Switch libc from using _sig{procmask,action,suspend} symbols, which

are aliases for the syscall stubs and are plt-interposed, to the
libc-private aliases of internally interposed sigprocmask() etc.

Since e.g. _sigaction is not interposed by libthr, calling signal()
removes thr_sighandler() from the handler slot etc.  The result was
breaking signal semantic and rtld locking.

The added __libc_sigprocmask and other symbols are hidden, they are
not exported and cannot be called through PLT.  The setjmp/longjmp
functions for x86 were changed to use direct calls, and since
PIC_PROLOGUE only needed for functional PLT indirection on i386, it is
removed as well.

The PowerPC bug of calling the syscall directly in the setjmp/longjmp
implementation is kept as is.

Reported by:	Pete French <petefrench@ingresso.co.uk>
Tested by:	Michiel Boland <boland37@xs4all.nl>
Reviewed by:	jilles (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

2 files changed, 16 insertions, 12 deletions

diff --git a/lib/libc/stdlib/abort.c b/lib/libc/stdlib/abort.c
index b137e49..022c6aa 100644
--- a/lib/libc/stdlib/abort.c
+++ b/lib/libc/stdlib/abort.c
@@ -61,7 +61,7 @@ abort()
 	 * any errors -- ISO C doesn't allow abort to return anyway.
 	 */
 	sigdelset(&act.sa_mask, SIGABRT);
-	(void)_sigprocmask(SIG_SETMASK, &act.sa_mask, NULL);
+	(void)__libc_sigprocmask(SIG_SETMASK, &act.sa_mask, NULL);
 	(void)raise(SIGABRT);
 
 	/*
@@ -71,9 +71,9 @@ abort()
 	act.sa_handler = SIG_DFL;
 	act.sa_flags = 0;
 	sigfillset(&act.sa_mask);
-	(void)_sigaction(SIGABRT, &act, NULL);
+	(void)__libc_sigaction(SIGABRT, &act, NULL);
 	sigdelset(&act.sa_mask, SIGABRT);
-	(void)_sigprocmask(SIG_SETMASK, &act.sa_mask, NULL);
+	(void)__libc_sigprocmask(SIG_SETMASK, &act.sa_mask, NULL);
 	(void)raise(SIGABRT);
 	exit(1);
 }
diff --git a/lib/libc/stdlib/system.c b/lib/libc/stdlib/system.c
index bd9ea5a..2b298e4 100644
--- a/lib/libc/stdlib/system.c
+++ b/lib/libc/stdlib/system.c
@@ -70,16 +70,20 @@ __libc_system(const char *command)
 	(void)sigaddset(&newsigblock, SIGCHLD);
 	(void)sigaddset(&newsigblock, SIGINT);
 	(void)sigaddset(&newsigblock, SIGQUIT);
-	(void)_sigprocmask(SIG_BLOCK, &newsigblock, &oldsigblock);
+	(void)__libc_sigprocmask(SIG_BLOCK, &newsigblock, &oldsigblock);
 	switch(pid = vfork()) {
+	/*
+	 * In the child, use unwrapped syscalls.  libthr is in
+	 * undefined state after vfork().
+	 */
 	case -1:			/* error */
-		(void)_sigprocmask(SIG_SETMASK, &oldsigblock, NULL);
+		(void)__libc_sigprocmask(SIG_SETMASK, &oldsigblock, NULL);
 		return (-1);
 	case 0:				/* child */
 		/*
 		 * Restore original signal dispositions and exec the command.
 		 */
-		(void)_sigprocmask(SIG_SETMASK, &oldsigblock, NULL);
+		(void)__sys_sigprocmask(SIG_SETMASK, &oldsigblock, NULL);
 		execl(_PATH_BSHELL, "sh", "-c", command, (char *)NULL);
 		_exit(127);
 	}
@@ -92,16 +96,16 @@ __libc_system(const char *command)
 	memset(&ign, 0, sizeof(ign));
 	ign.sa_handler = SIG_IGN;
 	(void)sigemptyset(&ign.sa_mask);
-	(void)_sigaction(SIGINT, &ign, &intact);
-	(void)_sigaction(SIGQUIT, &ign, &quitact);
+	(void)__libc_sigaction(SIGINT, &ign, &intact);
+	(void)__libc_sigaction(SIGQUIT, &ign, &quitact);
 	savedpid = pid;
 	do {
 		pid = _wait4(savedpid, &pstat, 0, (struct rusage *)0);
 	} while (pid == -1 && errno == EINTR);
-	(void)_sigaction(SIGINT, &intact, NULL);
-	(void)_sigaction(SIGQUIT,  &quitact, NULL);
-	(void)_sigprocmask(SIG_SETMASK, &oldsigblock, NULL);
-	return(pid == -1 ? -1 : pstat);
+	(void)__libc_sigaction(SIGINT, &intact, NULL);
+	(void)__libc_sigaction(SIGQUIT,  &quitact, NULL);
+	(void)__libc_sigprocmask(SIG_SETMASK, &oldsigblock, NULL);
+	return (pid == -1 ? -1 : pstat);
 }
 
 __weak_reference(__libc_system, __system);