[Xen-changelog] [xen-unstable] tools/x86_64: Fix cpuid() inline asm to not clobber stack's red zone

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir@xxxxxxx>
# Date 1322836274 28800
# Node ID 72f4e4cb7440c6ab64d4c08dfdc3158112cc95ac
# Parent  109b99239b21275ee2249873dcdb9a413741142d
tools/x86_64: Fix cpuid() inline asm to not clobber stack's red zone

Pushing stuff onto the stack on x86-64 when we do not specify
-mno-red-zone is unsafe. Since the complicated asm is due to register
pressure on i386, we simply implement an all-new simpler alternative
for x86-64.

Signed-off-by: Keir Fraser <keir@xxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxxxx>
---


diff -r 109b99239b21 -r 72f4e4cb7440 tools/libxc/xc_cpuid_x86.c
--- a/tools/libxc/xc_cpuid_x86.c        Fri Dec 02 06:07:52 2011 -0800
+++ b/tools/libxc/xc_cpuid_x86.c        Fri Dec 02 06:31:14 2011 -0800
@@ -43,23 +43,23 @@
 static void cpuid(const unsigned int *input, unsigned int *regs)
 {
     unsigned int count = (input[1] == XEN_CPUID_INPUT_UNUSED) ? 0 : input[1];
+#ifdef __i386__
+    /* Use the stack to avoid reg constraint failures with some gcc flags */
     asm (
-#ifdef __i386__
         "push %%ebx; push %%edx\n\t"
-#else
-        "push %%rbx; push %%rdx\n\t"
-#endif
         "cpuid\n\t"
         "mov %%ebx,4(%4)\n\t"
         "mov %%edx,12(%4)\n\t"
-#ifdef __i386__
         "pop %%edx; pop %%ebx\n\t"
+        : "=a" (regs[0]), "=c" (regs[2])
+        : "0" (input[0]), "1" (count), "S" (_regs)
+        : "memory" );
 #else
-        "pop %%rdx; pop %%rbx\n\t"
+    asm (
+        "cpuid"
+        : "=a" (regs[0]), "=b" (regs[1]), "=c" (regs[2]), "=d" (regs[3])
+        : "0" (input[0]), "2" (count) );
 #endif
-        : "=a" (regs[0]), "=c" (regs[2])
-        : "0" (input[0]), "1" (count), "S" (regs)
-        : "memory" );
 }
 
 /* Get the manufacturer brand name of the host processor. */
diff -r 109b99239b21 -r 72f4e4cb7440 tools/misc/xen-detect.c
--- a/tools/misc/xen-detect.c   Fri Dec 02 06:07:52 2011 -0800
+++ b/tools/misc/xen-detect.c   Fri Dec 02 06:31:14 2011 -0800
@@ -35,18 +35,21 @@
 
 static void cpuid(uint32_t idx, uint32_t *regs, int pv_context)
 {
+#ifdef __i386__
+    /* Use the stack to avoid reg constraint failures with some gcc flags */
     asm volatile (
-#ifdef __i386__
-#define R(x) "%%e"#x"x"
-#else
-#define R(x) "%%r"#x"x"
-#endif
-        "push "R(a)"; push "R(b)"; push "R(c)"; push "R(d)"\n\t"
+        "push %%eax; push %%ebx; push %%ecx; push %%edx\n\t"
         "test %1,%1 ; jz 1f ; ud2a ; .ascii \"xen\" ; 1: cpuid\n\t"
         "mov %%eax,(%2); mov %%ebx,4(%2)\n\t"
         "mov %%ecx,8(%2); mov %%edx,12(%2)\n\t"
-        "pop "R(d)"; pop "R(c)"; pop "R(b)"; pop "R(a)"\n\t"
+        "pop %%edx; pop %%ecx; pop %%ebx; pop %%eax\n\t"
         : : "a" (idx), "c" (pv_context), "S" (regs) : "memory" );
+#else
+    asm volatile (
+        "test %5,%5 ; jz 1f ; ud2a ; .ascii \"xen\" ; 1: cpuid\n\t"
+        : "=a" (regs[0]), "=b" (regs[1]), "=c" (regs[2]), "=d" (regs[3])
+        : "0" (idx), "1" (pv_context), "2" (0) );
+#endif
 }
 
 static int check_for_xen(int pv_context)

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-changelog