From: Alan Modra <amodra@gmail.com>
Date: Sat, 17 Aug 2013 09:06:45 +0000 (+0930)
Subject: PowerPC makecontext
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fb2a1205a251c0fd1458fdfffc6641c382e83717;p=thirdparty%2Fglibc.git

PowerPC makecontext
http://sourceware.org/ml/libc-alpha/2013-08/msg00092.html

Use conditional form of branch and link to avoid destroying the cpu
link stack used to predict blr return addresses.

	* sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S: Use
	conditional form of branch and link when obtaining pc.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S: Likewise.
---

diff --git a/ChangeLog b/ChangeLog
index 2e6eb849d50..696a340db1e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2013-10-04  Alan Modra  <amodra@gmail.com>
+
+	* sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S: Use
+	conditional form of branch and link when obtaining pc.
+	* sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S: Likewise.
+
 2013-10-04  Alan Modra  <amodra@gmail.com>
 
 	* sysdeps/unix/sysv/linux/powerpc/powerpc32/getcontext-common.S: Use
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S b/sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S
index 95902b13f97..70e3c976266 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S
@@ -47,7 +47,9 @@ ENTRY(__makecontext)
 #ifdef PIC
 	mflr	r0
 	cfi_register(lr,r0)
-	bl	1f
+	/* Use this conditional form of branch and link to avoid destroying
+	   the cpu link stack used to predict blr return addresses.  */
+	bcl	20,31,1f
 1:	mflr	r6
 	addi	r6,r6,L(exitcode)-1b
 	mtlr	r0
@@ -136,7 +138,9 @@ ENTRY(__novec_makecontext)
 #ifdef PIC
 	mflr	r0
 	cfi_register(lr,r0)
-	bl	1f
+	/* Use this conditional form of branch and link to avoid destroying
+	   the cpu link stack used to predict blr return addresses.  */
+	bcl	20,31,1f
 1:	mflr	r6
 	addi	r6,r6,L(novec_exitcode)-1b
 	mtlr	r0
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S b/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
index 4a166693830..32fc47c3f3d 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
@@ -124,8 +124,10 @@ L(noparms):
 
   /* If the target function returns we need to do some cleanup.  We use a
      code trick to get the address of our cleanup function into the link
-     register.  Do not add any code between here and L(exitcode).  */
-  bl  L(gotexitcodeaddr);
+     register.  Do not add any code between here and L(exitcode).
+     Use this conditional form of branch and link to avoid destroying
+     the cpu link stack used to predict blr return addresses.  */
+  bcl	20,31,L(gotexitcodeaddr);
 
 	/* This is the helper code which gets called if a function which
 	   is registered with 'makecontext' returns.  In this case we