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From fc5ad7024c620cdfe9b76e94638aac83b99c5bf8 Mon Sep 17 00:00:00 2001
From: Andreas Schwab <schwab@suse.de>
Date: Tue, 8 Aug 2017 16:21:58 +0200
Subject: [PATCH] Don't use IFUNC resolver for longjmp or system in libpthread
(bug 21041)
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.
---
nptl/pt-longjmp.c | 31 ++++++++++---------------------
nptl/pt-system.c | 24 ++++++++----------------
3 files changed, 18 insertions(+), 37 deletions(-)
diff --git a/nptl/pt-longjmp.c b/nptl/pt-longjmp.c
index 2ef757e687f..8f3c6b3a09f 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 f8ca6ba0d94..b30ddf2b398 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
--
2.14.1
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