctx);
                }
        } else {
                emit(A64_MOVZ(is64, reg, lo, 0), ctx);
                if (hi)
                        emit(A64_MOVK(is64, reg, hi, 16), ctx);
        }
}

static inline int bpf2a64_offset(int bpf_to, int bpf_from,
                                 const struct jit_ctx *ctx)
{
        int to = ctx->offset[bpf_to];
        /* -1 to account for the Branch instruction */
        int from = ctx->offset[bpf_from] - 1;

        return to - from;
}

static void jit_fill_hole(void *area, unsigned int size)
{
        u32 *ptr;
        /* We are guaranteed to have aligned memory. */
        for (ptr = area; size >= sizeof(u32); size -= sizeof(u32))
                *ptr++ = cpu_to_le32(AARCH64_BREAK_FAULT);
}

static inline int epilogue_offset(const struct jit_ctx *ctx)
{
        int to = ctx->epilogue_offset;
        int from = ctx->idx;

        return to - from;
}

/* Stack must be multiples of 16B */
#define STACK_ALIGN(sz) (((sz) + 15) & ~15)

#define _STACK_SIZE \
        (MAX_BPF_STACK \
         + 4 /* extra for skb_copy_bits buffer */)

#define STACK_SIZE STACK_ALIGN(_STACK_SIZE)

static void build_prologue(struct jit_ctx *ctx)
{
        const u8 r6 = bpf2a64[BPF_REG_6];
        const u8 r7 = bpf2a64[BPF_REG_7];
        const u8 r8 = bpf2a64[BPF_REG_8];
        const u8 r9 = bpf2a64[BPF_REG_9];
        const u8 fp = bpf2a64[BPF_REG_FP];
        const u8 tmp1 = bpf2a64[TMP_REG_1];
        const u8 tmp2 = bpf2a64[TMP_REG_2];

        /*
         * BPF prog stack layout
         *
         *                         high
         * original A64_SP =>   0:+-----+ BPF prologue
         *                        |FP/LR|
         * current A64_FP =>  -16:+-----+
         *                        | ... | callee saved registers
         *                        +-----+
         *                        |     | x25/x26
         * BPF fp register => -80:+-----+ <= (BPF_FP)
         *                        |     |
         *                        | ... | BPF prog stack
         *                        |     |
         *                        +-----+ <= (BPF_FP - MAX_BPF_STACK)
         *                        |RSVD | JIT scratchpad
         * current A64_SP =>      +-----+ <= (BPF_FP - STACK_SIZE)
         *                        |     |
         *                        | ... | Function call stack
         *                        |     |
         *                        +-----+
         *                          low
         *
         */

        /* Save FP and LR registers to stay align with ARM64 AAPCS */
        emit(A64_PUSH(A64_FP, A64_LR, A64_SP), ctx);
        emit(A64_MOV(1, A64_FP, A64_SP), ctx);

        /* Save callee-saved register */
        emit(A64_PUSH(r6, r7, A64_SP), ctx);
        emit(A64_PUSH(r8, r9, A64_SP), ctx);
        if (ctx->tmp_used)
                emit(A64_PUSH(tmp1, tmp2, A64_SP), ctx);

        /* Save fp (x25) and x26. SP requires 16 bytes alignment */
        emit(A64_PUSH(fp, A64_R(26), A64_SP), ctx);

        /* Set up BPF prog stack base register (x25) */
        emit(A64_MOV(1, fp, A64_SP), ctx);

        /* Set up function call stack */
        emit(A64_SUB_I(1, A64_SP, A64_SP, STACK_SIZE), ctx);
}

static void build_epilogue(struct jit_ctx *ctx)
{
        const u8 r0 = bpf2a64[BPF_REG_0];
        const u8 r6 = bpf2a64[BPF_REG_6];
        const u8 r7 = bpf2a64[BPF_REG_7];
        const u8 r8 = bpf2a64[BPF_REG_8];
        const u8 r9 = bpf2a64[BPF_REG_9];
        const u8 fp = bpf2a64[BPF_REG_FP];
        const u8 tmp1 = bpf2a64[TMP_REG_1];
        const u8 tmp2 = bpf2a64[TMP_REG_2];

        /* We're done with BPF stack */
        emit(A64_ADD_I(1, A64_SP, A64_SP, STACK_SIZE), ctx);

        /* Restore fs (x25) and x26 */
        emit(A64_POP(fp, A64_R(26), A64_SP), ctx);

        /* Restore callee-saved register */
        if (ctx->tmp_used)
                emit(A64_POP(tmp1, tmp2, A64_SP), ctx);
        emit(A64_POP(r8, r9, A64_SP), ctx);
        emit(A64_POP(r6, r7, A64_SP), ctx);

        /* Restore FP/LR registers */
        emit(A64_POP(A64_FP, A64_LR, A64_SP), ctx);

        /* Set return value */
        emit(A64_MOV(1, A64_R(0), r0), ctx);

        emit(A64_RET(A64_LR), ctx);
}

/* JITs an eBPF instruction.
 * Returns:
 * 0  - successfully JITed an 8-byte eBPF instruction.
 * >0 - successfully JITed a 16-byte eBPF instruction.
 * <0 - failed to JIT.
 */
static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx)
{
        const u8 code = insn->code;
        const u8 dst = bpf2a64[insn->dst_reg];
        const u8 src = bpf2a64[insn->src_reg];
        const u8 tmp = bpf2a64[TMP_REG_1];
        const u8 tmp2 = bpf2a64[TMP_REG_2];
        const s16 off = insn->off;
        const s32 imm = insn->imm;
        const int i = insn - ctx->prog->insnsi;
        const bool is64 = BPF_CLASS(code) == BPF_ALU64;
        u8 jmp_cond;
        s32 jmp_offset;

#define check_imm(bits, imm) do {                               \
        if ((((imm) > 0) && ((imm) >> (bits))) ||               \
            (((imm) < 0) && (~(imm) >> (bits)))) {              \
                pr_info("[%2d] imm=%d(0x%x) out of range\n",    \
                        i, imm, imm);                           \
                return -EINVAL;                                 \
        }                                                       \
} while (0)
#define check_imm19(imm) check_imm(19, imm)
#define check_imm26(imm) check_imm(26, imm)

        switch (code) {
        /* dst = src */
        case BPF_ALU | BPF_MOV | BPF_X:
        case BPF_ALU64 | BPF_MOV | BPF_X:
                emit(A64_MOV(is64, dst, src), ctx);
                break;
        /* dst = dst OP src */
        case BPF_ALU | BPF_ADD | BPF_X:
        case BPF_ALU64 | BPF_ADD | BPF_X:
                emit(A64_ADD(is64, dst, dst, src), ctx);
                break;
        case BPF_ALU | BPF_SUB | BPF_X:
        case BPF_ALU64 | BPF_SUB | BPF_X:
                emit(A64_SUB(is64, dst, dst, src), ctx);
                break;
        case BPF_ALU | BPF_AND | BPF_X:
        case BPF_ALU64 | BPF_AND | BPF_X:
                emit(A64_AND(is64, dst, dst, src), ctx);
                break;
        case BPF_ALU | BPF_OR | BPF_X:
        case BPF_ALU64 | BPF_OR | BPF_X:
                emit(A64_ORR(is64, dst, dst, src), ctx);
                break;
        case BPF_ALU | BPF_XOR | BPF_X:
        case BPF_ALU64 | BPF_XOR | BPF_X:
                emit(A64_EOR(is64, dst, dst, src), ctx);
                break;
        case BPF_ALU | BPF_MUL | BPF_X:
        case BPF_ALU64 | BPF_MUL | BPF_X:
                emit(A64_MUL(is64, dst, dst, src), ctx);
                break;
        case BPF_ALU | BPF_DIV | BPF_X:
        case BPF_ALU64 | BPF_DIV | BPF_X:
        case BPF_ALU | BPF_MOD | BPF_X:
        case BPF_ALU64 | BPF_MOD | BPF_X:
        {
                const u8 r0 = bpf2a64[BPF_REG_0];

                /* if (src == 0) return 0 */
                jmp_offset = 3; /* skip ahead to else path */
                check_imm19(jmp_offset);
                emit(A64_CBNZ(is64, src, jmp_offset), ctx);
                emit(A64_MOVZ(1, r0, 0, 0), ctx);
                jmp_offset = epilogue_offset(ctx);
                check_imm26(jmp_offset);
                emit(A64_B(jmp_offset), ctx);
                /* else */
                switch (BPF_OP(code)) {
                case BPF_DIV:
                        emit(A64_UDIV(is64, dst, dst, src), ctx);
                        break;
                case BPF_MOD:
                        ctx->tmp_used = 1;
                        emit(A64_UDIV(is64, tmp, dst, src), ctx);
                        emit(A64_MUL(is64, tmp, tmp, src), ctx);
                        emit(A64_SUB(is64, dst, dst, tmp), ctx);
                        break;
                }
                break;
        }
        case BPF_ALU | BPF_LSH | BPF_X:
        case BPF_ALU64 | BPF_LSH | BPF_X:
                emit(A64_LSLV(is64, dst, dst, src), ctx);
                break;
        case BPF_ALU | BPF_RSH | BPF_X:
        case BPF_ALU64 | BPF_RSH | BPF_X:
                emit(A64_LSRV(is64, dst, dst, src), ctx);
                break;
        case BPF_ALU | BPF_ARSH | BPF_X:
        case BPF_ALU64 | BPF_ARSH | BPF_X:
                emit(A64_ASRV(is64, dst, dst, src), ctx);
                break;
        /* dst = -dst */
        case BPF_ALU | BPF_NEG:
        case BPF_ALU64 | BPF_NEG:
                emit(A64_NEG(is64, dst, dst), ctx);
                break;
        /* dst = BSWAP##imm(dst) */
        case BPF_ALU | BPF_END | BPF_FROM_LE:
        case BPF_ALU | BPF_END | BPF_FROM_BE:
#ifdef CONFIG_CPU_BIG_ENDIAN
                if (BPF_SRC(code) == BPF_FROM_BE)
                        goto emit_bswap_uxt;
#else /* !CONFIG_CPU_BIG_ENDIAN */
                if (BPF_SRC(code) == BPF_FROM_LE)
                        goto emit_bswap_uxt;
#endif
                switch (imm) {
                case 16:
                        emit(A64_REV16(is64, dst, dst), ctx);
                        /* zero-extend 16 bits into 64 bits */
                        emit(A64_UXTH(is64, dst, dst), ctx);
                        break;
                case 32:
                        emit(A64_REV32(is64, dst, dst), ctx);
                        /* upper 32 bits already cleared */
                        break;
                case 64:
                        emit(A64_REV64(dst, dst), ctx);
                        break;
                }
                break;
emit_bswap_uxt:
                switch (imm) {
                case 16:
                        /* zero-extend 16 bits into 64 bits */
                        emit(A64_UXTH(is64, dst, dst), ctx);
                        break;
                case 32:
                        /* zero-extend 32 bits into 64 bits */
                        emit(A64_UXTW(is64, dst, dst), ctx);
                        break;
                case 64:
                        /* nop */
                        break;
                }
                break;
        /* dst = imm */
        case BPF_ALU | BPF_MOV | BPF_K:
        case BPF_ALU64 | BPF_MOV | BPF_K:
                emit_a64_mov_i(is64, dst, imm, ctx);
                break;
        /* dst = dst OP imm */
        case BPF_ALU | BPF_ADD | BPF_K:
        case BPF_ALU64 | BPF_ADD | BPF_K:
                ctx->tmp_used = 1;
                emit_a64_mov_i(is64, tmp, imm, ctx);
                emit(A64_ADD(is64, dst, dst, tmp), ctx);
                break;
        case BPF_ALU | BPF_SUB | BPF_K:
        case BPF_ALU64 | BPF_SUB | BPF_K:
                ctx->tmp_used = 1;
                emit_a64_mov_i(is64, tmp, imm, ctx);
                emit(A64_SUB(is64, dst, dst, tmp), ctx);
                break;
        case BPF_ALU | BPF_AND | BPF_K:
        case BPF_ALU64 | BPF_AND | BPF_K:
                ctx->tmp_used = 1;
                emit_a64_mov_i(is64, tmp, imm, ctx);
                emit(A64_AND(is64, dst, dst, tmp), ctx);
                break;
        case BPF_ALU | BPF_OR | BPF_K:
        case BPF_ALU64 | BPF_OR | BPF_K:
                ctx->tmp_used = 1;
                emit_a64_mov_i(is64, tmp, imm, ctx);
                emit(A64_ORR(is64, dst, dst, tmp), ctx);
                break;
        case BPF_ALU | BPF_XOR | BPF_K:
        case BPF_ALU64 | BPF_XOR | BPF_K:
                ctx->tmp_used = 1;
                emit_a64_mov_i(is64, tmp, imm, ctx);
                emit(A64_EOR(is64, dst, dst, tmp), ctx);
                break;
        case BPF_ALU | BPF_MUL | BPF_K:
        case BPF_ALU64 | BPF_MUL | BPF_K:
                ctx->tmp_used = 1;
                emit_a64_mov_i(is64, tmp, imm, ctx);
                emit(A64_MUL(is64, dst, dst, tmp), ctx);
                break;
        case BPF_ALU | BPF_DIV | BPF_K:
        case BPF_ALU64 | BPF_DIV | BPF_K:
                ctx->tmp_used = 1;
                emit_a64_mov_i(is64, tmp, imm, ctx);
                emit(A64_UDIV(is64, dst, dst, tmp), ctx);
                break;
        case BPF_ALU | BPF_MOD | BPF_K:
        case BPF_ALU64 | BPF_MOD | BPF_K:
                ctx->tmp_used = 1;
                emit_a64_mov_i(is64, tmp2, imm, ctx);
                emit(A64_UDIV(is64, tmp, dst, tmp2), ctx);
                emit(A64_MUL(is64, tmp, tmp, tmp2), ctx);
                emit(A64_SUB(is64, dst, dst, tmp), ctx);
                break;
        case BPF_ALU | BPF_LSH | BPF_K:
        case BPF_ALU64 | BPF_LSH | BPF_K:
                emit(A64_LSL(is64, dst, dst, imm), ctx);
                break;
        case BPF_ALU | BPF_RSH | BPF_K:
        case BPF_ALU64 | BPF_RSH | BPF_K:
                emit(A64_LSR(is64, dst, dst, imm), ctx);
                break;
        case BPF_ALU | BPF_ARSH | BPF_K:
        case BPF_ALU64 | BPF_ARSH | BPF_K:
                emit(A64_ASR(is64, dst, dst, imm), ctx);
                break;

        /* JUMP off */
        case BPF_JMP | BPF_JA:
                jmp_offset = bpf2a64_offset(i + off, i, ctx);
                check_imm26(jmp_offset);
                emit(A64_B(jmp_offset), ctx);
                break;
        /* IF (dst COND src) JUMP off */
        case BPF_JMP | BPF_JEQ | BPF_X:
        case BPF_JMP | BPF_JGT | BPF_X:
        case BPF_JMP | BPF_JGE | BPF_X:
        case BPF_JMP | BPF_JNE | BPF_X:
        case BPF_JMP | BPF_JSGT | BPF_X:
        case BPF_JMP | BPF_JSGE | BPF_X:
                emit(A64_CMP(1, dst, src), ctx);
emit_cond_jmp:
                jmp_offset = bpf2a64_offset(i + off, i, ctx);
                check_imm19(jmp_offset);
                switch (BPF_OP(code)) {
                case BPF_JEQ:
                        jmp_cond = A64_COND_EQ;
                        break;
                case BPF_JGT:
                        jmp_cond = A64_COND_HI;
                        break;
                case BPF_JGE:
                        jmp_cond = A64_COND_CS;
                        break;
                case BPF_JSET:
                case BPF_JNE:
                        jmp_cond = A64_COND_NE;
                        break;
                case BPF_JSGT:
                        jmp_cond = A64_COND_GT;
                        break;
                case BPF_JSGE:
                        jmp_cond = A64_COND_GE;
                        break;
                default:
                        return -EFAULT;
                }
                emit(A64_B_(jmp_cond, jmp_offset), ctx);
                break;
        case BPF_JMP | BPF_JSET | BPF_X:
                emit(A64_TST(1, dst, src), ctx);
                goto emit_cond_jmp;
        /* IF (dst COND imm) JUMP off */
        case BPF_JMP | BPF_JEQ | BPF_K:
        case BPF_JMP | BPF_JGT | BPF_K:
        case BPF_JMP | BPF_JGE | BPF_K:
        case BPF_JMP | BPF_JNE | BPF_K:
        case BPF_JMP | BPF_JSGT | BPF_K:
        case BPF_JMP | BPF_JSGE | BPF_K:
                ctx->tmp_used = 1;
                emit_a64_mov_i(1, tmp, imm, ctx);
                emit(A64_CMP(1, dst, tmp), ctx);
                goto emit_cond_jmp;
        case BPF_JMP | BPF_JSET | BPF_K:
                ctx->tmp_used = 1;
                emit_a64_mov_i(1, tmp, imm, ctx);
                emit(A64_TST(1, dst, tmp), ctx);
                goto emit_cond_jmp;
        /* function call */
        case BPF_JMP | BPF_CALL:
        {
                const u8 r0 = bpf2a64[BPF_REG_0];
                const u64 func = (u64)__bpf_call_base + imm;

                ctx->tmp_used = 1;
                emit_a64_mov_i64(tmp, func, ctx);
                emit(A64_PUSH(A64_FP, A64_LR, A64_SP), ctx);
                emit(A64_MOV(1, A64_FP, A64_SP), ctx);
                emit(A64_BLR(tmp), ctx);
                emit(A64_MOV(1, r0, A64_R(0)), ctx);
                emit(A64_POP(A64_FP, A64_LR, A64_SP), ctx);
                break;
        }
        /* function return */
        case BPF_JMP | BPF_EXIT:
                /* Optimization: when last instruction is EXIT,
                   simply fallthrough to epilogue. */
                if (i == ctx->prog->len - 1)
                        break;
                jmp_offset = epilogue_offset(ctx);
                check_imm26(jmp_offset);
                emit(A64_B(jmp_offset), ctx);
                break;

        /* dst = imm64 */
        case BPF_LD | BPF_IMM | BPF_DW:
        {
                const struct bpf_insn insn1 = insn[1];
                u64 imm64;

                if (insn1.code != 0 || insn1.src_reg != 0 ||
                    insn1.dst_reg != 0 || insn1.off != 0) {
                        /* Note: verifier in BPF core must catch invalid
                         * instructions.
                         */
                        pr_err_once("Invalid BPF_LD_IMM64 instruction\n");
                        return -EINVAL;
                }

                imm64 = (u64)insn1.imm << 32 | (u32)imm;
                emit_a64_mov_i64(dst, imm64, ctx);

                return 1;
        }

        /* LDX: dst = *(size *)(src + off) */
        case BPF_LDX | BPF_MEM | BPF_W:
        case BPF_LDX | BPF_MEM | BPF_H:
        case BPF_LDX | BPF_MEM | BPF_B:
        case BPF_LDX | BPF_MEM | BPF_DW:
                ctx->tmp_used = 1;
                emit_a64_mov_i(1, tmp, off, ctx);
                switch (BPF_SIZE(code)) {
                case BPF_W:
                        emit(A64_LDR32(dst, src, tmp), ctx);
                        break;
                case BPF_H:
                        emit(A64_LDRH(dst, src, tmp), ctx);
                        break;
                case BPF_B:
                        emit(A64_LDRB(dst, src, tmp), ctx);
                        break;
                case BPF_DW:
                        emit(A64_LDR64(dst, src, tmp), ctx);
                        break;
                }
                break;

        /* ST: *(size *)(dst + off) = imm */
        case BPF_ST | BPF_MEM | BPF_W:
        case BPF_ST | BPF_MEM | BPF_H:
        case BPF_ST | BPF_MEM | BPF_B:
        case BPF_ST | BPF_MEM | BPF_DW:
                /* Load imm to a register then store it */
                ctx->tmp_used = 1;
                emit_a64_mov_i(1, tmp2, off, ctx);
                emit_a64_mov_i(1, tmp, imm, ctx);
                switch (BPF_SIZE(code)) {
                case BPF_W:
                        emit(A64_STR32(tmp, dst, tmp2), ctx);
                        break;
                case BPF_H:
                        emit(A64_STRH(tmp, dst, tmp2), ctx);
                        break;
                case BPF_B:
                        emit(A64_STRB(tmp, dst, tmp2), ctx);
                        break;
                case BPF_DW:
                        emit(A64_STR64(tmp, dst, tmp2), ctx);
                        break;
                }
                break;

        /* STX: *(size *)(dst + off) = src */
        case BPF_STX | BPF_MEM | BPF_W:
        case BPF_STX | BPF_MEM | BPF_H:
        case BPF_STX | BPF_MEM | BPF_B:
        case BPF_STX | BPF_MEM | BPF_DW:
                ctx->tmp_used = 1;
                emit_a64_mov_i(1, tmp, off, ctx);
                switch (BPF_SIZE(code)) {
                case BPF_W:
                        emit(A64_STR32(src, dst, tmp), ctx);
                        break;
                case BPF_H:
                        emit(A64_STRH(src, dst, tmp), ctx);
                        break;
                case BPF_B:
                        emit(A64_STRB(src, dst, tmp), ctx);
                        break;
                case BPF_DW:
                        emit(A64_STR64(src, dst, tmp), ctx);
                        break;
                }
                break;
        /* STX XADD: lock *(u32 *)(dst + off) += src */
        case BPF_STX | BPF_XADD | BPF_W:
        /* STX XADD: lock *(u64 *)(dst + off) += src */
        case BPF_STX | BPF_XADD | BPF_DW:
                goto notyet;

        /* R0 = ntohx(*(size *)(((struct sk_buff *)R6)->data + imm)) */
        case BPF_LD | BPF_ABS | BPF_W:
        case BPF_LD | BPF_ABS | BPF_H:
        case BPF_LD | BPF_ABS | BPF_B:
        /* R0 = ntohx(*(size *)(((struct sk_buff *)R6)->data + src + imm)) */
        case BPF_LD | BPF_IND | BPF_W:
        case BPF_LD | BPF_IND | BPF_H:
        case BPF_LD | BPF_IND | BPF_B:
        {
                const u8 r0 = bpf2a64[BPF_REG_0]; /* r0 = return value */
                const u8 r6 = bpf2a64[BPF_REG_6]; /* r6 = pointer to sk_buff */
                const u8 fp = bpf2a64[BPF_REG_FP];
                const u8 r1 = bpf2a64[BPF_REG_1]; /* r1: struct sk_buff *skb */
                const u8 r2 = bpf2a64[BPF_REG_2]; /* r2: int k */
                const u8 r3 = bpf2a64[BPF_REG_3]; /* r3: unsigned int size */
                const u8 r4 = bpf2a64[BPF_REG_4]; /* r4: void *buffer */
                const u8 r5 = bpf2a64[BPF_REG_5]; /* r5: void *(*func)(...) */
                int size;

                emit(A64_MOV(1, r1, r6), ctx);
                emit_a64_mov_i(0, r2, imm, ctx);
                if (BPF_MODE(code) == BPF_IND)
                        emit(A64_ADD(0, r2, r2, src), ctx);
                switch (BPF_SIZE(code)) {
                case BPF_W:
                        size = 4;
                        break;
                case BPF_H:
                        size = 2;
                        break;
                case BPF_B:
                        size = 1;
                        break;
                default:
                        return -EINVAL;
                }
                emit_a64_mov_i64(r3, size, ctx);
                emit(A64_SUB_I(1, r4, fp, STACK_SIZE), ctx);
                emit_a64_mov_i64(r5, (unsigned long)bpf_load_pointer, ctx);
                emit(A64_PUSH(A64_FP, A64_LR, A64_SP), ctx);
                emit(A64_MOV(1, A64_FP, A64_SP), ctx);
                emit(A64_BLR(r5), ctx);
                emit(A64_MOV(1, r0, A64_R(0)), ctx);
                emit(A64_POP(A64_FP, A64_LR, A64_SP), ctx);

                jmp_offset = epilogue_offset(ctx);
                check_imm19(jmp_offset);
                emit(A64_CBZ(1, r0, jmp_offset), ctx);
                emit(A64_MOV(1, r5, r0), ctx);
                switch (BPF_SIZE(code)) {
                case BPF_W:
                        emit(A64_LDR32(r0, r5, A64_ZR), ctx);
#ifndef CONFIG_CPU_BIG_ENDIAN
                        emit(A64_REV32(0, r0, r0), ctx);
#endif
                        break;
                case BPF_H:
                        emit(A64_LDRH(r0, r5, A64_ZR), ctx);
#ifndef CONFIG_CPU_BIG_ENDIAN
                        emit(A64_REV16(0, r0, r0), ctx);
#endif
                        break;
                case BPF_B:
                        emit(A64_LDRB(r0, r5, A64_ZR), ctx);
                        break;
                }
                break;
        }
notyet:
                pr_info_once("*** NOT YET: opcode %02x ***\n", code);
                return -EFAULT;

        default:
                pr_err_once("unknown opcode %02x\n", code);
                return -EINVAL;
        }

        return 0;
}

static int build_body(struct jit_ctx *ctx)
{
        const struct bpf_prog *prog = ctx->prog;
        int i;

        for (i = 0; i < prog->len; i++) {
                const struct bpf_insn *insn = &prog->insnsi[i];
                int ret;

                ret = build_insn(insn, ctx);

                if (ctx->image == NULL)
                        ctx->offset[i] = ctx->idx;

                if (ret > 0) {
                        i++;
                        continue;
                }
                if (ret)
                        return ret;
        }

        return 0;
}

static int validate_code(struct jit_ctx *ctx)
{
        int i;

        for (i = 0; i < ctx->idx; i++) {
                u32 a64_insn = le32_to_cpu(ctx->image[i]);

                if (a64_insn == AARCH64_BREAK_FAULT)
                        return -1;
        }

        return 0;
}

static inline void bpf_flush_icache(void *start, void *end)
{
        flush_icache_range((unsigned long)start, (unsigned long)end);
}

void bpf_jit_compile(struct bpf_prog *prog)
{
        /* Nothing to do here. We support Internal BPF. */
}

void bpf_int_jit_compile(struct bpf_prog *prog)
{
        struct bpf_binary_header *header;
        struct jit_ctx ctx;
        int image_size;
        u8 *image_ptr;

        if (!bpf_jit_enable)
                return;

        if (!prog || !prog->len)
                return;

        memset(&ctx, 0, sizeof(ctx));
        ctx.prog = prog;

        ctx.offset = kcalloc(prog->len, sizeof(int), GFP_KERNEL);
        if (ctx.offset == NULL)
                return;

        /* 1. Initial fake pass to compute ctx->idx. */

        /* Fake pass to fill in ctx->offset and ctx->tmp_used. */
        if (build_body(&ctx))
                goto out;

        build_prologue(&ctx);

        ctx.epilogue_offset = ctx.idx;
        build_epilogue(&ctx);

        /* Now we know the actual image size. */
        image_size = sizeof(u32) * ctx.idx;
        header = bpf_jit_binary_alloc(image_size, &image_ptr,
                                      sizeof(u32), jit_fill_hole);
        if (header == NULL)
                goto out;

        /* 2. Now, the actual pass. */

        ctx.image = (u32 *)image_ptr;
        ctx.idx = 0;

        build_prologue(&ctx);

        if (build_body(&ctx)) {
                bpf_jit_binary_free(header);
                goto out;
        }

        build_epilogue(&ctx);

        /* 3. Extra pass to validate JITed code. */
        if (validate_code(&ctx)) {
                bpf_jit_binary_free(header);
                goto out;
        }

        /* And we're done. */
        if (bpf_jit_enable > 1)
                bpf_jit_dump(prog->len, image_size, 2, ctx.image);

        bpf_flush_icache(header, ctx.image + ctx.idx);

        set_memory_ro((unsigned long)header, header->pages);
        prog->bpf_func = (void *)ctx.image;
        prog->jited = 1;
out:
        kfree(ctx.offset);
}

void bpf_jit_free(struct bpf_prog *prog)
{
        unsigned long addr = (unsigned long)prog->bpf_func & PAGE_MASK;
        struct bpf_binary_header *header = (void *)addr;

        if (!prog->jited)
                goto free_filter;

        set_memory_rw(addr, header->pages);
        bpf_jit_binary_free(header);

free_filter:
        bpf_prog_unlock_free(prog);
}