accel/tcg/perf.c

   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 (tb_cflags(tb) & CF_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 }