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bpf: jmp_offset() and verbose_insn() utility functions

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Extract two utility functions:
- One BPF jump instruction uses .imm field to encode jump offset,
  while the rest use .off. Encapsulate this detail as jmp_offset()
  function.
- Avoid duplicating instruction printing callback definitions by
  defining a verbose_insn() function, which disassembles an
  instruction into the verifier log while hiding this detail.

These functions will be used in the next patch.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250304195024.2478889-2-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman 2025-03-04 11:50:20 -08:00 committed by Alexei Starovoitov
parent 5bde575013
commit 80ca3f1d77
1 changed files with 23 additions and 17 deletions
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40
kernel/bpf/verifier.c
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@ -3360,6 +3360,15 @@ static int add_subprog_and_kfunc(struct bpf_verifier_env *env)
return 0;
}
static int jmp_offset(struct bpf_insn *insn)
{
u8 code = insn->code;
if (code == (BPF_JMP32 | BPF_JA))
return insn->imm;
return insn->off;
}
static int check_subprogs(struct bpf_verifier_env *env)
{
int i, subprog_start, subprog_end, off, cur_subprog = 0;
@ -3386,10 +3395,7 @@ static int check_subprogs(struct bpf_verifier_env *env)
goto next;
if (BPF_OP(code) == BPF_EXIT || BPF_OP(code) == BPF_CALL)
goto next;
if (code == (BPF_JMP32 | BPF_JA))
off = i + insn[i].imm + 1;
else
off = i + insn[i].off + 1;
off = i + jmp_offset(&insn[i]) + 1;
if (off < subprog_start || off >= subprog_end) {
verbose(env, "jump out of range from insn %d to %d\n", i, off);
return -EINVAL;
@ -3919,6 +3925,17 @@ static const char *disasm_kfunc_name(void *data, const struct bpf_insn *insn)
return btf_name_by_offset(desc_btf, func->name_off);
}
static void verbose_insn(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
const struct bpf_insn_cbs cbs = {
.cb_call = disasm_kfunc_name,
.cb_print = verbose,
.private_data = env,
};
print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);
}
static inline void bt_init(struct backtrack_state *bt, u32 frame)
{
bt->frame = frame;
@ -4119,11 +4136,6 @@ static bool calls_callback(struct bpf_verifier_env *env, int insn_idx);
static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx,
struct bpf_insn_hist_entry *hist, struct backtrack_state *bt)
{
const struct bpf_insn_cbs cbs = {
.cb_call = disasm_kfunc_name,
.cb_print = verbose,
.private_data = env,
};
struct bpf_insn *insn = env->prog->insnsi + idx;
u8 class = BPF_CLASS(insn->code);
u8 opcode = BPF_OP(insn->code);
@ -4141,7 +4153,7 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx,
fmt_stack_mask(env->tmp_str_buf, TMP_STR_BUF_LEN, bt_stack_mask(bt));
verbose(env, "stack=%s before ", env->tmp_str_buf);
verbose(env, "%d: ", idx);
print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);
verbose_insn(env, insn);
}
/* If there is a history record that some registers gained range at this insn,
@ -19273,19 +19285,13 @@ static int do_check(struct bpf_verifier_env *env)
}
if (env->log.level & BPF_LOG_LEVEL) {
const struct bpf_insn_cbs cbs = {
.cb_call = disasm_kfunc_name,
.cb_print = verbose,
.private_data = env,
};
if (verifier_state_scratched(env))
print_insn_state(env, state, state->curframe);
verbose_linfo(env, env->insn_idx, "; ");
env->prev_log_pos = env->log.end_pos;
verbose(env, "%d: ", env->insn_idx);
print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);
verbose_insn(env, insn);
env->prev_insn_print_pos = env->log.end_pos - env->prev_log_pos;
env->prev_log_pos = env->log.end_pos;
}