util/oslib-posix.c

   1 /*
   2  * os-posix-lib.c
   3  *
   4  * Copyright (c) 2003-2008 Fabrice Bellard
   5  * Copyright (c) 2010 Red Hat, Inc.
   6  *
   7  * QEMU library functions on POSIX which are shared between QEMU and
   8  * the QEMU tools.
   9  *
  10  * Permission is hereby granted, free of charge, to any person obtaining a copy
  11  * of this software and associated documentation files (the "Software"), to deal
  12  * in the Software without restriction, including without limitation the rights
  13  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  14  * copies of the Software, and to permit persons to whom the Software is
  15  * furnished to do so, subject to the following conditions:
  16  *
  17  * The above copyright notice and this permission notice shall be included in
  18  * all copies or substantial portions of the Software.
  19  *
  20  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  21  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  23  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  24  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  25  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  26  * THE SOFTWARE.
  27  */
  28
  29 #include "qemu/osdep.h"
  30 #include <termios.h>
  31
  32 #include <glib/gprintf.h>
  33
  34 #include "qemu-common.h"
  35 #include "sysemu/sysemu.h"
  36 #include "trace.h"
  37 #include "qapi/error.h"
  38 #include "qemu/sockets.h"
  39 #include "qemu/thread.h"
  40 #include <libgen.h>
  41 #include <sys/signal.h>
  42 #include "qemu/cutils.h"
  43
  44 #ifdef CONFIG_LINUX
  45 #include <sys/syscall.h>
  46 #endif
  47
  48 #ifdef __FreeBSD__
  49 #include <sys/sysctl.h>
  50 #include <sys/user.h>
  51 #include <libutil.h>
  52 #endif
  53
  54 #ifdef __NetBSD__
  55 #include <sys/sysctl.h>
  56 #endif
  57
  58 #include "qemu/mmap-alloc.h"
  59
  60 #ifdef CONFIG_DEBUG_STACK_USAGE
  61 #include "qemu/error-report.h"
  62 #endif
  63
  64 #define MAX_MEM_PREALLOC_THREAD_COUNT 16
  65
  66 struct MemsetThread {
  67     char *addr;
  68     size_t numpages;
  69     size_t hpagesize;
  70     QemuThread pgthread;
  71     sigjmp_buf env;
  72 };
  73 typedef struct MemsetThread MemsetThread;
  74
  75 static MemsetThread *memset_thread;
  76 static int memset_num_threads;
  77 static bool memset_thread_failed;
  78
  79 static QemuMutex page_mutex;
  80 static QemuCond page_cond;
  81 static bool threads_created_flag;
  82
  83 int qemu_get_thread_id(void)
  84 {
  85 #if defined(__linux__)
  86     return syscall(SYS_gettid);
  87 #else
  88     return getpid();
  89 #endif
  90 }
  91
  92 int qemu_daemon(int nochdir, int noclose)
  93 {
  94     return daemon(nochdir, noclose);
  95 }
  96
  97 bool qemu_write_pidfile(const char *path, Error **errp)
  98 {
  99     int fd;
 100     char pidstr[32];
 101
 102     while (1) {
 103         struct stat a, b;
 104         struct flock lock = {
 105             .l_type = F_WRLCK,
 106             .l_whence = SEEK_SET,
 107             .l_len = 0,
 108         };
 109
 110         fd = qemu_open(path, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR);
 111         if (fd == -1) {
 112             error_setg_errno(errp, errno, "Cannot open pid file");
 113             return false;
 114         }
 115
 116         if (fstat(fd, &b) < 0) {
 117             error_setg_errno(errp, errno, "Cannot stat file");
 118             goto fail_close;
 119         }
 120
 121         if (fcntl(fd, F_SETLK, &lock)) {
 122             error_setg_errno(errp, errno, "Cannot lock pid file");
 123             goto fail_close;
 124         }
 125
 126         /*
 127          * Now make sure the path we locked is the same one that now
 128          * exists on the filesystem.
 129          */
 130         if (stat(path, &a) < 0) {
 131             /*
 132              * PID file disappeared, someone else must be racing with
 133              * us, so try again.
 134              */
 135             close(fd);
 136             continue;
 137         }
 138
 139         if (a.st_ino == b.st_ino) {
 140             break;
 141         }
 142
 143         /*
 144          * PID file was recreated, someone else must be racing with
 145          * us, so try again.
 146          */
 147         close(fd);
 148     }
 149
 150     if (ftruncate(fd, 0) < 0) {
 151         error_setg_errno(errp, errno, "Failed to truncate pid file");
 152         goto fail_unlink;
 153     }
 154
 155     snprintf(pidstr, sizeof(pidstr), FMT_pid "\n", getpid());
 156     if (write(fd, pidstr, strlen(pidstr)) != strlen(pidstr)) {
 157         error_setg(errp, "Failed to write pid file");
 158         goto fail_unlink;
 159     }
 160
 161     return true;
 162
 163 fail_unlink:
 164     unlink(path);
 165 fail_close:
 166     close(fd);
 167     return false;
 168 }
 169
 170 void *qemu_oom_check(void *ptr)
 171 {
 172     if (ptr == NULL) {
 173         fprintf(stderr, "Failed to allocate memory: %s\n", strerror(errno));
 174         abort();
 175     }
 176     return ptr;
 177 }
 178
 179 void *qemu_try_memalign(size_t alignment, size_t size)
 180 {
 181     void *ptr;
 182
 183     if (alignment < sizeof(void*)) {
 184         alignment = sizeof(void*);
 185     }
 186
 187 #if defined(CONFIG_POSIX_MEMALIGN)
 188     int ret;
 189     ret = posix_memalign(&ptr, alignment, size);
 190     if (ret != 0) {
 191         errno = ret;
 192         ptr = NULL;
 193     }
 194 #elif defined(CONFIG_BSD)
 195     ptr = valloc(size);
 196 #else
 197     ptr = memalign(alignment, size);
 198 #endif
 199     trace_qemu_memalign(alignment, size, ptr);
 200     return ptr;
 201 }
 202
 203 void *qemu_memalign(size_t alignment, size_t size)
 204 {
 205     return qemu_oom_check(qemu_try_memalign(alignment, size));
 206 }
 207
 208 /* alloc shared memory pages */
 209 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared)
 210 {
 211     size_t align = QEMU_VMALLOC_ALIGN;
 212     void *ptr = qemu_ram_mmap(-1, size, align, shared, false);
 213
 214     if (ptr == MAP_FAILED) {
 215         return NULL;
 216     }
 217
 218     if (alignment) {
 219         *alignment = align;
 220     }
 221
 222     trace_qemu_anon_ram_alloc(size, ptr);
 223     return ptr;
 224 }
 225
 226 void qemu_vfree(void *ptr)
 227 {
 228     trace_qemu_vfree(ptr);
 229     free(ptr);
 230 }
 231
 232 void qemu_anon_ram_free(void *ptr, size_t size)
 233 {
 234     trace_qemu_anon_ram_free(ptr, size);
 235     qemu_ram_munmap(-1, ptr, size);
 236 }
 237
 238 void qemu_set_block(int fd)
 239 {
 240     int f;
 241     f = fcntl(fd, F_GETFL);
 242     assert(f != -1);
 243     f = fcntl(fd, F_SETFL, f & ~O_NONBLOCK);
 244     assert(f != -1);
 245 }
 246
 247 void qemu_set_nonblock(int fd)
 248 {
 249     int f;
 250     f = fcntl(fd, F_GETFL);
 251     assert(f != -1);
 252     f = fcntl(fd, F_SETFL, f | O_NONBLOCK);
 253 #ifdef __OpenBSD__
 254     if (f == -1) {
 255         /*
 256          * Previous to OpenBSD 6.3, fcntl(F_SETFL) is not permitted on
 257          * memory devices and sets errno to ENODEV.
 258          * It's OK if we fail to set O_NONBLOCK on devices like /dev/null,
 259          * because they will never block anyway.
 260          */
 261         assert(errno == ENODEV);
 262     }
 263 #else
 264     assert(f != -1);
 265 #endif
 266 }
 267
 268 int socket_set_fast_reuse(int fd)
 269 {
 270     int val = 1, ret;
 271
 272     ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
 273                      (const char *)&val, sizeof(val));
 274
 275     assert(ret == 0);
 276
 277     return ret;
 278 }
 279
 280 void qemu_set_cloexec(int fd)
 281 {
 282     int f;
 283     f = fcntl(fd, F_GETFD);
 284     assert(f != -1);
 285     f = fcntl(fd, F_SETFD, f | FD_CLOEXEC);
 286     assert(f != -1);
 287 }
 288
 289 /*
 290  * Creates a pipe with FD_CLOEXEC set on both file descriptors
 291  */
 292 int qemu_pipe(int pipefd[2])
 293 {
 294     int ret;
 295
 296 #ifdef CONFIG_PIPE2
 297     ret = pipe2(pipefd, O_CLOEXEC);
 298     if (ret != -1 || errno != ENOSYS) {
 299         return ret;
 300     }
 301 #endif
 302     ret = pipe(pipefd);
 303     if (ret == 0) {
 304         qemu_set_cloexec(pipefd[0]);
 305         qemu_set_cloexec(pipefd[1]);
 306     }
 307
 308     return ret;
 309 }
 310
 311 char *
 312 qemu_get_local_state_pathname(const char *relative_pathname)
 313 {
 314     return g_strdup_printf("%s/%s", CONFIG_QEMU_LOCALSTATEDIR,
 315                            relative_pathname);
 316 }
 317
 318 void qemu_set_tty_echo(int fd, bool echo)
 319 {
 320     struct termios tty;
 321
 322     tcgetattr(fd, &tty);
 323
 324     if (echo) {
 325         tty.c_lflag |= ECHO | ECHONL | ICANON | IEXTEN;
 326     } else {
 327         tty.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
 328     }
 329
 330     tcsetattr(fd, TCSANOW, &tty);
 331 }
 332
 333 static char exec_dir[PATH_MAX];
 334
 335 void qemu_init_exec_dir(const char *argv0)
 336 {
 337     char *dir;
 338     char *p = NULL;
 339     char buf[PATH_MAX];
 340
 341     assert(!exec_dir[0]);
 342
 343 #if defined(__linux__)
 344     {
 345         int len;
 346         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
 347         if (len > 0) {
 348             buf[len] = 0;
 349             p = buf;
 350         }
 351     }
 352 #elif defined(__FreeBSD__) \
 353       || (defined(__NetBSD__) && defined(KERN_PROC_PATHNAME))
 354     {
 355 #if defined(__FreeBSD__)
 356         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
 357 #else
 358         static int mib[4] = {CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME};
 359 #endif
 360         size_t len = sizeof(buf) - 1;
 361
 362         *buf = '\0';
 363         if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
 364             *buf) {
 365             buf[sizeof(buf) - 1] = '\0';
 366             p = buf;
 367         }
 368     }
 369 #endif
 370     /* If we don't have any way of figuring out the actual executable
 371        location then try argv[0].  */
 372     if (!p) {
 373         if (!argv0) {
 374             return;
 375         }
 376         p = realpath(argv0, buf);
 377         if (!p) {
 378             return;
 379         }
 380     }
 381     dir = g_path_get_dirname(p);
 382
 383     pstrcpy(exec_dir, sizeof(exec_dir), dir);
 384
 385     g_free(dir);
 386 }
 387
 388 char *qemu_get_exec_dir(void)
 389 {
 390     return g_strdup(exec_dir);
 391 }
 392
 393 static void sigbus_handler(int signal)
 394 {
 395     int i;
 396     if (memset_thread) {
 397         for (i = 0; i < memset_num_threads; i++) {
 398             if (qemu_thread_is_self(&memset_thread[i].pgthread)) {
 399                 siglongjmp(memset_thread[i].env, 1);
 400             }
 401         }
 402     }
 403 }
 404
 405 static void *do_touch_pages(void *arg)
 406 {
 407     MemsetThread *memset_args = (MemsetThread *)arg;
 408     sigset_t set, oldset;
 409
 410     /*
 411      * On Linux, the page faults from the loop below can cause mmap_sem
 412      * contention with allocation of the thread stacks.  Do not start
 413      * clearing until all threads have been created.
 414      */
 415     qemu_mutex_lock(&page_mutex);
 416     while(!threads_created_flag){
 417         qemu_cond_wait(&page_cond, &page_mutex);
 418     }
 419     qemu_mutex_unlock(&page_mutex);
 420
 421     /* unblock SIGBUS */
 422     sigemptyset(&set);
 423     sigaddset(&set, SIGBUS);
 424     pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
 425
 426     if (sigsetjmp(memset_args->env, 1)) {
 427         memset_thread_failed = true;
 428     } else {
 429         char *addr = memset_args->addr;
 430         size_t numpages = memset_args->numpages;
 431         size_t hpagesize = memset_args->hpagesize;
 432         size_t i;
 433         for (i = 0; i < numpages; i++) {
 434             /*
 435              * Read & write back the same value, so we don't
 436              * corrupt existing user/app data that might be
 437              * stored.
 438              *
 439              * 'volatile' to stop compiler optimizing this away
 440              * to a no-op
 441              *
 442              * TODO: get a better solution from kernel so we
 443              * don't need to write at all so we don't cause
 444              * wear on the storage backing the region...
 445              */
 446             *(volatile char *)addr = *addr;
 447             addr += hpagesize;
 448         }
 449     }
 450     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 451     return NULL;
 452 }
 453
 454 static inline int get_memset_num_threads(int smp_cpus)
 455 {
 456     long host_procs = sysconf(_SC_NPROCESSORS_ONLN);
 457     int ret = 1;
 458
 459     if (host_procs > 0) {
 460         ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus);
 461     }
 462     /* In case sysconf() fails, we fall back to single threaded */
 463     return ret;
 464 }
 465
 466 static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages,
 467                             int smp_cpus)
 468 {
 469     size_t numpages_per_thread, leftover;
 470     char *addr = area;
 471     int i = 0;
 472
 473     memset_thread_failed = false;
 474     threads_created_flag = false;
 475     memset_num_threads = get_memset_num_threads(smp_cpus);
 476     memset_thread = g_new0(MemsetThread, memset_num_threads);
 477     numpages_per_thread = numpages / memset_num_threads;
 478     leftover = numpages % memset_num_threads;
 479     for (i = 0; i < memset_num_threads; i++) {
 480         memset_thread[i].addr = addr;
 481         memset_thread[i].numpages = numpages_per_thread + (i < leftover);
 482         memset_thread[i].hpagesize = hpagesize;
 483         qemu_thread_create(&memset_thread[i].pgthread, "touch_pages",
 484                            do_touch_pages, &memset_thread[i],
 485                            QEMU_THREAD_JOINABLE);
 486         addr += memset_thread[i].numpages * hpagesize;
 487     }
 488     threads_created_flag = true;
 489     qemu_cond_broadcast(&page_cond);
 490
 491     for (i = 0; i < memset_num_threads; i++) {
 492         qemu_thread_join(&memset_thread[i].pgthread);
 493     }
 494     g_free(memset_thread);
 495     memset_thread = NULL;
 496
 497     return memset_thread_failed;
 498 }
 499
 500 void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
 501                      Error **errp)
 502 {
 503     int ret;
 504     struct sigaction act, oldact;
 505     size_t hpagesize = qemu_fd_getpagesize(fd);
 506     size_t numpages = DIV_ROUND_UP(memory, hpagesize);
 507
 508     memset(&act, 0, sizeof(act));
 509     act.sa_handler = &sigbus_handler;
 510     act.sa_flags = 0;
 511
 512     ret = sigaction(SIGBUS, &act, &oldact);
 513     if (ret) {
 514         error_setg_errno(errp, errno,
 515             "os_mem_prealloc: failed to install signal handler");
 516         return;
 517     }
 518
 519     /* touch pages simultaneously */
 520     if (touch_all_pages(area, hpagesize, numpages, smp_cpus)) {
 521         error_setg(errp, "os_mem_prealloc: Insufficient free host memory "
 522             "pages available to allocate guest RAM");
 523     }
 524
 525     ret = sigaction(SIGBUS, &oldact, NULL);
 526     if (ret) {
 527         /* Terminate QEMU since it can't recover from error */
 528         perror("os_mem_prealloc: failed to reinstall signal handler");
 529         exit(1);
 530     }
 531 }
 532
 533 char *qemu_get_pid_name(pid_t pid)
 534 {
 535     char *name = NULL;
 536
 537 #if defined(__FreeBSD__)
 538     /* BSDs don't have /proc, but they provide a nice substitute */
 539     struct kinfo_proc *proc = kinfo_getproc(pid);
 540
 541     if (proc) {
 542         name = g_strdup(proc->ki_comm);
 543         free(proc);
 544     }
 545 #else
 546     /* Assume a system with reasonable procfs */
 547     char *pid_path;
 548     size_t len;
 549
 550     pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
 551     g_file_get_contents(pid_path, &name, &len, NULL);
 552     g_free(pid_path);
 553 #endif
 554
 555     return name;
 556 }
 557
 558
 559 pid_t qemu_fork(Error **errp)
 560 {
 561     sigset_t oldmask, newmask;
 562     struct sigaction sig_action;
 563     int saved_errno;
 564     pid_t pid;
 565
 566     /*
 567      * Need to block signals now, so that child process can safely
 568      * kill off caller's signal handlers without a race.
 569      */
 570     sigfillset(&newmask);
 571     if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
 572         error_setg_errno(errp, errno,
 573                          "cannot block signals");
 574         return -1;
 575     }
 576
 577     pid = fork();
 578     saved_errno = errno;
 579
 580     if (pid < 0) {
 581         /* attempt to restore signal mask, but ignore failure, to
 582          * avoid obscuring the fork failure */
 583         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 584         error_setg_errno(errp, saved_errno,
 585                          "cannot fork child process");
 586         errno = saved_errno;
 587         return -1;
 588     } else if (pid) {
 589         /* parent process */
 590
 591         /* Restore our original signal mask now that the child is
 592          * safely running. Only documented failures are EFAULT (not
 593          * possible, since we are using just-grabbed mask) or EINVAL
 594          * (not possible, since we are using correct arguments).  */
 595         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 596     } else {
 597         /* child process */
 598         size_t i;
 599
 600         /* Clear out all signal handlers from parent so nothing
 601          * unexpected can happen in our child once we unblock
 602          * signals */
 603         sig_action.sa_handler = SIG_DFL;
 604         sig_action.sa_flags = 0;
 605         sigemptyset(&sig_action.sa_mask);
 606
 607         for (i = 1; i < NSIG; i++) {
 608             /* Only possible errors are EFAULT or EINVAL The former
 609              * won't happen, the latter we expect, so no need to check
 610              * return value */
 611             (void)sigaction(i, &sig_action, NULL);
 612         }
 613
 614         /* Unmask all signals in child, since we've no idea what the
 615          * caller's done with their signal mask and don't want to
 616          * propagate that to children */
 617         sigemptyset(&newmask);
 618         if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) {
 619             Error *local_err = NULL;
 620             error_setg_errno(&local_err, errno,
 621                              "cannot unblock signals");
 622             error_report_err(local_err);
 623             _exit(1);
 624         }
 625     }
 626     return pid;
 627 }
 628
 629 void *qemu_alloc_stack(size_t *sz)
 630 {
 631     void *ptr, *guardpage;
 632     int flags;
 633 #ifdef CONFIG_DEBUG_STACK_USAGE
 634     void *ptr2;
 635 #endif
 636     size_t pagesz = qemu_real_host_page_size;
 637 #ifdef _SC_THREAD_STACK_MIN
 638     /* avoid stacks smaller than _SC_THREAD_STACK_MIN */
 639     long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
 640     *sz = MAX(MAX(min_stack_sz, 0), *sz);
 641 #endif
 642     /* adjust stack size to a multiple of the page size */
 643     *sz = ROUND_UP(*sz, pagesz);
 644     /* allocate one extra page for the guard page */
 645     *sz += pagesz;
 646
 647     flags = MAP_PRIVATE | MAP_ANONYMOUS;
 648 #if defined(MAP_STACK) && defined(__OpenBSD__)
 649     /* Only enable MAP_STACK on OpenBSD. Other OS's such as
 650      * Linux/FreeBSD/NetBSD have a flag with the same name
 651      * but have differing functionality. OpenBSD will SEGV
 652      * if it spots execution with a stack pointer pointing
 653      * at memory that was not allocated with MAP_STACK.
 654      */
 655     flags |= MAP_STACK;
 656 #endif
 657
 658     ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -1, 0);
 659     if (ptr == MAP_FAILED) {
 660         perror("failed to allocate memory for stack");
 661         abort();
 662     }
 663
 664 #if defined(HOST_IA64)
 665     /* separate register stack */
 666     guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
 667 #elif defined(HOST_HPPA)
 668     /* stack grows up */
 669     guardpage = ptr + *sz - pagesz;
 670 #else
 671     /* stack grows down */
 672     guardpage = ptr;
 673 #endif
 674     if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
 675         perror("failed to set up stack guard page");
 676         abort();
 677     }
 678
 679 #ifdef CONFIG_DEBUG_STACK_USAGE
 680     for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) {
 681         *(uint32_t *)ptr2 = 0xdeadbeaf;
 682     }
 683 #endif
 684
 685     return ptr;
 686 }
 687
 688 #ifdef CONFIG_DEBUG_STACK_USAGE
 689 static __thread unsigned int max_stack_usage;
 690 #endif
 691
 692 void qemu_free_stack(void *stack, size_t sz)
 693 {
 694 #ifdef CONFIG_DEBUG_STACK_USAGE
 695     unsigned int usage;
 696     void *ptr;
 697
 698     for (ptr = stack + qemu_real_host_page_size; ptr < stack + sz;
 699          ptr += sizeof(uint32_t)) {
 700         if (*(uint32_t *)ptr != 0xdeadbeaf) {
 701             break;
 702         }
 703     }
 704     usage = sz - (uintptr_t) (ptr - stack);
 705     if (usage > max_stack_usage) {
 706         error_report("thread %d max stack usage increased from %u to %u",
 707                      qemu_get_thread_id(), max_stack_usage, usage);
 708         max_stack_usage = usage;
 709     }
 710 #endif
 711
 712     munmap(stack, sz);
 713 }
 714
 715 void sigaction_invoke(struct sigaction *action,
 716                       struct qemu_signalfd_siginfo *info)
 717 {
 718     siginfo_t si = {};
 719     si.si_signo = info->ssi_signo;
 720     si.si_errno = info->ssi_errno;
 721     si.si_code = info->ssi_code;
 722
 723     /* Convert the minimal set of fields defined by POSIX.
 724      * Positive si_code values are reserved for kernel-generated
 725      * signals, where the valid siginfo fields are determined by
 726      * the signal number.  But according to POSIX, it is unspecified
 727      * whether SI_USER and SI_QUEUE have values less than or equal to
 728      * zero.
 729      */
 730     if (info->ssi_code == SI_USER || info->ssi_code == SI_QUEUE ||
 731         info->ssi_code <= 0) {
 732         /* SIGTERM, etc.  */
 733         si.si_pid = info->ssi_pid;
 734         si.si_uid = info->ssi_uid;
 735     } else if (info->ssi_signo == SIGILL || info->ssi_signo == SIGFPE ||
 736                info->ssi_signo == SIGSEGV || info->ssi_signo == SIGBUS) {
 737         si.si_addr = (void *)(uintptr_t)info->ssi_addr;
 738     } else if (info->ssi_signo == SIGCHLD) {
 739         si.si_pid = info->ssi_pid;
 740         si.si_status = info->ssi_status;
 741         si.si_uid = info->ssi_uid;
 742     }
 743     action->sa_sigaction(info->ssi_signo, &si, NULL);
 744 }