From: Ulrich Drepper <drepper@redhat.com>
Date: Wed, 14 Apr 1999 13:42:16 +0000 (+0000)
Subject: mmap calls could not be restarted after being interrupted by
X-Git-Tag: glibc-2.16-ports-before-merge~2909
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=45c6c04d8db529cb9b5d534e747318aac5f9334f;p=thirdparty%2Fglibc.git

mmap calls could not be restarted after being interrupted by
a signal.  The parameters on the stack were corrupted by the
signal handler.
---

diff --git a/sysdeps/unix/sysv/linux/arm/mmap.S b/sysdeps/unix/sysv/linux/arm/mmap.S
index f9a773fc689..fcff57c55d1 100644
--- a/sysdeps/unix/sysv/linux/arm/mmap.S
+++ b/sysdeps/unix/sysv/linux/arm/mmap.S
@@ -26,10 +26,26 @@ ENTRY (__mmap)
 	   mmap() takes six, we need to build a parameter block and pass its	
 	   address instead.  The 386 port does a similar trick.  */
 
-	mov	ip, sp
-	stmdb	ip!, {a1-a4}
-	mov	a1, ip
+	/* This code previously moved sp into ip and stored the args using
+	   stmdb ip!, {a1-a4}.  It did not modify sp, so the stack never had 
+	   to be restored after the syscall completed.  It saved an 
+	   instruction and meant no stack cleanup work was required.
+
+	   This will not work in the case of a mmap call being interrupted
+	   by a signal.  If the signal handler uses any stack the arguments
+	   to mmap will be trashed.  The results of a restart of mmap are
+	   then unpredictable. */
+
+	/* store args on the stack */
+	stmdb	sp!, {a1-a4}
+
+	/* do the syscall */
+	mov	a1, sp
 	swi	SYS_ify (mmap)
+
+	/* pop args off the stack. */
+	add	sp, sp, #16
+
 	cmn	r0, $4096
 	bhs	PLTJMP(syscall_error);
 	ret