[2.25 COMMITTED 1/3] Don't use IFUNC resolver for longjmp or system in libpthread (bug 21041)

[2.25 COMMITTED 1/3] Don't use IFUNC resolver for longjmp or system in libpthread (bug 21041)

[Aurelien Jarno]

From: Andreas Schwab <schwab@suse.de>

Unlike the vfork forwarder and like the fork forwarder as in bug 19861,
there won't be a problem when the compiler does not turn this into a tail
call.

(cherry picked from commit fc5ad7024c620cdfe9b76e94638aac83b99c5bf8)
---
 ChangeLog         |  6 ++++++
 nptl/pt-longjmp.c | 31 ++++++++++---------------------
 nptl/pt-system.c  | 24 ++++++++----------------
 3 files changed, 24 insertions(+), 37 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 687fd20c46..3cf3c8013c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2017-08-08  Andreas Schwab  <schwab@suse.de>
+
+	[BZ #21041]
+	* nptl/pt-longjmp.c (longjmp, siglongjmp): Don't use IFUNC resolver.
+	* nptl/pt-system.c (system): Likewise.
+
 2017-10-13  James Clarke  <jrtc27@jrtc27.com>
 
 	* sysdeps/powerpc/powerpc32/dl-machine.h (elf_machine_rela):
diff --git a/nptl/pt-longjmp.c b/nptl/pt-longjmp.c
index 2ef757e687..8f3c6b3a09 100644
--- a/nptl/pt-longjmp.c
+++ b/nptl/pt-longjmp.c
@@ -25,21 +25,14 @@
    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.  */
+   longjmp and siglongjmp symbols in libpthread.so.
 
-#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_22)
-
-# if HAVE_IFUNC
-
-#  undef INIT_ARCH
-#  define INIT_ARCH()
-#  define DEFINE_LONGJMP(name) libc_ifunc (name, &__libc_longjmp)
-
-extern __typeof(longjmp) longjmp_ifunc;
-extern __typeof(siglongjmp) siglongjmp_ifunc;
+   With an IFUNC resolver, it would be possible to avoid the indirection,
+   but the IFUNC resolver might run before the __libc_longjmp symbol has
+   been relocated, in which case the IFUNC resolver would not be able to
+   provide the correct address.  */
 
-# else  /* !HAVE_IFUNC */
+#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_22)
 
 static void __attribute__ ((noreturn, used))
 longjmp_compat (jmp_buf env, int val)
@@ -47,14 +40,10 @@ longjmp_compat (jmp_buf env, int val)
   __libc_longjmp (env, val);
 }
 
-# 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);
+strong_alias (longjmp_compat, longjmp_alias)
+compat_symbol (libpthread, longjmp_alias, longjmp, GLIBC_2_0);
 
-strong_alias (longjmp_ifunc, siglongjmp_ifunc)
-compat_symbol (libpthread, siglongjmp_ifunc, siglongjmp, GLIBC_2_0);
+strong_alias (longjmp_alias, siglongjmp_alias)
+compat_symbol (libpthread, siglongjmp_alias, siglongjmp, GLIBC_2_0);
 
 #endif
diff --git a/nptl/pt-system.c b/nptl/pt-system.c
index f8ca6ba0d9..b30ddf2b39 100644
--- a/nptl/pt-system.c
+++ b/nptl/pt-system.c
@@ -25,29 +25,21 @@
    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 a
-   'system' symbol in libpthread.so; so we define it using IFUNC to
-   redirect to the libc function.  */
+   'system' symbol in libpthread.so.
 
-#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_22)
-
-# if HAVE_IFUNC
-
-extern __typeof(system) system_ifunc;
-#  undef INIT_ARCH
-#  define INIT_ARCH()
-libc_ifunc (system_ifunc, &__libc_system)
+   With an IFUNC resolver, it would be possible to avoid the indirection,
+   but the IFUNC resolver might run before the __libc_system symbol has
+   been relocated, in which case the IFUNC resolver would not be able to
+   provide the correct address.  */
 
-# else  /* !HAVE_IFUNC */
+#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_22)
 
 static int __attribute__ ((used))
 system_compat (const char *line)
 {
   return __libc_system (line);
 }
-strong_alias (system_compat, system_ifunc)
-
-# endif  /* HAVE_IFUNC */
-
-compat_symbol (libpthread, system_ifunc, system, GLIBC_2_0);
+strong_alias (system_compat, system_alias)
+compat_symbol (libpthread, system_alias, system, GLIBC_2_0);
 
 #endif
-- 
2.15.0

[2.25 COMMITTED 2/3] Fix s390 version of pt-longjmp.c

[Aurelien Jarno]

From: Andreas Schwab <schwab@suse.de>

(cherry picked from commit 5797b410a87f6f6f6d3661d730fac320cbd5f270)
---
 ChangeLog                                 | 5 +++++
 sysdeps/unix/sysv/linux/s390/pt-longjmp.c | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 3cf3c8013c..368459008d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-08-09  Andreas Schwab  <schwab@suse.de>
+
+	* sysdeps/unix/sysv/linux/s390/pt-longjmp.c: Update reference to
+	renamed alias.
+
 2017-08-08  Andreas Schwab  <schwab@suse.de>
 
 	[BZ #21041]
diff --git a/sysdeps/unix/sysv/linux/s390/pt-longjmp.c b/sysdeps/unix/sysv/linux/s390/pt-longjmp.c
index d324237edd..0221ac2cf5 100644
--- a/sysdeps/unix/sysv/linux/s390/pt-longjmp.c
+++ b/sysdeps/unix/sysv/linux/s390/pt-longjmp.c
@@ -26,8 +26,8 @@
 /* In glibc release 2.19 new versions of longjmp-functions were introduced,
    but were reverted before 2.20. Thus both versions are the same function.  */
 
-strong_alias (longjmp_ifunc, __v2longjmp)
+strong_alias (longjmp_alias, __v2longjmp)
 compat_symbol (libpthread, __v2longjmp, longjmp, GLIBC_2_19);
-strong_alias (siglongjmp_ifunc, __v2siglongjmp)
+strong_alias (siglongjmp_alias, __v2siglongjmp)
 compat_symbol (libpthread, __v2siglongjmp, siglongjmp, GLIBC_2_19);
 #endif /* SHLIB_COMPAT (libpthread, GLIBC_2_19, GLIBC_2_20))  */
-- 
2.15.0

[2.25 COMMITTED 3/3] Add test for bug 21041

[Aurelien Jarno]

From: Andreas Schwab <schwab@suse.de>

(cherry picked from commit 40c06a3d0450365e9675fe26f34fc56ce8497325)
---
 ChangeLog                       | 10 ++++++++++
 nptl/Makefile                   |  6 ++++--
 nptl/tst-compat-forwarder-mod.c | 28 ++++++++++++++++++++++++++++
 nptl/tst-compat-forwarder.c     | 35 +++++++++++++++++++++++++++++++++++
 4 files changed, 77 insertions(+), 2 deletions(-)
 create mode 100644 nptl/tst-compat-forwarder-mod.c
 create mode 100644 nptl/tst-compat-forwarder.c

diff --git a/ChangeLog b/ChangeLog
index 368459008d..d3c5570239 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2017-08-09  Andreas Schwab  <schwab@suse.de>
+
+	* nptl/Makefile (tests) [$(build-shared) = yes]: Add
+	tst-compat-forwarder.
+	(modules-names): Add tst-compat-forwarder-mod.
+	($(objpfx)tst-compat-forwarder): Depend on
+	$(objpfx)tst-compat-forwarder-mod.so.
+	* nptl/tst-compat-forwarder.c: New file.
+	* nptl/tst-compat-forwarder-mod.c: New file.
+
 2017-08-09  Andreas Schwab  <schwab@suse.de>
 
 	* sysdeps/unix/sysv/linux/s390/pt-longjmp.c: Update reference to
diff --git a/nptl/Makefile b/nptl/Makefile
index 24067768ed..8def69ae22 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -356,7 +356,7 @@ tests += tst-cancelx2 tst-cancelx3 tst-cancelx4 tst-cancelx5 \
 	 tst-oncex3 tst-oncex4
 ifeq ($(build-shared),yes)
 tests += tst-atfork2 tst-tls3 tst-tls3-malloc tst-tls4 tst-tls5 tst-_res1 \
-	 tst-fini1 tst-stackguard1
+	 tst-fini1 tst-stackguard1 tst-compat-forwarder
 tests-nolibpthread += tst-fini1
 ifeq ($(have-z-execstack),yes)
 tests += tst-execstack
@@ -367,7 +367,7 @@ modules-names = tst-atfork2mod tst-tls3mod tst-tls4moda tst-tls4modb \
 		tst-tls5mod tst-tls5moda tst-tls5modb tst-tls5modc \
 		tst-tls5modd tst-tls5mode tst-tls5modf tst-stack4mod \
 		tst-_res1mod1 tst-_res1mod2 tst-execstack-mod tst-fini1mod \
-		tst-join7mod
+		tst-join7mod tst-compat-forwarder-mod
 extra-test-objs += $(addsuffix .os,$(strip $(modules-names))) \
 		   tst-cleanup4aux.o tst-cleanupx4aux.o
 test-extras += $(modules-names) tst-cleanup4aux tst-cleanupx4aux
@@ -705,6 +705,8 @@ $(objpfx)tst-oddstacklimit.out: $(objpfx)tst-oddstacklimit $(objpfx)tst-basic1
 	$(evaluate-test)
 endif
 
+$(objpfx)tst-compat-forwarder: $(objpfx)tst-compat-forwarder-mod.so
+
 # The tests here better do not run in parallel
 ifneq ($(filter %tests,$(MAKECMDGOALS)),)
 .NOTPARALLEL:
diff --git a/nptl/tst-compat-forwarder-mod.c b/nptl/tst-compat-forwarder-mod.c
new file mode 100644
index 0000000000..823bfa22de
--- /dev/null
+++ b/nptl/tst-compat-forwarder-mod.c
@@ -0,0 +1,28 @@
+/* Copyright (C) 2017 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/>.  */
+
+/* Call the function system through a statically initialized pointer.  */
+
+#include <stdlib.h>
+
+int (*system_function) (const char *) = system;
+
+void
+call_system (void)
+{
+  system_function (NULL);
+}
diff --git a/nptl/tst-compat-forwarder.c b/nptl/tst-compat-forwarder.c
new file mode 100644
index 0000000000..f96806b7fe
--- /dev/null
+++ b/nptl/tst-compat-forwarder.c
@@ -0,0 +1,35 @@
+/* Copyright (C) 2017 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/>.  */
+
+/* Test that the compat forwaders in libpthread work correctly.  */
+
+#include <support/test-driver.h>
+
+extern void call_system (void);
+
+int
+do_test (void)
+{
+  /* Calling the system function from a shared library that is not linked
+     against libpthread, when the main program is linked against
+     libpthread, should not crash.  */
+  call_system ();
+
+  return 0;
+}
+
+#include <support/test-driver.c>
-- 
2.15.0