// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
#include <bpf/bpf.h>
#include "disasm.h"
struct print_insn_context {
char scratch[16];
char *buf;
size_t sz;
};
static void print_insn_cb(void *private_data, const char *fmt, ...)
{
struct print_insn_context *ctx = private_data;
va_list args;
va_start(args, fmt);
vsnprintf(ctx->buf, ctx->sz, fmt, args);
va_end(args);
}
static const char *print_call_cb(void *private_data, const struct bpf_insn *insn)
{
struct print_insn_context *ctx = private_data;
/* For pseudo calls verifier.c:jit_subprogs() hides original
* imm to insn->off and changes insn->imm to be an index of
* the subprog instead.
*/
if (insn->src_reg == BPF_PSEUDO_CALL) {
snprintf(ctx->scratch, sizeof(ctx->scratch), "%+d", insn->off);
return ctx->scratch;
}
return NULL;
}
struct bpf_insn *disasm_insn(struct bpf_insn *insn, char *buf, size_t buf_sz)
{
struct print_insn_context ctx = {
.buf = buf,
.sz = buf_sz,
};
struct bpf_insn_cbs cbs = {
.cb_print = print_insn_cb,
.cb_call = print_call_cb,
.private_data = &ctx,
};
char *tmp, *pfx_end, *sfx_start;
bool double_insn;
int len;
print_bpf_insn(&cbs, insn, true);
/* We share code with kernel BPF disassembler, it adds '(FF) ' prefix
* for each instruction (FF stands for instruction `code` byte).
* Remove the prefix inplace, and also simplify call instructions.
* E.g.: "(85) call foo#10" -> "call foo".
* Also remove newline in the end (the 'max(strlen(buf) - 1, 0)' thing).
*/
pfx_end = buf + 5;
sfx_start = buf + max((int)strlen(buf) - 1, 0);
if (strncmp(pfx_end, "call ", 5) == 0 && (tmp = strrchr(buf, '#')))
sfx_start = tmp;
len = sfx_start - pfx_end;
memmove(buf, pfx_end, len);
buf[len] = 0;
double_insn = insn->code == (BPF_LD | BPF_IMM | BPF_DW);
return insn + (double_insn ? 2 : 1);
}