From 766c7efe28fb066252eeb9b8e47e22970307c09e Mon Sep 17 00:00:00 2001
From: Chris Dearman <chris.dearman@imgtec.com>
Date: Mon, 16 Dec 2013 14:10:13 -0800
Subject: [PATCH] Allocate additional space on stack for indirect syscall

The caller is only required to allocate 16 bytes on the
stack for a0-a3. syscall is handling up to 6 arguments so
additional space is needed on the stack to avoid corrupting the
callers frame.

Change-Id: I054b31696decc3e17d9c70af18cd278b852235d1
---
 libc/arch-mips/bionic/syscall.S | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/libc/arch-mips/bionic/syscall.S b/libc/arch-mips/bionic/syscall.S
index 60754e82e..af5bcc9ab 100644
--- a/libc/arch-mips/bionic/syscall.S
+++ b/libc/arch-mips/bionic/syscall.S
@@ -32,6 +32,12 @@
     .align 4
     .ent syscall
 
+/*
+ * The caller is only required to allocate 16 bytes of stack for a0-a3.
+ * syscall has up to 6 arguments, so we need space for the extra two arguments.
+ */
+#define STACKSIZE 2*4
+
 syscall:
     .set noreorder
     .cpload $t9
@@ -42,9 +48,11 @@ syscall:
     lw      $a3, 16($sp)
     lw      $t0, 20($sp)
     lw      $t1, 24($sp)
+    subu    $sp, STACKSIZE
     sw      $t0, 16($sp)
     sw      $t1, 20($sp)
     syscall
+    addu    $sp, STACKSIZE
     bnez    $a3, 1f
     move    $a0, $v0
     j       $ra