Re: [PATCH bpf v2 1/2] bpf: Factor out stack_map_build_id_set_ip() in stackmap.c

[Mykyta Yatsenko]

On 4/9/26 2:06 AM, Ihor Solodrai wrote:
> Factor out a small helper from stack_map_get_build_id_offset() in
> preparation for adding a sleepable build ID resolution path.
>
> No functional changes.
>
> Signed-off-by: Ihor Solodrai <ihor.solodrai@xxxxxxxxx>
> ---
The refactoring looks correct.
Acked-by: Mykyta Yatsenko <yatsenko@xxxxxxxx>
>   kernel/bpf/stackmap.c | 21 ++++++++++++---------
>   1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
> index da3d328f5c15..4ef0fd06cea5 100644
> --- a/kernel/bpf/stackmap.c
> +++ b/kernel/bpf/stackmap.c
> @@ -152,6 +152,12 @@ static int fetch_build_id(struct vm_area_struct *vma, unsigned char *build_id, b
>   			 : build_id_parse_nofault(vma, build_id, NULL);
>   }
>   
> +static inline void stack_map_build_id_set_ip(struct bpf_stack_build_id *id)
> +{
> +	id->status = BPF_STACK_BUILD_ID_IP;
> +	memset(id->build_id, 0, BUILD_ID_SIZE_MAX);
> +}
> +
>   /*
>    * Expects all id_offs[i].ip values to be set to correct initial IPs.
>    * They will be subsequently:
> @@ -165,23 +171,21 @@ static int fetch_build_id(struct vm_area_struct *vma, unsigned char *build_id, b
>   static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
>   					  u32 trace_nr, bool user, bool may_fault)
>   {
> -	int i;
>   	struct mmap_unlock_irq_work *work = NULL;
>   	bool irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
> +	bool has_user_ctx = user && current && current->mm;
>   	struct vm_area_struct *vma, *prev_vma = NULL;
>   	const char *prev_build_id;
> +	int i;
>   
>   	/* If the irq_work is in use, fall back to report ips. Same
>   	 * fallback is used for kernel stack (!user) on a stackmap with
>   	 * build_id.
>   	 */
> -	if (!user || !current || !current->mm || irq_work_busy ||
> -	    !mmap_read_trylock(current->mm)) {
> +	if (!has_user_ctx || irq_work_busy || !mmap_read_trylock(current->mm)) {
>   		/* cannot access current->mm, fall back to ips */
> -		for (i = 0; i < trace_nr; i++) {
> -			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
> -			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
> -		}
> +		for (i = 0; i < trace_nr; i++)
> +			stack_map_build_id_set_ip(&id_offs[i]);
>   		return;
>   	}
>   
> @@ -196,8 +200,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
>   		vma = find_vma(current->mm, ip);
>   		if (!vma || fetch_build_id(vma, id_offs[i].build_id, may_fault)) {
>   			/* per entry fall back to ips */
> -			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
> -			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
> +			stack_map_build_id_set_ip(&id_offs[i]);
>   			continue;
>   		}
>   build_id_valid: