46 lines
1.7 KiB
Diff
46 lines
1.7 KiB
Diff
From ec87511d9cd2dc31434e939b6351d74a38d4ceaa Mon Sep 17 00:00:00 2001
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From: Jussi Kivilinna <jussi.kivilinna@iki.fi>
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Date: Wed, 28 Apr 2021 19:19:15 +0300
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Subject: [PATCH] hwf-x86: fix use of wrong operand type
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* src/hwf-x86.c (get_cpuid): Use xchg for swapping %ebx back
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and forth between operand register.
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--
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HW feature routine was giving wrong results with certain compiler &
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compiler flag combinations on i386. Issue was that "=g" operand was
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used which caused problem if compiler allocated %ebx register for
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this operand. CPUID assembly block attempts to save %ebx as in older
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GCC versions this register was fixed for GOT pointer use and could
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not be modified otherwise (could not be used as operand or clobber).
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Reported-by: Iru Cai <vimacs@disroot.org>
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Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
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---
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src/hwf-x86.c | 12 +++++-------
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1 file changed, 5 insertions(+), 7 deletions(-)
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diff --git a/src/hwf-x86.c b/src/hwf-x86.c
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index 91e4c411e..a1aa02e78 100644
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--- a/src/hwf-x86.c
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+++ b/src/hwf-x86.c
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@@ -83,14 +83,12 @@ get_cpuid(unsigned int in, unsigned int *eax, unsigned int *ebx,
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unsigned int regs[4];
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asm volatile
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- ("movl %%ebx, %%edi\n\t" /* Save GOT register. */
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- "xorl %%ebx, %%ebx\n\t"
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+ ("xchgl %%ebx, %1\n\t" /* Save GOT register. */
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"cpuid\n\t"
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- "movl %%ebx, %1\n\t"
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- "movl %%edi, %%ebx\n\t" /* Restore GOT register. */
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- : "=a" (regs[0]), "=g" (regs[1]), "=c" (regs[2]), "=d" (regs[3])
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- : "0" (in), "2" (0), "3" (0)
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- : "cc", "edi"
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+ "xchgl %%ebx, %1\n\t" /* Restore GOT register. */
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+ : "=a" (regs[0]), "=D" (regs[1]), "=c" (regs[2]), "=d" (regs[3])
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+ : "0" (in), "1" (0), "2" (0), "3" (0)
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+ : "cc"
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);
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if (eax)
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