Received-SPF: pass (google.com: domain of linux-kernel+bounces-133659-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Precedence: bulk
MIME-Version: 1.0
References: <20240405204919.1003409-1-arnd@kernel.org>
In-Reply-To: <20240405204919.1003409-1-arnd@kernel.org>
From: Justin Stitt <justinstitt@google.com>
Date: Fri, 5 Apr 2024 14:55:01 -0700
Message-ID: <CAFhGd8rj+czcvzKsFjcBs1L_jJiar1H9n7mHmnfWKNH0MpFueA@mail.gmail.com>
Subject: Re: [PATCH] x86: microcode: avoid -Wformat warning with clang-15
To: Arnd Bergmann <arnd@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>, Arnd Bergmann <arnd@arndb.de>, Thomas Gleixner <tglx@linutronix.de>, 
	Ingo Molnar <mingo@redhat.com>, Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org, 
	"H. Peter Anvin" <hpa@zytor.com>, Nathan Chancellor <nathan@kernel.org>, 
	Nick Desaulniers <ndesaulniers@google.com>, Bill Wendling <morbo@google.com>, 
	Ashok Raj <ashok.raj@intel.com>, Nathan Fontenot <nathan.fontenot@amd.com>, 
	Paolo Bonzini <pbonzini@redhat.com>, linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Fri, Apr 5, 2024 at 1:49=E2=80=AFPM Arnd Bergmann <arnd@kernel.org> wrot=
e:
>
> From: Arnd Bergmann <arnd@arndb.de>
>
> Older versions of clang show a warning for amd.c after a fix for a gcc
> warning:
>
> arch/x86/kernel/cpu/microcode/amd.c:478:47: error: format specifies type =
'unsigned char' but the argument has type 'u16' (aka 'unsigned short') [-We=
rror,-Wformat]
>                          "amd-ucode/microcode_amd_fam%02hhxh.bin", family=
);
>                                                      ~~~~~~        ^~~~~~
>                                                      %02hx
>
> In clang-16 and higher, this warning is disabled by default, but clang-15=
 is
> still supported, and it's trivial to avoid by adapting the types accordin=
g
> to the range of the passed data and the format string.
>
> Fixes: 2e9064faccd1 ("x86/microcode/amd: Fix snprintf() format string war=
ning in W=3D1 build")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Yeah the family only needs a byte so this is OK.

Reviewed-by: Justin Stitt <justinstitt@google.com>

> ---
>  arch/x86/kernel/cpu/microcode/amd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/mi=
crocode/amd.c
> index 13b45b9c806d..620f0af713ca 100644
> --- a/arch/x86/kernel/cpu/microcode/amd.c
> +++ b/arch/x86/kernel/cpu/microcode/amd.c
> @@ -465,7 +465,7 @@ static bool early_apply_microcode(u32 cpuid_1_eax, u3=
2 old_rev, void *ucode, siz
>         return !__apply_microcode_amd(mc);
>  }
>
> -static bool get_builtin_microcode(struct cpio_data *cp, unsigned int fam=
ily)
> +static bool get_builtin_microcode(struct cpio_data *cp, u8 family)
>  {
>         char fw_name[36] =3D "amd-ucode/microcode_amd.bin";
>         struct firmware fw;
> --
> 2.39.2
>