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bpf: Fix arg_track_join log to use sa prefix for stack arg slots

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arg_track_join() logs state transitions at CFG merge points. For
stack arg slots (r >= MAX_BPF_REG), it printed "r11:", "r12:", etc.,
which is misleading since r11 is a special register (BPF_REG_PARAMS)
not meaningful to the user.

Fix it to print "sa0:", "sa1:", etc., matching the per-instruction
transition log in arg_track_log() which already uses the "sa" prefix.

Update the existing stack_arg_pruning_type_mismatch selftest to expect
the corrected format.

Fixes: 2af4e79277 ("bpf: Extend liveness analysis to track stack argument slots")
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260515225056.823086-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Yonghong Song
2026-05-15 15:50:56 -07:00
committed by Alexei Starovoitov
parent 0e2647792f
commit d1dbe443a0
2 changed files with 4 additions and 2 deletions
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kernel/bpf/liveness.c
+3 -1
View File
@@ -806,7 +806,9 @@ static bool arg_track_join(struct bpf_verifier_env *env, int idx, int target, in
return true;
verbose(env, "arg JOIN insn %d -> %d ", idx, target);
if (r >= 0)
if (r >= MAX_BPF_REG)
verbose(env, "sa%d: ", r - MAX_BPF_REG);
else if (r >= 0)
verbose(env, "r%d: ", r);
else
verbose(env, "fp%+d: ", r * 8);
tools/testing/selftests/bpf/progs/verifier_stack_arg.c
+1 -1
View File
@@ -117,7 +117,7 @@ __description("stack_arg: pruning with different stack arg types")
__failure __log_level(2)
__flag(BPF_F_TEST_STATE_FREQ)
__msg("arg JOIN insn 9 -> 10 r1: fp0-8 + _ => fp0-8|fp0+0")
__msg("arg JOIN insn 9 -> 10 r11: fp0-8 + _ => fp0-8|fp0+0")
__msg("arg JOIN insn 9 -> 10 sa0: fp0-8 + _ => fp0-8|fp0+0")
__msg("R{{[0-9]}} invalid mem access 'scalar'")
__naked void stack_arg_pruning_type_mismatch(void)
{