135 lines
4.4 KiB
C++
135 lines
4.4 KiB
C++
//===-- hwasan_dynamic_shadow.cpp -------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// This file is a part of HWAddressSanitizer. It reserves dynamic shadow memory
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/// region and handles ifunc resolver case, when necessary.
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///
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//===----------------------------------------------------------------------===//
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#include "hwasan_dynamic_shadow.h"
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#include <elf.h>
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#include <link.h>
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#include "hwasan.h"
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#include "hwasan_mapping.h"
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#include "hwasan_thread_list.h"
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#include "sanitizer_common/sanitizer_common.h"
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#include "sanitizer_common/sanitizer_posix.h"
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// The code in this file needs to run in an unrelocated binary. It should not
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// access any external symbol, including its own non-hidden globals.
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#if SANITIZER_ANDROID
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extern "C" {
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INTERFACE_ATTRIBUTE void __hwasan_shadow();
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decltype(__hwasan_shadow)* __hwasan_premap_shadow();
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} // extern "C"
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namespace __hwasan {
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// Conservative upper limit.
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static uptr PremapShadowSize() {
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return RoundUpTo(GetMaxVirtualAddress() >> kShadowScale,
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GetMmapGranularity());
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}
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static uptr PremapShadow() {
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return MapDynamicShadow(PremapShadowSize(), kShadowScale,
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kShadowBaseAlignment, kHighMemEnd);
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}
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static bool IsPremapShadowAvailable() {
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const uptr shadow = reinterpret_cast<uptr>(&__hwasan_shadow);
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const uptr resolver = reinterpret_cast<uptr>(&__hwasan_premap_shadow);
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// shadow == resolver is how Android KitKat and older handles ifunc.
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// shadow == 0 just in case.
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return shadow != 0 && shadow != resolver;
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}
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static uptr FindPremappedShadowStart(uptr shadow_size_bytes) {
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const uptr granularity = GetMmapGranularity();
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const uptr shadow_start = reinterpret_cast<uptr>(&__hwasan_shadow);
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const uptr premap_shadow_size = PremapShadowSize();
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const uptr shadow_size = RoundUpTo(shadow_size_bytes, granularity);
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// We may have mapped too much. Release extra memory.
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UnmapFromTo(shadow_start + shadow_size, shadow_start + premap_shadow_size);
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return shadow_start;
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}
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} // namespace __hwasan
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extern "C" {
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decltype(__hwasan_shadow)* __hwasan_premap_shadow() {
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// The resolver might be called multiple times. Map the shadow just once.
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static __sanitizer::uptr shadow = 0;
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if (!shadow)
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shadow = __hwasan::PremapShadow();
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return reinterpret_cast<decltype(__hwasan_shadow)*>(shadow);
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}
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// __hwasan_shadow is a "function" that has the same address as the first byte
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// of the shadow mapping.
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INTERFACE_ATTRIBUTE __attribute__((ifunc("__hwasan_premap_shadow")))
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void __hwasan_shadow();
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extern __attribute((weak, visibility("hidden"))) ElfW(Rela) __rela_iplt_start[],
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__rela_iplt_end[];
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} // extern "C"
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namespace __hwasan {
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void InitShadowGOT() {
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// Call the ifunc resolver for __hwasan_shadow and fill in its GOT entry. This
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// needs to be done before other ifunc resolvers (which are handled by libc)
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// because a resolver might read __hwasan_shadow.
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typedef ElfW(Addr) (*ifunc_resolver_t)(void);
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for (ElfW(Rela) *r = __rela_iplt_start; r != __rela_iplt_end; ++r) {
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ElfW(Addr)* offset = reinterpret_cast<ElfW(Addr)*>(r->r_offset);
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ElfW(Addr) resolver = r->r_addend;
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if (resolver == reinterpret_cast<ElfW(Addr)>(&__hwasan_premap_shadow)) {
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*offset = reinterpret_cast<ifunc_resolver_t>(resolver)();
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break;
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}
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}
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}
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uptr FindDynamicShadowStart(uptr shadow_size_bytes) {
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if (IsPremapShadowAvailable())
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return FindPremappedShadowStart(shadow_size_bytes);
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return MapDynamicShadow(shadow_size_bytes, kShadowScale, kShadowBaseAlignment,
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kHighMemEnd);
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}
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} // namespace __hwasan
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#else
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namespace __hwasan {
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void InitShadowGOT() {}
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uptr FindDynamicShadowStart(uptr shadow_size_bytes) {
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# if defined(HWASAN_ALIASING_MODE)
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constexpr uptr kAliasSize = 1ULL << kAddressTagShift;
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constexpr uptr kNumAliases = 1ULL << kTagBits;
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return MapDynamicShadowAndAliases(shadow_size_bytes, kAliasSize, kNumAliases,
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RingBufferSize());
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# endif
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return MapDynamicShadow(shadow_size_bytes, kShadowScale, kShadowBaseAlignment,
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kHighMemEnd);
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}
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} // namespace __hwasan
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#endif // SANITIZER_ANDROID
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