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make sure GCC knows about the effect of the xchg.

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Kalamatee
2025-10-27 16:54:43 +00:00
committed by deadwood
parent 899c4cbb74
commit 33da7fb6eb
1 changed files with 10 additions and 12 deletions
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22
arch/x86_64-all/include/asm/cpu.h
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@ -226,28 +226,26 @@ void cpuid2(unsigned int leaf, unsigned int subleaf,
#if defined(__x86_64__)
unsigned int a = leaf, b, c = subleaf, d;
__asm__ volatile(
"mov %%rbx, %%rdi\n\t"
"mov %%rbx, %%rdi\n\t" /* save RBX (used by PIC) */
"cpuid\n\t"
"xchg %%rbx, %%rdi\n\t"
: "+a"(a), "=r"(b), "+c"(c), "=d"(d)
"xchg %%rbx, %%rdi\n\t" /* restore RBX */
: "+a"(a), "=D"(b), "+c"(c), "=d"(d)
:
: "rdi", "memory");
: "memory");
if (eax) *eax = a;
if (ebx) *ebx = b;
if (ecx) *ecx = c;
if (edx) *edx = d;
#elif defined(__i386__)
unsigned int a, b, c, d;
unsigned int a = leaf, b, c = subleaf, d;
__asm__ volatile(
"xchg %%ebx, %%edi\n\t"
"mov %4, %%eax\n\t"
"mov %5, %%ecx\n\t"
"xchg %%ebx, %%edi\n\t" /* save EBX (PIC-safe) */
"cpuid\n\t"
"xchg %%ebx, %%edi\n\t"
: "=a"(a), "=r"(b), "=c"(c), "=d"(d)
: "r"(leaf), "r"(subleaf)
: "edi", "memory");
"xchg %%ebx, %%edi\n\t" /* restore EBX */
: "=a"(a), "=D"(b), "=c"(c), "=d"(d)
: "a"(leaf), "c"(subleaf)
: "memory");
if (eax) *eax = a;
if (ebx) *ebx = b;
if (ecx) *ecx = c;