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Diffstat (limited to 'compiler-rt/lib/hwasan/hwasan_dynamic_shadow.cc')
-rw-r--r-- | compiler-rt/lib/hwasan/hwasan_dynamic_shadow.cc | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/compiler-rt/lib/hwasan/hwasan_dynamic_shadow.cc b/compiler-rt/lib/hwasan/hwasan_dynamic_shadow.cc new file mode 100644 index 00000000000..17338003aa6 --- /dev/null +++ b/compiler-rt/lib/hwasan/hwasan_dynamic_shadow.cc @@ -0,0 +1,132 @@ +//===-- hwasan_dynamic_shadow.cc --------------------------------*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +/// +/// \file +/// This file is a part of HWAddressSanitizer. It reserves dynamic shadow memory +/// region and handles ifunc resolver case, when necessary. +/// +//===----------------------------------------------------------------------===// + +#include "hwasan_dynamic_shadow.h" +#include "hwasan_mapping.h" +#include "sanitizer_common/sanitizer_common.h" +#include "sanitizer_common/sanitizer_posix.h" + +// The code in this file needs to run in an unrelocated binary. It should not +// access any external symbol, including its own non-hidden globals. + +namespace __hwasan { + +static void UnmapFromTo(uptr from, uptr to) { + if (to == from) + return; + CHECK(to >= from); + uptr res = internal_munmap(reinterpret_cast<void *>(from), to - from); + if (UNLIKELY(internal_iserror(res))) { + Report("ERROR: %s failed to unmap 0x%zx (%zd) bytes at address %p\n", + SanitizerToolName, to - from, to - from, from); + CHECK("unable to unmap" && 0); + } +} + +// Returns an address aligned to 8 pages, such that one page on the left and +// shadow_size_bytes bytes on the right of it are mapped r/o. +static uptr MapDynamicShadow(uptr shadow_size_bytes) { + const uptr granularity = GetMmapGranularity(); + const uptr alignment = granularity * SHADOW_GRANULARITY; + const uptr left_padding = granularity; + const uptr shadow_size = + RoundUpTo(shadow_size_bytes, granularity); + const uptr map_size = shadow_size + left_padding + alignment; + + const uptr map_start = (uptr)MmapNoAccess(map_size); + CHECK_NE(map_start, ~(uptr)0); + + const uptr shadow_start = RoundUpTo(map_start + left_padding, alignment); + + UnmapFromTo(map_start, shadow_start - left_padding); + UnmapFromTo(shadow_start + shadow_size, map_start + map_size); + + return shadow_start; +} + +} // namespace __hwasan + +#if HWASAN_PREMAP_SHADOW + +extern "C" { + +INTERFACE_ATTRIBUTE void __hwasan_shadow(); +decltype(__hwasan_shadow)* __hwasan_premap_shadow(); + +} // extern "C" + +namespace __hwasan { + +// Conservative upper limit. +static uptr PremapShadowSize() { + return RoundUpTo(GetMaxVirtualAddress() >> kShadowScale, + GetMmapGranularity()); +} + +static uptr PremapShadow() { + return MapDynamicShadow(PremapShadowSize()); +} + +static bool IsPremapShadowAvailable() { + const uptr shadow = reinterpret_cast<uptr>(&__hwasan_shadow); + const uptr resolver = reinterpret_cast<uptr>(&__hwasan_premap_shadow); + // shadow == resolver is how Android KitKat and older handles ifunc. + // shadow == 0 just in case. + return shadow != 0 && shadow != resolver; +} + +static uptr FindPremappedShadowStart(uptr shadow_size_bytes) { + const uptr granularity = GetMmapGranularity(); + const uptr shadow_start = reinterpret_cast<uptr>(&__hwasan_shadow); + const uptr premap_shadow_size = PremapShadowSize(); + const uptr shadow_size = RoundUpTo(shadow_size_bytes, granularity); + + // We may have mapped too much. Release extra memory. + UnmapFromTo(shadow_start + shadow_size, shadow_start + premap_shadow_size); + return shadow_start; +} + +} // namespace __hwasan + +extern "C" { + +decltype(__hwasan_shadow)* __hwasan_premap_shadow() { + // The resolver might be called multiple times. Map the shadow just once. + static __sanitizer::uptr shadow = 0; + if (!shadow) + shadow = __hwasan::PremapShadow(); + return reinterpret_cast<decltype(__hwasan_shadow)*>(shadow); +} + +// __hwasan_shadow is a "function" that has the same address as the first byte +// of the shadow mapping. +INTERFACE_ATTRIBUTE __attribute__((ifunc("__hwasan_premap_shadow"))) +void __hwasan_shadow(); + +} // extern "C" + +#endif // HWASAN_PREMAP_SHADOW + +namespace __hwasan { + +uptr FindDynamicShadowStart(uptr shadow_size_bytes) { +#if HWASAN_PREMAP_SHADOW + if (IsPremapShadowAvailable()) + return FindPremappedShadowStart(shadow_size_bytes); +#endif + return MapDynamicShadow(shadow_size_bytes); +} + +} // namespace __hwasan |