forked from OSchip/llvm-project
80 lines
2.7 KiB
C++
80 lines
2.7 KiB
C++
|
//===-- asan_premap_shadow.cc ---------------------------------------------===//
|
||
|
|
//
|
||
|
|
// The LLVM Compiler Infrastructure
|
||
|
|
//
|
||
|
|
// This file is distributed under the University of Illinois Open Source
|
||
|
|
// License. See LICENSE.TXT for details.
|
||
|
|
//
|
||
|
|
//===----------------------------------------------------------------------===//
|
||
|
|
//
|
||
|
|
// This file is a part of AddressSanitizer, an address sanity checker.
|
||
|
|
//
|
||
|
|
// Reserve shadow memory with an ifunc resolver.
|
||
|
|
//===----------------------------------------------------------------------===//
|
||
|
|
|
||
|
|
#include "asan_mapping.h"
|
||
|
|
|
||
|
|
#if ASAN_PREMAP_SHADOW
|
||
|
|
|
||
|
|
#include "asan_premap_shadow.h"
|
||
|
|
#include "sanitizer_common/sanitizer_posix.h"
|
||
|
|
|
||
|
|
namespace __asan {
|
||
|
|
|
||
|
|
// The code in this file needs to run in an unrelocated binary. It may not
|
||
|
|
// access any external symbol, including its own non-hidden globals.
|
||
|
|
|
||
|
|
// Conservative upper limit.
|
||
|
|
uptr PremapShadowSize() {
|
||
|
|
uptr granularity = GetMmapGranularity();
|
||
|
|
return RoundUpTo(GetMaxVirtualAddress() >> SHADOW_SCALE, granularity);
|
||
|
|
}
|
||
|
|
|
||
|
|
// Returns an address aligned to 8 pages, such that one page on the left and
|
||
|
|
// PremapShadowSize() bytes on the right of it are mapped r/o.
|
||
|
|
uptr PremapShadow() {
|
||
|
|
uptr granularity = GetMmapGranularity();
|
||
|
|
uptr alignment = granularity * 8;
|
||
|
|
uptr left_padding = granularity;
|
||
|
|
uptr shadow_size = PremapShadowSize();
|
||
|
|
uptr map_size = shadow_size + left_padding + alignment;
|
||
|
|
|
||
|
|
uptr map_start = (uptr)MmapNoAccess(map_size);
|
||
|
|
CHECK_NE(map_start, ~(uptr)0);
|
||
|
|
|
||
|
|
uptr shadow_start = RoundUpTo(map_start + left_padding, alignment);
|
||
|
|
uptr shadow_end = shadow_start + shadow_size;
|
||
|
|
internal_munmap(reinterpret_cast<void *>(map_start),
|
||
|
|
shadow_start - left_padding - map_start);
|
||
|
|
internal_munmap(reinterpret_cast<void *>(shadow_end),
|
||
|
|
map_start + map_size - shadow_end);
|
||
|
|
return shadow_start;
|
||
|
|
}
|
||
|
|
|
||
|
|
bool PremapShadowFailed() {
|
||
|
|
uptr shadow = reinterpret_cast<uptr>(&__asan_shadow);
|
||
|
|
uptr resolver = reinterpret_cast<uptr>(&__asan_premap_shadow);
|
||
|
|
// shadow == resolver is how Android KitKat and older handles ifunc.
|
||
|
|
// shadow == 0 just in case.
|
||
|
|
if (shadow == 0 || shadow == resolver)
|
||
|
|
return true;
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
} // namespace __asan
|
||
|
|
|
||
|
|
extern "C" {
|
||
|
|
decltype(__asan_shadow)* __asan_premap_shadow() {
|
||
|
|
// The resolver may be called multiple times. Map the shadow just once.
|
||
|
|
static uptr premapped_shadow = 0;
|
||
|
|
if (!premapped_shadow) premapped_shadow = __asan::PremapShadow();
|
||
|
|
return reinterpret_cast<decltype(__asan_shadow)*>(premapped_shadow);
|
||
|
|
}
|
||
|
|
|
||
|
|
// __asan_shadow is a "function" that has the same address as the first byte of
|
||
|
|
// the shadow mapping.
|
||
|
|
INTERFACE_ATTRIBUTE __attribute__((ifunc("__asan_premap_shadow"))) void
|
||
|
|
__asan_shadow();
|
||
|
|
}
|
||
|
|
|
||
|
|
#endif // ASAN_PREMAP_SHADOW
|