2006-12-13  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* sysdeps/unix/sysv/linux/i386/clone.S: CFI `clone' unwinding
	outermost frame indicator replaced by more unwinders compatible
	termination indication of `PC == 0'.
	* sysdeps/unix/sysv/linux/x86_64/clone.S: Likewise.

--- libc/sysdeps/unix/sysv/linux/i386/clone.S	3 Dec 2006 23:12:36 -0000	1.27
+++ libc/sysdeps/unix/sysv/linux/i386/clone.S	13 Dec 2006 11:20:55 -0000
@@ -68,6 +68,8 @@ ENTRY (BP_SYM (__clone))
 	   thread is started with an alignment of (mod 16).  */
 	andl	$0xfffffff0, %ecx
 	subl	$28,%ecx
+	/* Terminate the stack frame by pretended return address 0.  */
+	movl	$0,16(%ecx)
 	movl	ARG(%esp),%eax		/* no negative argument counts */
 	movl	%eax,12(%ecx)
 
@@ -121,10 +123,15 @@ L(pseudo_end):
 
 L(thread_start):
 	cfi_startproc;
-	/* Clearing frame pointer is insufficient, use CFI.  */
-	cfi_undefined (eip);
-	/* Note: %esi is zero.  */
-	movl	%esi,%ebp	/* terminate the stack frame */
+	/* This CFI recommended way of unwindable function is incompatible
+	   across unwinders incl. the libgcc_s one.
+	   cfi_undefined (eip);
+	   */
+	/* Frame pointer 0 was considered as the stack frame termination
+	   before but it is no longer valid for -fomit-frame-pointer code.
+	   Still keep the backward compatibility and clear the register.
+	   Note: %esi is zero.  */
+	movl	%esi,%ebp
 #ifdef RESET_PID
 	testl	$CLONE_THREAD, %edi
 	je	L(newpid)
--- libc/sysdeps/unix/sysv/linux/x86_64/clone.S	3 Dec 2006 23:12:36 -0000	1.7
+++ libc/sysdeps/unix/sysv/linux/x86_64/clone.S	13 Dec 2006 11:20:55 -0000
@@ -61,8 +61,12 @@ ENTRY (BP_SYM (__clone))
 	testq	%rsi,%rsi		/* no NULL stack pointers */
 	jz	SYSCALL_ERROR_LABEL
 
+	/* Prepare the data located at %rsp after `syscall' below.
+	   Used only 3*8 bytes but the stack is 16 bytes aligned.  */
+	subq	$32,%rsi
+	/* Terminate the stack frame by pretended return address 0.  */
+	movq	$0,16(%rsi)
 	/* Insert the argument onto the new stack.  */
-	subq	$16,%rsi
 	movq	%rcx,8(%rsi)
 
 	/* Save the function pointer.  It will be popped off in the
@@ -90,10 +94,15 @@ L(pseudo_end):
 
 L(thread_start):
 	cfi_startproc;
-	/* Clearing frame pointer is insufficient, use CFI.  */
-	cfi_undefined (rip);
-	/* Clear the frame pointer.  The ABI suggests this be done, to mark
-	   the outermost frame obviously.  */
+	/* This CFI recommended way of unwindable function is incompatible
+	   across unwinders incl. the libgcc_s one.
+	   cfi_undefined (rip);
+	   */
+	/* Frame pointer 0 was considered as the stack frame termination
+	   before but it is no longer valid for -fomit-frame-pointer code.
+	   Still keep the backward compatibility and clear the register,
+	   the ABI suggests this be done, to mark the outermost frame
+	   obviously.  */
 	xorl	%ebp, %ebp
 
 #ifdef RESET_PID