x86/include/arch/cpuid.h: Fix inline assembly
In the cpuid helper functions eax is always written to
by the cpuid instruction, so add it to the output clobbered list.
This prevents GCC from generating code with undefined behaviour
when the function is inlined.
Test: Verified that the generated assembly is sane and runtime
tests showed no "strange" behaviour when calling cpuid
functions.
Change-Id: I5dc0bb620184a355716b9c8d4206d55554b41ab9
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78192
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Krystian Hebel <krystian.hebel@3mdeb.com>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
diff --git a/src/arch/x86/include/arch/cpuid.h b/src/arch/x86/include/arch/cpuid.h
index 70a5beb..b2780be 100644
--- a/src/arch/x86/include/arch/cpuid.h
+++ b/src/arch/x86/include/arch/cpuid.h
@@ -56,39 +56,36 @@
return eax;
}
-static inline uint32_t cpuid_ebx(const uint32_t eax)
+static inline uint32_t cpuid_ebx(uint32_t eax)
{
uint32_t ebx;
asm volatile(
"cpuid;"
- : "=b" (ebx)
- : "a" (eax)
- : "ecx", "edx");
+ : "=b" (ebx), "+a" (eax)
+ :: "ecx", "edx");
return ebx;
}
-static inline uint32_t cpuid_ecx(const uint32_t eax)
+static inline uint32_t cpuid_ecx(uint32_t eax)
{
uint32_t ecx;
asm volatile(
"cpuid;"
- : "=c" (ecx)
- : "a" (eax)
- : "ebx", "edx");
+ : "=c" (ecx), "+a" (eax)
+ :: "ebx", "edx");
return ecx;
}
-static inline uint32_t cpuid_edx(const uint32_t eax)
+static inline uint32_t cpuid_edx(uint32_t eax)
{
uint32_t edx;
asm volatile(
"cpuid;"
- : "=d" (edx)
- : "a" (eax)
- : "ebx", "ecx");
+ : "=d" (edx), "+a" (eax)
+ :: "ebx", "ecx");
return edx;
}