Re: [PATCH bpf-next v2 01/11] LoongArch: BPF: Fix tail call count pointer offset for arena programs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] The newly added multi-line comments violate the BPF subsystem's preferred comment style.
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commit a7174bab96fc4c6edb488f83bc8733f74eac78c7
Author: George Guo <guodongtai@kylinos.cn>

LoongArch: BPF: Fix tail call count pointer offset for arena programs

This commit replaces the BPF_TAIL_CALL_CNT_PTR_STACK_OFF macro with a helper
function, tail_call_cnt_ptr_stack_off(). This function properly accounts for 
the REG_ARENA slot in arena programs, resolving an issue where the JIT loaded
the counter value instead of the tail call count pointer.

Link: https://lore.kernel.org/all/20260629085511.359546-1-dongtai.guo@linux.dev

> diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
> index ad7e28375aa95..5e34e9e3f5086 100644
> --- a/arch/loongarch/net/bpf_jit.c
> +++ b/arch/loongarch/net/bpf_jit.c
> @@ -25,7 +25,23 @@
>  
>  #define REG_TCC		LOONGARCH_GPR_A6
>  #define REG_ARENA	LOONGARCH_GPR_S6 /* For storing arena_vm_start */
> -#define BPF_TAIL_CALL_CNT_PTR_STACK_OFF(stack) (round_up(stack, 16) - 80)
> +
> +static int tail_call_cnt_ptr_stack_off(struct jit_ctx *ctx)
> +{
> +	/* Ten words are pushed below the BPF stack: ra, fp, s0-s5, and the
> +	 * tail call count plus its pointer, which occupy the two deepest
> +	 * slots of the callee-saved area.
> +	 */

[Severity: Low]
This isn't a bug, but does this multi-line comment format adhere to the BPF
subsystem's preferred style? Multi-line comments in BPF-related paths usually
require the opening /* to be on its own line.

> +	int offset = sizeof(long) * 10;
> +
> +	/* An arena program reserves one extra word above them (REG_ARENA),
> +	 * which pushes the tail call count pointer down by one slot.
> +	 */

[Severity: Low]
This isn't a bug, but this comment also doesn't follow the preferred BPF
subsystem multi-line comment style of placing the opening /* on its own line.

> +	if (ctx->arena_vm_start)
> +		offset += sizeof(long);
> +
> +	return round_up(ctx->stack_size, 16) - offset;
> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260702022322.51033-1-dongtai.guo@linux.dev?part=1