Index: lib/safestack/safestack_platform.h
===================================================================
--- lib/safestack/safestack_platform.h
+++ lib/safestack/safestack_platform.h
@@ -13,9 +13,13 @@
 #ifndef SAFESTACK_PLATFORM_H
 #define SAFESTACK_PLATFORM_H
 
+#include "safestack_util.h"
 #include "sanitizer_common/sanitizer_platform.h"
 
+#include <dlfcn.h>
 #include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
 #include <sys/mman.h>
 #include <sys/syscall.h>
 #include <sys/types.h>
@@ -27,6 +31,8 @@
 
 #if SANITIZER_NETBSD
 #include <lwp.h>
+
+extern "C" void *__mmap(void *, size_t, int, int, int, int, off_t);
 #endif
 
 #if SANITIZER_FREEBSD
@@ -35,11 +41,34 @@
 
 namespace safestack {
 
+#if SANITIZER_NETBSD
+static void *GetRealLibcAddress(const char *symbol) {
+  void *real = dlsym(RTLD_NEXT, symbol);
+  if (!real)
+    real = dlsym(RTLD_DEFAULT, symbol);
+  if (!real) {
+    fprintf(stderr, "safestack GetRealLibcAddress failed for symbol=%s",
+            symbol);
+    abort();
+  }
+  return real;
+}
+
+#define _REAL(func, ...) real##_##func(__VA_ARGS__)
+#define DEFINE__REAL(ret_type, func, ...)                              \
+  static ret_type (*real_##func)(__VA_ARGS__) = NULL;                  \
+  if (!real_##func) {                                                  \
+    real_##func = (ret_type(*)(__VA_ARGS__))GetRealLibcAddress(#func); \
+  }                                                                    \
+  SFS_CHECK(real_##func);
+#endif
+
 using ThreadId = uint64_t;
 
 inline ThreadId GetTid() {
 #if SANITIZER_NETBSD
-  return _lwp_self();
+  DEFINE__REAL(int, _lwp_self);
+  return _REAL(_lwp_self);
 #elif SANITIZER_FREEBSD
   long Tid;
   thr_self(&Tid);
@@ -51,8 +80,9 @@
 
 inline int TgKill(pid_t pid, ThreadId tid, int sig) {
 #if SANITIZER_NETBSD
+  DEFINE__REAL(int, _lwp_kill, int a, int b);
   (void)pid;
-  return _lwp_kill(tid, sig);
+  return _REAL(_lwp_kill, tid, sig);
 #elif SANITIZER_FREEBSD
   return syscall(SYS_thr_kill2, pid, tid, sig);
 #else
@@ -63,7 +93,7 @@
 inline void *Mmap(void *addr, size_t length, int prot, int flags, int fd,
                   off_t offset) {
 #if SANITIZER_NETBSD
-  return mmap(addr, length, prot, flags, fd, offset);
+  return __mmap(addr, length, prot, flags, fd, 0, offset);
 #elif defined(__x86_64__) && (SANITIZER_FREEBSD)
   return (void *)__syscall(SYS_mmap, addr, length, prot, flags, fd, offset);
 #else
@@ -73,7 +103,8 @@
 
 inline int Munmap(void *addr, size_t length) {
 #if SANITIZER_NETBSD
-  return munmap(addr, length);
+  DEFINE__REAL(int, munmap, void *a, size_t b);
+  return _REAL(munmap, addr, length);
 #else
   return syscall(SYS_munmap, addr, length);
 #endif
@@ -81,7 +112,8 @@
 
 inline int Mprotect(void *addr, size_t length, int prot) {
 #if SANITIZER_NETBSD
-  return mprotect(addr, length, prot);
+  DEFINE__REAL(int, mprotect, void *a, size_t b, int c);
+  return _REAL(mprotect, addr, length, prot);
 #else
   return syscall(SYS_mprotect, addr, length, prot);
 #endif