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_ORDERFILE_START INSTR_PROF_SECT_START(INSTR_PROF_ORDERFILE_COMMON)
39 #define PROF_VNODES_START INSTR_PROF_SECT_START(INSTR_PROF_VNODES_COMMON)
40 #define PROF_VNODES_STOP INSTR_PROF_SECT_STOP(INSTR_PROF_VNODES_COMMON)
41
42 /* Declare section start and stop symbols for various sections
43 * generated by compiler instrumentation.
44 */
45 extern __llvm_profile_data PROF_DATA_START COMPILER_RT_VISIBILITY
46 COMPILER_RT_WEAK;
47 extern __llvm_profile_data PROF_DATA_STOP COMPILER_RT_VISIBILITY
48 COMPILER_RT_WEAK;
49 extern char PROF_CNTS_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
50 extern char PROF_CNTS_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
51 extern uint32_t PROF_ORDERFILE_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
52 extern char PROF_NAME_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
53 extern char PROF_NAME_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
54 extern ValueProfNode PROF_VNODES_START COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
55 extern ValueProfNode PROF_VNODES_STOP COMPILER_RT_VISIBILITY COMPILER_RT_WEAK;
56
57 COMPILER_RT_VISIBILITY const __llvm_profile_data *
__llvm_profile_begin_data(void)58 __llvm_profile_begin_data(void) {
59 return &PROF_DATA_START;
60 }
61 COMPILER_RT_VISIBILITY const __llvm_profile_data *
__llvm_profile_end_data(void)62 __llvm_profile_end_data(void) {
63 return &PROF_DATA_STOP;
64 }
__llvm_profile_begin_names(void)65 COMPILER_RT_VISIBILITY const char *__llvm_profile_begin_names(void) {
66 return &PROF_NAME_START;
67 }
__llvm_profile_end_names(void)68 COMPILER_RT_VISIBILITY const char *__llvm_profile_end_names(void) {
69 return &PROF_NAME_STOP;
70 }
__llvm_profile_begin_counters(void)71 COMPILER_RT_VISIBILITY char *__llvm_profile_begin_counters(void) {
72 return &PROF_CNTS_START;
73 }
__llvm_profile_end_counters(void)74 COMPILER_RT_VISIBILITY char *__llvm_profile_end_counters(void) {
75 return &PROF_CNTS_STOP;
76 }
__llvm_profile_begin_orderfile(void)77 COMPILER_RT_VISIBILITY uint32_t *__llvm_profile_begin_orderfile(void) {
78 return &PROF_ORDERFILE_START;
79 }
80
81 COMPILER_RT_VISIBILITY ValueProfNode *
__llvm_profile_begin_vnodes(void)82 __llvm_profile_begin_vnodes(void) {
83 return &PROF_VNODES_START;
84 }
__llvm_profile_end_vnodes(void)85 COMPILER_RT_VISIBILITY ValueProfNode *__llvm_profile_end_vnodes(void) {
86 return &PROF_VNODES_STOP;
87 }
88 COMPILER_RT_VISIBILITY ValueProfNode *CurrentVNode = &PROF_VNODES_START;
89 COMPILER_RT_VISIBILITY ValueProfNode *EndVNode = &PROF_VNODES_STOP;
90
91 #ifdef NT_GNU_BUILD_ID
RoundUp(size_t size,size_t align)92 static size_t RoundUp(size_t size, size_t align) {
93 return (size + align - 1) & ~(align - 1);
94 }
95
96 /*
97 * Write binary id length and then its data, because binary id does not
98 * have a fixed length.
99 */
WriteOneBinaryId(ProfDataWriter * Writer,uint64_t BinaryIdLen,const uint8_t * BinaryIdData,uint64_t BinaryIdPadding)100 static int WriteOneBinaryId(ProfDataWriter *Writer, uint64_t BinaryIdLen,
101 const uint8_t *BinaryIdData,
102 uint64_t BinaryIdPadding) {
103 ProfDataIOVec BinaryIdIOVec[] = {
104 {&BinaryIdLen, sizeof(uint64_t), 1, 0},
105 {BinaryIdData, sizeof(uint8_t), BinaryIdLen, 0},
106 {NULL, sizeof(uint8_t), BinaryIdPadding, 1},
107 };
108 if (Writer->Write(Writer, BinaryIdIOVec,
109 sizeof(BinaryIdIOVec) / sizeof(*BinaryIdIOVec)))
110 return -1;
111
112 /* Successfully wrote binary id, report success. */
113 return 0;
114 }
115
116 /*
117 * Look for the note that has the name "GNU\0" and type NT_GNU_BUILD_ID
118 * that contains build id. If build id exists, write binary id.
119 *
120 * Each note in notes section starts with a struct which includes
121 * n_namesz, n_descsz, and n_type members. It is followed by the name
122 * (whose length is defined in n_namesz) and then by the descriptor
123 * (whose length is defined in n_descsz).
124 *
125 * Note sections like .note.ABI-tag and .note.gnu.build-id are aligned
126 * to 4 bytes, so round n_namesz and n_descsz to the nearest 4 bytes.
127 */
WriteBinaryIdForNote(ProfDataWriter * Writer,const ElfW (Nhdr)* Note)128 static int WriteBinaryIdForNote(ProfDataWriter *Writer,
129 const ElfW(Nhdr) * Note) {
130 int BinaryIdSize = 0;
131 const char *NoteName = (const char *)Note + sizeof(ElfW(Nhdr));
132 if (Note->n_type == NT_GNU_BUILD_ID && Note->n_namesz == 4 &&
133 memcmp(NoteName, "GNU\0", 4) == 0) {
134 uint64_t BinaryIdLen = Note->n_descsz;
135 const uint8_t *BinaryIdData =
136 (const uint8_t *)(NoteName + RoundUp(Note->n_namesz, 4));
137 uint8_t BinaryIdPadding = __llvm_profile_get_num_padding_bytes(BinaryIdLen);
138 if (Writer != NULL && WriteOneBinaryId(Writer, BinaryIdLen, BinaryIdData,
139 BinaryIdPadding) == -1)
140 return -1;
141
142 BinaryIdSize = sizeof(BinaryIdLen) + BinaryIdLen + BinaryIdPadding;
143 }
144
145 return BinaryIdSize;
146 }
147
148 /*
149 * Helper function that iterates through notes section and find build ids.
150 * If writer is given, write binary ids into profiles.
151 * If an error happens while writing, return -1.
152 */
WriteBinaryIds(ProfDataWriter * Writer,const ElfW (Nhdr)* Note,const ElfW (Nhdr)* NotesEnd)153 static int WriteBinaryIds(ProfDataWriter *Writer, const ElfW(Nhdr) * Note,
154 const ElfW(Nhdr) * NotesEnd) {
155 int BinaryIdsSize = 0;
156 while (Note < NotesEnd) {
157 int OneBinaryIdSize = WriteBinaryIdForNote(Writer, Note);
158 if (OneBinaryIdSize == -1)
159 return -1;
160 BinaryIdsSize += OneBinaryIdSize;
161
162 /* Calculate the offset of the next note in notes section. */
163 size_t NoteOffset = sizeof(ElfW(Nhdr)) + RoundUp(Note->n_namesz, 4) +
164 RoundUp(Note->n_descsz, 4);
165 Note = (const ElfW(Nhdr) *)((const char *)(Note) + NoteOffset);
166 }
167
168 return BinaryIdsSize;
169 }
170
171 /*
172 * Write binary ids into profiles if writer is given.
173 * Return the total size of binary ids.
174 * If an error happens while writing, return -1.
175 */
__llvm_write_binary_ids(ProfDataWriter * Writer)176 COMPILER_RT_VISIBILITY int __llvm_write_binary_ids(ProfDataWriter *Writer) {
177 extern const ElfW(Ehdr) __ehdr_start __attribute__((visibility("hidden")));
178 const ElfW(Ehdr) *ElfHeader = &__ehdr_start;
179 const ElfW(Phdr) *ProgramHeader =
180 (const ElfW(Phdr) *)((uintptr_t)ElfHeader + ElfHeader->e_phoff);
181
182 int TotalBinaryIdsSize = 0;
183 uint32_t I;
184 /* Iterate through entries in the program header. */
185 for (I = 0; I < ElfHeader->e_phnum; I++) {
186 /* Look for the notes segment in program header entries. */
187 if (ProgramHeader[I].p_type != PT_NOTE)
188 continue;
189
190 /* There can be multiple notes segment, and examine each of them. */
191 const ElfW(Nhdr) * Note;
192 const ElfW(Nhdr) * NotesEnd;
193 /*
194 * When examining notes in file, use p_offset, which is the offset within
195 * the elf file, to find the start of notes.
196 */
197 if (ProgramHeader[I].p_memsz == 0 ||
198 ProgramHeader[I].p_memsz == ProgramHeader[I].p_filesz) {
199 Note = (const ElfW(Nhdr) *)((uintptr_t)ElfHeader +
200 ProgramHeader[I].p_offset);
201 NotesEnd = (const ElfW(Nhdr) *)((const char *)(Note) +
202 ProgramHeader[I].p_filesz);
203 } else {
204 /*
205 * When examining notes in memory, use p_vaddr, which is the address of
206 * section after loaded to memory, to find the start of notes.
207 */
208 Note =
209 (const ElfW(Nhdr) *)((uintptr_t)ElfHeader + ProgramHeader[I].p_vaddr);
210 NotesEnd =
211 (const ElfW(Nhdr) *)((const char *)(Note) + ProgramHeader[I].p_memsz);
212 }
213
214 int BinaryIdsSize = WriteBinaryIds(Writer, Note, NotesEnd);
215 if (TotalBinaryIdsSize == -1)
216 return -1;
217
218 TotalBinaryIdsSize += BinaryIdsSize;
219 }
220
221 return TotalBinaryIdsSize;
222 }
223 #else /* !NT_GNU_BUILD_ID */
224 /*
225 * Fallback implementation for targets that don't support the GNU
226 * extensions NT_GNU_BUILD_ID and __ehdr_start.
227 */
__llvm_write_binary_ids(ProfDataWriter * Writer)228 COMPILER_RT_VISIBILITY int __llvm_write_binary_ids(ProfDataWriter *Writer) {
229 return 0;
230 }
231 #endif
232
233 #if defined(_AIX)
234 // Empty stubs to allow linking object files using the registration-based scheme
235 COMPILER_RT_VISIBILITY
__llvm_profile_register_function(void * Data_)236 void __llvm_profile_register_function(void *Data_) {}
237
238 COMPILER_RT_VISIBILITY
__llvm_profile_register_names_function(void * NamesStart,uint64_t NamesSize)239 void __llvm_profile_register_names_function(void *NamesStart,
240 uint64_t NamesSize) {}
241
242 // The __start_SECNAME and __stop_SECNAME symbols (for SECNAME \in
243 // {"__llvm_prf_cnts", "__llvm_prf_data", "__llvm_prf_name", "__llvm_prf_vnds"})
244 // are always live when linking on AIX, regardless if the .o's being linked
245 // reference symbols from the profile library (for example when no files were
246 // compiled with -fprofile-generate). That's because these symbols are kept
247 // alive through references in constructor functions that are always live in the
248 // default linking model on AIX (-bcdtors:all). The __start_SECNAME and
249 // __stop_SECNAME symbols are only resolved by the linker when the SECNAME
250 // section exists. So for the scenario where the user objects have no such
251 // section (i.e. when they are compiled with -fno-profile-generate), we always
252 // define these zero length variables in each of the above 4 sections.
253 static int dummy_cnts[0] COMPILER_RT_SECTION(
254 COMPILER_RT_SEG INSTR_PROF_CNTS_SECT_NAME);
255 static int dummy_data[0] COMPILER_RT_SECTION(
256 COMPILER_RT_SEG INSTR_PROF_DATA_SECT_NAME);
257 static const int dummy_name[0] COMPILER_RT_SECTION(
258 COMPILER_RT_SEG INSTR_PROF_NAME_SECT_NAME);
259 static int dummy_vnds[0] COMPILER_RT_SECTION(
260 COMPILER_RT_SEG INSTR_PROF_VNODES_SECT_NAME);
261
262 // To avoid GC'ing of the dummy variables by the linker, reference them in an
263 // array and reference the array in the runtime registration code
264 // (InstrProfilingRuntime.cpp)
265 COMPILER_RT_VISIBILITY
266 void *__llvm_profile_keep[] = {(void *)&dummy_cnts, (void *)&dummy_data,
267 (void *)&dummy_name, (void *)&dummy_vnds};
268 #endif
269
270 #endif
271