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| author | Jussi Kivilinna <jussi.kivilinna@iki.fi> | 2021-04-28 19:19:15 +0300 |
|---|---|---|
| committer | Jussi Kivilinna <jussi.kivilinna@iki.fi> | 2021-04-28 21:26:17 +0300 |
| commit | ec87511d9cd2dc31434e939b6351d74a38d4ceaa (patch) | |
| tree | abdf2b75b900714ddab86ed7dc69f106b604eb7c /src/hwf-x86.c | |
| parent | 060c378c050e7ec6206358c681a313d6e1967dcf (diff) | |
| download | libgcrypt-ec87511d9cd2dc31434e939b6351d74a38d4ceaa.tar.gz | |
hwf-x86: fix use of wrong operand type
* src/hwf-x86.c (get_cpuid): Use xchg for swapping %ebx back
and forth between operand register.
--
HW feature routine was giving wrong results with certain compiler &
compiler flag combinations on i386. Issue was that "=g" operand was
used which caused problem if compiler allocated %ebx register for
this operand. CPUID assembly block attempts to save %ebx as in older
GCC versions this register was fixed for GOT pointer use and could
not be modified otherwise (could not be used as operand or clobber).
Reported-by: Iru Cai <vimacs@disroot.org>
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Diffstat (limited to 'src/hwf-x86.c')
| -rw-r--r-- | src/hwf-x86.c | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/src/hwf-x86.c b/src/hwf-x86.c index 91e4c411..a1aa02e7 100644 --- a/src/hwf-x86.c +++ b/src/hwf-x86.c @@ -83,14 +83,12 @@ get_cpuid(unsigned int in, unsigned int *eax, unsigned int *ebx, unsigned int regs[4]; asm volatile - ("movl %%ebx, %%edi\n\t" /* Save GOT register. */ - "xorl %%ebx, %%ebx\n\t" + ("xchgl %%ebx, %1\n\t" /* Save GOT register. */ "cpuid\n\t" - "movl %%ebx, %1\n\t" - "movl %%edi, %%ebx\n\t" /* Restore GOT register. */ - : "=a" (regs[0]), "=g" (regs[1]), "=c" (regs[2]), "=d" (regs[3]) - : "0" (in), "2" (0), "3" (0) - : "cc", "edi" + "xchgl %%ebx, %1\n\t" /* Restore GOT register. */ + : "=a" (regs[0]), "=D" (regs[1]), "=c" (regs[2]), "=d" (regs[3]) + : "0" (in), "1" (0), "2" (0), "3" (0) + : "cc" ); if (eax) |