Intercept tzset in MSan on NetBSD

[krytarowski]

Summary

Handle function renaming tzset -> __tzset50 on NetBSD.

Reset arguments passed to tzset() as it does not accept
input parameters.

The tzset() syscall must be called on NetBSD with
InterceptorScope. Once a user sets timezone (either
by TZ or /etc/localtime symlink), tzset() reloads the
internal data and this reports false-positive alarms.

Other functions (like the localtime() interceptor)
already use InterceptorScope.

Sponsored by <The NetBSD Foundation>

[vitalybuka]

lib/msan/msan_interceptors.cc

1142

Any idea why we had "int fake" there?

[krytarowski]

lib/msan/msan_interceptors.cc

1142

It looks like a bug, maybe @eugenis can share more insight.

[eugenis]

lib/msan/msan_interceptors.cc

1142

That's to suppress compiler warnings about vararg macros with no arguments, or something like that.

[krytarowski]

lib/msan/msan_interceptors.cc

1142

I'm not observing warnings locally. Unless I miss something, calling a function with fake arguments breaks ABI constraints (but it's tolerable in this particular case on x86_64).

[eugenis]

lib/msan/msan_interceptors.cc

1142

try search code history. Could have been GCC.

[devnexen]

lib/msan/msan_interceptors.cc

1142

Just to add a point, it helps to solves an issue in my pending request, in FreeBSD we really need to have the correct signature.

[krytarowski]

I've entirely switched to NetBSD kernel fixes in order to host fully-functional LLDB. Once I will be done with the debugger, I will be back to sanitizers and work on connecting a buildbot and remaining fixes and cleanup.

[krytarowski]

Ping?

[krytarowski]

I will abandon it for now, if it will make problems again I will show up with a new patch.

lib/msan/msan_interceptors.cc

 #include "sanitizer_common/sanitizer_libc.h"
 #include "sanitizer_common/sanitizer_linux.h"
 #include "sanitizer_common/sanitizer_tls_get_addr.h"
 
 #if SANITIZER_NETBSD
 #define fstat __fstat50
 #define gettimeofday __gettimeofday50
 #define getrusage __getrusage50
+#define tzset __tzset50
 #endif
 
 #include <stdarg.h>
 // ACHTUNG! No other system header includes in this file.
 // Ideally, we should get rid of stdarg.h as well.
 
 using namespace __msan;
 
INTERCEPTOR(int, pthread_join, void *th, void **retval) {
   int res = REAL(pthread_join)(th, retval);
   if (!res && retval)
     __msan_unpoison(retval, sizeof(*retval));
   return res;
 }
 
 extern char *tzname[2];
 
-INTERCEPTOR(void, tzset, int fake) {
+INTERCEPTOR(void, tzset, void) {
   ENSURE_MSAN_INITED();
-  REAL(tzset)(fake);
+  // Required for NetBSD, as there might be reloaded internal structs and we
+  // don't sanitize them.
+  InterceptorScope interceptor_scope;
+  REAL(tzset)();
   if (tzname[0])
     __msan_unpoison(tzname[0], REAL(strlen)(tzname[0]) + 1);
   if (tzname[1])
     __msan_unpoison(tzname[1], REAL(strlen)(tzname[1]) + 1);
   return;
 }
 
 struct MSanAtExitRecord {