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bpf: set 'changed' status if propagate_liveness() did any updates

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Add an out parameter to `propagate_liveness()` to record whether any
new liveness bits were set during its execution.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250611200836.4135542-6-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman 2025-06-11 13:08:31 -07:00 • committed by Alexei Starovoitov
parent 23b37d6165
commit dfb2d4c64b
1 changed files with 7 additions and 2 deletions
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9
kernel/bpf/verifier.c
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@ -18856,12 +18856,15 @@ static int propagate_liveness_reg(struct bpf_verifier_env *env,
*/
static int propagate_liveness(struct bpf_verifier_env *env,
const struct bpf_verifier_state *vstate,
struct bpf_verifier_state *vparent)
struct bpf_verifier_state *vparent,
bool *changed)
{
struct bpf_reg_state *state_reg, *parent_reg;
struct bpf_func_state *state, *parent;
int i, frame, err = 0;
bool tmp;
changed = changed ?: &tmp;
if (vparent->curframe != vstate->curframe) {
WARN(1, "propagate_live: parent frame %d current frame %d\n",
vparent->curframe, vstate->curframe);
@ -18880,6 +18883,7 @@ static int propagate_liveness(struct bpf_verifier_env *env,
&parent_reg[i]);
if (err < 0)
return err;
*changed |= err > 0;
if (err == REG_LIVE_READ64)
mark_insn_zext(env, &parent_reg[i]);
}
@ -18891,6 +18895,7 @@ static int propagate_liveness(struct bpf_verifier_env *env,
state_reg = &state->stack[i].spilled_ptr;
err = propagate_liveness_reg(env, state_reg,
parent_reg);
*changed |= err > 0;
if (err < 0)
return err;
}
@ -19266,7 +19271,7 @@ hit:
* they'll be immediately forgotten as we're pruning
* this state and will pop a new one.
*/
err = propagate_liveness(env, &sl->state, cur);
err = propagate_liveness(env, &sl->state, cur, NULL);
/* if previous state reached the exit with precision and
* current state is equivalent to it (except precision marks)