compiler-rt/lib/profile/InstrProfilingPlatformLinux.c

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