Author: kib
Date: Sat Jun 7 02:45:24 2014
New Revision: 267200
URL: http://svnweb.freebsd.org/changeset/base/267200
Log:
MFC r266609:
Change the _rtld_atfork() to lock the bind lock in write mode.
Modified:
stable/10/lib/libthr/thread/thr_fork.c
stable/10/lib/libthr/thread/thr_rtld.c
stable/10/libexec/rtld-elf/rtld_lock.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/lib/libthr/thread/thr_fork.c
==============================================================================
--- stable/10/lib/libthr/thread/thr_fork.c Sat Jun 7 02:38:13 2014
(r267199)
+++ stable/10/lib/libthr/thread/thr_fork.c Sat Jun 7 02:45:24 2014
(r267200)
@@ -57,6 +57,7 @@
*
*/
+#include <sys/syscall.h>
#include "namespace.h"
#include <errno.h>
#include <link.h>
@@ -174,8 +175,15 @@ _fork(void)
was_threaded = 0;
}
- /* Fork a new process: */
- if ((ret = __sys_fork()) == 0) {
+ /*
+ * Fork a new process.
+ * There is no easy way to pre-resolve the __sys_fork symbol
+ * without performing the fork. Use the syscall(2)
+ * indirection, the syscall symbol is resolved in
+ * _thr_rtld_init() with side-effect free call.
+ */
+ ret = syscall(SYS_fork);
+ if (ret == 0) {
/* Child process */
errsave = errno;
curthread->cancel_pending = 0;
@@ -250,6 +258,5 @@ _fork(void)
}
errno = errsave;
- /* Return the process ID: */
return (ret);
}
Modified: stable/10/lib/libthr/thread/thr_rtld.c
==============================================================================
--- stable/10/lib/libthr/thread/thr_rtld.c Sat Jun 7 02:38:13 2014
(r267199)
+++ stable/10/lib/libthr/thread/thr_rtld.c Sat Jun 7 02:45:24 2014
(r267200)
@@ -32,10 +32,12 @@
*/
#include <sys/cdefs.h>
#include <sys/mman.h>
+#include <sys/syscall.h>
#include <link.h>
#include <stdlib.h>
#include <string.h>
+#include "libc_private.h"
#include "rtld_lock.h"
#include "thr_private.h"
@@ -207,7 +209,24 @@ _thr_rtld_init(void)
li.thread_set_flag = _thr_rtld_set_flag;
li.thread_clr_flag = _thr_rtld_clr_flag;
li.at_fork = NULL;
-
+
+ /*
+ * Preresolve the symbols needed for the fork interposer. We
+ * call _rtld_atfork_pre() and _rtld_atfork_post() with NULL
+ * argument to indicate that no actual locking inside the
+ * functions should happen. Neither rtld compat locks nor
+ * libthr rtld locks cannot work there:
+ * - compat locks do not handle the case of two locks taken
+ * in write mode (the signal mask for the thread is corrupted);
+ * - libthr locks would work, but locked rtld_bind_lock prevents
+ * symbol resolution for _rtld_atfork_post.
+ */
+ _rtld_atfork_pre(NULL);
+ _rtld_atfork_post(NULL);
+ _malloc_prefork();
+ _malloc_postfork();
+ syscall(SYS_getpid);
+
/* mask signals, also force to resolve __sys_sigprocmask PLT */
_thr_signal_block(curthread);
_rtld_thread_init(&li);
Modified: stable/10/libexec/rtld-elf/rtld_lock.c
==============================================================================
--- stable/10/libexec/rtld-elf/rtld_lock.c Sat Jun 7 02:38:13 2014
(r267199)
+++ stable/10/libexec/rtld-elf/rtld_lock.c Sat Jun 7 02:45:24 2014
(r267200)
@@ -365,8 +365,19 @@ _rtld_atfork_pre(int *locks)
{
RtldLockState ls[2];
+ if (locks == NULL)
+ return;
+
+ /*
+ * Warning: this does not work with the rtld compat locks
+ * above, since the thread signal mask is corrupted (set to
+ * all signals blocked) if two locks are taken in write mode.
+ * The caller of the _rtld_atfork_pre() must provide the
+ * working implementation of the locks, and libthr locks are
+ * fine.
+ */
wlock_acquire(rtld_phdr_lock, &ls[0]);
- rlock_acquire(rtld_bind_lock, &ls[1]);
+ wlock_acquire(rtld_bind_lock, &ls[1]);
/* XXXKIB: I am really sorry for this. */
locks[0] = ls[1].lockstate;
@@ -378,6 +389,9 @@ _rtld_atfork_post(int *locks)
{
RtldLockState ls[2];
+ if (locks == NULL)
+ return;
+
bzero(ls, sizeof(ls));
ls[0].lockstate = locks[2];
ls[1].lockstate = locks[0];
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