/*
 * BPF Jit compiler for s390.
 *
 * Minimum build requirements:
 *
 *  - HAVE_MARCH_Z196_FEATURES: laal, laalg
 *  - HAVE_MARCH_Z10_FEATURES: msfi, cgrj, clgrj
 *  - HAVE_MARCH_Z9_109_FEATURES: alfi, llilf, clfi, oilf, nilf
 *  - PACK_STACK
 *  - 64BIT
 *
 * Copyright IBM Corp. 2012,2015
 *
 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
 *            Michael Holzheu <holzheu@linux.vnet.ibm.com>
 */

#define KMSG_COMPONENT "bpf_jit"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/netdevice.h>
#include <linux/filter.h>
#include <linux/init.h>
#include <linux/bpf.h>
#include <asm/cacheflush.h>
#include <asm/dis.h>
#include "bpf_jit.h"

int bpf_jit_enable __read_mostly;

struct bpf_jit {
        u32 seen;               /* Flags to remember seen eBPF instructions */
        u32 seen_reg[16];       /* Array to remember which registers are used */
        u32 *addrs;             /* Array with relative instruction addresses */
        u8 *prg_buf;            /* Start of program */
        int size;               /* Size of program and literal pool */
        int size_prg;           /* Size of program */
        int prg;                /* Current position in program */
        int lit_start;          /* Start of literal pool */
        int lit;                /* Current position in literal pool */
        int base_ip;            /* Base address for literal pool */
        int ret0_ip;            /* Address of return 0 */
        int exit_ip;            /* Address of exit */
        int tail_call_start;    /* Tail call start offset */
        int labels[1];          /* Labels for local jumps */
};

#define BPF_SIZE_MAX    0x7ffff /* Max size for program (20 bit signed displ) */

#define SEEN_SKB        1       /* skb access */
#define SEEN_MEM        2       /* use mem[] for temporary storage */
#define SEEN_RET0       4       /* ret0_ip points to a valid return 0 */
#define SEEN_LITERAL    8       /* code uses literals */
#define SEEN_FUNC       16      /* calls C functions */
#define SEEN_TAIL_CALL  32      /* code uses tail calls */
#define SEEN_SKB_CHANGE 64      /* code changes skb data */
#define SEEN_STACK      (SEEN_FUNC | SEEN_MEM | SEEN_SKB)

/*
 * s390 registers
 */
#define REG_W0          (__MAX_BPF_REG+0)       /* Work register 1 (even) */
#define REG_W1          (__MAX_BPF_REG+1)       /* Work register 2 (odd) */
#define REG_SKB_DATA    (__MAX_BPF_REG+2)       /* SKB data register */
#define REG_L           (__MAX_BPF_REG+3)       /* Literal pool register */
#define REG_15          (__MAX_BPF_REG+4)       /* Register 15 */
#define REG_0           REG_W0                  /* Register 0 */
#define REG_1           REG_W1                  /* Register 1 */
#define REG_2           BPF_REG_1               /* Register 2 */
#define REG_14          BPF_REG_0               /* Register 14 */

/*
 * Mapping of BPF registers to s390 registers
 */
static const int reg2hex[] = {
        /* Return code */
        [BPF_REG_0]     = 14,
        /* Function parameters */
        [BPF_REG_1]     = 2,
        [BPF_REG_2]     = 3,
        [BPF_REG_3]     = 4,
        [BPF_REG_4]     = 5,
        [BPF_REG_5]     = 6,
        /* Call saved registers */
        [BPF_REG_6]     = 7,
        [BPF_REG_7]     = 8,
        [BPF_REG_8]     = 9,
        [BPF_REG_9]     = 10,
        /* BPF stack pointer */
        [BPF_REG_FP]    = 13,
        /* SKB data pointer */
        [REG_SKB_DATA]  = 12,
        /* Work registers for s390x backend */
        [REG_W0]        = 0,
        [REG_W1]        = 1,
        [REG_L]         = 11,
        [REG_15]        = 15,
};

static inline u32 reg(u32 dst_reg, u32 src_reg)
{
        return reg2hex[dst_reg] << 4 | reg2hex[src_reg];
}

static inline u32 reg_high(u32 reg)
{
        return reg2hex[reg] << 4;
}

static inline void reg_set_seen(struct bpf_jit *jit, u32 b1)
{
        u32 r1 = reg2hex[b1];

        if (!jit->seen_reg[r1] && r1 >= 6 && r1 <= 15)
                jit->seen_reg[r1] = 1;
}

#define REG_SET_SEEN(b1)                                        \
({                                                              \
        reg_set_seen(jit, b1);                                  \
})

#define REG_SEEN(b1) jit->seen_reg[reg2hex[(b1)]]

/*
 * EMIT macros for code generation
 */

#define _EMIT2(op)                                              \
({                                                              \
        if (jit->prg_buf)                                       \
                *(u16 *) (jit->prg_buf + jit->prg) = op;        \
        jit->prg += 2;                                          \
})

#define EMIT2(op, b1, b2)                                       \
({                                                              \
        _EMIT2(op | reg(b1, b2));                               \
        REG_SET_SEEN(b1);                                       \
        REG_SET_SEEN(b2);                                       \
})

#define _EMIT4(op)                                              \
({                                                              \
        if (jit->prg_buf)                                       \
                *(u32 *) (jit->prg_buf + jit->prg) = op;        \
        jit->prg += 4;                                          \
})

#define EMIT4(op, b1, b2)                                       \
({                                                              \
        _EMIT4(op | reg(b1, b2));                               \
        REG_SET_SEEN(b1);                                       \
        REG_SET_SEEN(b2);                                       \
})

#define EMIT4_RRF(op, b1, b2, b3)                               \
({                                                              \
        _EMIT4(op | reg_high(b3) << 8 | reg(b1, b2));           \
        REG_SET_SEEN(b1);                                       \
        REG_SET_SEEN(b2);                                       \
        REG_SET_SEEN(b3);                                       \
})

#define _EMIT4_DISP(op, disp)                                   \
({                                                              \
        unsigned int __disp = (disp) & 0xfff;                   \
        _EMIT4(op | __disp);                                    \
})

#define EMIT4_DISP(op, b1, b2, disp)                            \
({                                                              \
        _EMIT4_DISP(op | reg_high(b1) << 16 |                   \
                    reg_high(b2) << 8, disp);                   \
        REG_SET_SEEN(b1);                                       \
        REG_SET_SEEN(b2);                                       \
})

#define EMIT4_IMM(op, b1, imm)                                  \
({                                                              \
        unsigned int __imm = (imm) & 0xffff;                    \
        _EMIT4(op | reg_high(b1) << 16 | __imm);                \
        REG_SET_SEEN(b1);                                       \
})

#define EMIT4_PCREL(op, pcrel)                                  \
({                                                              \
        long __pcrel = ((pcrel) >> 1) & 0xffff;                 \
        _EMIT4(op | __pcrel);                                   \
})

#define _EMIT6(op1, op2)                                        \
({                                                              \
        if (jit->prg_buf) {                                     \
                *(u32 *) (jit->prg_buf + jit->prg) = op1;       \
                *(u16 *) (jit->prg_buf + jit->prg + 4) = op2;   \
        }                                                       \
        jit->prg += 6;                                          \
})

#define _EMIT6_DISP(op1, op2, disp)                             \
({                                                              \
        unsigned int __disp = (disp) & 0xfff;                   \
        _EMIT6(op1 | __disp, op2);                              \
})

#define _EMIT6_DISP_LH(op1, op2, disp)                          \
({                                                              \
        u32 _disp = (u32) disp;                                 \
        unsigned int __disp_h = _disp & 0xff000;                \
        unsigned int __disp_l = _disp & 0x00fff;                \
        _EMIT6(op1 | __disp_l, op2 | __disp_h >> 4);            \
})

#define EMIT6_DISP_LH(op1, op2, b1, b2, b3, disp)               \
({                                                              \
        _EMIT6_DISP_LH(op1 | reg(b1, b2) << 16 |                \
                       reg_high(b3) << 8, op2, disp);           \
        REG_SET_SEEN(b1);                                       \
        REG_SET_SEEN(b2);                                       \
        REG_SET_SEEN(b3);                                       \
})

#define EMIT6_PCREL_LABEL(op1, op2, b1, b2, label, mask)        \
({                                                              \
        int rel = (jit->labels[label] - jit->prg) >> 1;         \
        _EMIT6(op1 | reg(b1, b2) << 16 | (rel & 0xffff),        \
               op2 | mask << 12);                               \
        REG_SET_SEEN(b1);                                       \
        REG_SET_SEEN(b2);                                       \
})

#define EMIT6_PCREL_IMM_LABEL(op1, op2, b1, imm, label, mask)   \
({                                                              \
        int rel = (jit->labels[label] - jit->prg) >> 1;         \
        _EMIT6(op1 | (reg_high(b1) | mask) << 16 |              \
                (rel & 0xffff), op2 | (imm & 0xff) << 8);       \
        REG_SET_SEEN(b1);                                       \
        BUILD_BUG_ON(((unsigned long) imm) > 0xff);             \
})

#define EMIT6_PCREL(op1, op2, b1, b2, i, off, mask)             \
({                                                              \
        /* Branch instruction needs 6 bytes */                  \
        int rel = (addrs[i + off + 1] - (addrs[i + 1] - 6)) / 2;\
        _EMIT6(op1 | reg(b1, b2) << 16 | (rel & 0xffff), op2 | mask);   \
        REG_SET_SEEN(b1);                                       \
        REG_SET_SEEN(b2);                                       \
})

#define _EMIT6_IMM(op, imm)                                     \
({                                                              \
        unsigned int __imm = (imm);                             \
        _EMIT6(op | (__imm >> 16), __imm & 0xffff);             \
})

#define EMIT6_IMM(op, b1, imm)                                  \
({                                                              \
        _EMIT6_IMM(op | reg_high(b1) << 16, imm);               \
        REG_SET_SEEN(b1);                                       \
})

#define EMIT_CONST_U32(val)                                     \
({                                                              \
        unsigned int ret;                                       \
        ret = jit->lit - jit->base_ip;                          \
        jit->seen |= SEEN_LITERAL;                              \
        if (jit->prg_buf)                                       \
                *(u32 *) (jit->prg_buf + jit->lit) = (u32) val; \
        jit->lit += 4;                                          \
        ret;                                                    \
})

#define EMIT_CONST_U64(val)                                     \
({                                                              \
        unsigned int ret;                                       \
        ret = jit->lit - jit->base_ip;                          \
        jit->seen |= SEEN_LITERAL;                              \
        if (jit->prg_buf)                                       \
                *(u64 *) (jit->prg_buf + jit->lit) = (u64) val; \
        jit->lit += 8;                                          \
        ret;                                                    \
})

#define EMIT_ZERO(b1)                                           \
({                                                              \
        /* llgfr %dst,%dst (zero extend to 64 bit) */           \
        EMIT4(0xb9160000, b1, b1);                              \
        REG_SET_SEEN(b1);                                       \
})

/*
 * Fill whole space with illegal instructions
 */
static void jit_fill_hole(void *area, unsigned int size)
{
        memset(area, 0, size);
}

/*
 * Save registers from "rs" (register start) to "re" (register end) on stack
 */
static void save_regs(struct bpf_jit *jit, u32 rs, u32 re)
{
        u32 off = STK_OFF_R6 + (rs - 6) * 8;

        if (rs == re)
                /* stg %rs,off(%r15) */
                _EMIT6(0xe300f000 | rs << 20 | off, 0x0024);
        else
                /* stmg %rs,%re,off(%r15) */
                _EMIT6_DISP(0xeb00f000 | rs << 20 | re << 16, 0x0024, off);
}

/*
 * Restore registers from "rs" (register start) to "re" (register end) on stack
 */
static void restore_regs(struct bpf_jit *jit, u32 rs, u32 re)
{
        u32 off = STK_OFF_R6 + (rs - 6) * 8;

        if (jit->seen & SEEN_STACK)
                off += STK_OFF;

        if (rs == re)
                /* lg %rs,off(%r15) */
                _EMIT6(0xe300f000 | rs << 20 | off, 0x0004);
        else
                /* lmg %rs,%re,off(%r15) */
                _EMIT6_DISP(0xeb00f000 | rs << 20 | re << 16, 0x0004, off);
}

/*
 * Return first seen register (from start)
 */
static int get_start(struct bpf_jit *jit, int start)
{
        int i;

        for (i = start; i <= 15; i++) {
                if (jit->seen_reg[i])
                        return i;
        }
        return 0;
}

/*
 * Return last seen register (from start) (gap >= 2)
 */
static int get_end(struct bpf_jit *jit, int start)
{
        int i;

        for (i = start; i < 15; i++) {
                if (!jit->seen_reg[i] && !jit->seen_reg[i + 1])
                        return i - 1;
        }
        return jit->seen_reg[15] ? 15 : 14;
}

#define REGS_SAVE       1
#define REGS_RESTORE    0
/*
 * Save and restore clobbered registers (6-15) on stack.
 * We save/restore registers in chunks with gap >= 2 registers.
 */
static void save_restore_regs(struct bpf_jit *jit, int op)
{

        int re = 6, rs;

        do {
                rs = get_start(jit, re);
                if (!rs)
                        break;
                re = get_end(jit, rs + 1);
                if (op == REGS_SAVE)
                        save_regs(jit, rs, re);
                else
                        restore_regs(jit, rs, re);
                re++;
        } while (re <= 15);
}

/*
 * For SKB access %b1 contains the SKB pointer. For "bpf_jit.S"
 * we store the SKB header length on the stack and the SKB data
 * pointer in REG_SKB_DATA.
 */
static void emit_load_skb_data_hlen(struct bpf_jit *jit)
{
        /* Header length: llgf %w1,<len>(%b1) */
        EMIT6_DISP_LH(0xe3000000, 0x0016, REG_W1, REG_0, BPF_REG_1,
                      offsetof(struct sk_buff, len));
        /* s %w1,<data_len>(%b1) */
        EMIT4_DISP(0x5b000000, REG_W1, BPF_REG_1,
                   offsetof(struct sk_buff, data_len));
        /* stg %w1,ST_OFF_HLEN(%r0,%r15) */
        EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0, REG_15, STK_OFF_HLEN);
        /* lg %skb_data,data_off(%b1) */
        EMIT6_DISP_LH(0xe3000000, 0x0004, REG_SKB_DATA, REG_0,
                      BPF_REG_1, offsetof(struct sk_buff, data));
}

/*
 * Emit function prologue
 *
 * Save registers and create stack frame if necessary.
 * See stack frame layout desription in "bpf_jit.h"!
 */
static void bpf_jit_prologue(struct bpf_jit *jit)
{
        if (jit->seen & SEEN_TAIL_CALL) {
                /* xc STK_OFF_TCCNT(4,%r15),STK_OFF_TCCNT(%r15) */
                _EMIT6(0xd703f000 | STK_OFF_TCCNT, 0xf000 | STK_OFF_TCCNT);
        } else {
                /* j tail_call_start: NOP if no tail calls are used */
                EMIT4_PCREL(0xa7f40000, 6);
                _EMIT2(0);
        }
        /* Tail calls have to skip above initialization */
        jit->tail_call_start = jit->prg;
        /* Save registers */
        save_restore_regs(jit, REGS_SAVE);
        /* Setup literal pool */
        if (jit->seen & SEEN_LITERAL) {
                /* basr %r13,0 */
                EMIT2(0x0d00, REG_L, REG_0);
                jit->base_ip = jit->prg;
        }
        /* Setup stack and backchain */
        if (jit->seen & SEEN_STACK) {
                if (jit->seen & SEEN_FUNC)
                        /* lgr %w1,%r15 (backchain) */
                        EMIT4(0xb9040000, REG_W1, REG_15);
                /* la %bfp,STK_160_UNUSED(%r15) (BPF frame pointer) */
                EMIT4_DISP(0x41000000, BPF_REG_FP, REG_15, STK_160_UNUSED);
                /* aghi %r15,-STK_OFF */
                EMIT4_IMM(0xa70b0000, REG_15, -STK_OFF);
                if (jit->seen & SEEN_FUNC)
                        /* stg %w1,152(%r15) (backchain) */
                        EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0,
                                      REG_15, 152);
        }
        if (jit->seen & SEEN_SKB)
                emit_load_skb_data_hlen(jit);
        if (jit->seen & SEEN_SKB_CHANGE)
                /* stg %b1,ST_OFF_SKBP(%r0,%r15) */
                EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0, REG_15,
                              STK_OFF_SKBP);
}

/*
 * Function epilogue
 */
static void bpf_jit_epilogue(struct bpf_jit *jit)
{
        /* Return 0 */
        if (jit->seen & SEEN_RET0) {
                jit->ret0_ip = jit->prg;
                /* lghi %b0,0 */
                EMIT4_IMM(0xa7090000, BPF_REG_0, 0);
        }
        jit->exit_ip = jit->prg;
        /* Load exit code: lgr %r2,%b0 */
        EMIT4(0xb9040000, REG_2, BPF_REG_0);
        /* Restore registers */
        save_restore_regs(jit, REGS_RESTORE);
        /* br %r14 */
        _EMIT2(0x07fe);
}

/*
 * Compile one eBPF instruction into s390x code
 *
 * NOTE: Use noinline because for gcov (-fprofile-arcs) gcc allocates a lot of
 * stack space for the large switch statement.
 */
static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i)
{
        struct bpf_insn *insn = &fp->insnsi[i];
        int jmp_off, last, insn_count = 1;
        unsigned int func_addr, mask;
        u32 dst_reg = insn->dst_reg;
        u32 src_reg = insn->src_reg;
        u32 *addrs = jit->addrs;
        s32 imm = insn->imm;
        s16 off = insn->off;

        switch (insn->code) {
        /*
         * BPF_MOV
         */
        case BPF_ALU | BPF_MOV | BPF_X: /* dst = (u32) src */
                /* llgfr %dst,%src */
                EMIT4(0xb9160000, dst_reg, src_reg);
                break;
        case BPF_ALU64 | BPF_MOV | BPF_X: /* dst = src */
                /* lgr %dst,%src */
                EMIT4(0xb9040000, dst_reg, src_reg);
                break;
        case BPF_ALU | BPF_MOV | BPF_K: /* dst = (u32) imm */
                /* llilf %dst,imm */
                EMIT6_IMM(0xc00f0000, dst_reg, imm);
                break;
        case BPF_ALU64 | BPF_MOV | BPF_K: /* dst = imm */
                /* lgfi %dst,imm */
                EMIT6_IMM(0xc0010000, dst_reg, imm);
                break;
        /*
         * BPF_LD 64
         */
        case BPF_LD | BPF_IMM | BPF_DW: /* dst = (u64) imm */
        {
                /* 16 byte instruction that uses two 'struct bpf_insn' */
                u64 imm64;

                imm64 = (u64)(u32) insn[0].imm | ((u64)(u32) insn[1].imm) << 32;
                /* lg %dst,<d(imm)>(%l) */
                EMIT6_DISP_LH(0xe3000000, 0x0004, dst_reg, REG_0, REG_L,
                              EMIT_CONST_U64(imm64));
                insn_count = 2;
                break;
        }
        /*
         * BPF_ADD
         */
        case BPF_ALU | BPF_ADD | BPF_X: /* dst = (u32) dst + (u32) src */
                /* ar %dst,%src */
                EMIT2(0x1a00, dst_reg, src_reg);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_ADD | BPF_X: /* dst = dst + src */
                /* agr %dst,%src */
                EMIT4(0xb9080000, dst_reg, src_reg);
                break;
        case BPF_ALU | BPF_ADD | BPF_K: /* dst = (u32) dst + (u32) imm */
                if (!imm)
                        break;
                /* alfi %dst,imm */
                EMIT6_IMM(0xc20b0000, dst_reg, imm);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_ADD | BPF_K: /* dst = dst + imm */
                if (!imm)
                        break;
                /* agfi %dst,imm */
                EMIT6_IMM(0xc2080000, dst_reg, imm);
                break;
        /*
         * BPF_SUB
         */
        case BPF_ALU | BPF_SUB | BPF_X: /* dst = (u32) dst - (u32) src */
                /* sr %dst,%src */
                EMIT2(0x1b00, dst_reg, src_reg);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_SUB | BPF_X: /* dst = dst - src */
                /* sgr %dst,%src */
                EMIT4(0xb9090000, dst_reg, src_reg);
                break;
        case BPF_ALU | BPF_SUB | BPF_K: /* dst = (u32) dst - (u32) imm */
                if (!imm)
                        break;
                /* alfi %dst,-imm */
                EMIT6_IMM(0xc20b0000, dst_reg, -imm);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_SUB | BPF_K: /* dst = dst - imm */
                if (!imm)
                        break;
                /* agfi %dst,-imm */
                EMIT6_IMM(0xc2080000, dst_reg, -imm);
                break;
        /*
         * BPF_MUL
         */
        case BPF_ALU | BPF_MUL | BPF_X: /* dst = (u32) dst * (u32) src */
                /* msr %dst,%src */
                EMIT4(0xb2520000, dst_reg, src_reg);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_MUL | BPF_X: /* dst = dst * src */
                /* msgr %dst,%src */
                EMIT4(0xb90c0000, dst_reg, src_reg);
                break;
        case BPF_ALU | BPF_MUL | BPF_K: /* dst = (u32) dst * (u32) imm */
                if (imm == 1)
                        break;
                /* msfi %r5,imm */
                EMIT6_IMM(0xc2010000, dst_reg, imm);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_MUL | BPF_K: /* dst = dst * imm */
                if (imm == 1)
                        break;
                /* msgfi %dst,imm */
                EMIT6_IMM(0xc2000000, dst_reg, imm);
                break;
        /*
         * BPF_DIV / BPF_MOD
         */
        case BPF_ALU | BPF_DIV | BPF_X: /* dst = (u32) dst / (u32) src */
        case BPF_ALU | BPF_MOD | BPF_X: /* dst = (u32) dst % (u32) src */
        {
                int rc_reg = BPF_OP(insn->code) == BPF_DIV ? REG_W1 : REG_W0;

                jit->seen |= SEEN_RET0;
                /* ltr %src,%src (if src == 0 goto fail) */
                EMIT2(0x1200, src_reg, src_reg);
                /* jz <ret0> */
                EMIT4_PCREL(0xa7840000, jit->ret0_ip - jit->prg);
                /* lhi %w0,0 */
                EMIT4_IMM(0xa7080000, REG_W0, 0);
                /* lr %w1,%dst */
                EMIT2(0x1800, REG_W1, dst_reg);
                /* dlr %w0,%src */
                EMIT4(0xb9970000, REG_W0, src_reg);
                /* llgfr %dst,%rc */
                EMIT4(0xb9160000, dst_reg, rc_reg);
                break;
        }
        case BPF_ALU64 | BPF_DIV | BPF_X: /* dst = dst / src */
        case BPF_ALU64 | BPF_MOD | BPF_X: /* dst = dst % src */
        {
                int rc_reg = BPF_OP(insn->code) == BPF_DIV ? REG_W1 : REG_W0;

                jit->seen |= SEEN_RET0;
                /* ltgr %src,%src (if src == 0 goto fail) */
                EMIT4(0xb9020000, src_reg, src_reg);
                /* jz <ret0> */
                EMIT4_PCREL(0xa7840000, jit->ret0_ip - jit->prg);
                /* lghi %w0,0 */
                EMIT4_IMM(0xa7090000, REG_W0, 0);
                /* lgr %w1,%dst */
                EMIT4(0xb9040000, REG_W1, dst_reg);
                /* dlgr %w0,%dst */
                EMIT4(0xb9870000, REG_W0, src_reg);
                /* lgr %dst,%rc */
                EMIT4(0xb9040000, dst_reg, rc_reg);
                break;
        }
        case BPF_ALU | BPF_DIV | BPF_K: /* dst = (u32) dst / (u32) imm */
        case BPF_ALU | BPF_MOD | BPF_K: /* dst = (u32) dst % (u32) imm */
        {
                int rc_reg = BPF_OP(insn->code) == BPF_DIV ? REG_W1 : REG_W0;

                if (imm == 1) {
                        if (BPF_OP(insn->code) == BPF_MOD)
                                /* lhgi %dst,0 */
                                EMIT4_IMM(0xa7090000, dst_reg, 0);
                        break;
                }
                /* lhi %w0,0 */
                EMIT4_IMM(0xa7080000, REG_W0, 0);
                /* lr %w1,%dst */
                EMIT2(0x1800, REG_W1, dst_reg);
                /* dl %w0,<d(imm)>(%l) */
                EMIT6_DISP_LH(0xe3000000, 0x0097, REG_W0, REG_0, REG_L,
                              EMIT_CONST_U32(imm));
                /* llgfr %dst,%rc */
                EMIT4(0xb9160000, dst_reg, rc_reg);
                break;
        }
        case BPF_ALU64 | BPF_DIV | BPF_K: /* dst = dst / imm */
        case BPF_ALU64 | BPF_MOD | BPF_K: /* dst = dst % imm */
        {
                int rc_reg = BPF_OP(insn->code) == BPF_DIV ? REG_W1 : REG_W0;

                if (imm == 1) {
                        if (BPF_OP(insn->code) == BPF_MOD)
                                /* lhgi %dst,0 */
                                EMIT4_IMM(0xa7090000, dst_reg, 0);
                        break;
                }
                /* lghi %w0,0 */
                EMIT4_IMM(0xa7090000, REG_W0, 0);
                /* lgr %w1,%dst */
                EMIT4(0xb9040000, REG_W1, dst_reg);
                /* dlg %w0,<d(imm)>(%l) */
                EMIT6_DISP_LH(0xe3000000, 0x0087, REG_W0, REG_0, REG_L,
                              EMIT_CONST_U64(imm));
                /* lgr %dst,%rc */
                EMIT4(0xb9040000, dst_reg, rc_reg);
                break;
        }
        /*
         * BPF_AND
         */
        case BPF_ALU | BPF_AND | BPF_X: /* dst = (u32) dst & (u32) src */
                /* nr %dst,%src */
                EMIT2(0x1400, dst_reg, src_reg);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_AND | BPF_X: /* dst = dst & src */
                /* ngr %dst,%src */
                EMIT4(0xb9800000, dst_reg, src_reg);
                break;
        case BPF_ALU | BPF_AND | BPF_K: /* dst = (u32) dst & (u32) imm */
                /* nilf %dst,imm */
                EMIT6_IMM(0xc00b0000, dst_reg, imm);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_AND | BPF_K: /* dst = dst & imm */
                /* ng %dst,<d(imm)>(%l) */
                EMIT6_DISP_LH(0xe3000000, 0x0080, dst_reg, REG_0, REG_L,
                              EMIT_CONST_U64(imm));
                break;
        /*
         * BPF_OR
         */
        case BPF_ALU | BPF_OR | BPF_X: /* dst = (u32) dst | (u32) src */
                /* or %dst,%src */
                EMIT2(0x1600, dst_reg, src_reg);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_OR | BPF_X: /* dst = dst | src */
                /* ogr %dst,%src */
                EMIT4(0xb9810000, dst_reg, src_reg);
                break;
        case BPF_ALU | BPF_OR | BPF_K: /* dst = (u32) dst | (u32) imm */
                /* oilf %dst,imm */
                EMIT6_IMM(0xc00d0000, dst_reg, imm);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_OR | BPF_K: /* dst = dst | imm */
                /* og %dst,<d(imm)>(%l) */
                EMIT6_DISP_LH(0xe3000000, 0x0081, dst_reg, REG_0, REG_L,
                              EMIT_CONST_U64(imm));
                break;
        /*
         * BPF_XOR
         */
        case BPF_ALU | BPF_XOR | BPF_X: /* dst = (u32) dst ^ (u32) src */
                /* xr %dst,%src */
                EMIT2(0x1700, dst_reg, src_reg);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_XOR | BPF_X: /* dst = dst ^ src */
                /* xgr %dst,%src */
                EMIT4(0xb9820000, dst_reg, src_reg);
                break;
        case BPF_ALU | BPF_XOR | BPF_K: /* dst = (u32) dst ^ (u32) imm */
                if (!imm)
                        break;
                /* xilf %dst,imm */
                EMIT6_IMM(0xc0070000, dst_reg, imm);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_XOR | BPF_K: /* dst = dst ^ imm */
                /* xg %dst,<d(imm)>(%l) */
                EMIT6_DISP_LH(0xe3000000, 0x0082, dst_reg, REG_0, REG_L,
                              EMIT_CONST_U64(imm));
                break;
        /*
         * BPF_LSH
         */
        case BPF_ALU | BPF_LSH | BPF_X: /* dst = (u32) dst << (u32) src */
                /* sll %dst,0(%src) */
                EMIT4_DISP(0x89000000, dst_reg, src_reg, 0);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_LSH | BPF_X: /* dst = dst << src */
                /* sllg %dst,%dst,0(%src) */
                EMIT6_DISP_LH(0xeb000000, 0x000d, dst_reg, dst_reg, src_reg, 0);
                break;
        case BPF_ALU | BPF_LSH | BPF_K: /* dst = (u32) dst << (u32) imm */
                if (imm == 0)
                        break;
                /* sll %dst,imm(%r0) */
                EMIT4_DISP(0x89000000, dst_reg, REG_0, imm);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_LSH | BPF_K: /* dst = dst << imm */
                if (imm == 0)
                        break;
                /* sllg %dst,%dst,imm(%r0) */
                EMIT6_DISP_LH(0xeb000000, 0x000d, dst_reg, dst_reg, REG_0, imm);
                break;
        /*
         * BPF_RSH
         */
        case BPF_ALU | BPF_RSH | BPF_X: /* dst = (u32) dst >> (u32) src */
                /* srl %dst,0(%src) */
                EMIT4_DISP(0x88000000, dst_reg, src_reg, 0);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_RSH | BPF_X: /* dst = dst >> src */
                /* srlg %dst,%dst,0(%src) */
                EMIT6_DISP_LH(0xeb000000, 0x000c, dst_reg, dst_reg, src_reg, 0);
                break;
        case BPF_ALU | BPF_RSH | BPF_K: /* dst = (u32) dst >> (u32) imm */
                if (imm == 0)
                        break;
                /* srl %dst,imm(%r0) */
                EMIT4_DISP(0x88000000, dst_reg, REG_0, imm);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_RSH | BPF_K: /* dst = dst >> imm */
                if (imm == 0)
                        break;
                /* srlg %dst,%dst,imm(%r0) */
                EMIT6_DISP_LH(0xeb000000, 0x000c, dst_reg, dst_reg, REG_0, imm);
                break;
        /*
         * BPF_ARSH
         */
        case BPF_ALU64 | BPF_ARSH | BPF_X: /* ((s64) dst) >>= src */
                /* srag %dst,%dst,0(%src) */
                EMIT6_DISP_LH(0xeb000000, 0x000a, dst_reg, dst_reg, src_reg, 0);
                break;
        case BPF_ALU64 | BPF_ARSH | BPF_K: /* ((s64) dst) >>= imm */
                if (imm == 0)
                        break;
                /* srag %dst,%dst,imm(%r0) */
                EMIT6_DISP_LH(0xeb000000, 0x000a, dst_reg, dst_reg, REG_0, imm);
                break;
        /*
         * BPF_NEG
         */
        case BPF_ALU | BPF_NEG: /* dst = (u32) -dst */
                /* lcr %dst,%dst */
                EMIT2(0x1300, dst_reg, dst_reg);
                EMIT_ZERO(dst_reg);
                break;
        case BPF_ALU64 | BPF_NEG: /* dst = -dst */
                /* lcgr %dst,%dst */
                EMIT4(0xb9130000, dst_reg, dst_reg);
                break;
        /*
         * BPF_FROM_BE/LE
         */
        case BPF_ALU | BPF_END | BPF_FROM_BE:
                /* s390 is big endian, therefore only clear high order bytes */
                switch (imm) {
                case 16: /* dst = (u16) cpu_to_be16(dst) */
                        /* llghr %dst,%dst */
                        EMIT4(0xb9850000, dst_reg, dst_reg);
                        break;
                case 32: /* dst = (u32) cpu_to_be32(dst) */
                        /* llgfr %dst,%dst */
                        EMIT4(0xb9160000, dst_reg, dst_reg);
                        break;
                case 64: /* dst = (u64) cpu_to_be64(dst) */
                        break;
                }
                break;
        case BPF_ALU | BPF_END | BPF_FROM_LE:
                switch (imm) {
                case 16: /* dst = (u16) cpu_to_le16(dst) */
                        /* lrvr %dst,%dst */
                        EMIT4(0xb91f0000, dst_reg, dst_reg);
                        /* srl %dst,16(%r0) */
                        EMIT4_DISP(0x88000000, dst_reg, REG_0, 16);
                        /* llghr %dst,%dst */
                        EMIT4(0xb9850000, dst_reg, dst_reg);
                        break;
                case 32: /* dst = (u32) cpu_to_le32(dst) */
                        /* lrvr %dst,%dst */
                        EMIT4(0xb91f0000, dst_reg, dst_reg);
                        /* llgfr %dst,%dst */
                        EMIT4(0xb9160000, dst_reg, dst_reg);
                        break;
                case 64: /* dst = (u64) cpu_to_le64(dst) */
                        /* lrvgr %dst,%dst */
                        EMIT4(0xb90f0000, dst_reg, dst_reg);
                        break;
                }
                break;
        /*
         * BPF_ST(X)
         */
        case BPF_STX | BPF_MEM | BPF_B: /* *(u8 *)(dst + off) = src_reg */
                /* stcy %src,off(%dst) */
                EMIT6_DISP_LH(0xe3000000, 0x0072, src_reg, dst_reg, REG_0, off);
                jit->seen |= SEEN_MEM;
                break;
        case BPF_STX | BPF_MEM | BPF_H: /* (u16 *)(dst + off) = src */
                /* sthy %src,off(%dst) */
                EMIT6_DISP_LH(0xe3000000, 0x0070, src_reg, dst_reg, REG_0, off);
                jit->seen |= SEEN_MEM;
                break;
        case BPF_STX | BPF_MEM | BPF_W: /* *(u32 *)(dst + off) = src */
                /* sty %src,off(%dst) */
                EMIT6_DISP_LH(0xe3000000, 0x0050, src_reg, dst_reg, REG_0, off);
                jit->seen |= SEEN_MEM;
                break;
        case BPF_STX | BPF_MEM | BPF_DW: /* (u64 *)(dst + off) = src */
                /* stg %src,off(%dst) */
                EMIT6_DISP_LH(0xe3000000, 0x0024, src_reg, dst_reg, REG_0, off);
                jit->seen |= SEEN_MEM;
                break;
        case BPF_ST | BPF_MEM | BPF_B: /* *(u8 *)(dst + off) = imm */
                /* lhi %w0,imm */
                EMIT4_IMM(0xa7080000, REG_W0, (u8) imm);
                /* stcy %w0,off(dst) */
                EMIT6_DISP_LH(0xe3000000, 0x0072, REG_W0, dst_reg, REG_0, off);
                jit->seen |= SEEN_MEM;
                break;
        case BPF_ST | BPF_MEM | BPF_H: /* (u16 *)(dst + off) = imm */
                /* lhi %w0,imm */
                EMIT4_IMM(0xa7080000, REG_W0, (u16) imm);
                /* sthy %w0,off(dst) */
                EMIT6_DISP_LH(0xe3000000, 0x0070, REG_W0, dst_reg, REG_0, off);
                jit->seen |= SEEN_MEM;
                break;
        case BPF_ST | BPF_MEM | BPF_W: /* *(u32 *)(dst + off) = imm */
                /* llilf %w0,imm  */
                EMIT6_IMM(0xc00f0000, REG_W0, (u32) imm);
                /* sty %w0,off(%dst) */
                EMIT6_DISP_LH(0xe3000000, 0x0050, REG_W0, dst_reg, REG_0, off);
                jit->seen |= SEEN_MEM;
                break;
        case BPF_ST | BPF_MEM | BPF_DW: /* *(u64 *)(dst + off) = imm */
                /* lgfi %w0,imm */
                EMIT6_IMM(0xc0010000, REG_W0, imm);
                /* stg %w0,off(%dst) */
                EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W0, dst_reg, REG_0, off);
                jit->seen |= SEEN_MEM;
                break;
        /*
         * BPF_STX XADD (atomic_add)
         */
        case BPF_STX | BPF_XADD | BPF_W: /* *(u32 *)(dst + off) += src */
                /* laal %w0,%src,off(%dst) */
                EMIT6_DISP_LH(0xeb000000, 0x00fa, REG_W0, src_reg,
                              dst_reg, off);
                jit->seen |= SEEN_MEM;
                break;
        case BPF_STX | BPF_XADD | BPF_DW: /* *(u64 *)(dst + off) += src */
                /* laalg %w0,%src,off(%dst) */
                EMIT6_DISP_LH(0xeb000000, 0x00ea, REG_W0, src_reg,
                              dst_reg, off);
                jit->seen |= SEEN_MEM;
                break;
        /*
         * BPF_LDX
         */
        case BPF_LDX | BPF_MEM | BPF_B: /* dst = *(u8 *)(ul) (src + off) */
                /* llgc %dst,0(off,%src) */
                EMIT6_DISP_LH(0xe3000000, 0x0090, dst_reg, src_reg, REG_0, off);
                jit->seen |= SEEN_MEM;
                break;
        case BPF_LDX | BPF_MEM | BPF_H: /* dst = *(u16 *)(ul) (src + off) */
                /* llgh %dst,0(off,%src) */
                EMIT6_DISP_LH(0xe3000000, 0x0091, dst_reg, src_reg, REG_0, off);
                jit->seen |= SEEN_MEM;
                break;
        case BPF_LDX | BPF_MEM | BPF_W: /* dst = *(u32 *)(ul) (src + off) */
                /* llgf %dst,off(%src) */
                jit->seen |= SEEN_MEM;
                EMIT6_DISP_LH(0xe3000000, 0x0016, dst_reg, src_reg, REG_0, off);
                break;
        case BPF_LDX | BPF_MEM | BPF_DW: /* dst = *(u64 *)(ul) (src + off) */
                /* lg %dst,0(off,%src) */
                jit->seen |= SEEN_MEM;
                EMIT6_DISP_LH(0xe3000000, 0x0004, dst_reg, src_reg, REG_0, off);
                break;
        /*
         * BPF_JMP / CALL
         */
        case BPF_JMP | BPF_CALL:
        {
                /*
                 * b0 = (__bpf_call_base + imm)(b1, b2, b3, b4, b5)
                 */
                const u64 func = (u64)__bpf_call_base + imm;

                REG_SET_SEEN(BPF_REG_5);
                jit->seen |= SEEN_FUNC;
                /* lg %w1,<d(imm)>(%l) */
                EMIT6_DISP_LH(0xe3000000, 0x0004, REG_W1, REG_0, REG_L,
                              EMIT_CONST_U64(func));
                /* basr %r14,%w1 */
                EMIT2(0x0d00, REG_14, REG_W1);
                /* lgr %b0,%r2: load return value into %b0 */
                EMIT4(0xb9040000, BPF_REG_0, REG_2);
                if (bpf_helper_changes_skb_data((void *)func)) {
                        jit->seen |= SEEN_SKB_CHANGE;
                        /* lg %b1,ST_OFF_SKBP(%r15) */
                        EMIT6_DISP_LH(0xe3000000, 0x0004, BPF_REG_1, REG_0,
                                      REG_15, STK_OFF_SKBP);
                        emit_load_skb_data_hlen(jit);
                }
                break;
        }
        case BPF_JMP | BPF_CALL | BPF_X:
                /*
                 * Implicit input:
                 *  B1: pointer to ctx
                 *  B2: pointer to bpf_array
                 *  B3: index in bpf_array
                 */
                jit->seen |= SEEN_TAIL_CALL;

                /*
                 * if (index >= array->map.max_entries)
                 *         goto out;
                 */

                /* llgf %w1,map.max_entries(%b2) */
                EMIT6_DISP_LH(0xe3000000, 0x0016, REG_W1, REG_0, BPF_REG_2,
                              offsetof(struct bpf_array, map.max_entries));
                /* clgrj %b3,%w1,0xa,label0: if %b3 >= %w1 goto out */
                EMIT6_PCREL_LABEL(0xec000000, 0x0065, BPF_REG_3,
                                  REG_W1, 0, 0xa);

                /*
                 * if (tail_call_cnt++ > MAX_TAIL_CALL_CNT)
                 *         goto out;
                 */

                if (jit->seen & SEEN_STACK)
                        off = STK_OFF_TCCNT + STK_OFF;
                else
                        off = STK_OFF_TCCNT;
                /* lhi %w0,1 */
                EMIT4_IMM(0xa7080000, REG_W0, 1);
                /* laal %w1,%w0,off(%r15) */
                EMIT6_DISP_LH(0xeb000000, 0x00fa, REG_W1, REG_W0, REG_15, off);
                /* clij %w1,MAX_TAIL_CALL_CNT,0x2,label0 */
                EMIT6_PCREL_IMM_LABEL(0xec000000, 0x007f, REG_W1,
                                      MAX_TAIL_CALL_CNT, 0, 0x2);

                /*
                 * prog = array->ptrs[index];
                 * if (prog == NULL)
                 *         goto out;
                 */

                /* sllg %r1,%b3,3: %r1 = index * 8 */
                EMIT6_DISP_LH(0xeb000000, 0x000d, REG_1, BPF_REG_3, REG_0, 3);
                /* lg %r1,prog(%b2,%r1) */
                EMIT6_DISP_LH(0xe3000000, 0x0004, REG_1, BPF_REG_2,
                              REG_1, offsetof(struct bpf_array, ptrs));
                /* clgij %r1,0,0x8,label0 */
                EMIT6_PCREL_IMM_LABEL(0xec000000, 0x007d, REG_1, 0, 0, 0x8);

                /*
                 * Restore registers before calling function
                 */
                save_restore_regs(jit, REGS_RESTORE);

                /*
                 * goto *(prog->bpf_func + tail_call_start);
                 */

                /* lg %r1,bpf_func(%r1) */
                EMIT6_DISP_LH(0xe3000000, 0x0004, REG_1, REG_1, REG_0,
                              offsetof(struct bpf_prog, bpf_func));
                /* bc 0xf,tail_call_start(%r1) */
                _EMIT4(0x47f01000 + jit->tail_call_start);
                /* out: */
                jit->labels[0] = jit->prg;
                break;
        case BPF_JMP | BPF_EXIT: /* return b0 */
                last = (i == fp->len - 1) ? 1 : 0;
                if (last && !(jit->seen & SEEN_RET0))
                        break;
                /* j <exit> */
                EMIT4_PCREL(0xa7f40000, jit->exit_ip - jit->prg);
                break;
        /*
         * Branch relative (number of skipped instructions) to offset on
         * condition.
         *
         * Condition code to mask mapping:
         *
         * CC | Description        | Mask
         * ------------------------------
         * 0  | Operands equal     |    8
         * 1  | First operand low  |    4
         * 2  | First operand high |    2
         * 3  | Unused             |    1
         *
         * For s390x relative branches: ip = ip + off_bytes
         * For BPF relative branches:   insn = insn + off_insns + 1
         *
         * For example for s390x with offset 0 we jump to the branch
         * instruction itself (loop) and for BPF with offset 0 we
         * branch to the instruction behind the branch.
         */
        case BPF_JMP | BPF_JA: /* if (true) */
                mask = 0xf000; /* j */
                goto branch_oc;
        case BPF_JMP | BPF_JSGT | BPF_K: /* ((s64) dst > (s64) imm) */
                mask = 0x2000; /* jh */
                goto branch_ks;
        case BPF_JMP | BPF_JSGE | BPF_K: /* ((s64) dst >= (s64) imm) */
                mask = 0xa000; /* jhe */
                goto branch_ks;
        case BPF_JMP | BPF_JGT | BPF_K: /* (dst_reg > imm) */
                mask = 0x2000; /* jh */
                goto branch_ku;
        case BPF_JMP | BPF_JGE | BPF_K: /* (dst_reg >= imm) */
                mask = 0xa000; /* jhe */
                goto branch_ku;
        case BPF_JMP | BPF_JNE | BPF_K: /* (dst_reg != imm) */
                mask = 0x7000; /* jne */
                goto branch_ku;
        case BPF_JMP | BPF_JEQ | BPF_K: /* (dst_reg == imm) */
                mask = 0x8000; /* je */
                goto branch_ku;
        case BPF_JMP | BPF_JSET | BPF_K: /* (dst_reg & imm) */
                mask = 0x7000; /* jnz */
                /* lgfi %w1,imm (load sign extend imm) */
                EMIT6_IMM(0xc0010000, REG_W1, imm);
                /* ngr %w1,%dst */
                EMIT4(0xb9800000, REG_W1, dst_reg);
                goto branch_oc;

        case BPF_JMP | BPF_JSGT | BPF_X: /* ((s64) dst > (s64) src) */
                mask = 0x2000; /* jh */
                goto branch_xs;
        case BPF_JMP | BPF_JSGE | BPF_X: /* ((s64) dst >= (s64) src) */
                mask = 0xa000; /* jhe */
                goto branch_xs;
        case BPF_JMP | BPF_JGT | BPF_X: /* (dst > src) */
                mask = 0x2000; /* jh */
                goto branch_xu;
        case BPF_JMP | BPF_JGE | BPF_X: /* (dst >= src) */
                mask = 0xa000; /* jhe */
                goto branch_xu;
        case BPF_JMP | BPF_JNE | BPF_X: /* (dst != src) */
                mask = 0x7000; /* jne */
                goto branch_xu;
        case BPF_JMP | BPF_JEQ | BPF_X: /* (dst == src) */
                mask = 0x8000; /* je */
                goto branch_xu;
        case BPF_JMP | BPF_JSET | BPF_X: /* (dst & src) */
                mask = 0x7000; /* jnz */
                /* ngrk %w1,%dst,%src */
                EMIT4_RRF(0xb9e40000, REG_W1, dst_reg, src_reg);
                goto branch_oc;
branch_ks:
                /* lgfi %w1,imm (load sign extend imm) */
                EMIT6_IMM(0xc0010000, REG_W1, imm);
                /* cgrj %dst,%w1,mask,off */
                EMIT6_PCREL(0xec000000, 0x0064, dst_reg, REG_W1, i, off, mask);
                break;
branch_ku:
                /* lgfi %w1,imm (load sign extend imm) */
                EMIT6_IMM(0xc0010000, REG_W1, imm);
                /* clgrj %dst,%w1,mask,off */
                EMIT6_PCREL(0xec000000, 0x0065, dst_reg, REG_W1, i, off, mask);
                break;
branch_xs:
                /* cgrj %dst,%src,mask,off */
                EMIT6_PCREL(0xec000000, 0x0064, dst_reg, src_reg, i, off, mask);
                break;
branch_xu:
                /* clgrj %dst,%src,mask,off */
                EMIT6_PCREL(0xec000000, 0x0065, dst_reg, src_reg, i, off, mask);
                break;
branch_oc:
                /* brc mask,jmp_off (branch instruction needs 4 bytes) */
                jmp_off = addrs[i + off + 1] - (addrs[i + 1] - 4);
                EMIT4_PCREL(0xa7040000 | mask << 8, jmp_off);
                break;
        /*
         * BPF_LD
         */
        case BPF_LD | BPF_ABS | BPF_B: /* b0 = *(u8 *) (skb->data+imm) */
        case BPF_LD | BPF_IND | BPF_B: /* b0 = *(u8 *) (skb->data+imm+src) */
                if ((BPF_MODE(insn->code) == BPF_ABS) && (imm >= 0))
                        func_addr = __pa(sk_load_byte_pos);
                else
                        func_addr = __pa(sk_load_byte);
                goto call_fn;
        case BPF_LD | BPF_ABS | BPF_H: /* b0 = *(u16 *) (skb->data+imm) */
        case BPF_LD | BPF_IND | BPF_H: /* b0 = *(u16 *) (skb->data+imm+src) */
                if ((BPF_MODE(insn->code) == BPF_ABS) && (imm >= 0))
                        func_addr = __pa(sk_load_half_pos);
                else
                        func_addr = __pa(sk_load_half);
                goto call_fn;
        case BPF_LD | BPF_ABS | BPF_W: /* b0 = *(u32 *) (skb->data+imm) */
        case BPF_LD | BPF_IND | BPF_W: /* b0 = *(u32 *) (skb->data+imm+src) */
                if ((BPF_MODE(insn->code) == BPF_ABS) && (imm >= 0))
                        func_addr = __pa(sk_load_word_pos);
                else
                        func_addr = __pa(sk_load_word);
                goto call_fn;
call_fn:
                jit->seen |= SEEN_SKB | SEEN_RET0 | SEEN_FUNC;
                REG_SET_SEEN(REG_14); /* Return address of possible func call */

                /*
                 * Implicit input:
                 *  BPF_REG_6    (R7) : skb pointer
                 *  REG_SKB_DATA (R12): skb data pointer
                 *
                 * Calculated input:
                 *  BPF_REG_2    (R3) : offset of byte(s) to fetch in skb
                 *  BPF_REG_5    (R6) : return address
                 *
                 * Output:
                 *  BPF_REG_0    (R14): data read from skb
                 *
                 * Scratch registers (BPF_REG_1-5)
                 */

                /* Call function: llilf %w1,func_addr  */
                EMIT6_IMM(0xc00f0000, REG_W1, func_addr);

                /* Offset: lgfi %b2,imm */
                EMIT6_IMM(0xc0010000, BPF_REG_2, imm);
                if (BPF_MODE(insn->code) == BPF_IND)
                        /* agfr %b2,%src (%src is s32 here) */
                        EMIT4(0xb9180000, BPF_REG_2, src_reg);

                /* basr %b5,%w1 (%b5 is call saved) */
                EMIT2(0x0d00, BPF_REG_5, REG_W1);

                /*
                 * Note: For fast access we jump directly after the
                 * jnz instruction from bpf_jit.S
                 */
                /* jnz <ret0> */
                EMIT4_PCREL(0xa7740000, jit->ret0_ip - jit->prg);
                break;
        default: /* too complex, give up */
                pr_err("Unknown opcode %02x\n", insn->code);
                return -1;
        }
        return insn_count;
}

/*
 * Compile eBPF program into s390x code
 */
static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp)
{
        int i, insn_count;

        jit->lit = jit->lit_start;
        jit->prg = 0;

        bpf_jit_prologue(jit);
        for (i = 0; i < fp->len; i += insn_count) {
                insn_count = bpf_jit_insn(jit, fp, i);
                if (insn_count < 0)
                        return -1;
                jit->addrs[i + 1] = jit->prg; /* Next instruction address */
        }
        bpf_jit_epilogue(jit);

        jit->lit_start = jit->prg;
        jit->size = jit->lit;
        jit->size_prg = jit->prg;
        return 0;
}

/*
 * Classic BPF function stub. BPF programs will be converted into
 * eBPF and then bpf_int_jit_compile() will be called.
 */
void bpf_jit_compile(struct bpf_prog *fp)
{
}

/*
 * Compile eBPF program "fp"
 */
void bpf_int_jit_compile(struct bpf_prog *fp)
{
        struct bpf_binary_header *header;
        struct bpf_jit jit;
        int pass;

        if (!bpf_jit_enable)
                return;
        memset(&jit, 0, sizeof(jit));
        jit.addrs = kcalloc(fp->len + 1, sizeof(*jit.addrs), GFP_KERNEL);
        if (jit.addrs == NULL)
                return;
        /*
         * Three initial passes:
         *   - 1/2: Determine clobbered registers
         *   - 3:   Calculate program size and addrs arrray
         */
        for (pass = 1; pass <= 3; pass++) {
                if (bpf_jit_prog(&jit, fp))
                        goto free_addrs;
        }
        /*
         * Final pass: Allocate and generate program
         */
        if (jit.size >= BPF_SIZE_MAX)
                goto free_addrs;
        header = bpf_jit_binary_alloc(jit.size, &jit.prg_buf, 2, jit_fill_hole);
        if (!header)
                goto free_addrs;
        if (bpf_jit_prog(&jit, fp))
                goto free_addrs;
        if (bpf_jit_enable > 1) {
                bpf_jit_dump(fp->len, jit.size, pass, jit.prg_buf);
                if (jit.prg_buf)
                        print_fn_code(jit.prg_buf, jit.size_prg);
        }
        if (jit.prg_buf) {
                set_memory_ro((unsigned long)header, header->pages);
                fp->bpf_func = (void *) jit.prg_buf;
                fp->jited = 1;
        }
free_addrs:
        kfree(jit.addrs);
}

/*
 * Free eBPF program
 */
void bpf_jit_free(struct bpf_prog *fp)
{
        unsigned long addr = (unsigned long)fp->bpf_func & PAGE_MASK;
        struct bpf_binary_header *header = (void *)addr;

        if (!fp->jited)
                goto free_filter;

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

free_filter:
        bpf_prog_unlock_free(fp);
}