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// This file defines profile data symbols for ELF, wasm, XCOFF. It assumes
10// __start_ and __stop_ symbols for profile data point at the beginning and
11// end of the sections in question. (This is technically a linker feature,
12// not a file format feature, but linkers for these targets support it.)
13//
14// MachO (MacOS/iOS) and PE-COFF (Windows) have a similar support, but the
15// identifiers are different, so the support is in separate files.
16//
17// Support for targets which don't have linker support is in
18// InstrProfilingPlatformOther.c.
19//
20// This file also contains code to extract ELF build IDs from the ELF file,
21// to identify the build which generated the file.
22
23#if defined(__linux__) || defined(__FreeBSD__) || defined(__Fuchsia__) || \
24 (defined(__sun__) && defined(__svr4__)) || defined(__NetBSD__) || \
25 defined(_AIX) || defined(__wasm__) || defined(__HAIKU__) || \
26 defined(COMPILER_RT_PROFILE_BAREMETAL)
27
28#if !defined(_AIX) && !defined(__wasm__) && \
29 !defined(COMPILER_RT_PROFILE_BAREMETAL)
30// Includes for non-baremetal ELF targets, used to output build IDs.
31#include <elf.h>
32#include <link.h>
33#include <stdlib.h>
34#include <string.h>
35#endif
36
37#include "InstrProfiling.h"
38#include "InstrProfilingInternal.h"
39
40#define PROF_DATA_START INSTR_PROF_SECT_START(INSTR_PROF_DATA_COMMON)
41#define PROF_DATA_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_DATA_COMMON)
42#define PROF_NAME_START INSTR_PROF_SECT_START(INSTR_PROF_NAME_COMMON)
43#define PROF_NAME_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_NAME_COMMON)
44#define PROF_VNAME_START INSTR_PROF_SECT_START(INSTR_PROF_VNAME_COMMON)
45#define PROF_VNAME_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_VNAME_COMMON)
46#define PROF_CNTS_START INSTR_PROF_SECT_START(INSTR_PROF_CNTS_COMMON)
47#define PROF_CNTS_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_CNTS_COMMON)
48#define PROF_VTABLE_START INSTR_PROF_SECT_START(INSTR_PROF_VTAB_COMMON)
49#define PROF_VTABLE_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_VTAB_COMMON)
50#define PROF_BITS_START INSTR_PROF_SECT_START(INSTR_PROF_BITS_COMMON)
51#define PROF_BITS_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_BITS_COMMON)
52#define PROF_VNODES_START INSTR_PROF_SECT_START(INSTR_PROF_VNODES_COMMON)
53#define PROF_VNODES_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_VNODES_COMMON)
54#define PROF_COVINIT_START INSTR_PROF_SECT_START(INSTR_PROF_COVINIT_COMMON)
55#define PROF_COVINIT_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_COVINIT_COMMON)
56
57/* Declare section start and stop symbols for various sections
58 * generated by compiler instrumentation.
59 */
60extern __llvm_profile_data PROF_DATA_START COMPILER_RT_VISIBILITY
61 COMPILER_RT_WEAK;
62extern __llvm_profile_data PROF_DATA_STOP COMPILER_RT_VISIBILITY
63 COMPILER_RT_WEAK;
64extern char PROF_CNTS_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
65extern char PROF_CNTS_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
66extern VTableProfData PROF_VTABLE_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
67extern VTableProfData PROF_VTABLE_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
68extern char PROF_VNAME_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
69extern char PROF_VNAME_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
70extern char PROF_BITS_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
71extern char PROF_BITS_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
72extern char PROF_NAME_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
73extern char PROF_NAME_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
74extern ValueProfNode PROF_VNODES_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
75extern ValueProfNode PROF_VNODES_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
76extern __llvm_gcov_init_func_struct PROF_COVINIT_START COMPILER_RT_VISIBILITY
77 COMPILER_RT_WEAK;
78extern __llvm_gcov_init_func_struct PROF_COVINIT_STOP COMPILER_RT_VISIBILITY
79 COMPILER_RT_WEAK;
80
81COMPILER_RT_VISIBILITY const __llvm_profile_data *
82__llvm_profile_begin_data(void) {
83 return &PROF_DATA_START;
84}
85COMPILER_RT_VISIBILITY const __llvm_profile_data *
86__llvm_profile_end_data(void) {
87 return &PROF_DATA_STOP;
88}
89COMPILER_RT_VISIBILITY const char *__llvm_profile_begin_names(void) {
90 return &PROF_NAME_START;
91}
92COMPILER_RT_VISIBILITY const char *__llvm_profile_end_names(void) {
93 return &PROF_NAME_STOP;
94}
95COMPILER_RT_VISIBILITY const char *__llvm_profile_begin_vtabnames(void) {
96 return &PROF_VNAME_START;
97}
98COMPILER_RT_VISIBILITY const char *__llvm_profile_end_vtabnames(void) {
99 return &PROF_VNAME_STOP;
100}
101COMPILER_RT_VISIBILITY const VTableProfData *
102__llvm_profile_begin_vtables(void) {
103 return &PROF_VTABLE_START;
104}
105COMPILER_RT_VISIBILITY const VTableProfData *__llvm_profile_end_vtables(void) {
106 return &PROF_VTABLE_STOP;
107}
108COMPILER_RT_VISIBILITY char *__llvm_profile_begin_counters(void) {
109 return &PROF_CNTS_START;
110}
111COMPILER_RT_VISIBILITY char *__llvm_profile_end_counters(void) {
112 return &PROF_CNTS_STOP;
113}
114COMPILER_RT_VISIBILITY char *__llvm_profile_begin_bitmap(void) {
115 return &PROF_BITS_START;
116}
117COMPILER_RT_VISIBILITY char *__llvm_profile_end_bitmap(void) {
118 return &PROF_BITS_STOP;
119}
120
121COMPILER_RT_VISIBILITY ValueProfNode *
122__llvm_profile_begin_vnodes(void) {
123 return &PROF_VNODES_START;
124}
125COMPILER_RT_VISIBILITY ValueProfNode *__llvm_profile_end_vnodes(void) {
126 return &PROF_VNODES_STOP;
127}
128COMPILER_RT_VISIBILITY ValueProfNode *CurrentVNode = &PROF_VNODES_START;
129COMPILER_RT_VISIBILITY ValueProfNode *EndVNode = &PROF_VNODES_STOP;
130
131COMPILER_RT_VISIBILITY const __llvm_gcov_init_func_struct *
132__llvm_profile_begin_covinit() {
133 return &PROF_COVINIT_START;
134}
135
136COMPILER_RT_VISIBILITY const __llvm_gcov_init_func_struct *
137__llvm_profile_end_covinit() {
138 return &PROF_COVINIT_STOP;
139}
140
141#ifdef NT_GNU_BUILD_ID
142static size_t RoundUp(size_t size, size_t align) {
143 return (size + align - 1) & ~(align - 1);
144}
145
146/*
147 * Look for the note that has the name "GNU\0" and type NT_GNU_BUILD_ID
148 * that contains build id. If build id exists, write binary id.
149 *
150 * Each note in notes section starts with a struct which includes
151 * n_namesz, n_descsz, and n_type members. It is followed by the name
152 * (whose length is defined in n_namesz) and then by the descriptor
153 * (whose length is defined in n_descsz).
154 *
155 * Note sections like .note.ABI-tag and .note.gnu.build-id are aligned
156 * to 4 bytes, so round n_namesz and n_descsz to the nearest 4 bytes.
157 */
158static int WriteBinaryIdForNote(ProfDataWriter *Writer,
159 const ElfW(Nhdr) * Note) {
160 int BinaryIdSize = 0;
161 const char *NoteName = (const char *)Note + sizeof(ElfW(Nhdr));
162 if (Note->n_type == NT_GNU_BUILD_ID && Note->n_namesz == 4 &&
163 memcmp(s1: NoteName, s2: "GNU\0", n: 4) == 0) {
164 uint64_t BinaryIdLen = Note->n_descsz;
165 const uint8_t *BinaryIdData =
166 (const uint8_t *)(NoteName + RoundUp(size: Note->n_namesz, align: 4));
167 uint8_t BinaryIdPadding = __llvm_profile_get_num_padding_bytes(SizeInBytes: BinaryIdLen);
168 if (Writer != NULL &&
169 lprofWriteOneBinaryId(Writer, BinaryIdLen, BinaryIdData,
170 BinaryIdPadding) == -1)
171 return -1;
172
173 BinaryIdSize = sizeof(BinaryIdLen) + BinaryIdLen + BinaryIdPadding;
174 }
175
176 return BinaryIdSize;
177}
178
179/*
180 * Helper function that iterates through notes section and find build ids.
181 * If writer is given, write binary ids into profiles.
182 * If an error happens while writing, return -1.
183 */
184static int WriteBinaryIds(ProfDataWriter *Writer, const ElfW(Nhdr) * Note,
185 const ElfW(Nhdr) * NotesEnd) {
186 int BinaryIdsSize = 0;
187 while (Note < NotesEnd) {
188 int OneBinaryIdSize = WriteBinaryIdForNote(Writer, Note);
189 if (OneBinaryIdSize == -1)
190 return -1;
191 BinaryIdsSize += OneBinaryIdSize;
192
193 /* Calculate the offset of the next note in notes section. */
194 size_t NoteOffset = sizeof(ElfW(Nhdr)) + RoundUp(size: Note->n_namesz, align: 4) +
195 RoundUp(size: Note->n_descsz, align: 4);
196 Note = (const ElfW(Nhdr) *)((const char *)(Note) + NoteOffset);
197 }
198
199 return BinaryIdsSize;
200}
201
202/*
203 * Write binary ids into profiles if writer is given.
204 * Return the total size of binary ids.
205 * If an error happens while writing, return -1.
206 */
207COMPILER_RT_VISIBILITY int __llvm_write_binary_ids(ProfDataWriter *Writer) {
208 extern const ElfW(Ehdr) __ehdr_start __attribute__((visibility("hidden")));
209 extern ElfW(Dyn) _DYNAMIC[] __attribute__((weak, visibility("hidden")));
210
211 const ElfW(Ehdr) *ElfHeader = &__ehdr_start;
212 const ElfW(Phdr) *ProgramHeader =
213 (const ElfW(Phdr) *)((uintptr_t)ElfHeader + ElfHeader->e_phoff);
214
215 /* Compute the added base address in case of position-independent code. */
216 uintptr_t Base = 0;
217 for (uint32_t I = 0; I < ElfHeader->e_phnum; I++) {
218 if (ProgramHeader[I].p_type == PT_PHDR)
219 Base = (uintptr_t)ProgramHeader - ProgramHeader[I].p_vaddr;
220 if (ProgramHeader[I].p_type == PT_DYNAMIC && _DYNAMIC)
221 Base = (uintptr_t)_DYNAMIC - ProgramHeader[I].p_vaddr;
222 }
223
224 int TotalBinaryIdsSize = 0;
225 /* Iterate through entries in the program header. */
226 for (uint32_t I = 0; I < ElfHeader->e_phnum; I++) {
227 /* Look for the notes segment in program header entries. */
228 if (ProgramHeader[I].p_type != PT_NOTE)
229 continue;
230
231 /* There can be multiple notes segment, and examine each of them. */
232 const ElfW(Nhdr) *Note =
233 (const ElfW(Nhdr) *)(Base + ProgramHeader[I].p_vaddr);
234 const ElfW(Nhdr) *NotesEnd =
235 (const ElfW(Nhdr) *)((const char *)(Note) + ProgramHeader[I].p_memsz);
236
237 int BinaryIdsSize = WriteBinaryIds(Writer, Note, NotesEnd);
238 if (TotalBinaryIdsSize == -1)
239 return -1;
240
241 TotalBinaryIdsSize += BinaryIdsSize;
242 }
243
244 return TotalBinaryIdsSize;
245}
246#elif !defined(_AIX) /* !NT_GNU_BUILD_ID */
247/*
248 * Fallback implementation for targets that don't support the GNU
249 * extensions NT_GNU_BUILD_ID and __ehdr_start.
250 */
251COMPILER_RT_VISIBILITY int __llvm_write_binary_ids(ProfDataWriter *Writer) {
252 return 0;
253}
254#endif
255
256#endif
257