[uml-devel] [PATCH 4/3] UML - Add missing __volatile__

[uml-devel] [PATCH 4/3] UML - Add missing __volatile__

[Jeff Dike]

We were missing __volatile__ on some bits of asm in the segfault
handlers.  On x86_64, this was messing up the move from %rdx to uc
because that was moved to after the GET_FAULTINFO_FROM_SC, which
changed %rdx.

Also changed the other bit of asm and the one in the i386 handler to
prevent any similar occurrences.

Signed-off-by: Jeff Dike <jdike@addtoit.com>

Index: linux-2.6.16-mm/arch/um/sys-x86_64/stub_segv.c
===================================================================
--- linux-2.6.16-mm.orig/arch/um/sys-x86_64/stub_segv.c	2006-01-03 17:39:46.000000000 -0500
+++ linux-2.6.16-mm/arch/um/sys-x86_64/stub_segv.c	2006-04-10 19:56:10.000000000 -0400
@@ -33,7 +33,7 @@ stub_segv_handler(int sig)
 	struct ucontext *uc;
         int pid;
 
-	__asm__("movq %%rdx, %0" : "=g" (uc) :);
+	__asm__ __volatile__("movq %%rdx, %0" : "=g" (uc) :);
 	GET_FAULTINFO_FROM_SC(*((struct faultinfo *) UML_CONFIG_STUB_DATA),
 			      &uc->uc_mcontext);
 
@@ -44,8 +44,8 @@ stub_segv_handler(int sig)
 	 * the signal frame.  So, we use the ucontext pointer, which we know
 	 * already, to get the signal frame pointer, and add 8 to that.
 	 */
-	__asm__("movq %0, %%rsp; movq %1, %%rax ; syscall": :
-		"g" ((unsigned long) container_of(uc, struct rt_sigframe, 
-						  uc) + 8),
-                "g" (__NR_rt_sigreturn));
+	__asm__ __volatile__("movq %0, %%rsp; movq %1, %%rax ; syscall": :
+                             "g" ((unsigned long)
+                                  container_of(uc, struct rt_sigframe, uc) + 8),
+                             "g" (__NR_rt_sigreturn));
 }
Index: linux-2.6.16-mm/arch/um/sys-i386/stub_segv.c
===================================================================
--- linux-2.6.16-mm.orig/arch/um/sys-i386/stub_segv.c	2006-01-03 17:39:46.000000000 -0500
+++ linux-2.6.16-mm/arch/um/sys-i386/stub_segv.c	2006-04-10 19:55:53.000000000 -0400
@@ -27,6 +27,6 @@ stub_segv_handler(int sig)
 	 * the stack in its original form when we do the sigreturn here, by
 	 * hand.
 	 */
-	__asm__("mov %0,%%esp ; movl %1, %%eax ; "
-		"int $0x80" : : "a" (sc), "g" (__NR_sigreturn));
+	__asm__ __volatile__("mov %0,%%esp ; movl %1, %%eax ; "
+			     "int $0x80" : : "a" (sc), "g" (__NR_sigreturn));
 }



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