[PATCH] D57179: Enhance support for NetBSD in SafeStack

[Vitaly Buka via Phabricator via llvm-commits]

vitalybuka accepted this revision.
vitalybuka added inline comments.
This revision is now accepted and ready to land.


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Comment at: lib/safestack/safestack_platform.h:97
 #if SANITIZER_NETBSD
-  return mmap(addr, length, prot, flags, fd, offset);
+  SFS_CHECK(&__mmap);
+  return __mmap(addr, length, prot, flags, fd, 0, offset);
----------------
This SFS_CHECK (like the on in sanitizer_common) is not useful with or without weak
It will crash anyway with obvious stack on null pointer.


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Comment at: lib/safestack/safestack_platform.h:116
 inline int Mprotect(void *addr, size_t length, int prot) {
 #if SANITIZER_NETBSD
+  DEFINE__REAL(int, mprotect, void *a, size_t b, int c);
----------------
krytarowski wrote:
> vitalybuka wrote:
> > We don't want to hit interpector here, because it can be called called from preinit_array.
> > DEFINE__REAL will avoid interceptors, however dlsym from preinit_array may crash as it can to try to allocate memory.
> > So we use syscall on linux. 
> > sanitizer_common/sanitizer_netbsd still had such problem, so I didn't bother to copy DEFINE_REAL.
> > 
> NetBSD does not use/support `preinit_array`, except on archs that demand it (amd64/i386 aren't in the set).
> 
> How does it crash with allocating the memory? By calling real malloc? Dynamic loader on NetBSD uses its internal copy of xmalloc() for allocations.
> 
> According to my quick testing with gdb(1) and an example program, dlsym(3) does not allocate anything through xmalloc() (at least for RTLD_SELF).
Yes, on linux it crashes with malloc which can be not initialized (if its non standard allocator)




Repository:
  rL LLVM

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  https://reviews.llvm.org/D57179/new/

https://reviews.llvm.org/D57179