Patchwork [11/11] nptl: Use <unwind-link.h> for accessing the libgcc_s unwinder

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Submitter Florian Weimer
Date Feb. 13, 2020, 5:08 p.m.
Message ID <f76766bb3e960981c0e2ccadafaea916174cf86c.1581613260.git.fweimer@redhat.com>
Download mbox | patch
Permalink /patch/38048/
State New
Headers show

Comments

Florian Weimer - Feb. 13, 2020, 5:08 p.m.
---
 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 +++---------------
 .../sysv/linux/ia64/unwind-forcedunwind.c     |  16 +--
 7 files changed, 50 insertions(+), 146 deletions(-)
 create mode 100644 sysdeps/arm/nptl/unwind-forcedunwind.c

Patch

diff --git a/nptl/nptlfreeres.c b/nptl/nptlfreeres.c
index dda11e5922..644d196ab4 100644
--- a/nptl/nptlfreeres.c
+++ b/nptl/nptlfreeres.c
@@ -27,5 +27,4 @@  __libpthread_freeres (void)
 {
   call_function_static_weak (__nptl_stacks_freeres);
   call_function_static_weak (__shm_directory_freeres);
-  call_function_static_weak (__nptl_unwind_freeres);
 }
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index 7e0ab8ef42..2f370ae0ae 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -290,9 +290,11 @@  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 8e7be996e9..42b58b7034 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..ae64e61b85
--- /dev/null
+++ b/sysdeps/arm/nptl/unwind-forcedunwind.c
@@ -0,0 +1,25 @@ 
+/* Unwinder function forwarders for libpthread.  Arm version.
+   Copyright (C) 2020 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 86ff5cbeea..d01e129cf4 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 50a089282b..f57a3d0c18 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 4c953bf63c..17c35aa68a 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);
 }