91 lines
4.0 KiB
Diff
91 lines
4.0 KiB
Diff
#
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# Posted upstream:
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# https://sourceware.org/ml/libc-alpha/2013-10/msg00065.html
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#
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# This is related to bug 1013801 in that it fixes the problem
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# by modifying the runtime. In bug 1013801 we have libselinux
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# using pthread_atfork which pulls in libpthread, but we don't
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# want that, we want libpthread to be pulled in only when
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# actually needed by the application. This patch makes it
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# possible to avoid requiring libpthread and still use
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# pthread_atfork.
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#
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# The general idea for the design is in the leading comment
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# in the source code.
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#
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diff --git a/nptl/sysdeps/unix/sysv/linux/Makefile b/nptl/sysdeps/unix/sysv/linux/Makefile
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index 6078e2d..36fd50b 100644
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--- a/nptl/Makefile
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+++ b/nptl/Makefile
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@@ -18,7 +18,9 @@
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routines = alloca_cutoff forward libc-lowlevellock libc-cancellation \
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libc-cleanup libc_pthread_init libc_multiple_threads \
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- register-atfork unregister-atfork
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+ register-atfork unregister-atfork libc_pthread_atfork
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+
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+static-only-routines += libc_pthread_atfork
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shared-only-routines = forward
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libpthread-routines = nptl-init vars events version \
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diff --git a/nptl/libc_pthread_atfork.c b/nptl/libc_pthread_atfork.c
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new file mode 100644
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index 0000000..667049a
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--- /dev/null
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+++ b/nptl/libc_pthread_atfork.c
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@@ -0,0 +1,54 @@
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+/* Copyright (C) 2013 Free Software Foundation, Inc.
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+ This file is part of the GNU C Library.
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+ Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, see
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+ <http://www.gnu.org/licenses/>. */
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+
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+/* The standard design pattern for making it optional to link against
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+ libpthread is to mark the function weak, test if the function
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+ address is non-zero and call the function, otherwise use a fallback.
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+ The problem with pthread_atfork is that there is no viable
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+ fallback. If you need to do something during fork it has to be done
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+ via pthread_atfork. This makes having libpthread optional and using
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+ pthread_atfork impossible. We make it possible by providing
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+ pthread_atfork in libc_nonshared.a. The real work of pthread_atfork
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+ is done by __register_atfork which is already provided in
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+ libc_nonshared.a. It's included in libc_nonshared.a because
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+ __dso_handle has to be unique to each DSO such that unloading the DSO
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+ can unregister the atfork handlers. We build pthread_atfork again
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+ under a different file name and include it into libc_nonshared.a and
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+ libc.a. We keep pthread_atfork in libpthread_nonshared.a and
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+ libpthread.a for compatibility and completeness.
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+
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+ Applications that can't rely on a new glibc should use the following
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+ code to optionally include libpthread and still register a function
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+ via pthread_atfork i.e. use __register_atfork directly:
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+
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+ extern void *__dso_handle __attribute__ ((__weak__, __visibility__ ("hidden")));
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+ extern int __register_atfork (void (*) (void), void (*) (void), void (*) (void), void *);
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+
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+ static int __app_atfork (void (*prepare) (void), void (*parent) (void), void (*child) (void))
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+ {
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+ return __register_atfork (prepare, parent, child,
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+ &__dso_handle == NULL ? NULL : __dso_handle);
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+ }
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+
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+ This code requires glibc 2.3.2 or newer. Previous to 2.3.2 no such
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+ interfaces exist and at that point is is impossible to have an
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+ optional libpthread and call pthread_atfork.
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+
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+ This code adds no more ABI requirements than already exist since
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+ __dso_handle and __register_atfork are already part of the ABI. */
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+#include <pthread_atfork.c>
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