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 <libgen.h>
  40 #include <sys/signal.h>
  41 #include "qemu/cutils.h"
  42
  43 #ifdef CONFIG_LINUX
  44 #include <sys/syscall.h>
  45 #endif
  46
  47 #ifdef __FreeBSD__
  48 #include <sys/sysctl.h>
  49 #include <sys/user.h>
  50 #include <libutil.h>
  51 #endif
  52
  53 #ifdef __NetBSD__
  54 #include <sys/sysctl.h>
  55 #endif
  56
  57 #include "qemu/mmap-alloc.h"
  58
  59 #ifdef CONFIG_DEBUG_STACK_USAGE
  60 #include "qemu/error-report.h"
  61 #endif
  62
  63 #define MAX_MEM_PREALLOC_THREAD_COUNT 16
  64
  65 struct MemsetThread {
  66     char *addr;
  67     size_t numpages;
  68     size_t hpagesize;
  69     QemuThread pgthread;
  70     sigjmp_buf env;
  71 };
  72 typedef struct MemsetThread MemsetThread;
  73
  74 static MemsetThread *memset_thread;
  75 static int memset_num_threads;
  76 static bool memset_thread_failed;
  77
  78 int qemu_get_thread_id(void)
  79 {
  80 #if defined(__linux__)
  81     return syscall(SYS_gettid);
  82 #else
  83     return getpid();
  84 #endif
  85 }
  86
  87 int qemu_daemon(int nochdir, int noclose)
  88 {
  89     return daemon(nochdir, noclose);
  90 }
  91
  92 bool qemu_write_pidfile(const char *path, Error **errp)
  93 {
  94     int fd;
  95     char pidstr[32];
  96
  97     while (1) {
  98         struct stat a, b;
  99         struct flock lock = {
 100             .l_type = F_WRLCK,
 101             .l_whence = SEEK_SET,
 102             .l_len = 0,
 103         };
 104
 105         fd = qemu_open(path, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR);
 106         if (fd == -1) {
 107             error_setg_errno(errp, errno, "Cannot open pid file");
 108             return false;
 109         }
 110
 111         if (fstat(fd, &b) < 0) {
 112             error_setg_errno(errp, errno, "Cannot stat file");
 113             goto fail_close;
 114         }
 115
 116         if (fcntl(fd, F_SETLK, &lock)) {
 117             error_setg_errno(errp, errno, "Cannot lock pid file");
 118             goto fail_close;
 119         }
 120
 121         /*
 122          * Now make sure the path we locked is the same one that now
 123          * exists on the filesystem.
 124          */
 125         if (stat(path, &a) < 0) {
 126             /*
 127              * PID file disappeared, someone else must be racing with
 128              * us, so try again.
 129              */
 130             close(fd);
 131             continue;
 132         }
 133
 134         if (a.st_ino == b.st_ino) {
 135             break;
 136         }
 137
 138         /*
 139          * PID file was recreated, someone else must be racing with
 140          * us, so try again.
 141          */
 142         close(fd);
 143     }
 144
 145     if (ftruncate(fd, 0) < 0) {
 146         error_setg_errno(errp, errno, "Failed to truncate pid file");
 147         goto fail_unlink;
 148     }
 149
 150     snprintf(pidstr, sizeof(pidstr), FMT_pid "\n", getpid());
 151     if (write(fd, pidstr, strlen(pidstr)) != strlen(pidstr)) {
 152         error_setg(errp, "Failed to write pid file");
 153         goto fail_unlink;
 154     }
 155
 156     return true;
 157
 158 fail_unlink:
 159     unlink(path);
 160 fail_close:
 161     close(fd);
 162     return false;
 163 }
 164
 165 void *qemu_oom_check(void *ptr)
 166 {
 167     if (ptr == NULL) {
 168         fprintf(stderr, "Failed to allocate memory: %s\n", strerror(errno));
 169         abort();
 170     }
 171     return ptr;
 172 }
 173
 174 void *qemu_try_memalign(size_t alignment, size_t size)
 175 {
 176     void *ptr;
 177
 178     if (alignment < sizeof(void*)) {
 179         alignment = sizeof(void*);
 180     }
 181
 182 #if defined(CONFIG_POSIX_MEMALIGN)
 183     int ret;
 184     ret = posix_memalign(&ptr, alignment, size);
 185     if (ret != 0) {
 186         errno = ret;
 187         ptr = NULL;
 188     }
 189 #elif defined(CONFIG_BSD)
 190     ptr = valloc(size);
 191 #else
 192     ptr = memalign(alignment, size);
 193 #endif
 194     trace_qemu_memalign(alignment, size, ptr);
 195     return ptr;
 196 }
 197
 198 void *qemu_memalign(size_t alignment, size_t size)
 199 {
 200     return qemu_oom_check(qemu_try_memalign(alignment, size));
 201 }
 202
 203 /* alloc shared memory pages */
 204 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared)
 205 {
 206     size_t align = QEMU_VMALLOC_ALIGN;
 207     void *ptr = qemu_ram_mmap(-1, size, align, shared, false);
 208
 209     if (ptr == MAP_FAILED) {
 210         return NULL;
 211     }
 212
 213     if (alignment) {
 214         *alignment = align;
 215     }
 216
 217     trace_qemu_anon_ram_alloc(size, ptr);
 218     return ptr;
 219 }
 220
 221 void qemu_vfree(void *ptr)
 222 {
 223     trace_qemu_vfree(ptr);
 224     free(ptr);
 225 }
 226
 227 void qemu_anon_ram_free(void *ptr, size_t size)
 228 {
 229     trace_qemu_anon_ram_free(ptr, size);
 230     qemu_ram_munmap(-1, ptr, size);
 231 }
 232
 233 void qemu_set_block(int fd)
 234 {
 235     int f;
 236     f = fcntl(fd, F_GETFL);
 237     assert(f != -1);
 238     f = fcntl(fd, F_SETFL, f & ~O_NONBLOCK);
 239     assert(f != -1);
 240 }
 241
 242 void qemu_set_nonblock(int fd)
 243 {
 244     int f;
 245     f = fcntl(fd, F_GETFL);
 246     assert(f != -1);
 247     f = fcntl(fd, F_SETFL, f | O_NONBLOCK);
 248 #ifdef __OpenBSD__
 249     if (f == -1) {
 250         /*
 251          * Previous to OpenBSD 6.3, fcntl(F_SETFL) is not permitted on
 252          * memory devices and sets errno to ENODEV.
 253          * It's OK if we fail to set O_NONBLOCK on devices like /dev/null,
 254          * because they will never block anyway.
 255          */
 256         assert(errno == ENODEV);
 257     }
 258 #else
 259     assert(f != -1);
 260 #endif
 261 }
 262
 263 int socket_set_fast_reuse(int fd)
 264 {
 265     int val = 1, ret;
 266
 267     ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
 268                      (const char *)&val, sizeof(val));
 269
 270     assert(ret == 0);
 271
 272     return ret;
 273 }
 274
 275 void qemu_set_cloexec(int fd)
 276 {
 277     int f;
 278     f = fcntl(fd, F_GETFD);
 279     assert(f != -1);
 280     f = fcntl(fd, F_SETFD, f | FD_CLOEXEC);
 281     assert(f != -1);
 282 }
 283
 284 /*
 285  * Creates a pipe with FD_CLOEXEC set on both file descriptors
 286  */
 287 int qemu_pipe(int pipefd[2])
 288 {
 289     int ret;
 290
 291 #ifdef CONFIG_PIPE2
 292     ret = pipe2(pipefd, O_CLOEXEC);
 293     if (ret != -1 || errno != ENOSYS) {
 294         return ret;
 295     }
 296 #endif
 297     ret = pipe(pipefd);
 298     if (ret == 0) {
 299         qemu_set_cloexec(pipefd[0]);
 300         qemu_set_cloexec(pipefd[1]);
 301     }
 302
 303     return ret;
 304 }
 305
 306 char *
 307 qemu_get_local_state_pathname(const char *relative_pathname)
 308 {
 309     return g_strdup_printf("%s/%s", CONFIG_QEMU_LOCALSTATEDIR,
 310                            relative_pathname);
 311 }
 312
 313 void qemu_set_tty_echo(int fd, bool echo)
 314 {
 315     struct termios tty;
 316
 317     tcgetattr(fd, &tty);
 318
 319     if (echo) {
 320         tty.c_lflag |= ECHO | ECHONL | ICANON | IEXTEN;
 321     } else {
 322         tty.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
 323     }
 324
 325     tcsetattr(fd, TCSANOW, &tty);
 326 }
 327
 328 static char exec_dir[PATH_MAX];
 329
 330 void qemu_init_exec_dir(const char *argv0)
 331 {
 332     char *dir;
 333     char *p = NULL;
 334     char buf[PATH_MAX];
 335
 336     assert(!exec_dir[0]);
 337
 338 #if defined(__linux__)
 339     {
 340         int len;
 341         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
 342         if (len > 0) {
 343             buf[len] = 0;
 344             p = buf;
 345         }
 346     }
 347 #elif defined(__FreeBSD__) \
 348       || (defined(__NetBSD__) && defined(KERN_PROC_PATHNAME))
 349     {
 350 #if defined(__FreeBSD__)
 351         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
 352 #else
 353         static int mib[4] = {CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME};
 354 #endif
 355         size_t len = sizeof(buf) - 1;
 356
 357         *buf = '\0';
 358         if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
 359             *buf) {
 360             buf[sizeof(buf) - 1] = '\0';
 361             p = buf;
 362         }
 363     }
 364 #endif
 365     /* If we don't have any way of figuring out the actual executable
 366        location then try argv[0].  */
 367     if (!p) {
 368         if (!argv0) {
 369             return;
 370         }
 371         p = realpath(argv0, buf);
 372         if (!p) {
 373             return;
 374         }
 375     }
 376     dir = g_path_get_dirname(p);
 377
 378     pstrcpy(exec_dir, sizeof(exec_dir), dir);
 379
 380     g_free(dir);
 381 }
 382
 383 char *qemu_get_exec_dir(void)
 384 {
 385     return g_strdup(exec_dir);
 386 }
 387
 388 static void sigbus_handler(int signal)
 389 {
 390     int i;
 391     if (memset_thread) {
 392         for (i = 0; i < memset_num_threads; i++) {
 393             if (qemu_thread_is_self(&memset_thread[i].pgthread)) {
 394                 siglongjmp(memset_thread[i].env, 1);
 395             }
 396         }
 397     }
 398 }
 399
 400 static void *do_touch_pages(void *arg)
 401 {
 402     MemsetThread *memset_args = (MemsetThread *)arg;
 403     sigset_t set, oldset;
 404
 405     /* unblock SIGBUS */
 406     sigemptyset(&set);
 407     sigaddset(&set, SIGBUS);
 408     pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
 409
 410     if (sigsetjmp(memset_args->env, 1)) {
 411         memset_thread_failed = true;
 412     } else {
 413         char *addr = memset_args->addr;
 414         size_t numpages = memset_args->numpages;
 415         size_t hpagesize = memset_args->hpagesize;
 416         size_t i;
 417         for (i = 0; i < numpages; i++) {
 418             /*
 419              * Read & write back the same value, so we don't
 420              * corrupt existing user/app data that might be
 421              * stored.
 422              *
 423              * 'volatile' to stop compiler optimizing this away
 424              * to a no-op
 425              *
 426              * TODO: get a better solution from kernel so we
 427              * don't need to write at all so we don't cause
 428              * wear on the storage backing the region...
 429              */
 430             *(volatile char *)addr = *addr;
 431             addr += hpagesize;
 432         }
 433     }
 434     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 435     return NULL;
 436 }
 437
 438 static inline int get_memset_num_threads(int smp_cpus)
 439 {
 440     long host_procs = sysconf(_SC_NPROCESSORS_ONLN);
 441     int ret = 1;
 442
 443     if (host_procs > 0) {
 444         ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus);
 445     }
 446     /* In case sysconf() fails, we fall back to single threaded */
 447     return ret;
 448 }
 449
 450 static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages,
 451                             int smp_cpus)
 452 {
 453     size_t numpages_per_thread;
 454     size_t size_per_thread;
 455     char *addr = area;
 456     int i = 0;
 457
 458     memset_thread_failed = false;
 459     memset_num_threads = get_memset_num_threads(smp_cpus);
 460     memset_thread = g_new0(MemsetThread, memset_num_threads);
 461     numpages_per_thread = (numpages / memset_num_threads);
 462     size_per_thread = (hpagesize * numpages_per_thread);
 463     for (i = 0; i < memset_num_threads; i++) {
 464         memset_thread[i].addr = addr;
 465         memset_thread[i].numpages = (i == (memset_num_threads - 1)) ?
 466                                     numpages : numpages_per_thread;
 467         memset_thread[i].hpagesize = hpagesize;
 468         qemu_thread_create(&memset_thread[i].pgthread, "touch_pages",
 469                            do_touch_pages, &memset_thread[i],
 470                            QEMU_THREAD_JOINABLE);
 471         addr += size_per_thread;
 472         numpages -= numpages_per_thread;
 473     }
 474     for (i = 0; i < memset_num_threads; i++) {
 475         qemu_thread_join(&memset_thread[i].pgthread);
 476     }
 477     g_free(memset_thread);
 478     memset_thread = NULL;
 479
 480     return memset_thread_failed;
 481 }
 482
 483 void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
 484                      Error **errp)
 485 {
 486     int ret;
 487     struct sigaction act, oldact;
 488     size_t hpagesize = qemu_fd_getpagesize(fd);
 489     size_t numpages = DIV_ROUND_UP(memory, hpagesize);
 490
 491     memset(&act, 0, sizeof(act));
 492     act.sa_handler = &sigbus_handler;
 493     act.sa_flags = 0;
 494
 495     ret = sigaction(SIGBUS, &act, &oldact);
 496     if (ret) {
 497         error_setg_errno(errp, errno,
 498             "os_mem_prealloc: failed to install signal handler");
 499         return;
 500     }
 501
 502     /* touch pages simultaneously */
 503     if (touch_all_pages(area, hpagesize, numpages, smp_cpus)) {
 504         error_setg(errp, "os_mem_prealloc: Insufficient free host memory "
 505             "pages available to allocate guest RAM");
 506     }
 507
 508     ret = sigaction(SIGBUS, &oldact, NULL);
 509     if (ret) {
 510         /* Terminate QEMU since it can't recover from error */
 511         perror("os_mem_prealloc: failed to reinstall signal handler");
 512         exit(1);
 513     }
 514 }
 515
 516 uint64_t qemu_get_pmem_size(const char *filename, Error **errp)
 517 {
 518     struct stat st;
 519
 520     if (stat(filename, &st) < 0) {
 521         error_setg(errp, "unable to stat pmem file \"%s\"", filename);
 522         return 0;
 523     }
 524
 525 #if defined(__linux__)
 526     /* Special handling for devdax character devices */
 527     if (S_ISCHR(st.st_mode)) {
 528         char *subsystem_path = NULL;
 529         char *subsystem = NULL;
 530         char *size_path = NULL;
 531         char *size_str = NULL;
 532         uint64_t ret = 0;
 533
 534         subsystem_path = g_strdup_printf("/sys/dev/char/%d:%d/subsystem",
 535                                          major(st.st_rdev), minor(st.st_rdev));
 536         subsystem = g_file_read_link(subsystem_path, NULL);
 537         if (!subsystem) {
 538             error_setg(errp, "unable to read subsystem for pmem file \"%s\"",
 539                        filename);
 540             goto devdax_err;
 541         }
 542
 543         if (!g_str_has_suffix(subsystem, "/dax")) {
 544             error_setg(errp, "pmem file \"%s\" is not a dax device", filename);
 545             goto devdax_err;
 546         }
 547
 548         size_path = g_strdup_printf("/sys/dev/char/%d:%d/size",
 549                                     major(st.st_rdev), minor(st.st_rdev));
 550         if (!g_file_get_contents(size_path, &size_str, NULL, NULL)) {
 551             error_setg(errp, "unable to read size for pmem file \"%s\"",
 552                        size_path);
 553             goto devdax_err;
 554         }
 555
 556         ret = g_ascii_strtoull(size_str, NULL, 0);
 557
 558 devdax_err:
 559         g_free(size_str);
 560         g_free(size_path);
 561         g_free(subsystem);
 562         g_free(subsystem_path);
 563         return ret;
 564     }
 565 #endif /* defined(__linux__) */
 566
 567     return st.st_size;
 568 }
 569
 570 char *qemu_get_pid_name(pid_t pid)
 571 {
 572     char *name = NULL;
 573
 574 #if defined(__FreeBSD__)
 575     /* BSDs don't have /proc, but they provide a nice substitute */
 576     struct kinfo_proc *proc = kinfo_getproc(pid);
 577
 578     if (proc) {
 579         name = g_strdup(proc->ki_comm);
 580         free(proc);
 581     }
 582 #else
 583     /* Assume a system with reasonable procfs */
 584     char *pid_path;
 585     size_t len;
 586
 587     pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
 588     g_file_get_contents(pid_path, &name, &len, NULL);
 589     g_free(pid_path);
 590 #endif
 591
 592     return name;
 593 }
 594
 595
 596 pid_t qemu_fork(Error **errp)
 597 {
 598     sigset_t oldmask, newmask;
 599     struct sigaction sig_action;
 600     int saved_errno;
 601     pid_t pid;
 602
 603     /*
 604      * Need to block signals now, so that child process can safely
 605      * kill off caller's signal handlers without a race.
 606      */
 607     sigfillset(&newmask);
 608     if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
 609         error_setg_errno(errp, errno,
 610                          "cannot block signals");
 611         return -1;
 612     }
 613
 614     pid = fork();
 615     saved_errno = errno;
 616
 617     if (pid < 0) {
 618         /* attempt to restore signal mask, but ignore failure, to
 619          * avoid obscuring the fork failure */
 620         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 621         error_setg_errno(errp, saved_errno,
 622                          "cannot fork child process");
 623         errno = saved_errno;
 624         return -1;
 625     } else if (pid) {
 626         /* parent process */
 627
 628         /* Restore our original signal mask now that the child is
 629          * safely running. Only documented failures are EFAULT (not
 630          * possible, since we are using just-grabbed mask) or EINVAL
 631          * (not possible, since we are using correct arguments).  */
 632         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 633     } else {
 634         /* child process */
 635         size_t i;
 636
 637         /* Clear out all signal handlers from parent so nothing
 638          * unexpected can happen in our child once we unblock
 639          * signals */
 640         sig_action.sa_handler = SIG_DFL;
 641         sig_action.sa_flags = 0;
 642         sigemptyset(&sig_action.sa_mask);
 643
 644         for (i = 1; i < NSIG; i++) {
 645             /* Only possible errors are EFAULT or EINVAL The former
 646              * won't happen, the latter we expect, so no need to check
 647              * return value */
 648             (void)sigaction(i, &sig_action, NULL);
 649         }
 650
 651         /* Unmask all signals in child, since we've no idea what the
 652          * caller's done with their signal mask and don't want to
 653          * propagate that to children */
 654         sigemptyset(&newmask);
 655         if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) {
 656             Error *local_err = NULL;
 657             error_setg_errno(&local_err, errno,
 658                              "cannot unblock signals");
 659             error_report_err(local_err);
 660             _exit(1);
 661         }
 662     }
 663     return pid;
 664 }
 665
 666 void *qemu_alloc_stack(size_t *sz)
 667 {
 668     void *ptr, *guardpage;
 669     int flags;
 670 #ifdef CONFIG_DEBUG_STACK_USAGE
 671     void *ptr2;
 672 #endif
 673     size_t pagesz = getpagesize();
 674 #ifdef _SC_THREAD_STACK_MIN
 675     /* avoid stacks smaller than _SC_THREAD_STACK_MIN */
 676     long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
 677     *sz = MAX(MAX(min_stack_sz, 0), *sz);
 678 #endif
 679     /* adjust stack size to a multiple of the page size */
 680     *sz = ROUND_UP(*sz, pagesz);
 681     /* allocate one extra page for the guard page */
 682     *sz += pagesz;
 683
 684     flags = MAP_PRIVATE | MAP_ANONYMOUS;
 685 #if defined(MAP_STACK) && defined(__OpenBSD__)
 686     /* Only enable MAP_STACK on OpenBSD. Other OS's such as
 687      * Linux/FreeBSD/NetBSD have a flag with the same name
 688      * but have differing functionality. OpenBSD will SEGV
 689      * if it spots execution with a stack pointer pointing
 690      * at memory that was not allocated with MAP_STACK.
 691      */
 692     flags |= MAP_STACK;
 693 #endif
 694
 695     ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -1, 0);
 696     if (ptr == MAP_FAILED) {
 697         perror("failed to allocate memory for stack");
 698         abort();
 699     }
 700
 701 #if defined(HOST_IA64)
 702     /* separate register stack */
 703     guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
 704 #elif defined(HOST_HPPA)
 705     /* stack grows up */
 706     guardpage = ptr + *sz - pagesz;
 707 #else
 708     /* stack grows down */
 709     guardpage = ptr;
 710 #endif
 711     if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
 712         perror("failed to set up stack guard page");
 713         abort();
 714     }
 715
 716 #ifdef CONFIG_DEBUG_STACK_USAGE
 717     for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) {
 718         *(uint32_t *)ptr2 = 0xdeadbeaf;
 719     }
 720 #endif
 721
 722     return ptr;
 723 }
 724
 725 #ifdef CONFIG_DEBUG_STACK_USAGE
 726 static __thread unsigned int max_stack_usage;
 727 #endif
 728
 729 void qemu_free_stack(void *stack, size_t sz)
 730 {
 731 #ifdef CONFIG_DEBUG_STACK_USAGE
 732     unsigned int usage;
 733     void *ptr;
 734
 735     for (ptr = stack + getpagesize(); ptr < stack + sz;
 736          ptr += sizeof(uint32_t)) {
 737         if (*(uint32_t *)ptr != 0xdeadbeaf) {
 738             break;
 739         }
 740     }
 741     usage = sz - (uintptr_t) (ptr - stack);
 742     if (usage > max_stack_usage) {
 743         error_report("thread %d max stack usage increased from %u to %u",
 744                      qemu_get_thread_id(), max_stack_usage, usage);
 745         max_stack_usage = usage;
 746     }
 747 #endif
 748
 749     munmap(stack, sz);
 750 }
 751
 752 void sigaction_invoke(struct sigaction *action,
 753                       struct qemu_signalfd_siginfo *info)
 754 {
 755     siginfo_t si = {};
 756     si.si_signo = info->ssi_signo;
 757     si.si_errno = info->ssi_errno;
 758     si.si_code = info->ssi_code;
 759
 760     /* Convert the minimal set of fields defined by POSIX.
 761      * Positive si_code values are reserved for kernel-generated
 762      * signals, where the valid siginfo fields are determined by
 763      * the signal number.  But according to POSIX, it is unspecified
 764      * whether SI_USER and SI_QUEUE have values less than or equal to
 765      * zero.
 766      */
 767     if (info->ssi_code == SI_USER || info->ssi_code == SI_QUEUE ||
 768         info->ssi_code <= 0) {
 769         /* SIGTERM, etc.  */
 770         si.si_pid = info->ssi_pid;
 771         si.si_uid = info->ssi_uid;
 772     } else if (info->ssi_signo == SIGILL || info->ssi_signo == SIGFPE ||
 773                info->ssi_signo == SIGSEGV || info->ssi_signo == SIGBUS) {
 774         si.si_addr = (void *)(uintptr_t)info->ssi_addr;
 775     } else if (info->ssi_signo == SIGCHLD) {
 776         si.si_pid = info->ssi_pid;
 777         si.si_status = info->ssi_status;
 778         si.si_uid = info->ssi_uid;
 779     }
 780     action->sa_sigaction(info->ssi_signo, &si, NULL);
 781 }