/* bpf_jit_comp.c : BPF JIT compiler
 *
 * Copyright (C) 2011 Eric Dumazet (eric.dumazet@gmail.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/moduleloader.h>
#include <asm/cacheflush.h>
#include <linux/netdevice.h>
#include <linux/filter.h>

/*
 * Conventions :
 *  EAX : BPF A accumulator
 *  EBX : BPF X accumulator
 *  RDI : pointer to skb   (first argument given to JIT function)
 *  RBP : frame pointer (even if CONFIG_FRAME_POINTER=n)
 *  ECX,EDX,ESI : scratch registers
 *  r9d : skb->len - skb->data_len (headlen)
 *  r8  : skb->data
 * -8(RBP) : saved RBX value
 * -16(RBP)..-80(RBP) : BPF_MEMWORDS values
 */
int bpf_jit_enable __read_mostly;

/*
 * assembly code in arch/x86/net/bpf_jit.S
 */
extern u8 sk_load_word[], sk_load_half[], sk_load_byte[], sk_load_byte_msh[];
extern u8 sk_load_word_positive_offset[], sk_load_half_positive_offset[];
extern u8 sk_load_byte_positive_offset[], sk_load_byte_msh_positive_offset[];
extern u8 sk_load_word_negative_offset[], sk_load_half_negative_offset[];
extern u8 sk_load_byte_negative_offset[], sk_load_byte_msh_negative_offset[];

static inline u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len)
{
        if (len == 1)
                *ptr = bytes;
        else if (len == 2)
                *(u16 *)ptr = bytes;
        else {
                *(u32 *)ptr = bytes;
                barrier();
        }
        return ptr + len;
}

#define EMIT(bytes, len)        do { prog = emit_code(prog, bytes, len); } while (0)

#define EMIT1(b1)               EMIT(b1, 1)
#define EMIT2(b1, b2)           EMIT((b1) + ((b2) << 8), 2)
#define EMIT3(b1, b2, b3)       EMIT((b1) + ((b2) << 8) + ((b3) << 16), 3)
#define EMIT4(b1, b2, b3, b4)   EMIT((b1) + ((b2) << 8) + ((b3) << 16) + ((b4) << 24), 4)
#define EMIT1_off32(b1, off)    do { EMIT1(b1); EMIT(off, 4);} while (0)

#define CLEAR_A() EMIT2(0x31, 0xc0) /* xor %eax,%eax */
#define CLEAR_X() EMIT2(0x31, 0xdb) /* xor %ebx,%ebx */

static inline bool is_imm8(int value)
{
        return value <= 127 && value >= -128;
}

static inline bool is_near(int offset)
{
        return offset <= 127 && offset >= -128;
}

#define EMIT_JMP(offset)                                                \
do {                                                                    \
        if (offset) {                                                   \
                if (is_near(offset))                                    \
                        EMIT2(0xeb, offset); /* jmp .+off8 */           \
                else                                                    \
                        EMIT1_off32(0xe9, offset); /* jmp .+off32 */    \
        }                                                               \
} while (0)

/* list of x86 cond jumps opcodes (. + s8)
 * Add 0x10 (and an extra 0x0f) to generate far jumps (. + s32)
 */
#define X86_JB  0x72
#define X86_JAE 0x73
#define X86_JE  0x74
#define X86_JNE 0x75
#define X86_JBE 0x76
#define X86_JA  0x77

#define EMIT_COND_JMP(op, offset)                               \
do {                                                            \
        if (is_near(offset))                                    \
                EMIT2(op, offset); /* jxx .+off8 */             \
        else {                                                  \
                EMIT2(0x0f, op + 0x10);                         \
                EMIT(offset, 4); /* jxx .+off32 */              \
        }                                                       \
} while (0)

#define COND_SEL(CODE, TOP, FOP)        \
        case CODE:                      \
                t_op = TOP;             \
                f_op = FOP;             \
                goto cond_branch


#define SEEN_DATAREF 1 /* might call external helpers */
#define SEEN_XREG    2 /* ebx is used */
#define SEEN_MEM     4 /* use mem[] for temporary storage */

static inline void bpf_flush_icache(void *start, void *end)
{
        mm_segment_t old_fs = get_fs();

        set_fs(KERNEL_DS);
        smp_wmb();
        flush_icache_range((unsigned long)start, (unsigned long)end);
        set_fs(old_fs);
}

#define CHOOSE_LOAD_FUNC(K, func) \
        ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)

void bpf_jit_compile(struct sk_filter *fp)
{
        u8 temp[64];
        u8 *prog;
        unsigned int proglen, oldproglen = 0;
        int ilen, i;
        int t_offset, f_offset;
        u8 t_op, f_op, seen = 0, pass;
        u8 *image = NULL;
        u8 *func;
        int pc_ret0 = -1; /* bpf index of first RET #0 instruction (if any) */
        unsigned int cleanup_addr; /* epilogue code offset */
        unsigned int *addrs;
        const struct sock_filter *filter = fp->insns;
        int flen = fp->len;

        if (!bpf_jit_enable)
                return;

        addrs = kmalloc(flen * sizeof(*addrs), GFP_KERNEL);
        if (addrs == NULL)
                return;

        /* Before first pass, make a rough estimation of addrs[]
         * each bpf instruction is translated to less than 64 bytes
         */
        for (proglen = 0, i = 0; i < flen; i++) {
                proglen += 64;
                addrs[i] = proglen;
        }
        cleanup_addr = proglen; /* epilogue address */

        for (pass = 0; pass < 10; pass++) {
                u8 seen_or_pass0 = (pass == 0) ? (SEEN_XREG | SEEN_DATAREF | SEEN_MEM) : seen;
                /* no prologue/epilogue for trivial filters (RET something) */
                proglen = 0;
                prog = temp;

                if (seen_or_pass0) {
                        EMIT4(0x55, 0x48, 0x89, 0xe5); /* push %rbp; mov %rsp,%rbp */
                        EMIT4(0x48, 0x83, 0xec, 96);    /* subq  $96,%rsp       */
                        /* note : must save %rbx in case bpf_error is hit */
                        if (seen_or_pass0 & (SEEN_XREG | SEEN_DATAREF))
                                EMIT4(0x48, 0x89, 0x5d, 0xf8); /* mov %rbx, -8(%rbp) */
                        if (seen_or_pass0 & SEEN_XREG)
                                CLEAR_X(); /* make sure we dont leek kernel memory */

                        /*
                         * If this filter needs to access skb data,
                         * loads r9 and r8 with :
                         *  r9 = skb->len - skb->data_len
                         *  r8 = skb->data
                         */
                        if (seen_or_pass0 & SEEN_DATAREF) {
                                if (offsetof(struct sk_buff, len) <= 127)
                                        /* mov    off8(%rdi),%r9d */
                                        EMIT4(0x44, 0x8b, 0x4f, offsetof(struct sk_buff, len));
                                else {
                                        /* mov    off32(%rdi),%r9d */
                                        EMIT3(0x44, 0x8b, 0x8f);
                                        EMIT(offsetof(struct sk_buff, len), 4);
                                }
                                if (is_imm8(offsetof(struct sk_buff, data_len)))
                                        /* sub    off8(%rdi),%r9d */
                                        EMIT4(0x44, 0x2b, 0x4f, offsetof(struct sk_buff, data_len));
                                else {
                                        EMIT3(0x44, 0x2b, 0x8f);
                                        EMIT(offsetof(struct sk_buff, data_len), 4);
                                }

                                if (is_imm8(offsetof(struct sk_buff, data)))
                                        /* mov off8(%rdi),%r8 */
                                        EMIT4(0x4c, 0x8b, 0x47, offsetof(struct sk_buff, data));
                                else {
                                        /* mov off32(%rdi),%r8 */
                                        EMIT3(0x4c, 0x8b, 0x87);
                                        EMIT(offsetof(struct sk_buff, data), 4);
                                }
                        }
                }

                switch (filter[0].code) {
                case BPF_S_RET_K:
                case BPF_S_LD_W_LEN:
                case BPF_S_ANC_PROTOCOL:
                case BPF_S_ANC_IFINDEX:
                case BPF_S_ANC_MARK:
                case BPF_S_ANC_RXHASH:
                case BPF_S_ANC_CPU:
                case BPF_S_ANC_QUEUE:
                case BPF_S_LD_W_ABS:
                case BPF_S_LD_H_ABS:
                case BPF_S_LD_B_ABS:
                        /* first instruction sets A register (or is RET 'constant') */
                        break;
                default:
                        /* make sure we dont leak kernel information to user */
                        CLEAR_A(); /* A = 0 */
                }

                for (i = 0; i < flen; i++) {
                        unsigned int K = filter[i].k;

                        switch (filter[i].code) {
                        case BPF_S_ALU_ADD_X: /* A += X; */
                                seen |= SEEN_XREG;
                                EMIT2(0x01, 0xd8);              /* add %ebx,%eax */
                                break;
                        case BPF_S_ALU_ADD_K: /* A += K; */
                                if (!K)
                                        break;
                                if (is_imm8(K))
                                        EMIT3(0x83, 0xc0, K);   /* add imm8,%eax */
                                else
                                        EMIT1_off32(0x05, K);   /* add imm32,%eax */
                                break;
                        case BPF_S_ALU_SUB_X: /* A -= X; */
                                seen |= SEEN_XREG;
                                EMIT2(0x29, 0xd8);              /* sub    %ebx,%eax */
                                break;
                        case BPF_S_ALU_SUB_K: /* A -= K */
                                if (!K)
                                        break;
                                if (is_imm8(K))
                                        EMIT3(0x83, 0xe8, K); /* sub imm8,%eax */
                                else
                                        EMIT1_off32(0x2d, K); /* sub imm32,%eax */
                                break;
                        case BPF_S_ALU_MUL_X: /* A *= X; */
                                seen |= SEEN_XREG;
                                EMIT3(0x0f, 0xaf, 0xc3);        /* imul %ebx,%eax */
                                break;
                        case BPF_S_ALU_MUL_K: /* A *= K */
                                if (is_imm8(K))
                                        EMIT3(0x6b, 0xc0, K); /* imul imm8,%eax,%eax */
                                else {
                                        EMIT2(0x69, 0xc0);              /* imul imm32,%eax */
                                        EMIT(K, 4);
                                }
                                break;
                        case BPF_S_ALU_DIV_X: /* A /= X; */
                                seen |= SEEN_XREG;
                                EMIT2(0x85, 0xdb);      /* test %ebx,%ebx */
                                if (pc_ret0 > 0) {
                                        /* addrs[pc_ret0 - 1] is start address of target
                                         * (addrs[i] - 4) is the address following this jmp
                                         * ("xor %edx,%edx; div %ebx" being 4 bytes long)
                                         */
                                        EMIT_COND_JMP(X86_JE, addrs[pc_ret0 - 1] -
                                                                (addrs[i] - 4));
                                } else {
                                        EMIT_COND_JMP(X86_JNE, 2 + 5);
                                        CLEAR_A();
                                        EMIT1_off32(0xe9, cleanup_addr - (addrs[i] - 4)); /* jmp .+off32 */
                                }
                                EMIT4(0x31, 0xd2, 0xf7, 0xf3); /* xor %edx,%edx; div %ebx */
                                break;
                        case BPF_S_ALU_DIV_K: /* A = reciprocal_divide(A, K); */
                                EMIT3(0x48, 0x69, 0xc0); /* imul imm32,%rax,%rax */
                                EMIT(K, 4);
                                EMIT4(0x48, 0xc1, 0xe8, 0x20); /* shr $0x20,%rax */
                                break;
                        case BPF_S_ALU_AND_X:
                                seen |= SEEN_XREG;
                                EMIT2(0x21, 0xd8);              /* and %ebx,%eax */
                                break;
                        case BPF_S_ALU_AND_K:
                                if (K >= 0xFFFFFF00) {
                                        EMIT2(0x24, K & 0xFF); /* and imm8,%al */
                                } else if (K >= 0xFFFF0000) {
                                        EMIT2(0x66, 0x25);      /* and imm16,%ax */
                                        EMIT(K, 2);
                                } else {
                                        EMIT1_off32(0x25, K);   /* and imm32,%eax */
                                }
                                break;
                        case BPF_S_ALU_OR_X:
                                seen |= SEEN_XREG;
                                EMIT2(0x09, 0xd8);              /* or %ebx,%eax */
                                break;
                        case BPF_S_ALU_OR_K:
                                if (is_imm8(K))
                                        EMIT3(0x83, 0xc8, K); /* or imm8,%eax */
                                else
                                        EMIT1_off32(0x0d, K);   /* or imm32,%eax */
                                break;
                        case BPF_S_ANC_ALU_XOR_X: /* A ^= X; */
                                seen |= SEEN_XREG;
                                EMIT2(0x31, 0xd8);              /* xor %ebx,%eax */
                                break;
                        case BPF_S_ALU_LSH_X: /* A <<= X; */
                                seen |= SEEN_XREG;
                                EMIT4(0x89, 0xd9, 0xd3, 0xe0);  /* mov %ebx,%ecx; shl %cl,%eax */
                                break;
                        case BPF_S_ALU_LSH_K:
                                if (K == 0)
                                        break;
                                else if (K == 1)
                                        EMIT2(0xd1, 0xe0); /* shl %eax */
                                else
                                        EMIT3(0xc1, 0xe0, K);
                                break;
                        case BPF_S_ALU_RSH_X: /* A >>= X; */
                                seen |= SEEN_XREG;
                                EMIT4(0x89, 0xd9, 0xd3, 0xe8);  /* mov %ebx,%ecx; shr %cl,%eax */
                                break;
                        case BPF_S_ALU_RSH_K: /* A >>= K; */
                                if (K == 0)
                                        break;
                                else if (K == 1)
                                        EMIT2(0xd1, 0xe8); /* shr %eax */
                                else
                                        EMIT3(0xc1, 0xe8, K);
                                break;
                        case BPF_S_ALU_NEG:
                                EMIT2(0xf7, 0xd8);              /* neg %eax */
                                break;
                        case BPF_S_RET_K:
                                if (!K) {
                                        if (pc_ret0 == -1)
                                                pc_ret0 = i;
                                        CLEAR_A();
                                } else {
                                        EMIT1_off32(0xb8, K);   /* mov $imm32,%eax */
                                }
                                /* fallinto */
                        case BPF_S_RET_A:
                                if (seen_or_pass0) {
                                        if (i != flen - 1) {
                                                EMIT_JMP(cleanup_addr - addrs[i]);
                                                break;
                                        }
                                        if (seen_or_pass0 & SEEN_XREG)
                                                EMIT4(0x48, 0x8b, 0x5d, 0xf8);  /* mov  -8(%rbp),%rbx */
                                        EMIT1(0xc9);            /* leaveq */
                                }
                                EMIT1(0xc3);            /* ret */
                                break;
                        case BPF_S_MISC_TAX: /* X = A */
                                seen |= SEEN_XREG;
                                EMIT2(0x89, 0xc3);      /* mov    %eax,%ebx */
                                break;
                        case BPF_S_MISC_TXA: /* A = X */
                                seen |= SEEN_XREG;
                                EMIT2(0x89, 0xd8);      /* mov    %ebx,%eax */
                                break;
                        case BPF_S_LD_IMM: /* A = K */
                                if (!K)
                                        CLEAR_A();
                                else
                                        EMIT1_off32(0xb8, K); /* mov $imm32,%eax */
                                break;
                        case BPF_S_LDX_IMM: /* X = K */
                                seen |= SEEN_XREG;
                                if (!K)
                                        CLEAR_X();
                                else
                                        EMIT1_off32(0xbb, K); /* mov $imm32,%ebx */
                                break;
                        case BPF_S_LD_MEM: /* A = mem[K] : mov off8(%rbp),%eax */
                                seen |= SEEN_MEM;
                                EMIT3(0x8b, 0x45, 0xf0 - K*4);
                                break;
                        case BPF_S_LDX_MEM: /* X = mem[K] : mov off8(%rbp),%ebx */
                                seen |= SEEN_XREG | SEEN_MEM;
                                EMIT3(0x8b, 0x5d, 0xf0 - K*4);
                                break;
                        case BPF_S_ST: /* mem[K] = A : mov %eax,off8(%rbp) */
                                seen |= SEEN_MEM;
                                EMIT3(0x89, 0x45, 0xf0 - K*4);
                                break;
                        case BPF_S_STX: /* mem[K] = X : mov %ebx,off8(%rbp) */
                                seen |= SEEN_XREG | SEEN_MEM;
                                EMIT3(0x89, 0x5d, 0xf0 - K*4);
                                break;
                        case BPF_S_LD_W_LEN: /* A = skb->len; */
                                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
                                if (is_imm8(offsetof(struct sk_buff, len)))
                                        /* mov    off8(%rdi),%eax */
                                        EMIT3(0x8b, 0x47, offsetof(struct sk_buff, len));
                                else {
                                        EMIT2(0x8b, 0x87);
                                        EMIT(offsetof(struct sk_buff, len), 4);
                                }
                                break;
                        case BPF_S_LDX_W_LEN: /* X = skb->len; */
                                seen |= SEEN_XREG;
                                if (is_imm8(offsetof(struct sk_buff, len)))
                                        /* mov off8(%rdi),%ebx */
                                        EMIT3(0x8b, 0x5f, offsetof(struct sk_buff, len));
                                else {
                                        EMIT2(0x8b, 0x9f);
                                        EMIT(offsetof(struct sk_buff, len), 4);
                                }
                                break;
                        case BPF_S_ANC_PROTOCOL: /* A = ntohs(skb->protocol); */
                                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);
                                if (is_imm8(offsetof(struct sk_buff, protocol))) {
                                        /* movzwl off8(%rdi),%eax */
                                        EMIT4(0x0f, 0xb7, 0x47, offsetof(struct sk_buff, protocol));
                                } else {
                                        EMIT3(0x0f, 0xb7, 0x87); /* movzwl off32(%rdi),%eax */
                                        EMIT(offsetof(struct sk_buff, protocol), 4);
                                }
                                EMIT2(0x86, 0xc4); /* ntohs() : xchg   %al,%ah */
                                break;
                        case BPF_S_ANC_IFINDEX:
                                if (is_imm8(offsetof(struct sk_buff, dev))) {
                                        /* movq off8(%rdi),%rax */
                                        EMIT4(0x48, 0x8b, 0x47, offsetof(struct sk_buff, dev));
                                } else {
                                        EMIT3(0x48, 0x8b, 0x87); /* movq off32(%rdi),%rax */
                                        EMIT(offsetof(struct sk_buff, dev), 4);
                                }
                                EMIT3(0x48, 0x85, 0xc0);        /* test %rax,%rax */
                                EMIT_COND_JMP(X86_JE, cleanup_addr - (addrs[i] - 6));
                                BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
                                EMIT2(0x8b, 0x80);      /* mov off32(%rax),%eax */
                                EMIT(offsetof(struct net_device, ifindex), 4);
                                break;
                        case BPF_S_ANC_MARK:
                                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
                                if (is_imm8(offsetof(struct sk_buff, mark))) {
                                        /* mov off8(%rdi),%eax */
                                        EMIT3(0x8b, 0x47, offsetof(struct sk_buff, mark));
                                } else {
                                        EMIT2(0x8b, 0x87);
                                        EMIT(offsetof(struct sk_buff, mark), 4);
                                }
                                break;
                        case BPF_S_ANC_RXHASH:
                                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4);
                                if (is_imm8(offsetof(struct sk_buff, rxhash))) {
                                        /* mov off8(%rdi),%eax */
                                        EMIT3(0x8b, 0x47, offsetof(struct sk_buff, rxhash));
                                } else {
                                        EMIT2(0x8b, 0x87);
                                        EMIT(offsetof(struct sk_buff, rxhash), 4);
                                }
                                break;
                        case BPF_S_ANC_QUEUE:
                                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, queue_mapping) != 2);
                                if (is_imm8(offsetof(struct sk_buff, queue_mapping))) {
                                        /* movzwl off8(%rdi),%eax */
                                        EMIT4(0x0f, 0xb7, 0x47, offsetof(struct sk_buff, queue_mapping));
                                } else {
                                        EMIT3(0x0f, 0xb7, 0x87); /* movzwl off32(%rdi),%eax */
                                        EMIT(offsetof(struct sk_buff, queue_mapping), 4);
                                }
                                break;
                        case BPF_S_ANC_CPU:
#ifdef CONFIG_SMP
                                EMIT4(0x65, 0x8b, 0x04, 0x25); /* mov %gs:off32,%eax */
                                EMIT((u32)(unsigned long)&cpu_number, 4); /* A = smp_processor_id(); */
#else
                                CLEAR_A();
#endif
                                break;
                        case BPF_S_LD_W_ABS:
                                func = CHOOSE_LOAD_FUNC(K, sk_load_word);
common_load:                    seen |= SEEN_DATAREF;
                                t_offset = func - (image + addrs[i]);
                                EMIT1_off32(0xbe, K); /* mov imm32,%esi */
                                EMIT1_off32(0xe8, t_offset); /* call */
                                break;
                        case BPF_S_LD_H_ABS:
                                func = CHOOSE_LOAD_FUNC(K, sk_load_half);
                                goto common_load;
                        case BPF_S_LD_B_ABS:
                                func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
                                goto common_load;
                        case BPF_S_LDX_B_MSH:
                                func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
                                seen |= SEEN_DATAREF | SEEN_XREG;
                                t_offset = func - (image + addrs[i]);
                                EMIT1_off32(0xbe, K);   /* mov imm32,%esi */
                                EMIT1_off32(0xe8, t_offset); /* call sk_load_byte_msh */
                                break;
                        case BPF_S_LD_W_IND:
                                func = sk_load_word;
common_load_ind:                seen |= SEEN_DATAREF | SEEN_XREG;
                                t_offset = func - (image + addrs[i]);
                                if (K) {
                                        if (is_imm8(K)) {
                                                EMIT3(0x8d, 0x73, K); /* lea imm8(%rbx), %esi */
                                        } else {
                                                EMIT2(0x8d, 0xb3); /* lea imm32(%rbx),%esi */
                                                EMIT(K, 4);
                                        }
                                } else {
                                        EMIT2(0x89,0xde); /* mov %ebx,%esi */
                                }
                                EMIT1_off32(0xe8, t_offset);    /* call sk_load_xxx_ind */
                                break;
                        case BPF_S_LD_H_IND:
                                func = sk_load_half;
                                goto common_load_ind;
                        case BPF_S_LD_B_IND:
                                func = sk_load_byte;
                                goto common_load_ind;
                        case BPF_S_JMP_JA:
                                t_offset = addrs[i + K] - addrs[i];
                                EMIT_JMP(t_offset);
                                break;
                        COND_SEL(BPF_S_JMP_JGT_K, X86_JA, X86_JBE);
                        COND_SEL(BPF_S_JMP_JGE_K, X86_JAE, X86_JB);
                        COND_SEL(BPF_S_JMP_JEQ_K, X86_JE, X86_JNE);
                        COND_SEL(BPF_S_JMP_JSET_K,X86_JNE, X86_JE);
                        COND_SEL(BPF_S_JMP_JGT_X, X86_JA, X86_JBE);
                        COND_SEL(BPF_S_JMP_JGE_X, X86_JAE, X86_JB);
                        COND_SEL(BPF_S_JMP_JEQ_X, X86_JE, X86_JNE);
                        COND_SEL(BPF_S_JMP_JSET_X,X86_JNE, X86_JE);

cond_branch:                    f_offset = addrs[i + filter[i].jf] - addrs[i];
                                t_offset = addrs[i + filter[i].jt] - addrs[i];

                                /* same targets, can avoid doing the test :) */
                                if (filter[i].jt == filter[i].jf) {
                                        EMIT_JMP(t_offset);
                                        break;
                                }

                                switch (filter[i].code) {
                                case BPF_S_JMP_JGT_X:
                                case BPF_S_JMP_JGE_X:
                                case BPF_S_JMP_JEQ_X:
                                        seen |= SEEN_XREG;
                                        EMIT2(0x39, 0xd8); /* cmp %ebx,%eax */
                                        break;
                                case BPF_S_JMP_JSET_X:
                                        seen |= SEEN_XREG;
                                        EMIT2(0x85, 0xd8); /* test %ebx,%eax */
                                        break;
                                case BPF_S_JMP_JEQ_K:
                                        if (K == 0) {
                                                EMIT2(0x85, 0xc0); /* test   %eax,%eax */
                                                break;
                                        }
                                case BPF_S_JMP_JGT_K:
                                case BPF_S_JMP_JGE_K:
                                        if (K <= 127)
                                                EMIT3(0x83, 0xf8, K); /* cmp imm8,%eax */
                                        else
                                                EMIT1_off32(0x3d, K); /* cmp imm32,%eax */
                                        break;
                                case BPF_S_JMP_JSET_K:
                                        if (K <= 0xFF)
                                                EMIT2(0xa8, K); /* test imm8,%al */
                                        else if (!(K & 0xFFFF00FF))
                                                EMIT3(0xf6, 0xc4, K >> 8); /* test imm8,%ah */
                                        else if (K <= 0xFFFF) {
                                                EMIT2(0x66, 0xa9); /* test imm16,%ax */
                                                EMIT(K, 2);
                                        } else {
                                                EMIT1_off32(0xa9, K); /* test imm32,%eax */
                                        }
                                        break;
                                }
                                if (filter[i].jt != 0) {
                                        if (filter[i].jf && f_offset)
                                                t_offset += is_near(f_offset) ? 2 : 5;
                                        EMIT_COND_JMP(t_op, t_offset);
                                        if (filter[i].jf)
                                                EMIT_JMP(f_offset);
                                        break;
                                }
                                EMIT_COND_JMP(f_op, f_offset);
                                break;
                        default:
                                /* hmm, too complex filter, give up with jit compiler */
                                goto out;
                        }
                        ilen = prog - temp;
                        if (image) {
                                if (unlikely(proglen + ilen > oldproglen)) {
                                        pr_err("bpb_jit_compile fatal error\n");
                                        kfree(addrs);
                                        module_free(NULL, image);
                                        return;
                                }
                                memcpy(image + proglen, temp, ilen);
                        }
                        proglen += ilen;
                        addrs[i] = proglen;
                        prog = temp;
                }
                /* last bpf instruction is always a RET :
                 * use it to give the cleanup instruction(s) addr
                 */
                cleanup_addr = proglen - 1; /* ret */
                if (seen_or_pass0)
                        cleanup_addr -= 1; /* leaveq */
                if (seen_or_pass0 & SEEN_XREG)
                        cleanup_addr -= 4; /* mov  -8(%rbp),%rbx */

                if (image) {
                        if (proglen != oldproglen)
                                pr_err("bpb_jit_compile proglen=%u != oldproglen=%u\n", proglen, oldproglen);
                        break;
                }
                if (proglen == oldproglen) {
                        image = module_alloc(max_t(unsigned int,
                                                   proglen,
                                                   sizeof(struct work_struct)));
                        if (!image)
                                goto out;
                }
                oldproglen = proglen;
        }
        if (bpf_jit_enable > 1)
                pr_err("flen=%d proglen=%u pass=%d image=%p\n",
                       flen, proglen, pass, image);

        if (image) {
                if (bpf_jit_enable > 1)
                        print_hex_dump(KERN_ERR, "JIT code: ", DUMP_PREFIX_ADDRESS,
                                       16, 1, image, proglen, false);

                bpf_flush_icache(image, image + proglen);

                fp->bpf_func = (void *)image;
        }
out:
        kfree(addrs);
        return;
}

static void jit_free_defer(struct work_struct *arg)
{
        module_free(NULL, arg);
}

/* run from softirq, we must use a work_struct to call
 * module_free() from process context
 */
void bpf_jit_free(struct sk_filter *fp)
{
        if (fp->bpf_func != sk_run_filter) {
                struct work_struct *work = (struct work_struct *)fp->bpf_func;

                INIT_WORK(work, jit_free_defer);
                schedule_work(work);
        }
}