1 /* 2 * Copyright (C) 2016 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #ifndef _LINKER_CFI_H_ 30 #define _LINKER_CFI_H_ 31 32 #include "linker.h" 33 #include "linker_debug.h" 34 35 #include <algorithm> 36 37 #include "private/CFIShadow.h" 38 39 // This class keeps the contents of CFI shadow up-to-date with the current set of loaded libraries. 40 // See the comment in CFIShadow.h for more context. 41 // See documentation in http://clang.llvm.org/docs/ControlFlowIntegrityDesign.html#shared-library-support. 42 // 43 // Shadow is mapped and initialized lazily as soon as the first CFI-enabled DSO is loaded. 44 // It is updated after any library is loaded (but before any constructors are ran), and 45 // before any library is unloaded. 46 class CFIShadowWriter : private CFIShadow { 47 // Returns pointer to the shadow element for an address. MemToShadow(uintptr_t x)48 uint16_t* MemToShadow(uintptr_t x) { 49 return reinterpret_cast<uint16_t*>(*shadow_start + MemToShadowOffset(x)); 50 } 51 52 // Update shadow for the address range to the given constant value. 53 void AddConstant(uintptr_t begin, uintptr_t end, uint16_t v); 54 55 // Update shadow for the address range to kUncheckedShadow. 56 void AddUnchecked(uintptr_t begin, uintptr_t end); 57 58 // Update shadow for the address range to kInvalidShadow. 59 void AddInvalid(uintptr_t begin, uintptr_t end); 60 61 // Update shadow for the address range to the given __cfi_check value. 62 void Add(uintptr_t begin, uintptr_t end, uintptr_t cfi_check); 63 64 // Add a DSO to CFI shadow. 65 bool AddLibrary(soinfo* si); 66 67 // Map CFI shadow. 68 uintptr_t MapShadow(); 69 70 // Initialize CFI shadow and update its contents for everything in solist if any loaded library is 71 // CFI-enabled. If new_si != nullptr, do an incremental check by looking only at new_si; otherwise 72 // look at the entire solist. 73 bool MaybeInit(soinfo *new_si, soinfo *solist); 74 75 // Set a human readable name for the entire shadow region. 76 void FixupVmaName(); 77 78 // Pass the pointer to the mapped shadow region to libdl. Must only be called once. 79 // Flips shadow_start to a non-nullptr value. 80 bool NotifyLibDl(soinfo *solist, uintptr_t p); 81 82 // Pointer to the shadow start address. 83 uintptr_t *shadow_start; 84 85 bool initial_link_done; 86 87 public: 88 // Update shadow after loading a DSO. 89 // This function will initialize the shadow if it sees a CFI-enabled DSO for the first time. 90 // In that case it will retroactively update shadow for all previously loaded DSOs. "solist" is a 91 // pointer to the global list. 92 // This function must be called before any user code has observed the newly loaded DSO. 93 bool AfterLoad(soinfo* si, soinfo *solist); 94 95 // Update shadow before unloading a DSO. 96 void BeforeUnload(soinfo* si); 97 98 // This is called as soon as the initial set of libraries is linked. 99 bool InitialLinkDone(soinfo *solist); 100 101 // Handle failure to locate __cfi_check for a target address. 102 static void CfiFail(uint64_t CallSiteTypeId, void* Ptr, void* DiagData, void *caller_pc); 103 }; 104 105 CFIShadowWriter* get_cfi_shadow(); 106 107 #endif // _LINKER_CFI_H_ 108