Re: [PATCH RFC bpf-next 3/6] selftests/bpf: test cases for loop hierarchy computation

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The expected verifier log output in `fwd_edges_no_loop` incorrectly expects an unconditional jump `(05)` for a conditional jump instruction, which will cause the selftest to fail.
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commit f35c2f4d237eac02dd241fbf85f69d40722f62de
Author: Eduard Zingerman <eddyz87@gmail.com>

selftests/bpf: test cases for loop hierarchy computation

This commit adds test cases covering various branches in bpf_compute_loops
for loop hierarchy computation. It includes tests for single bounded loops,
independent loops, nested loops, diamond control flow graphs, and irreducible
loops.

> diff --git a/tools/testing/selftests/bpf/progs/verifier_loop_hierarchy.c b/tools/testing/selftests/bpf/progs/verifier_loop_hierarchy.c
> new file mode 100644
> index 0000000000000..db26157e3e14a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/verifier_loop_hierarchy.c

[ ... ]

> +/* Case C: forward edges, no loops. */
> +SEC("socket")
> +__success
> +__log_level(2)
> +__msg("          0: {{.*}} (b7) r0 = 1")
> +__msg("          1: {{.*}} (05) goto pc+2")

[Severity: Medium]
Will this test case fail because of a mismatch in the expected verifier log?

The inline assembly below uses "if r0 > 0 goto 1f;", which is a conditional
jump. This translates to opcode 0x25 (if r0 > 0x0 goto pc+2), but the __msg
assertion explicitly expects opcode 0x05 (goto pc+2), which is an
unconditional jump.

> +__msg("          2: {{.*}} (b7) r0 = 2")
> +__msg("          3: {{.*}} (05) goto pc+1")
> +__msg("          4: {{.*}} (b7) r0 = 3")
> +__msg("          5: {{.*}} (95) exit")
> +__naked void fwd_edges_no_loop(void)
> +{
> +	asm volatile ("					\
> +	r0 = 1;						\
> +	if r0 > 0 goto 1f;				\
> +	r0 = 2;						\
> +	goto 2f;					\
> +1:	r0 = 3;						\
> +2:	exit;						\
> +"	::: __clobber_all);
> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260526-better-1m-reporting-v1-0-51e4f2c59780@gmail.com?part=3