Fix known issues which blow up the process after dlopen("libthr.so")

(or loading a dso linked to libthr.so into process which was not
linked against threading library).

MFC r276630:
Remove interposing, fix malloc, reinstall signal handlers wrappers on
libthr load.

MFC r276681:
Avoid calling internal libc function through PLT or accessing data
though GOT.

MFC r277032:
Reduce the size of the interposing table and amount of
cancellation-handling code in the libthr.

MFC note:
r276646 ("do not erronously export 'openat' symbol from rtld") is not
applicable to stable/10 yet, since PATHFDS support was not merged.

1 files changed, 21 insertions, 1 deletions

diff --git a/lib/libc/sys/fcntl.c b/lib/libc/sys/fcntl.c
index 480cc40..4cb887b 100644
--- a/lib/libc/sys/fcntl.c
+++ b/lib/libc/sys/fcntl.c
@@ -34,7 +34,23 @@ __FBSDID("$FreeBSD$");
 #include <sys/syscall.h>
 #include "libc_private.h"
 
-__weak_reference(__fcntl_compat, fcntl);
+#pragma weak fcntl
+int
+fcntl(int fd, int cmd, ...)
+{
+	va_list args;
+	long arg;
+
+	va_start(args, cmd);
+	arg = va_arg(args, long);
+	va_end(args);
+
+	return (((int (*)(int, int, ...))
+	    __libc_interposing[INTERPOS_fcntl])(fd, cmd, arg));
+}
+
+#ifdef SYSCALL_COMPAT
+__weak_reference(__fcntl_compat, __fcntl);
 
 int
 __fcntl_compat(int fd, int cmd, ...)
@@ -87,3 +103,7 @@ __fcntl_compat(int fd, int cmd, ...)
 		return (__sys_fcntl(fd, cmd, arg));
 	}
 }
+#else
+__weak_reference(__sys_fcntl, __fcntl_compat);
+__weak_reference(__sys_fcntl, __fcntl);
+#endif