cpuid: fix build on 64-bit systems
authorAhmed Samy <f.fallen45@gmail.com>
Fri, 11 Oct 2013 11:05:03 +0000 (13:05 +0200)
committerAhmed Samy <f.fallen45@gmail.com>
Fri, 11 Oct 2013 11:05:03 +0000 (13:05 +0200)
Some instructions needed to use their correct prefix and correct
registers, such as "eax -> rax" and "pushl -> pushq"

Reported-by: Emilio G. Cota <cota@braap.org>
Tested-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Ahmed Samy <f.fallen45@gmail.com>
ccan/cpuid/cpuid.c

index 6133e13f03c420144348f8d08ea9901d643985f9..cab887b16f9236c83148c9aee9ca6b1f91636e1d 100644 (file)
@@ -108,27 +108,58 @@ static bool has_feature(int feature, uint32_t ecx, uint32_t edx)
 
 bool cpuid_is_supported(void)
 {
-       int ret = 0;
+       /* The following assembly code uses EAX as the return value,
+        * but we store the value of EAX into ret since GCC uses EAX
+        * as the return register for every C function.  That's a double
+        * operation, but there's no other way to do this unless doing this
+        * function entirely in assembly.  */
+
+       /* This check is to make sure that the compiler is actually compiling
+        * for 64-bit.
+        *
+        * The compiler can be 32-bit and the system 64-bit so the 
+        * following would be true:
+        *      #if defined(__x86_64) ...
+        */
+
+#if UINTPTR_MAX == 0xffffffffffffffff
+#define ASM_PUSHF      "pushfq\n\t"
+#define ASM_POPF       "popfq\n\t"
+#define ASM_PUSHEAX    "pushq %%rax\n\t"
+#define ASM_POPEAX     "popq %%rax\n\t"
+#define ASM_PUSHECX    "popq %%rcx\n\t"
+#elif UINTPTR_MAX == 0xffffffff
+#define ASM_PUSHF      "pushfl\n\t"
+#define ASM_POPF       "popfl\n\t"
+#define ASM_PUSHEAX    "pushl %%eax\n\t"
+#define ASM_POPEAX     "popl %%eax\n\t"
+#define ASM_PUSHECX    "popl %%ecx\n\t"
+#endif
 
+       int ret = 0;
        asm volatile(
-               "pushfl\n\t"
-               "popl %%eax\n\t"
+               ASM_PUSHF
+               ASM_POPEAX
                "movl %%eax, %%ecx\n\t"
                "xorl $0x200000, %%eax\n\t"
-               "pushl %%eax\n\t"
-               "popfl\n\t"
-
-               "pushfl\n\t"
-               "popl %%eax\n\t"
+               ASM_PUSHEAX
+               ASM_POPF
+               ASM_PUSHF
+               ASM_POPEAX
                "xorl %%ecx, %%eax\n\t"
                "shrl $21, %%eax\n\t"
                "andl $1, %%eax\n\t"
-               "pushl %%ecx\n\t"
-               "popfl\n\t"
-
+               ASM_PUSHECX
+               ASM_POPF
                : "=a" (ret)
        );
 
+#undef ASM_PUSHF
+#undef ASM_POPF
+#undef ASM_PUSHEAX
+#undef ASM_POPEAX
+#undef ASM_PUSHECX
+
        return !!ret;
 }