Re: [PATCH bpf-next] bpf: Remove unused BTF_FMODEL_STRUCT_ARG

On Sun, Aug 02, 2026 at 10:27:26PM -0700, Yonghong Song wrote:
> Commit 814cba835ef6 ("bpf, x86: Fix trampoline stack size for 128-bit
> arguments") changed the x86 trampoline to compute the number of
> registers from arg_size for every argument, which removed the last user
> of BTF_FMODEL_STRUCT_ARG. No other architecture or verifier code looks
> at the flag, so remove the macro and the code in __get_type_fmodel_flags()
> which sets it.
> 
> Keep BTF_FMODEL_SIGNED_ARG at BIT(1) rather than renumbering it to
> BIT(0), so BIT(0) is available for a future flag.
> 
> No functional change.
> 
> Signed-off-by: Yonghong Song <[email protected]>

Acked-by: Jiri Olsa <[email protected]>

jirka

> ---
>  include/linux/bpf.h | 3 ---
>  kernel/bpf/btf.c    | 2 --
>  2 files changed, 5 deletions(-)
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 356884587ae1..73bacfc6444d 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1207,9 +1207,6 @@ struct bpf_prog_offload {
>  	u32			jited_len;
>  };
>  
> -/* The argument is a structure or a union. */
> -#define BTF_FMODEL_STRUCT_ARG		BIT(0)
> -
>  /* The argument is signed. */
>  #define BTF_FMODEL_SIGNED_ARG		BIT(1)
>  
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 5e8ac45ce56a..42414633cf26 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -7533,8 +7533,6 @@ static u8 __get_type_fmodel_flags(const struct btf_type *t)
>  {
>  	u8 flags = 0;
>  
> -	if (btf_type_is_struct(t))
> -		flags |= BTF_FMODEL_STRUCT_ARG;
>  	if (btf_type_is_signed_int(t))
>  		flags |= BTF_FMODEL_SIGNED_ARG;
>  
> -- 
> 2.53.0-Meta
> 
>