[PATCH bpf-next] bpf, arm64: Remove unused-but-set function and variable.

[PATCH bpf-next] bpf, arm64: Remove unused-but-set function and variable.

[Alexei Starovoitov]

From: Alexei Starovoitov <ast@kernel.org>

Remove unused-but-set function and variable to fix the build warning:
   arch/arm64/net/bpf_jit_comp.c: In function 'arch_bpf_trampoline_size':
>> arch/arm64/net/bpf_jit_comp.c:2547:6: warning: variable 'nregs' set but not used [-Wunused-but-set-variable]
    2547 |  int nregs, ret;
         |      ^~~~~

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202505280643.h0qYcSCM-lkp@intel.com/
Fixes: 9014cf56f13d ("bpf, arm64: Support up to 12 function arguments")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 arch/arm64/net/bpf_jit_comp.c | 21 ++-------------------
 1 file changed, 2 insertions(+), 19 deletions(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index b5c3ab623536..14d4c6ac4ca0 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -2520,21 +2520,6 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
 	return ctx->idx;
 }
 
-static int btf_func_model_nregs(const struct btf_func_model *m)
-{
-	int nregs = m->nr_args;
-	int i;
-
-	/* extra registers needed for struct argument */
-	for (i = 0; i < MAX_BPF_FUNC_ARGS; i++) {
-		/* The arg_size is at most 16 bytes, enforced by the verifier. */
-		if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG)
-			nregs += (m->arg_size[i] + 7) / 8 - 1;
-	}
-
-	return nregs;
-}
-
 int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
 			     struct bpf_tramp_links *tlinks, void *func_addr)
 {
@@ -2543,10 +2528,8 @@ int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
 		.idx = 0,
 	};
 	struct bpf_tramp_image im;
-	struct arg_aux  aaux;
-	int nregs, ret;
-
-	nregs = btf_func_model_nregs(m);
+	struct arg_aux aaux;
+	int ret;
 
 	ret = calc_arg_aux(m, &aaux);
 	if (ret < 0)
-- 
2.47.1

Re: [PATCH bpf-next] bpf, arm64: Remove unused-but-set function and variable.

[Xu Kuohai]

On 5/28/2025 8:27 AM, Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@kernel.org>
> 
> Remove unused-but-set function and variable to fix the build warning:
>     arch/arm64/net/bpf_jit_comp.c: In function 'arch_bpf_trampoline_size':
>>> arch/arm64/net/bpf_jit_comp.c:2547:6: warning: variable 'nregs' set but not used [-Wunused-but-set-variable]
>      2547 |  int nregs, ret;
>           |      ^~~~~
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202505280643.h0qYcSCM-lkp@intel.com/
> Fixes: 9014cf56f13d ("bpf, arm64: Support up to 12 function arguments")
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---
>   arch/arm64/net/bpf_jit_comp.c | 21 ++-------------------
>   1 file changed, 2 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index b5c3ab623536..14d4c6ac4ca0 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -2520,21 +2520,6 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
>   	return ctx->idx;
>   }
>   
> -static int btf_func_model_nregs(const struct btf_func_model *m)
> -{
> -	int nregs = m->nr_args;
> -	int i;
> -
> -	/* extra registers needed for struct argument */
> -	for (i = 0; i < MAX_BPF_FUNC_ARGS; i++) {
> -		/* The arg_size is at most 16 bytes, enforced by the verifier. */
> -		if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG)
> -			nregs += (m->arg_size[i] + 7) / 8 - 1;
> -	}
> -
> -	return nregs;
> -}
> -
>   int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
>   			     struct bpf_tramp_links *tlinks, void *func_addr)
>   {
> @@ -2543,10 +2528,8 @@ int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
>   		.idx = 0,
>   	};
>   	struct bpf_tramp_image im;
> -	struct arg_aux  aaux;
> -	int nregs, ret;
> -
> -	nregs = btf_func_model_nregs(m);
> +	struct arg_aux aaux;
> +	int ret;
>   
>   	ret = calc_arg_aux(m, &aaux);
>   	if (ret < 0)

Oops, sorry for not noticing that nregs is set but not used.

Now that the number of regs for both struct and non-struct
args is calculated in calc_arg_aux(), we can safely drop
btf_func_model_nregs().

Acked-by: Xu Kuohai <xukuohai@huawei.com>

Re: [PATCH bpf-next] bpf, arm64: Remove unused-but-set function and variable.

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Tue, 27 May 2025 17:27:04 -0700 you wrote:
> From: Alexei Starovoitov <ast@kernel.org>
> 
> Remove unused-but-set function and variable to fix the build warning:
>    arch/arm64/net/bpf_jit_comp.c: In function 'arch_bpf_trampoline_size':
> >> arch/arm64/net/bpf_jit_comp.c:2547:6: warning: variable 'nregs' set but not used [-Wunused-but-set-variable]
>     2547 |  int nregs, ret;
>          |      ^~~~~
> 
> [...]

Here is the summary with links:
  - [bpf-next] bpf, arm64: Remove unused-but-set function and variable.
    https://git.kernel.org/bpf/bpf-next/c/c5cebb241e27

You are awesome, thank you!
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