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, 12 insertions, 3 deletions

diff --git a/lib/libc/stdlib/system.c b/lib/libc/stdlib/system.c
index e018e6f..bd9ea5a 100644
--- a/lib/libc/stdlib/system.c
+++ b/lib/libc/stdlib/system.c
@@ -46,8 +46,17 @@ __FBSDID("$FreeBSD$");
 #include "un-namespace.h"
 #include "libc_private.h"
 
+#pragma weak system
 int
-__system(const char *command)
+system(const char *command)
+{
+
+	return (((int (*)(const char *))
+	    __libc_interposing[INTERPOS_system])(command));
+}
+
+int
+__libc_system(const char *command)
 {
 	pid_t pid, savedpid;
 	int pstat;
@@ -95,5 +104,5 @@ __system(const char *command)
 	return(pid == -1 ? -1 : pstat);
 }
 
-__weak_reference(__system, system);
-__weak_reference(__system, _system);
+__weak_reference(__libc_system, __system);
+__weak_reference(__libc_system, _system);