| //===-- hwasan_dynamic_shadow.cpp -------------------------------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| /// |
| /// \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 <elf.h> |
| #include <link.h> |
| |
| #include "hwasan.h" |
| #include "hwasan_mapping.h" |
| #include "hwasan_thread_list.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. |
| |
| #if SANITIZER_ANDROID |
| 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(), kShadowScale, |
| kShadowBaseAlignment, kHighMemEnd); |
| } |
| |
| 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 __attribute((weak, visibility("hidden"))) ElfW(Rela) __rela_iplt_start[], |
| __rela_iplt_end[]; |
| |
| } // extern "C" |
| |
| namespace __hwasan { |
| |
| void InitShadowGOT() { |
| // Call the ifunc resolver for __hwasan_shadow and fill in its GOT entry. This |
| // needs to be done before other ifunc resolvers (which are handled by libc) |
| // because a resolver might read __hwasan_shadow. |
| typedef ElfW(Addr) (*ifunc_resolver_t)(void); |
| for (ElfW(Rela) *r = __rela_iplt_start; r != __rela_iplt_end; ++r) { |
| ElfW(Addr)* offset = reinterpret_cast<ElfW(Addr)*>(r->r_offset); |
| ElfW(Addr) resolver = r->r_addend; |
| if (resolver == reinterpret_cast<ElfW(Addr)>(&__hwasan_premap_shadow)) { |
| *offset = reinterpret_cast<ifunc_resolver_t>(resolver)(); |
| break; |
| } |
| } |
| } |
| |
| uptr FindDynamicShadowStart(uptr shadow_size_bytes) { |
| if (IsPremapShadowAvailable()) |
| return FindPremappedShadowStart(shadow_size_bytes); |
| return MapDynamicShadow(shadow_size_bytes, kShadowScale, kShadowBaseAlignment, |
| kHighMemEnd); |
| } |
| |
| } // namespace __hwasan |
| |
| #elif SANITIZER_FUCHSIA |
| |
| namespace __hwasan { |
| |
| void InitShadowGOT() {} |
| |
| } // namespace __hwasan |
| |
| #else |
| namespace __hwasan { |
| |
| void InitShadowGOT() {} |
| |
| uptr FindDynamicShadowStart(uptr shadow_size_bytes) { |
| # if defined(HWASAN_ALIASING_MODE) |
| constexpr uptr kAliasSize = 1ULL << kAddressTagShift; |
| constexpr uptr kNumAliases = 1ULL << kTagBits; |
| return MapDynamicShadowAndAliases(shadow_size_bytes, kAliasSize, kNumAliases, |
| RingBufferSize()); |
| # endif |
| return MapDynamicShadow(shadow_size_bytes, kShadowScale, kShadowBaseAlignment, |
| kHighMemEnd); |
| } |
| |
| } // namespace __hwasan |
| |
| #endif // SANITIZER_ANDROID |