[2.23, PATCH] BZ #18661: Align stack to 16 bytes when calling __setcontext

[H.J. Lu]

Don't use pop to restore %rdi so that stack is aligned to 16 bytes
when calling __setcontext.

I am planning to check it in after 2.22 is branched.

H.J.
--

	[BZ #18661]
	* sysdeps/unix/sysv/linux/x86_64/__start_context.S
	(__start_context): Don't use pop to restore %rdi so that stack
	is aligned to 16 bytes when calling __setcontext.
---
 sysdeps/unix/sysv/linux/x86_64/__start_context.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/x86_64/__start_context.S b/sysdeps/unix/sysv/linux/x86_64/__start_context.S
index 52a5afa..96366e0 100644
--- a/sysdeps/unix/sysv/linux/x86_64/__start_context.S
+++ b/sysdeps/unix/sysv/linux/x86_64/__start_context.S
@@ -31,8 +31,8 @@ ENTRY(__start_context)
 	   on the stack pointer for the next context.  */
 	movq	%rbx, %rsp
 
-	popq	%rdi			/* This is the next context.  */
-	cfi_adjust_cfa_offset(-8)
+	/* Don't use pop here so that stack is aligned to 16 bytes.  */
+	movq	(%rsp), %rdi		/* This is the next context.  */
 	testq	%rdi, %rdi
 	je	2f			/* If it is zero exit.  */
 
-- 
2.4.3