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* [glibc] nptl: Use <unwind-link.h> for accessing the libgcc_s unwinder
@ 2021-03-01 16:35 Florian Weimer
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From: Florian Weimer @ 2021-03-01 16:35 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=97e42bd482b62d7b74889be11c98b0bbb4059dcd
commit 97e42bd482b62d7b74889be11c98b0bbb4059dcd
Author: Florian Weimer <fweimer@redhat.com>
Date: Mon Mar 1 15:56:36 2021 +0100
nptl: Use <unwind-link.h> for accessing the libgcc_s unwinder
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Diff:
---
nptl/nptlfreeres.c | 1 -
nptl/pthreadP.h | 6 +-
nptl/pthread_cancel.c | 3 +-
sysdeps/arm/nptl/unwind-forcedunwind.c | 25 +++++
sysdeps/arm/pt-arm-unwind-resume.S | 30 +-----
sysdeps/nptl/unwind-forcedunwind.c | 115 +++------------------
sysdeps/unix/sysv/linux/ia64/unwind-forcedunwind.c | 16 +--
7 files changed, 50 insertions(+), 146 deletions(-)
diff --git a/nptl/nptlfreeres.c b/nptl/nptlfreeres.c
index d295bcb3c3..4833f04714 100644
--- a/nptl/nptlfreeres.c
+++ b/nptl/nptlfreeres.c
@@ -27,5 +27,4 @@ __libpthread_freeres (void)
{
call_function_static_weak (__default_pthread_attr_freeres);
call_function_static_weak (__nptl_stacks_freeres);
- call_function_static_weak (__nptl_unwind_freeres);
}
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index d078128230..d2fd0826fe 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -287,9 +287,11 @@ hidden_proto (__pthread_unwind_next)
hidden_proto (__pthread_register_cancel)
hidden_proto (__pthread_unregister_cancel)
# ifdef SHARED
-extern void attribute_hidden pthread_cancel_init (void);
+/* The difference from __libc_unwind_link_get is that here, errors
+ terminate the process. */
+struct unwind_link ;
+struct unwind_link *__pthread_unwind_link_get (void) attribute_hidden;
# endif
-extern void __nptl_unwind_freeres (void) attribute_hidden;
#endif
diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c
index f88fa24e19..a011d72fa1 100644
--- a/nptl/pthread_cancel.c
+++ b/nptl/pthread_cancel.c
@@ -35,7 +35,8 @@ __pthread_cancel (pthread_t th)
return ESRCH;
#ifdef SHARED
- pthread_cancel_init ();
+ /* Trigger an error if libgcc_s cannot be loaded. */
+ __pthread_unwind_link_get ();
#endif
int result = 0;
int oldval;
diff --git a/sysdeps/arm/nptl/unwind-forcedunwind.c b/sysdeps/arm/nptl/unwind-forcedunwind.c
new file mode 100644
index 0000000000..61db34c0b5
--- /dev/null
+++ b/sysdeps/arm/nptl/unwind-forcedunwind.c
@@ -0,0 +1,25 @@
+/* Unwinder function forwarders for libpthread. Arm version.
+ Copyright (C) 2021 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; see the file COPYING.LIB. If
+ not, see <https://www.gnu.org/licenses/>. */
+
+#include <sysdeps/nptl/unwind-forcedunwind.c>
+
+void *
+__unwind_link_get_resume (void)
+{
+ return UNWIND_LINK_PTR (__pthread_unwind_link_get (), _Unwind_Resume);
+}
diff --git a/sysdeps/arm/pt-arm-unwind-resume.S b/sysdeps/arm/pt-arm-unwind-resume.S
index d579848696..c056eb38d0 100644
--- a/sysdeps/arm/pt-arm-unwind-resume.S
+++ b/sysdeps/arm/pt-arm-unwind-resume.S
@@ -16,31 +16,5 @@
License along with the GNU C Library. If not, see
<https://www.gnu.org/licenses/>. */
-#include <sysdep.h>
-
-/* This is just implementing exactly what the C version does.
- We do it in assembly just to ensure that we get an unmolested tail
- call to the libgcc function, which is necessary for the ARM unwinder. */
-
-ENTRY (_Unwind_Resume)
- LDR_HIDDEN (ip, ip, __libgcc_s_resume, 0)
- cmp ip, #0
- beq 1f
-0: PTR_DEMANGLE (ip, ip, r2, r3)
- bx ip
-
- /* We need to save and restore LR (for our own return address)
- and R0 (for the argument to _Unwind_Resume) around the call. */
-1: push {r0, lr}
- cfi_adjust_cfa_offset (8)
- cfi_rel_offset (r0, 0)
- cfi_rel_offset (lr, 4)
- bl pthread_cancel_init
- pop {r0, lr}
- cfi_adjust_cfa_offset (-8)
- cfi_restore (r0)
- cfi_restore (lr)
-
- LDR_HIDDEN (ip, ip, __libgcc_s_resume, 0)
- b 0b
-END (_Unwind_Resume)
+/* The implementation in libpthread is identical to the one in libc. */
+#include <sysdeps/arm/arm-unwind-resume.S>
diff --git a/sysdeps/nptl/unwind-forcedunwind.c b/sysdeps/nptl/unwind-forcedunwind.c
index b70aae06ae..c0234670cf 100644
--- a/sysdeps/nptl/unwind-forcedunwind.c
+++ b/sysdeps/nptl/unwind-forcedunwind.c
@@ -16,134 +16,49 @@
License along with the GNU C Library; see the file COPYING.LIB. If
not, see <https://www.gnu.org/licenses/>. */
-#include <dlfcn.h>
#include <stdio.h>
-#include <unwind.h>
+#include <unwind-link.h>
#include <pthreadP.h>
#include <sysdep.h>
#include <gnu/lib-names.h>
#include <unwind-resume.h>
-static void *libgcc_s_handle;
-void (*__libgcc_s_resume) (struct _Unwind_Exception *exc)
- attribute_hidden __attribute__ ((noreturn));
-static _Unwind_Reason_Code (*libgcc_s_personality) PERSONALITY_PROTO;
-static _Unwind_Reason_Code (*libgcc_s_forcedunwind)
- (struct _Unwind_Exception *, _Unwind_Stop_Fn, void *);
-static _Unwind_Word (*libgcc_s_getcfa) (struct _Unwind_Context *);
-
-void
-__attribute_noinline__
-pthread_cancel_init (void)
+struct unwind_link *
+__pthread_unwind_link_get (void)
{
- void *resume;
- void *personality;
- void *forcedunwind;
- void *getcfa;
- void *handle;
-
- if (__glibc_likely (libgcc_s_handle != NULL))
- {
- /* Force gcc to reload all values. */
- asm volatile ("" ::: "memory");
- return;
- }
-
- /* See include/dlfcn.h. Use of __libc_dlopen requires RTLD_NOW. */
- handle = __libc_dlopen (LIBGCC_S_SO);
-
- if (handle == NULL
- || (resume = __libc_dlsym (handle, "_Unwind_Resume")) == NULL
- || (personality = __libc_dlsym (handle, "__gcc_personality_v0")) == NULL
- || (forcedunwind = __libc_dlsym (handle, "_Unwind_ForcedUnwind"))
- == NULL
- || (getcfa = __libc_dlsym (handle, "_Unwind_GetCFA")) == NULL
-#ifdef ARCH_CANCEL_INIT
- || ARCH_CANCEL_INIT (handle)
-#endif
- )
- __libc_fatal (LIBGCC_S_SO " must be installed for pthread_cancel to work\n");
-
- PTR_MANGLE (resume);
- __libgcc_s_resume = resume;
- PTR_MANGLE (personality);
- libgcc_s_personality = personality;
- PTR_MANGLE (forcedunwind);
- libgcc_s_forcedunwind = forcedunwind;
- PTR_MANGLE (getcfa);
- libgcc_s_getcfa = getcfa;
- /* Make sure libgcc_s_handle is written last. Otherwise,
- pthread_cancel_init might return early even when the pointer the
- caller is interested in is not initialized yet. */
- atomic_write_barrier ();
- libgcc_s_handle = handle;
-}
-
-/* Register for cleanup in libpthread.so. */
-void
-__nptl_unwind_freeres (void)
-{
- void *handle = libgcc_s_handle;
- if (handle != NULL)
- {
- libgcc_s_handle = NULL;
- __libc_dlclose (handle);
- }
+ struct unwind_link *unwind_link = __libc_unwind_link_get ();
+ if (unwind_link == NULL)
+ __libc_fatal (LIBGCC_S_SO
+ " must be installed for pthread_cancel to work\n");
+ return unwind_link;
}
#if !HAVE_ARCH_UNWIND_RESUME
void
_Unwind_Resume (struct _Unwind_Exception *exc)
{
- if (__glibc_unlikely (libgcc_s_handle == NULL))
- pthread_cancel_init ();
- else
- atomic_read_barrier ();
-
- void (*resume) (struct _Unwind_Exception *exc) = __libgcc_s_resume;
- PTR_DEMANGLE (resume);
- resume (exc);
+ UNWIND_LINK_PTR (__pthread_unwind_link_get (), _Unwind_Resume) (exc);
}
#endif
_Unwind_Reason_Code
__gcc_personality_v0 PERSONALITY_PROTO
{
- if (__glibc_unlikely (libgcc_s_handle == NULL))
- pthread_cancel_init ();
- else
- atomic_read_barrier ();
-
- __typeof (libgcc_s_personality) personality = libgcc_s_personality;
- PTR_DEMANGLE (personality);
- return (*personality) PERSONALITY_ARGS;
+ return UNWIND_LINK_PTR (__pthread_unwind_link_get (), personality)
+ PERSONALITY_ARGS;
}
_Unwind_Reason_Code
_Unwind_ForcedUnwind (struct _Unwind_Exception *exc, _Unwind_Stop_Fn stop,
void *stop_argument)
{
- if (__glibc_unlikely (libgcc_s_handle == NULL))
- pthread_cancel_init ();
- else
- atomic_read_barrier ();
-
- _Unwind_Reason_Code (*forcedunwind)
- (struct _Unwind_Exception *, _Unwind_Stop_Fn, void *)
- = libgcc_s_forcedunwind;
- PTR_DEMANGLE (forcedunwind);
- return forcedunwind (exc, stop, stop_argument);
+ return UNWIND_LINK_PTR (__pthread_unwind_link_get (), _Unwind_ForcedUnwind)
+ (exc, stop, stop_argument);
}
_Unwind_Word
_Unwind_GetCFA (struct _Unwind_Context *context)
{
- if (__glibc_unlikely (libgcc_s_handle == NULL))
- pthread_cancel_init ();
- else
- atomic_read_barrier ();
-
- _Unwind_Word (*getcfa) (struct _Unwind_Context *) = libgcc_s_getcfa;
- PTR_DEMANGLE (getcfa);
- return getcfa (context);
+ return UNWIND_LINK_PTR (__pthread_unwind_link_get (), _Unwind_GetCFA)
+ (context);
}
diff --git a/sysdeps/unix/sysv/linux/ia64/unwind-forcedunwind.c b/sysdeps/unix/sysv/linux/ia64/unwind-forcedunwind.c
index e797ea22aa..eaed6cf2ef 100644
--- a/sysdeps/unix/sysv/linux/ia64/unwind-forcedunwind.c
+++ b/sysdeps/unix/sysv/linux/ia64/unwind-forcedunwind.c
@@ -16,23 +16,11 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-#include <dlfcn.h>
-#include <stdio.h>
-#include <unwind.h>
-#include <pthreadP.h>
-
-static _Unwind_Word (*libgcc_s_getbsp) (struct _Unwind_Context *);
-
-#define ARCH_CANCEL_INIT(handle) \
- ((libgcc_s_getbsp = __libc_dlsym (handle, "_Unwind_GetBSP")) == NULL)
-
#include <sysdeps/nptl/unwind-forcedunwind.c>
_Unwind_Word
_Unwind_GetBSP (struct _Unwind_Context *context)
{
- if (__builtin_expect (libgcc_s_getbsp == NULL, 0))
- pthread_cancel_init ();
-
- return libgcc_s_getbsp (context);
+ return UNWIND_LINK_PTR (__pthread_unwind_link_get (), _Unwind_GetBSP)
+ (context);
}
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