1 /* 2 * Linux perf perf-<pid>.map and jit-<pid>.dump integration. 3 * 4 * The jitdump spec can be found at [1]. 5 * 6 * [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/tools/perf/Documentation/jitdump-specification.txt 7 * 8 * SPDX-License-Identifier: GPL-2.0-or-later 9 */ 10 11 #include "qemu/osdep.h" 12 #include "elf.h" 13 #include "exec/exec-all.h" 14 #include "qemu/timer.h" 15 #include "tcg/tcg.h" 16 17 #include "debuginfo.h" 18 #include "perf.h" 19 20 static FILE *safe_fopen_w(const char *path) 21 { 22 int saved_errno; 23 FILE *f; 24 int fd; 25 26 /* Delete the old file, if any. */ 27 unlink(path); 28 29 /* Avoid symlink attacks by using O_CREAT | O_EXCL. */ 30 fd = open(path, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); 31 if (fd == -1) { 32 return NULL; 33 } 34 35 /* Convert fd to FILE*. */ 36 f = fdopen(fd, "w"); 37 if (f == NULL) { 38 saved_errno = errno; 39 close(fd); 40 errno = saved_errno; 41 return NULL; 42 } 43 44 return f; 45 } 46 47 static FILE *perfmap; 48 49 void perf_enable_perfmap(void) 50 { 51 char map_file[32]; 52 53 snprintf(map_file, sizeof(map_file), "/tmp/perf-%d.map", getpid()); 54 perfmap = safe_fopen_w(map_file); 55 if (perfmap == NULL) { 56 warn_report("Could not open %s: %s, proceeding without perfmap", 57 map_file, strerror(errno)); 58 } 59 } 60 61 /* Get PC and size of code JITed for guest instruction #INSN. */ 62 static void get_host_pc_size(uintptr_t *host_pc, uint16_t *host_size, 63 const void *start, size_t insn) 64 { 65 uint16_t start_off = insn ? tcg_ctx->gen_insn_end_off[insn - 1] : 0; 66 67 if (host_pc) { 68 *host_pc = (uintptr_t)start + start_off; 69 } 70 if (host_size) { 71 *host_size = tcg_ctx->gen_insn_end_off[insn] - start_off; 72 } 73 } 74 75 static const char *pretty_symbol(const struct debuginfo_query *q, size_t *len) 76 { 77 static __thread char buf[64]; 78 int tmp; 79 80 if (!q->symbol) { 81 tmp = snprintf(buf, sizeof(buf), "guest-0x%"PRIx64, q->address); 82 if (len) { 83 *len = MIN(tmp + 1, sizeof(buf)); 84 } 85 return buf; 86 } 87 88 if (!q->offset) { 89 if (len) { 90 *len = strlen(q->symbol) + 1; 91 } 92 return q->symbol; 93 } 94 95 tmp = snprintf(buf, sizeof(buf), "%s+0x%"PRIx64, q->symbol, q->offset); 96 if (len) { 97 *len = MIN(tmp + 1, sizeof(buf)); 98 } 99 return buf; 100 } 101 102 static void write_perfmap_entry(const void *start, size_t insn, 103 const struct debuginfo_query *q) 104 { 105 uint16_t host_size; 106 uintptr_t host_pc; 107 108 get_host_pc_size(&host_pc, &host_size, start, insn); 109 fprintf(perfmap, "%"PRIxPTR" %"PRIx16" %s\n", 110 host_pc, host_size, pretty_symbol(q, NULL)); 111 } 112 113 static FILE *jitdump; 114 115 #define JITHEADER_MAGIC 0x4A695444 116 #define JITHEADER_VERSION 1 117 118 struct jitheader { 119 uint32_t magic; 120 uint32_t version; 121 uint32_t total_size; 122 uint32_t elf_mach; 123 uint32_t pad1; 124 uint32_t pid; 125 uint64_t timestamp; 126 uint64_t flags; 127 }; 128 129 enum jit_record_type { 130 JIT_CODE_LOAD = 0, 131 JIT_CODE_DEBUG_INFO = 2, 132 }; 133 134 struct jr_prefix { 135 uint32_t id; 136 uint32_t total_size; 137 uint64_t timestamp; 138 }; 139 140 struct jr_code_load { 141 struct jr_prefix p; 142 143 uint32_t pid; 144 uint32_t tid; 145 uint64_t vma; 146 uint64_t code_addr; 147 uint64_t code_size; 148 uint64_t code_index; 149 }; 150 151 struct debug_entry { 152 uint64_t addr; 153 int lineno; 154 int discrim; 155 const char name[]; 156 }; 157 158 struct jr_code_debug_info { 159 struct jr_prefix p; 160 161 uint64_t code_addr; 162 uint64_t nr_entry; 163 struct debug_entry entries[]; 164 }; 165 166 static uint32_t get_e_machine(void) 167 { 168 Elf64_Ehdr elf_header; 169 FILE *exe; 170 size_t n; 171 172 QEMU_BUILD_BUG_ON(offsetof(Elf32_Ehdr, e_machine) != 173 offsetof(Elf64_Ehdr, e_machine)); 174 175 exe = fopen("/proc/self/exe", "r"); 176 if (exe == NULL) { 177 return EM_NONE; 178 } 179 180 n = fread(&elf_header, sizeof(elf_header), 1, exe); 181 fclose(exe); 182 if (n != 1) { 183 return EM_NONE; 184 } 185 186 return elf_header.e_machine; 187 } 188 189 void perf_enable_jitdump(void) 190 { 191 struct jitheader header; 192 char jitdump_file[32]; 193 void *perf_marker; 194 195 if (!use_rt_clock) { 196 warn_report("CLOCK_MONOTONIC is not available, proceeding without jitdump"); 197 return; 198 } 199 200 snprintf(jitdump_file, sizeof(jitdump_file), "jit-%d.dump", getpid()); 201 jitdump = safe_fopen_w(jitdump_file); 202 if (jitdump == NULL) { 203 warn_report("Could not open %s: %s, proceeding without jitdump", 204 jitdump_file, strerror(errno)); 205 return; 206 } 207 208 /* 209 * `perf inject` will see that the mapped file name in the corresponding 210 * PERF_RECORD_MMAP or PERF_RECORD_MMAP2 event is of the form jit-%d.dump 211 * and will process it as a jitdump file. 212 */ 213 perf_marker = mmap(NULL, qemu_real_host_page_size(), PROT_READ | PROT_EXEC, 214 MAP_PRIVATE, fileno(jitdump), 0); 215 if (perf_marker == MAP_FAILED) { 216 warn_report("Could not map %s: %s, proceeding without jitdump", 217 jitdump_file, strerror(errno)); 218 fclose(jitdump); 219 jitdump = NULL; 220 return; 221 } 222 223 header.magic = JITHEADER_MAGIC; 224 header.version = JITHEADER_VERSION; 225 header.total_size = sizeof(header); 226 header.elf_mach = get_e_machine(); 227 header.pad1 = 0; 228 header.pid = getpid(); 229 header.timestamp = get_clock(); 230 header.flags = 0; 231 fwrite(&header, sizeof(header), 1, jitdump); 232 } 233 234 void perf_report_prologue(const void *start, size_t size) 235 { 236 if (perfmap) { 237 fprintf(perfmap, "%"PRIxPTR" %zx tcg-prologue-buffer\n", 238 (uintptr_t)start, size); 239 } 240 } 241 242 /* Write a JIT_CODE_DEBUG_INFO jitdump entry. */ 243 static void write_jr_code_debug_info(const void *start, 244 const struct debuginfo_query *q, 245 size_t icount) 246 { 247 struct jr_code_debug_info rec; 248 struct debug_entry ent; 249 uintptr_t host_pc; 250 int insn; 251 252 /* Write the header. */ 253 rec.p.id = JIT_CODE_DEBUG_INFO; 254 rec.p.total_size = sizeof(rec) + sizeof(ent) + 1; 255 rec.p.timestamp = get_clock(); 256 rec.code_addr = (uintptr_t)start; 257 rec.nr_entry = 1; 258 for (insn = 0; insn < icount; insn++) { 259 if (q[insn].file) { 260 rec.p.total_size += sizeof(ent) + strlen(q[insn].file) + 1; 261 rec.nr_entry++; 262 } 263 } 264 fwrite(&rec, sizeof(rec), 1, jitdump); 265 266 /* Write the main debug entries. */ 267 for (insn = 0; insn < icount; insn++) { 268 if (q[insn].file) { 269 get_host_pc_size(&host_pc, NULL, start, insn); 270 ent.addr = host_pc; 271 ent.lineno = q[insn].line; 272 ent.discrim = 0; 273 fwrite(&ent, sizeof(ent), 1, jitdump); 274 fwrite(q[insn].file, strlen(q[insn].file) + 1, 1, jitdump); 275 } 276 } 277 278 /* Write the trailing debug_entry. */ 279 ent.addr = (uintptr_t)start + tcg_ctx->gen_insn_end_off[icount - 1]; 280 ent.lineno = 0; 281 ent.discrim = 0; 282 fwrite(&ent, sizeof(ent), 1, jitdump); 283 fwrite("", 1, 1, jitdump); 284 } 285 286 /* Write a JIT_CODE_LOAD jitdump entry. */ 287 static void write_jr_code_load(const void *start, uint16_t host_size, 288 const struct debuginfo_query *q) 289 { 290 static uint64_t code_index; 291 struct jr_code_load rec; 292 const char *symbol; 293 size_t symbol_size; 294 295 symbol = pretty_symbol(q, &symbol_size); 296 rec.p.id = JIT_CODE_LOAD; 297 rec.p.total_size = sizeof(rec) + symbol_size + host_size; 298 rec.p.timestamp = get_clock(); 299 rec.pid = getpid(); 300 rec.tid = qemu_get_thread_id(); 301 rec.vma = (uintptr_t)start; 302 rec.code_addr = (uintptr_t)start; 303 rec.code_size = host_size; 304 rec.code_index = code_index++; 305 fwrite(&rec, sizeof(rec), 1, jitdump); 306 fwrite(symbol, symbol_size, 1, jitdump); 307 fwrite(start, host_size, 1, jitdump); 308 } 309 310 void perf_report_code(uint64_t guest_pc, TranslationBlock *tb, 311 const void *start) 312 { 313 struct debuginfo_query *q; 314 size_t insn; 315 316 if (!perfmap && !jitdump) { 317 return; 318 } 319 320 q = g_try_malloc0_n(tb->icount, sizeof(*q)); 321 if (!q) { 322 return; 323 } 324 325 debuginfo_lock(); 326 327 /* Query debuginfo for each guest instruction. */ 328 for (insn = 0; insn < tb->icount; insn++) { 329 /* FIXME: This replicates the restore_state_to_opc() logic. */ 330 q[insn].address = tcg_ctx->gen_insn_data[insn][0]; 331 if (TARGET_TB_PCREL) { 332 q[insn].address |= (guest_pc & TARGET_PAGE_MASK); 333 } else { 334 #if defined(TARGET_I386) 335 q[insn].address -= tb->cs_base; 336 #endif 337 } 338 q[insn].flags = DEBUGINFO_SYMBOL | (jitdump ? DEBUGINFO_LINE : 0); 339 } 340 debuginfo_query(q, tb->icount); 341 342 /* Emit perfmap entries if needed. */ 343 if (perfmap) { 344 flockfile(perfmap); 345 for (insn = 0; insn < tb->icount; insn++) { 346 write_perfmap_entry(start, insn, &q[insn]); 347 } 348 funlockfile(perfmap); 349 } 350 351 /* Emit jitdump entries if needed. */ 352 if (jitdump) { 353 flockfile(jitdump); 354 write_jr_code_debug_info(start, q, tb->icount); 355 write_jr_code_load(start, tcg_ctx->gen_insn_end_off[tb->icount - 1], 356 q); 357 funlockfile(jitdump); 358 } 359 360 debuginfo_unlock(); 361 g_free(q); 362 } 363 364 void perf_exit(void) 365 { 366 if (perfmap) { 367 fclose(perfmap); 368 perfmap = NULL; 369 } 370 371 if (jitdump) { 372 fclose(jitdump); 373 jitdump = NULL; 374 } 375 } 376