[COMMITTED,2/3] Clean up NPTL longjmp to be compat-only.
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Message ID 20150206201926.EB1F52C3A9B@topped-with-meat.com
State New
Headers show

Commit Message

Roland McGrath Feb. 6, 2015, 8:19 p.m. UTC
I don't know if there was a historical reason for libpthread to have a
longjmp wrapper, but there is certainly none in the current code.  This
change makes it compat-only.

Tested x86_64-linux-gnu.


Thanks,
Roland


	* nptl/pt-longjmp.c: Rewritten.  Put everything under
	[SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_22)].
	Use IFUNC to redirect when possible.

Comments

Rich Felker Feb. 7, 2015, 4:47 p.m. UTC | #1
On Fri, Feb 06, 2015 at 12:19:26PM -0800, Roland McGrath wrote:
> I don't know if there was a historical reason for libpthread to have a
> longjmp wrapper,

There seems to have been at least one arch (I forget which) where the
pthread longjmp historically did stack unwinding to execute
cancellation cleanup handlers that were jumped over.

Rich

Patch
diff mbox

--- a/nptl/pt-longjmp.c
+++ b/nptl/pt-longjmp.c
@@ -1,4 +1,5 @@ 
-/* Copyright (C) 2002-2015 Free Software Foundation, Inc.
+/* ABI compatibility for 'longjmp' and 'siglongjmp' symbols in libpthread ABI.
+   Copyright (C) 2002-2015 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
 
@@ -17,12 +18,55 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #include <setjmp.h>
-#include <stdlib.h>
-#include "pthreadP.h"
+#include <shlib-compat.h>
 
-void
-longjmp (jmp_buf env, int val)
+/* libpthread once had its own longjmp (and siglongjmp alias), though there
+   was no apparent reason for it.  There is no use in having a separate
+   symbol in libpthread, but the historical ABI requires it.  For static
+   linking, there is no need to provide anything here--the libc version
+   will be linked in.  For shared library ABI compatibility, there must be
+   longjmp and siglongjmp symbols in libpthread.so; so we define them using
+   IFUNC to redirect to the libc function.  */
+
+#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_22)
+
+# if HAVE_IFUNC
+
+static __typeof (longjmp) *
+__attribute__ ((used))
+longjmp_resolve (void)
+{
+  return &__libc_longjmp;
+}
+
+#  ifdef HAVE_ASM_SET_DIRECTIVE
+#   define DEFINE_LONGJMP(name) \
+  asm (".set " #name ", longjmp_resolve\n" \
+       ".globl " #name "\n" \
+       ".type " #name ", %gnu_indirect_function");
+#  else
+#   define DEFINE_LONGJMP(name) \
+  asm (#name " = longjmp_resolve\n" \
+       ".globl " #name "\n" \
+       ".type " #name ", %gnu_indirect_function");
+#  endif
+
+# else  /* !HAVE_IFUNC */
+
+static void __attribute__ ((noreturn, used))
+longjmp_compat (jmp_buf env, int val)
 {
   __libc_longjmp (env, val);
 }
-weak_alias (longjmp, siglongjmp)
+
+# define DEFINE_LONGJMP(name) strong_alias (longjmp_compat, name)
+
+# endif  /* HAVE_IFUNC */
+
+DEFINE_LONGJMP (longjmp_ifunc)
+compat_symbol (libpthread, longjmp_ifunc, longjmp, GLIBC_2_0);
+
+DEFINE_LONGJMP (siglongjmp_ifunc)
+compat_symbol (libpthread, siglongjmp_ifunc, siglongjmp, GLIBC_2_0);
+
+#endif