linux-kernel - [PATCH] x86: microcode: avoid -Wformat warning with clang-15

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Message-Id: <20240405204919.1003409-1-arnd@kernel.org>
Date: Fri,  5 Apr 2024 22:49:07 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: Arnd Bergmann <arnd@...db.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Ashok Raj <ashok.raj@...el.com>,
	Nathan Fontenot <nathan.fontenot@....com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH] x86: microcode: avoid -Wformat warning with clang-15

From: Arnd Bergmann <arnd@...db.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') [-Werror,-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 according
to the range of the passed data and the format string.

Fixes: 2e9064faccd1 ("x86/microcode/amd: Fix snprintf() format string warning in W=1 build")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 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/microcode/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, u32 old_rev, void *ucode, siz
 	return !__apply_microcode_amd(mc);
 }
 
-static bool get_builtin_microcode(struct cpio_data *cp, unsigned int family)
+static bool get_builtin_microcode(struct cpio_data *cp, u8 family)
 {
 	char fw_name[36] = "amd-ucode/microcode_amd.bin";
 	struct firmware fw;
-- 
2.39.2