[PATCH COMMITTED] Fix NULL ucontext->uc_link handling on sparc64.

[David Miller <davem at davemloft dot net>]

This was pointed out to port maintainers several months ago, I just
didn't get around to implementing the fix until now.  Fortunately
the testcase provided a constant reminder :-)

	* sysdeps/unix/sysv/linux/sparc/sparc64/__start_context.S: New file.
	* sysdeps/unix/sysv/linux/sparc/sparc64/makecontext.c
	(__start_context): Declare.
	(__makecontext_ret): Delete.
	(__makecontext): Hook up __start_context instead of
	__makecontext_ret.
	* sysdeps/unix/sysv/linux/sparc/sparc64/Makefile
	(sysdep_routines): Add __start_context when in stdlib.
---
 ChangeLog                                          | 11 +++++++
 sysdeps/unix/sysv/linux/sparc/sparc64/Makefile     |  4 +++
 .../sysv/linux/sparc/sparc64/__start_context.S     | 36 ++++++++++++++++++++++
 .../unix/sysv/linux/sparc/sparc64/makecontext.c    | 15 ++-------
 4 files changed, 54 insertions(+), 12 deletions(-)
 create mode 100644 sysdeps/unix/sysv/linux/sparc/sparc64/__start_context.S

diff --git a/ChangeLog b/ChangeLog
index 3f7334d..bfccf93 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2012-11-07  David S. Miller  <davem@davemloft.net>
+
+	* sysdeps/unix/sysv/linux/sparc/sparc64/__start_context.S: New file.
+	* sysdeps/unix/sysv/linux/sparc/sparc64/makecontext.c
+	(__start_context): Declare.
+	(__makecontext_ret): Delete.
+	(__makecontext): Hook up __start_context instead of
+	__makecontext_ret.
+	* sysdeps/unix/sysv/linux/sparc/sparc64/Makefile
+	(sysdep_routines): Add __start_context when in stdlib.
+
 2012-11-07  Joseph Myers  <joseph@codesourcery.com>
 
 	* sysdeps/x86/Makefile ($(objpfx)tst-xmmymm.out): Pass $(NM),
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/Makefile b/sysdeps/unix/sysv/linux/sparc/sparc64/Makefile
index 3e29dd8..715af3d 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/Makefile
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/Makefile
@@ -3,3 +3,7 @@ default-abi := 64
 
 sysdep-CFLAGS += -fcall-used-g6
 LD += -melf64_sparc
+
+ifeq ($(subdir),stdlib)
+sysdep_routines += __start_context
+endif
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/__start_context.S b/sysdeps/unix/sysv/linux/sparc/sparc64/__start_context.S
new file mode 100644
index 0000000..f1d1adc
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/__start_context.S
@@ -0,0 +1,36 @@
+/* Copyright (C) 2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+
+	.text
+
+/* This is the helper code which gets called if a function which is
+   registered with 'makecontext' returns.  In this case we have to
+   install the context listed in the uc_link element of the context
+   'makecontext' manipulated at the time of the 'makecontext' call.
+   If the pointer is NULL the process must terminate.  */
+
+ENTRY(__start_context)
+	brz,pn	%i0, 1f
+	 mov	1, %o1
+	call	__setcontext
+	 mov	%i0, %o0
+1:	call	HIDDEN_JUMPTARGET(exit)
+	 mov	0, %o0
+	unimp	0
+END(__start_context)
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/makecontext.c b/sysdeps/unix/sysv/linux/sparc/sparc64/makecontext.c
index e925040..11e617e 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/makecontext.c
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/makecontext.c
@@ -21,6 +21,8 @@
 #include <stdlib.h>
 #include <ucontext.h>
 
+extern void __start_context (struct ucontext *ucp);
+
 void
 __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
 {
@@ -37,7 +39,7 @@ __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
   ucp->uc_mcontext.mc_gregs[MC_PC] = (long) func;
   ucp->uc_mcontext.mc_gregs[MC_NPC] = ((long) func) + 4;
   ucp->uc_mcontext.mc_gregs[MC_O6] = ((long) sp) - 0x7ff;
-  ucp->uc_mcontext.mc_gregs[MC_O7] = ((long) __makecontext_ret) - 8;
+  ucp->uc_mcontext.mc_gregs[MC_O7] = ((long) __start_context) - 8;
   ucp->uc_mcontext.mc_fp = ((long) topsp) - 0x7ff;
   ucp->uc_mcontext.mc_i7 = 0;
   topsp[14] = 0;
@@ -52,15 +54,4 @@ __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
   va_end (ap);
 }
 
-asm ("							\n\
-	.text						\n\
-	.type	__makecontext_ret, #function		\n\
-__makecontext_ret:					\n\
-	mov	1, %o1					\n\
-	call	__setcontext				\n\
-	 mov	%i0, %o0				\n\
-	unimp	0					\n\
-	.size	__makecontext_ret, .-__makecontext_ret	\n\
-     ");
-
 weak_alias (__makecontext, makecontext)
-- 
1.7.12.2.dirty