Mcount should not clobber any registers.

diff --git a/sys/cpu/i386/include/profile.h b/sys/cpu/i386/include/profile.h
index dcb2689..c3c6280 100644
--- a/sys/cpu/i386/include/profile.h
+++ b/sys/cpu/i386/include/profile.h
@@ -92,6 +92,9 @@
 void \
 mcount(void) \
 { \
+	register int c asm("ecx"); \
+	register int d asm("edx"); \
+	register int a asm("eax"); \
 	uintfptr_t selfpc, frompc; \
 	/* \
 	 * Find the return address for mcount, \
@@ -99,6 +102,9 @@ mcount(void) \
 	 * \
 	 * selfpc = pc pushed by call to mcount \
 	 */ \
+	asm("push %%ecx" : : "r" (c) : "memory"); \
+	asm("push %%edx" : : "r" (d): "memory"); \
+	asm("push %%eax" : : "r" (a) : "memory"); \
 	asm("movl 4(%%ebp),%0" : "=r" (selfpc)); \
 	/* \
 	 * frompc = pc pushed by call to mcount's caller. \
@@ -109,6 +115,9 @@ mcount(void) \
 	asm("movl (%%ebp),%0" : "=r" (frompc)); \
 	frompc = ((uintfptr_t *)frompc)[1]; \
 	_mcount(frompc, selfpc); \
+	asm volatile ("pop %%eax" : "=r" (a) : ); \
+	asm volatile ("pop %%edx" : "=r" (d) : ); \
+	asm volatile ("pop %%ecx" : "=r" (c) : ); \
 }
 
 typedef	unsigned int	uintfptr_t;