[PATCH] alpha: Fix stack alignment in makecontext

[Magnus Lindholm]

The Alpha ABI requires the stack pointer to be 16-byte aligned.
However, __makecontext did not realign it after reserving space for
arguments. Depending on uc_stack.ss_size, this could leave the stack
only 8-byte aligned.

Round the new stack pointer down to a 16-byte boundary after reserving
the argument area.

This fixes stdlib/tst-makecontext2.

Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
---
 sysdeps/unix/sysv/linux/alpha/makecontext.S | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sysdeps/unix/sysv/linux/alpha/makecontext.S b/sysdeps/unix/sysv/linux/alpha/makecontext.S
index b0479315d5..1de0dd2653 100644
--- a/sysdeps/unix/sysv/linux/alpha/makecontext.S
+++ b/sysdeps/unix/sysv/linux/alpha/makecontext.S
@@ -38,6 +38,9 @@ ENTRY(__makecontext)
 	s8addq	$1, 0, $2
 	subq	$8, $2, $8
 
+	/* The Alpha ABI requires a 16-byte-aligned stack pointer.  */
+	bic	$8, 15, $8
+
 	/* Copy all parameters.  Switch statement header here.  */
 	ldah	$3, $jumptable($29)	!gprelhigh
 	cmple	$18, 6, $1
-- 
2.53.0