1 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
2
3 #include <bpf/bpf.h>
4 #include "disasm.h"
5
6 struct print_insn_context {
7 char scratch[16];
8 char *buf;
9 size_t sz;
10 };
11
12 static void print_insn_cb(void *private_data, const char *fmt, ...)
13 {
14 struct print_insn_context *ctx = private_data;
15 va_list args;
16
17 va_start(args, fmt);
18 vsnprintf(ctx->buf, ctx->sz, fmt, args);
19 va_end(args);
20 }
21
22 static const char *print_call_cb(void *private_data, const struct bpf_insn *insn)
23 {
24 struct print_insn_context *ctx = private_data;
25
26 /* For pseudo calls verifier.c:jit_subprogs() hides original
27 * imm to insn->off and changes insn->imm to be an index of
28 * the subprog instead.
29 */
30 if (insn->src_reg == BPF_PSEUDO_CALL) {
31 snprintf(ctx->scratch, sizeof(ctx->scratch), "%+d", insn->off);
32 return ctx->scratch;
33 }
34
35 return NULL;
36 }
37
38 struct bpf_insn *disasm_insn(struct bpf_insn *insn, char *buf, size_t buf_sz)
39 {
40 struct print_insn_context ctx = {
41 .buf = buf,
42 .sz = buf_sz,
43 };
44 struct bpf_insn_cbs cbs = {
45 .cb_print = print_insn_cb,
46 .cb_call = print_call_cb,
47 .private_data = &ctx,
48 };
49 char *tmp, *pfx_end, *sfx_start;
50 bool double_insn;
51 int len;
52
53 print_bpf_insn(&cbs, insn, true);
54 /* We share code with kernel BPF disassembler, it adds '(FF) ' prefix
55 * for each instruction (FF stands for instruction `code` byte).
56 * Remove the prefix inplace, and also simplify call instructions.
57 * E.g.: "(85) call foo#10" -> "call foo".
58 * Also remove newline in the end (the 'max(strlen(buf) - 1, 0)' thing).
59 */
60 pfx_end = buf + 5;
61 sfx_start = buf + max((int)strlen(buf) - 1, 0);
62 if (strncmp(pfx_end, "call ", 5) == 0 && (tmp = strrchr(buf, '#')))
63 sfx_start = tmp;
64 len = sfx_start - pfx_end;
65 memmove(buf, pfx_end, len);
66 buf[len] = 0;
67 double_insn = insn->code == (BPF_LD | BPF_IMM | BPF_DW);
68 return insn + (double_insn ? 2 : 1);
69 }
70
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