Fix FPU context handling in getcontext on x86-64.

fnstenv on x86-64 seems to clear the state.  Work around.

(cherry picked from commit 75ea32abcde4e1699328354e1804ea94560d2950)

4 files changed, 67 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index a50025b7fe..9d8ecac572 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2011-04-17  Ulrich Drepper  <drepper@gmail.com>
+
+	[BZ #12420]
+	* sysdeps/unix/sysv/linux/x86_64/getcontext.S: Reload context after
+	storing it.
+	* stdlib/bug-getcontext.c: New file.
+	* stdlib/Makefile: Add rules to build and run bug-getcontext.
+
 2011-04-10  Ulrich Drepper  <drepper@gmail.com>
 
 	[BZ #12650]
diff --git a/stdlib/Makefile b/stdlib/Makefile
index d361dd8ffa..6b8e0219c5 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -1,4 +1,4 @@
-# Copyright (C) 1991-2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+# Copyright (C) 1991-2009, 2011 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
@@ -70,7 +70,7 @@ tests		:= tst-strtol tst-strtod testmb testrand testsort testdiv   \
 		   test-a64l tst-qsort tst-system testmb2 bug-strtod2	    \
 		   tst-atof1 tst-atof2 tst-strtod2 tst-strtod3 tst-rand48-2 \
 		   tst-makecontext tst-strtod4 tst-strtod5 tst-qsort2	    \
-		   tst-makecontext2 tst-strtod6 tst-unsetenv1
+		   tst-makecontext2 tst-strtod6 tst-unsetenv1 bug-getcontext
 
 include ../Makeconfig
 
@@ -144,3 +144,10 @@ $(objpfx)tst-putenv: $(objpfx)tst-putenvmod.so
 $(objpfx)tst-putenvmod.so: $(objpfx)tst-putenvmod.os
 	$(build-module)
 CFLAGS-tst-putenvmod.c = -DNOT_IN_libc=1
+
+ifeq ($(build-shared),yes)
+link-libm = $(common-objpfx)math/libm.so
+else
+link-libm = $(common-objpfx)math/libm.a
+endif
+$(objpfx)bug-getcontext: $(link-libm)
diff --git a/stdlib/bug-getcontext.c b/stdlib/bug-getcontext.c
new file mode 100644
index 0000000000..745aa1f207
--- /dev/null
+++ b/stdlib/bug-getcontext.c
@@ -0,0 +1,48 @@
+/* BZ 12420 */
+
+#include <errno.h>
+#include <fenv.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <ucontext.h>
+
+static int
+do_test (void)
+{
+  int except_mask =  FE_DIVBYZERO | FE_INVALID | FE_OVERFLOW | FE_UNDERFLOW;
+  int status = feenableexcept (except_mask);
+
+  except_mask = fegetexcept ();
+  if (except_mask == -1)
+    {
+      printf("\nBefore getcontext(): fegetexcept returned: %d\n",
+	     except_mask);
+      return 1;
+    }
+
+  ucontext_t ctx;
+  status = getcontext(&ctx);
+  if (status)
+    {
+      printf("\ngetcontext failed, errno: %d.\n", errno);
+      return 1;
+    }
+
+  printf ("\nDone with getcontext()!\n");
+  fflush (NULL);
+
+  int mask = fegetexcept ();
+  if (mask != except_mask)
+    {
+      printf("\nAfter getcontext(): fegetexcept returned: %d, expected: %d.\n",
+	     mask, except_mask);
+      return 1;
+    }
+
+  printf("\nAt end fegetexcept() returned %d, expected: %d.\n",
+	 mask, except_mask);
+  return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/sysdeps/unix/sysv/linux/x86_64/getcontext.S b/sysdeps/unix/sysv/linux/x86_64/getcontext.S
index 4bbc7a4d2e..1a31d72dad 100644
--- a/sysdeps/unix/sysv/linux/x86_64/getcontext.S
+++ b/sysdeps/unix/sysv/linux/x86_64/getcontext.S
@@ -1,5 +1,5 @@
 /* Save current context.
-   Copyright (C) 2002, 2005 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2005, 2011 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Andreas Jaeger <aj@suse.de>, 2002.
 
@@ -62,6 +62,7 @@ ENTRY(__getcontext)
 	movq	%rcx, oFPREGS(%rdi)
 	/* Save the floating-point environment.  */
 	fnstenv	(%rcx)
+	fldenv	(%rcx)
 	stmxcsr oMXCSR(%rdi)
 
 	/* Save the current signal mask with