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 #define PROF_DATA_START INSTR_PROF_SECT_START(INSTR_PROF_DATA_COMMON)
  24 #define PROF_DATA_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_DATA_COMMON)
  25 #define PROF_NAME_START INSTR_PROF_SECT_START(INSTR_PROF_NAME_COMMON)
  26 #define PROF_NAME_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_NAME_COMMON)
  27 #define PROF_VNAME_START INSTR_PROF_SECT_START(INSTR_PROF_VNAME_COMMON)
  28 #define PROF_VNAME_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_VNAME_COMMON)
  29 #define PROF_CNTS_START INSTR_PROF_SECT_START(INSTR_PROF_CNTS_COMMON)
  30 #define PROF_CNTS_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_CNTS_COMMON)
  31 #define PROF_VTABLE_START INSTR_PROF_SECT_START(INSTR_PROF_VTAB_COMMON)
  32 #define PROF_VTABLE_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_VTAB_COMMON)
  33 #define PROF_BITS_START INSTR_PROF_SECT_START(INSTR_PROF_BITS_COMMON)
  34 #define PROF_BITS_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_BITS_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 VTableProfData PROF_VTABLE_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
  49 extern VTableProfData PROF_VTABLE_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
  50 extern char PROF_VNAME_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
  51 extern char PROF_VNAME_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
  52 extern char PROF_BITS_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
  53 extern char PROF_BITS_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
  54 extern uint32_t PROF_ORDERFILE_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
  55 extern char PROF_NAME_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
  56 extern char PROF_NAME_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
  57 extern ValueProfNode PROF_VNODES_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
  58 extern ValueProfNode PROF_VNODES_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
  59
  60 COMPILER_RT_VISIBILITY const __llvm_profile_data *
  61 __llvm_profile_begin_data(void) {
  62   return &PROF_DATA_START;
  63 }
  64 COMPILER_RT_VISIBILITY const __llvm_profile_data *
  65 __llvm_profile_end_data(void) {
  66   return &PROF_DATA_STOP;
  67 }
  68 COMPILER_RT_VISIBILITY const char *__llvm_profile_begin_names(void) {
  69   return &PROF_NAME_START;
  70 }
  71 COMPILER_RT_VISIBILITY const char *__llvm_profile_end_names(void) {
  72   return &PROF_NAME_STOP;
  73 }
  74 COMPILER_RT_VISIBILITY const char *__llvm_profile_begin_vtabnames(void) {
  75   return &PROF_VNAME_START;
  76 }
  77 COMPILER_RT_VISIBILITY const char *__llvm_profile_end_vtabnames(void) {
  78   return &PROF_VNAME_STOP;
  79 }
  80 COMPILER_RT_VISIBILITY const VTableProfData *
  81 __llvm_profile_begin_vtables(void) {
  82   return &PROF_VTABLE_START;
  83 }
  84 COMPILER_RT_VISIBILITY const VTableProfData *__llvm_profile_end_vtables(void) {
  85   return &PROF_VTABLE_STOP;
  86 }
  87 COMPILER_RT_VISIBILITY char *__llvm_profile_begin_counters(void) {
  88   return &PROF_CNTS_START;
  89 }
  90 COMPILER_RT_VISIBILITY char *__llvm_profile_end_counters(void) {
  91   return &PROF_CNTS_STOP;
  92 }
  93 COMPILER_RT_VISIBILITY char *__llvm_profile_begin_bitmap(void) {
  94   return &PROF_BITS_START;
  95 }
  96 COMPILER_RT_VISIBILITY char *__llvm_profile_end_bitmap(void) {
  97   return &PROF_BITS_STOP;
  98 }
  99 COMPILER_RT_VISIBILITY uint32_t *__llvm_profile_begin_orderfile(void) {
 100   return &PROF_ORDERFILE_START;
 101 }
 102
 103 COMPILER_RT_VISIBILITY ValueProfNode *
 104 __llvm_profile_begin_vnodes(void) {
 105   return &PROF_VNODES_START;
 106 }
 107 COMPILER_RT_VISIBILITY ValueProfNode *__llvm_profile_end_vnodes(void) {
 108   return &PROF_VNODES_STOP;
 109 }
 110 COMPILER_RT_VISIBILITY ValueProfNode *CurrentVNode = &PROF_VNODES_START;
 111 COMPILER_RT_VISIBILITY ValueProfNode *EndVNode = &PROF_VNODES_STOP;
 112
 113 #ifdef NT_GNU_BUILD_ID
 114 static size_t RoundUp(size_t size, size_t align) {
 115   return (size + align - 1) & ~(align - 1);
 116 }
 117
 118 /*
 119  * Look for the note that has the name "GNU\0" and type NT_GNU_BUILD_ID
 120  * that contains build id. If build id exists, write binary id.
 121  *
 122  * Each note in notes section starts with a struct which includes
 123  * n_namesz, n_descsz, and n_type members. It is followed by the name
 124  * (whose length is defined in n_namesz) and then by the descriptor
 125  * (whose length is defined in n_descsz).
 126  *
 127  * Note sections like .note.ABI-tag and .note.gnu.build-id are aligned
 128  * to 4 bytes, so round n_namesz and n_descsz to the nearest 4 bytes.
 129  */
 130 static int WriteBinaryIdForNote(ProfDataWriter *Writer,
 131                                 const ElfW(Nhdr) * Note) {
 132   int BinaryIdSize = 0;
 133   const char *NoteName = (const char *)Note + sizeof(ElfW(Nhdr));
 134   if (Note->n_type == NT_GNU_BUILD_ID && Note->n_namesz == 4 &&
 135       memcmp(NoteName, "GNU\0", 4) == 0) {
 136     uint64_t BinaryIdLen = Note->n_descsz;
 137     const uint8_t *BinaryIdData =
 138         (const uint8_t *)(NoteName + RoundUp(Note->n_namesz, 4));
 139     uint8_t BinaryIdPadding = __llvm_profile_get_num_padding_bytes(BinaryIdLen);
 140     if (Writer != NULL &&
 141         lprofWriteOneBinaryId(Writer, BinaryIdLen, BinaryIdData,
 142                               BinaryIdPadding) == -1)
 143       return -1;
 144
 145     BinaryIdSize = sizeof(BinaryIdLen) + BinaryIdLen + BinaryIdPadding;
 146   }
 147
 148   return BinaryIdSize;
 149 }
 150
 151 /*
 152  * Helper function that iterates through notes section and find build ids.
 153  * If writer is given, write binary ids into profiles.
 154  * If an error happens while writing, return -1.
 155  */
 156 static int WriteBinaryIds(ProfDataWriter *Writer, const ElfW(Nhdr) * Note,
 157                           const ElfW(Nhdr) * NotesEnd) {
 158   int BinaryIdsSize = 0;
 159   while (Note < NotesEnd) {
 160     int OneBinaryIdSize = WriteBinaryIdForNote(Writer, Note);
 161     if (OneBinaryIdSize == -1)
 162       return -1;
 163     BinaryIdsSize += OneBinaryIdSize;
 164
 165     /* Calculate the offset of the next note in notes section. */
 166     size_t NoteOffset = sizeof(ElfW(Nhdr)) + RoundUp(Note->n_namesz, 4) +
 167                         RoundUp(Note->n_descsz, 4);
 168     Note = (const ElfW(Nhdr) *)((const char *)(Note) + NoteOffset);
 169   }
 170
 171   return BinaryIdsSize;
 172 }
 173
 174 /*
 175  * Write binary ids into profiles if writer is given.
 176  * Return the total size of binary ids.
 177  * If an error happens while writing, return -1.
 178  */
 179 COMPILER_RT_VISIBILITY int __llvm_write_binary_ids(ProfDataWriter *Writer) {
 180   extern const ElfW(Ehdr) __ehdr_start __attribute__((visibility("hidden")));
 181   const ElfW(Ehdr) *ElfHeader = &__ehdr_start;
 182   const ElfW(Phdr) *ProgramHeader =
 183       (const ElfW(Phdr) *)((uintptr_t)ElfHeader + ElfHeader->e_phoff);
 184
 185   int TotalBinaryIdsSize = 0;
 186   uint32_t I;
 187   /* Iterate through entries in the program header. */
 188   for (I = 0; I < ElfHeader->e_phnum; I++) {
 189     /* Look for the notes segment in program header entries. */
 190     if (ProgramHeader[I].p_type != PT_NOTE)
 191       continue;
 192
 193     /* There can be multiple notes segment, and examine each of them. */
 194     const ElfW(Nhdr) * Note;
 195     const ElfW(Nhdr) * NotesEnd;
 196     /*
 197      * When examining notes in file, use p_offset, which is the offset within
 198      * the elf file, to find the start of notes.
 199      */
 200     if (ProgramHeader[I].p_memsz == 0 ||
 201         ProgramHeader[I].p_memsz == ProgramHeader[I].p_filesz) {
 202       Note = (const ElfW(Nhdr) *)((uintptr_t)ElfHeader +
 203                                   ProgramHeader[I].p_offset);
 204       NotesEnd = (const ElfW(Nhdr) *)((const char *)(Note) +
 205                                       ProgramHeader[I].p_filesz);
 206     } else {
 207       /*
 208        * When examining notes in memory, use p_vaddr, which is the address of
 209        * section after loaded to memory, to find the start of notes.
 210        */
 211       Note =
 212           (const ElfW(Nhdr) *)((uintptr_t)ElfHeader + ProgramHeader[I].p_vaddr);
 213       NotesEnd =
 214           (const ElfW(Nhdr) *)((const char *)(Note) + ProgramHeader[I].p_memsz);
 215     }
 216
 217     int BinaryIdsSize = WriteBinaryIds(Writer, Note, NotesEnd);
 218     if (TotalBinaryIdsSize == -1)
 219       return -1;
 220
 221     TotalBinaryIdsSize += BinaryIdsSize;
 222   }
 223
 224   return TotalBinaryIdsSize;
 225 }
 226 #elif !defined(_AIX) /* !NT_GNU_BUILD_ID */
 227 /*
 228  * Fallback implementation for targets that don't support the GNU
 229  * extensions NT_GNU_BUILD_ID and __ehdr_start.
 230  */
 231 COMPILER_RT_VISIBILITY int __llvm_write_binary_ids(ProfDataWriter *Writer) {
 232   return 0;
 233 }
 234 #endif
 235
 236 #endif