1 /*===- InstrProfilingPlatformLinux.c - Profile data Linux platform ------===*\ 2 |* 3 |* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 |* See https://llvm.org/LICENSE.txt for license information. 5 |* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 |* 7 \*===----------------------------------------------------------------------===*/ 8 9 #if defined(__linux__) || defined(__FreeBSD__) || defined(__Fuchsia__) || \ 10 (defined(__sun__) && defined(__svr4__)) || defined(__NetBSD__) 11 12 #include <elf.h> 13 #include <link.h> 14 #include <stdlib.h> 15 #include <string.h> 16 17 #include "InstrProfiling.h" 18 #include "InstrProfilingInternal.h" 19 20 #if defined(__FreeBSD__) && !defined(ElfW) 21 /* 22 * FreeBSD's elf.h and link.h headers do not define the ElfW(type) macro yet. 23 * If this is added to all supported FreeBSD versions in the future, this 24 * compatibility macro can be removed. 25 */ 26 #define ElfW(type) __ElfN(type) 27 #endif 28 29 #define PROF_DATA_START INSTR_PROF_SECT_START(INSTR_PROF_DATA_COMMON) 30 #define PROF_DATA_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_DATA_COMMON) 31 #define PROF_NAME_START INSTR_PROF_SECT_START(INSTR_PROF_NAME_COMMON) 32 #define PROF_NAME_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_NAME_COMMON) 33 #define PROF_CNTS_START INSTR_PROF_SECT_START(INSTR_PROF_CNTS_COMMON) 34 #define PROF_CNTS_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_CNTS_COMMON) 35 #define PROF_ORDERFILE_START INSTR_PROF_SECT_START(INSTR_PROF_ORDERFILE_COMMON) 36 #define PROF_VNODES_START INSTR_PROF_SECT_START(INSTR_PROF_VNODES_COMMON) 37 #define PROF_VNODES_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_VNODES_COMMON) 38 39 /* Declare section start and stop symbols for various sections 40 * generated by compiler instrumentation. 41 */ 42 extern __llvm_profile_data PROF_DATA_START COMPILER_RT_VISIBILITY 43 COMPILER_RT_WEAK; 44 extern __llvm_profile_data PROF_DATA_STOP COMPILER_RT_VISIBILITY 45 COMPILER_RT_WEAK; 46 extern char PROF_CNTS_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK; 47 extern char PROF_CNTS_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK; 48 extern uint32_t PROF_ORDERFILE_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK; 49 extern char PROF_NAME_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK; 50 extern char PROF_NAME_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK; 51 extern ValueProfNode PROF_VNODES_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK; 52 extern ValueProfNode PROF_VNODES_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK; 53 54 COMPILER_RT_VISIBILITY const __llvm_profile_data * 55 __llvm_profile_begin_data(void) { 56 return &PROF_DATA_START; 57 } 58 COMPILER_RT_VISIBILITY const __llvm_profile_data * 59 __llvm_profile_end_data(void) { 60 return &PROF_DATA_STOP; 61 } 62 COMPILER_RT_VISIBILITY const char *__llvm_profile_begin_names(void) { 63 return &PROF_NAME_START; 64 } 65 COMPILER_RT_VISIBILITY const char *__llvm_profile_end_names(void) { 66 return &PROF_NAME_STOP; 67 } 68 COMPILER_RT_VISIBILITY char *__llvm_profile_begin_counters(void) { 69 return &PROF_CNTS_START; 70 } 71 COMPILER_RT_VISIBILITY char *__llvm_profile_end_counters(void) { 72 return &PROF_CNTS_STOP; 73 } 74 COMPILER_RT_VISIBILITY uint32_t *__llvm_profile_begin_orderfile(void) { 75 return &PROF_ORDERFILE_START; 76 } 77 78 COMPILER_RT_VISIBILITY ValueProfNode * 79 __llvm_profile_begin_vnodes(void) { 80 return &PROF_VNODES_START; 81 } 82 COMPILER_RT_VISIBILITY ValueProfNode *__llvm_profile_end_vnodes(void) { 83 return &PROF_VNODES_STOP; 84 } 85 COMPILER_RT_VISIBILITY ValueProfNode *CurrentVNode = &PROF_VNODES_START; 86 COMPILER_RT_VISIBILITY ValueProfNode *EndVNode = &PROF_VNODES_STOP; 87 88 #ifdef NT_GNU_BUILD_ID 89 static size_t RoundUp(size_t size, size_t align) { 90 return (size + align - 1) & ~(align - 1); 91 } 92 93 /* 94 * Write binary id length and then its data, because binary id does not 95 * have a fixed length. 96 */ 97 static int WriteOneBinaryId(ProfDataWriter *Writer, uint64_t BinaryIdLen, 98 const uint8_t *BinaryIdData, 99 uint64_t BinaryIdPadding) { 100 ProfDataIOVec BinaryIdIOVec[] = { 101 {&BinaryIdLen, sizeof(uint64_t), 1, 0}, 102 {BinaryIdData, sizeof(uint8_t), BinaryIdLen, 0}, 103 {NULL, sizeof(uint8_t), BinaryIdPadding, 1}, 104 }; 105 if (Writer->Write(Writer, BinaryIdIOVec, 106 sizeof(BinaryIdIOVec) / sizeof(*BinaryIdIOVec))) 107 return -1; 108 109 /* Successfully wrote binary id, report success. */ 110 return 0; 111 } 112 113 /* 114 * Look for the note that has the name "GNU\0" and type NT_GNU_BUILD_ID 115 * that contains build id. If build id exists, write binary id. 116 * 117 * Each note in notes section starts with a struct which includes 118 * n_namesz, n_descsz, and n_type members. It is followed by the name 119 * (whose length is defined in n_namesz) and then by the descriptor 120 * (whose length is defined in n_descsz). 121 * 122 * Note sections like .note.ABI-tag and .note.gnu.build-id are aligned 123 * to 4 bytes, so round n_namesz and n_descsz to the nearest 4 bytes. 124 */ 125 static int WriteBinaryIdForNote(ProfDataWriter *Writer, 126 const ElfW(Nhdr) * Note) { 127 int BinaryIdSize = 0; 128 const char *NoteName = (const char *)Note + sizeof(ElfW(Nhdr)); 129 if (Note->n_type == NT_GNU_BUILD_ID && Note->n_namesz == 4 && 130 memcmp(NoteName, "GNU\0", 4) == 0) { 131 uint64_t BinaryIdLen = Note->n_descsz; 132 const uint8_t *BinaryIdData = 133 (const uint8_t *)(NoteName + RoundUp(Note->n_namesz, 4)); 134 uint8_t BinaryIdPadding = __llvm_profile_get_num_padding_bytes(BinaryIdLen); 135 if (Writer != NULL && WriteOneBinaryId(Writer, BinaryIdLen, BinaryIdData, 136 BinaryIdPadding) == -1) 137 return -1; 138 139 BinaryIdSize = sizeof(BinaryIdLen) + BinaryIdLen + BinaryIdPadding; 140 } 141 142 return BinaryIdSize; 143 } 144 145 /* 146 * Helper function that iterates through notes section and find build ids. 147 * If writer is given, write binary ids into profiles. 148 * If an error happens while writing, return -1. 149 */ 150 static int WriteBinaryIds(ProfDataWriter *Writer, const ElfW(Nhdr) * Note, 151 const ElfW(Nhdr) * NotesEnd) { 152 int BinaryIdsSize = 0; 153 while (Note < NotesEnd) { 154 int OneBinaryIdSize = WriteBinaryIdForNote(Writer, Note); 155 if (OneBinaryIdSize == -1) 156 return -1; 157 BinaryIdsSize += OneBinaryIdSize; 158 159 /* Calculate the offset of the next note in notes section. */ 160 size_t NoteOffset = sizeof(ElfW(Nhdr)) + RoundUp(Note->n_namesz, 4) + 161 RoundUp(Note->n_descsz, 4); 162 Note = (const ElfW(Nhdr) *)((const char *)(Note) + NoteOffset); 163 } 164 165 return BinaryIdsSize; 166 } 167 168 /* 169 * Write binary ids into profiles if writer is given. 170 * Return the total size of binary ids. 171 * If an error happens while writing, return -1. 172 */ 173 COMPILER_RT_VISIBILITY int __llvm_write_binary_ids(ProfDataWriter *Writer) { 174 extern const ElfW(Ehdr) __ehdr_start __attribute__((visibility("hidden"))); 175 const ElfW(Ehdr) *ElfHeader = &__ehdr_start; 176 const ElfW(Phdr) *ProgramHeader = 177 (const ElfW(Phdr) *)((uintptr_t)ElfHeader + ElfHeader->e_phoff); 178 179 int TotalBinaryIdsSize = 0; 180 uint32_t I; 181 /* Iterate through entries in the program header. */ 182 for (I = 0; I < ElfHeader->e_phnum; I++) { 183 /* Look for the notes segment in program header entries. */ 184 if (ProgramHeader[I].p_type != PT_NOTE) 185 continue; 186 187 /* There can be multiple notes segment, and examine each of them. */ 188 const ElfW(Nhdr) * Note; 189 const ElfW(Nhdr) * NotesEnd; 190 /* 191 * When examining notes in file, use p_offset, which is the offset within 192 * the elf file, to find the start of notes. 193 */ 194 if (ProgramHeader[I].p_memsz == 0 || 195 ProgramHeader[I].p_memsz == ProgramHeader[I].p_filesz) { 196 Note = (const ElfW(Nhdr) *)((uintptr_t)ElfHeader + 197 ProgramHeader[I].p_offset); 198 NotesEnd = (const ElfW(Nhdr) *)((const char *)(Note) + 199 ProgramHeader[I].p_filesz); 200 } else { 201 /* 202 * When examining notes in memory, use p_vaddr, which is the address of 203 * section after loaded to memory, to find the start of notes. 204 */ 205 Note = 206 (const ElfW(Nhdr) *)((uintptr_t)ElfHeader + ProgramHeader[I].p_vaddr); 207 NotesEnd = 208 (const ElfW(Nhdr) *)((const char *)(Note) + ProgramHeader[I].p_memsz); 209 } 210 211 int BinaryIdsSize = WriteBinaryIds(Writer, Note, NotesEnd); 212 if (TotalBinaryIdsSize == -1) 213 return -1; 214 215 TotalBinaryIdsSize += BinaryIdsSize; 216 } 217 218 return TotalBinaryIdsSize; 219 } 220 #else /* !NT_GNU_BUILD_ID */ 221 /* 222 * Fallback implementation for targets that don't support the GNU 223 * extensions NT_GNU_BUILD_ID and __ehdr_start. 224 */ 225 COMPILER_RT_VISIBILITY int __llvm_write_binary_ids(ProfDataWriter *Writer) { 226 return 0; 227 } 228 #endif 229 230 #endif 231