xserver/fb fbmmx.c,1.12,1.13

[Billy Biggs]

Committed by: vektor

Update of /cvs/xserver/xserver/fb
In directory gabe:/tmp/cvs-serv20509/fb

Modified Files:
	fbmmx.c 
Log Message:
2005-08-27  Billy Biggs  <vektor at dumbterm.net>

	* fb/fbmmx.c (detectCPUFeatures): Make the code work with
	-fomit-frame-pointer by making sure that %esp isn't modified at
	the point where we access output operands. (#4269, Patch from
	Ronald Wahl)



Index: fbmmx.c
===================================================================
RCS file: /cvs/xserver/xserver/fb/fbmmx.c,v
retrieving revision 1.12
retrieving revision 1.13
diff -u -d -r1.12 -r1.13
--- fbmmx.c	19 Aug 2005 02:08:28 -0000	1.12
+++ fbmmx.c	28 Aug 2005 02:03:17 -0000	1.13
@@ -2487,28 +2487,38 @@
     vendor[0] = 0;
     vendor[12] = 0;
     /* see p. 118 of amd64 instruction set manual Vol3 */
-    __asm__ ("push %%ebx\n"
-             "pushf\n"
+    /* We need to be careful about the handling of %ebx and
+     * %esp here. We can't declare either one as clobbered
+     * since they are special registers (%ebx is the "PIC
+     * register" holding an offset to global data, %esp the
+     * stack pointer), so we need to make sure they have their
+     * original values when we access the output operands.
+     */
+    __asm__ ("pushf\n"
              "pop %%eax\n"
-             "mov %%eax, %%ebx\n"
+             "mov %%eax, %%ecx\n"
              "xor $0x00200000, %%eax\n"
              "push %%eax\n"
              "popf\n"
              "pushf\n"
              "pop %%eax\n"
              "mov $0x0, %%edx\n"
-             "xor %%ebx, %%eax\n"
+             "xor %%ecx, %%eax\n"
              "jz skip\n"
 
              "mov $0x00000000, %%eax\n"
+	     "push %%ebx\n"
              "cpuid\n"
-             "mov %%ebx, %1\n"
+             "mov %%ebx, %%eax\n"
+	     "pop %%ebx\n"
+             "mov %%eax, %1\n"
              "mov %%edx, %2\n"
              "mov %%ecx, %3\n"
              "mov $0x00000001, %%eax\n"
+	     "push %%ebx\n"
              "cpuid\n"
+	     "pop %%ebx\n"
              "skip:\n"
-             "pop %%ebx\n"
              "mov %%edx, %0\n"
              : "=r" (result), 
                "=m" (vendor[0]), 
@@ -2542,8 +2552,8 @@
                     "mov $0x80000001, %%eax\n"
                     "cpuid\n"
                     "skip2:\n"
-                    "mov %%edx, %0\n"
                     "pop %%ebx\n"
+                    "mov %%edx, %0\n"
                     : "=r" (result)
                     :
                     : "%eax", "%ecx", "%edx"