[PATCH] Don't use IFUNC resolver for longjmp or system in libpthread (bug 21041)

[Andreas Schwab <schwab at suse dot 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.

Andreas.

	* nptl/pt-longjmp.c (longjmp, siglongjmp): Don't use IFUNC resolver.
	* nptl/pt-system.c (system): Likewise.

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
-- 
2.14.0


-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."