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build: Use __register_atfork() only if really available

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This is a glibc-specific symbol that has no public declaration. But is
being used by the OpenBSD and this implementation as a hack to avoid
having to link against the pthread library. This interface is at least
included in LSB 5.0 [L], and using pthread_atfork() is otherwise
problematic anyway [P].

 [L] <https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/baselib---register-atfork.html>
 [P] <http://austingroupbugs.net/view.php?id=851>

One problem is that we were using it whenever __GLIBC__ is defined,
which is supposed to be defined only on an actual glibc, but uClibc
defines that macro, but it does not provide the symbol on its noMMU
variant.

We add a new configure check that will try to link a program that uses
that symbol to make sure it is present.

Closes: !2
Reported-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
This commit is contained in:
Guillem Jover 2019-08-06 23:16:42 +02:00
parent 73aea4f808
commit b0ebb0d4c2
4 changed files with 22 additions and 3 deletions
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17
configure.ac
View File

@ -145,6 +145,23 @@ AC_LINK_IFELSE(
AC_MSG_RESULT([yes])],
[AC_MSG_RESULT([no])])
AC_MSG_CHECKING([for __register_atfork])
AC_LINK_IFELSE(
[AC_LANG_PROGRAM([[
#include <stddef.h>
extern void *__dso_handle;
extern int __register_atfork(void (*)(void), void(*)(void), void (*)(void), void *);
]], [[
__register_atfork(NULL, NULL, NULL, __dso_handle);
]])],
[AC_DEFINE([HAVE___REGISTER_ATFORK], [1],
[Define to 1 if you have __register_atfork])
AC_MSG_RESULT([yes])],
[ARC4RANDOM_ATFORK_LIBS="-pthread"
AC_SUBST([ARC4RANDOM_ATFORK_LIBS])
AC_MSG_RESULT([no])
])
AC_CHECK_FUNCS([clearenv dirfd fopencookie __fpurge \
getauxval getentropy getexecname getline \
pstat_getproc sysconf])

4
src/Makefile.am
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@ -54,7 +54,9 @@ libbsd_la_DEPENDENCIES = \
$(libbsd_la_included_sources) \
libbsd.map
libbsd_la_LIBADD = \
$(CLOCK_GETTIME_LIBS)
$(CLOCK_GETTIME_LIBS) \
$(ARC4RANDOM_ATFORK_LIBS) \
$(nil)
libbsd_la_LDFLAGS = \
-Wl,--version-script=$(srcdir)/libbsd.map \
-version-number $(LIBBSD_ABI)

2
src/arc4random_linux.h
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@ -32,7 +32,7 @@ static pthread_mutex_t arc4random_mtx = PTHREAD_MUTEX_INITIALIZER;
#define _ARC4_LOCK() pthread_mutex_lock(&arc4random_mtx)
#define _ARC4_UNLOCK() pthread_mutex_unlock(&arc4random_mtx)
#ifdef __GLIBC__
#ifdef HAVE___REGISTER_ATFORK
extern void *__dso_handle;
extern int __register_atfork(void (*)(void), void(*)(void), void (*)(void), void *);
#define _ARC4_ATFORK(f) __register_atfork(NULL, NULL, (f), __dso_handle)

2
src/arc4random_unix.h
View File

@ -32,7 +32,7 @@ static pthread_mutex_t arc4random_mtx = PTHREAD_MUTEX_INITIALIZER;
#define _ARC4_LOCK() pthread_mutex_lock(&arc4random_mtx)
#define _ARC4_UNLOCK() pthread_mutex_unlock(&arc4random_mtx)
#ifdef __GLIBC__
#ifdef HAVE___REGISTER_ATFORK
extern void *__dso_handle;
extern int __register_atfork(void (*)(void), void(*)(void), void (*)(void), void *);
#define _ARC4_ATFORK(f) __register_atfork(NULL, NULL, (f), __dso_handle)