Re: [PATCH net-next v1] selftests/bpf: Fix insn count expectations in chained global subprogs test

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] The newly introduced multi-line comments violate the mandatory BPF kernel comment style by placing text on the same line as the opening `/*`.
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--- Patch [1]: [PATCH net-next v1] selftests/bpf: Fix insn count expectations in chained global subprogs test ---
commit 0f391b5a2f4f9b30c1e20dfe376da213cfa9c650
Author: Jiayuan Chen <jiayuan.chen@linux.dev>

selftests/bpf: Fix insn count expectations in chained global subprogs test

This commit rewrites the involved subprograms as naked functions with
hand-written instruction sequences using only v1 instructions. This ensures
that the verified instruction counts no longer depend on CPU version or
compiler codegen, resolving failures on the cpuv4 flavor.

Fixes: c2e6c7de8830 ("bpf: Show more useful info in stack depth stats")

> diff --git a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c
> index 7b65eea97ebc2..3352dc177ec15 100644
> --- a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c
> +++ b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c
> @@ -25,9 +25,22 @@ __noinline long global_bad(void)
>  	return arr[unkn_idx]; /* BOOM */
>  }
>  
> -__noinline long global_good(void)
> +/* Insn counts asserted in chained_global_func_calls_success() depend on
> + * the exact instruction sequences of this function and its callers, so
> + * they are written in inline asm to be independent of compiler codegen.
> + */

[Severity: Low]
This isn't a bug, but does this violate the preferred BPF multi-line comment
style? The BPF subsystem guidelines specify that multi-line comments should
have the opening /* on its own line.

> +__naked __noinline long global_good(void)

[ ... ]

> @@ -56,13 +73,30 @@ __msg("subprog 0 (chained_global_func_calls_success) main insns_self 7 insns_tot
>  __msg("subprog {{[0-9]+}} (global_calls_good_only) global insns_self 2 insns_total 2 stack")
>  __msg("subprog {{[0-9]+}} (global_good) global insns_self 5 insns_total 5 stack")
>  __msg("processed 14 insns")
> -int chained_global_func_calls_success(void)
> -{
> -	int sum = 0;
> -
> -	if (call_dead_subprog)
> -		sum += global_dead();
> -	return global_calls_good_only() + sum;
> +__naked int chained_global_func_calls_success(void)
> +{
> +	/* int sum = 0;
> +	 * if (call_dead_subprog)
> +	 *	sum += global_dead();
> +	 * return global_calls_good_only() + sum;
> +	 *
> +	 * call_dead_subprog is known false, so 7 insns are processed:
> +	 * the branch to l0 is always taken and global_dead() is dead code.
> +	 */

[Severity: Low]
This isn't a bug, but it looks like this comment block also places text on
the same line as the opening /*. Could this be updated to place the /* on
its own line to match the rest of the BPF subsystem?

> +	asm volatile (

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260813051635.121670-1-jiayuan.chen@linux.dev?part=1