From: Arnd Bergmann <arnd@kernel.org>
To: Bill Metzenthen <billm@melbpc.org.au>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, Nathan Chancellor <nathan@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>, "H. Peter Anvin" <hpa@zytor.com>,
Nick Desaulniers <nick.desaulniers+lkml@gmail.com>,
Bill Wendling <morbo@google.com>,
Justin Stitt <justinstitt@google.com>,
linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: [PATCH] x86: math-emu: fix div_Xsig prototype
Date: Thu, 7 Aug 2025 22:53:28 +0200 [thread overview]
Message-ID: <20250807205334.123231-1-arnd@kernel.org> (raw)
From: Arnd Bergmann <arnd@arndb.de>
The third argument of div_Xsig() is the output of the division, but is marked
'const', which means the compiler is not expecting it to be updated and may
generate bad code around the call. clang-21 now warns about the pattern since
an uninitialized variable is passed into two 'const' arguments by reference:
arch/x86/math-emu/poly_atan.c:93:28: error: variable 'argSignif' is uninitialized when passed as a const pointer argument here [-Werror,-Wuninitialized-const-pointer]
93 | div_Xsig(&Numer, &Denom, &argSignif);
| ^~~~~~~~~
arch/x86/math-emu/poly_l2.c:195:29: error: variable 'argSignif' is uninitialized when passed as a const pointer argument here [-Werror,-Wuninitialized-const-pointer]
195 | div_Xsig(&Numer, &Denom, &argSignif);
| ^~~~~~~~~
The implementation is in assembly, so the problem has gone unnoticed since the
code was added in the linux-1.1 days. Remove the 'const' marker here.
Fixes: e19a1bdb835c ("Import 1.1.38")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/x86/math-emu/poly.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/math-emu/poly.h b/arch/x86/math-emu/poly.h
index fc1c887ca073..654bfe4e29a0 100644
--- a/arch/x86/math-emu/poly.h
+++ b/arch/x86/math-emu/poly.h
@@ -39,7 +39,7 @@ asmlinkage void mul_Xsig_Xsig(Xsig *dest, const Xsig *mult);
asmlinkage void shr_Xsig(Xsig *, const int n);
asmlinkage int round_Xsig(Xsig *);
asmlinkage int norm_Xsig(Xsig *);
-asmlinkage void div_Xsig(Xsig *x1, const Xsig *x2, const Xsig *dest);
+asmlinkage void div_Xsig(Xsig *x1, const Xsig *x2, Xsig *dest);
/* Macro to extract the most significant 32 bits from a long long */
#define LL_MSW(x) (((unsigned long *)&x)[1])
--
2.39.5
reply other threads:[~2025-08-07 20:53 UTC|newest]
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