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bpf: frame_insn_idx() utility function

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A function to return IP for a given frame in a call stack of a state.
Will be used by a next patch.

The `state->insn_idx = env->insn_idx;` assignment in the do_check()
allows to use frame_insn_idx with env->cur_state.
At the moment bpf_verifier_state->insn_idx is set when new cached
state is added in is_state_visited() and accessed only in the contexts
when the state is already in the cache. Hence this assignment does not
change verifier behaviour.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250611200836.4135542-3-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman 2025-06-11 13:08:28 -07:00 committed by Alexei Starovoitov
parent 96c6aa4c63
commit 13f843c017
1 changed files with 10 additions and 3 deletions
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13
kernel/bpf/verifier.c
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@ -1964,6 +1964,14 @@ static void update_loop_entry(struct bpf_verifier_env *env,
}
}
/* Return IP for a given frame in a call stack */
static u32 frame_insn_idx(struct bpf_verifier_state *st, u32 frame)
{
return frame == st->curframe
? st->insn_idx
: st->frame[frame + 1]->callsite;
}
static void update_branch_counts(struct bpf_verifier_env *env, struct bpf_verifier_state *st)
{
struct bpf_verifier_state_list *sl = NULL, *parent_sl;
@ -18790,9 +18798,7 @@ static bool states_equal(struct bpf_verifier_env *env,
* and all frame states need to be equivalent
*/
for (i = 0; i <= old->curframe; i++) {
insn_idx = i == old->curframe
? env->insn_idx
: old->frame[i + 1]->callsite;
insn_idx = frame_insn_idx(old, i);
if (old->frame[i]->callsite != cur->frame[i]->callsite)
return false;
if (!func_states_equal(env, old->frame[i], cur->frame[i], insn_idx, exact))
@ -19687,6 +19693,7 @@ static int do_check(struct bpf_verifier_env *env)
}
state->last_insn_idx = env->prev_insn_idx;
state->insn_idx = env->insn_idx;
if (is_prune_point(env, env->insn_idx)) {
err = is_state_visited(env, env->insn_idx);