168d75effSDimitry Andric //===-- asan_premap_shadow.cpp --------------------------------------------===// 268d75effSDimitry Andric // 368d75effSDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 468d75effSDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 568d75effSDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 668d75effSDimitry Andric // 768d75effSDimitry Andric //===----------------------------------------------------------------------===// 868d75effSDimitry Andric // 968d75effSDimitry Andric // This file is a part of AddressSanitizer, an address sanity checker. 1068d75effSDimitry Andric // 1168d75effSDimitry Andric // Reserve shadow memory with an ifunc resolver. 1268d75effSDimitry Andric //===----------------------------------------------------------------------===// 1368d75effSDimitry Andric 1468d75effSDimitry Andric #include "asan_mapping.h" 1568d75effSDimitry Andric 1668d75effSDimitry Andric #if ASAN_PREMAP_SHADOW 1768d75effSDimitry Andric 1868d75effSDimitry Andric #include "asan_premap_shadow.h" 1968d75effSDimitry Andric #include "sanitizer_common/sanitizer_posix.h" 2068d75effSDimitry Andric 2168d75effSDimitry Andric namespace __asan { 2268d75effSDimitry Andric 2368d75effSDimitry Andric // The code in this file needs to run in an unrelocated binary. It may not 2468d75effSDimitry Andric // access any external symbol, including its own non-hidden globals. 2568d75effSDimitry Andric 2668d75effSDimitry Andric // Conservative upper limit. PremapShadowSize()2768d75effSDimitry Andricuptr PremapShadowSize() { 2868d75effSDimitry Andric uptr granularity = GetMmapGranularity(); 29*0eae32dcSDimitry Andric return RoundUpTo(GetMaxVirtualAddress() >> ASAN_SHADOW_SCALE, granularity); 3068d75effSDimitry Andric } 3168d75effSDimitry Andric 3268d75effSDimitry Andric // Returns an address aligned to 8 pages, such that one page on the left and 3368d75effSDimitry Andric // PremapShadowSize() bytes on the right of it are mapped r/o. PremapShadow()3468d75effSDimitry Andricuptr PremapShadow() { 35e8d8bef9SDimitry Andric return MapDynamicShadow(PremapShadowSize(), /*mmap_alignment_scale*/ 3, 36e8d8bef9SDimitry Andric /*min_shadow_base_alignment*/ 0, kHighMemEnd); 3768d75effSDimitry Andric } 3868d75effSDimitry Andric PremapShadowFailed()3968d75effSDimitry Andricbool PremapShadowFailed() { 4068d75effSDimitry Andric uptr shadow = reinterpret_cast<uptr>(&__asan_shadow); 4168d75effSDimitry Andric uptr resolver = reinterpret_cast<uptr>(&__asan_premap_shadow); 4268d75effSDimitry Andric // shadow == resolver is how Android KitKat and older handles ifunc. 4368d75effSDimitry Andric // shadow == 0 just in case. 4468d75effSDimitry Andric if (shadow == 0 || shadow == resolver) 4568d75effSDimitry Andric return true; 4668d75effSDimitry Andric return false; 4768d75effSDimitry Andric } 4868d75effSDimitry Andric } // namespace __asan 4968d75effSDimitry Andric 5068d75effSDimitry Andric extern "C" { __asan_premap_shadow()5168d75effSDimitry Andricdecltype(__asan_shadow)* __asan_premap_shadow() { 5268d75effSDimitry Andric // The resolver may be called multiple times. Map the shadow just once. 5368d75effSDimitry Andric static uptr premapped_shadow = 0; 5468d75effSDimitry Andric if (!premapped_shadow) premapped_shadow = __asan::PremapShadow(); 5568d75effSDimitry Andric return reinterpret_cast<decltype(__asan_shadow)*>(premapped_shadow); 5668d75effSDimitry Andric } 5768d75effSDimitry Andric 5868d75effSDimitry Andric // __asan_shadow is a "function" that has the same address as the first byte of 5968d75effSDimitry Andric // the shadow mapping. 6068d75effSDimitry Andric INTERFACE_ATTRIBUTE __attribute__((ifunc("__asan_premap_shadow"))) void 6168d75effSDimitry Andric __asan_shadow(); 6268d75effSDimitry Andric } 6368d75effSDimitry Andric 6468d75effSDimitry Andric #endif // ASAN_PREMAP_SHADOW 65