xref: /openbmc/qemu/util/oslib-posix.c (revision f7a6df5f)
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 "qemu/cutils.h"
42 #include "qemu/compiler.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 <sys/thr.h>
52 #include <libutil.h>
53 #endif
54 
55 #ifdef __NetBSD__
56 #include <sys/sysctl.h>
57 #include <lwp.h>
58 #endif
59 
60 #ifdef __APPLE__
61 #include <mach-o/dyld.h>
62 #endif
63 
64 #ifdef __HAIKU__
65 #include <kernel/image.h>
66 #endif
67 
68 #include "qemu/mmap-alloc.h"
69 
70 #ifdef CONFIG_DEBUG_STACK_USAGE
71 #include "qemu/error-report.h"
72 #endif
73 
74 #define MAX_MEM_PREALLOC_THREAD_COUNT 16
75 
76 struct MemsetThread {
77     char *addr;
78     size_t numpages;
79     size_t hpagesize;
80     QemuThread pgthread;
81     sigjmp_buf env;
82 };
83 typedef struct MemsetThread MemsetThread;
84 
85 static MemsetThread *memset_thread;
86 static int memset_num_threads;
87 static bool memset_thread_failed;
88 
89 static QemuMutex page_mutex;
90 static QemuCond page_cond;
91 static bool threads_created_flag;
92 
93 int qemu_get_thread_id(void)
94 {
95 #if defined(__linux__)
96     return syscall(SYS_gettid);
97 #elif defined(__FreeBSD__)
98     /* thread id is up to INT_MAX */
99     long tid;
100     thr_self(&tid);
101     return (int)tid;
102 #elif defined(__NetBSD__)
103     return _lwp_self();
104 #elif defined(__OpenBSD__)
105     return getthrid();
106 #else
107     return getpid();
108 #endif
109 }
110 
111 int qemu_daemon(int nochdir, int noclose)
112 {
113     return daemon(nochdir, noclose);
114 }
115 
116 bool qemu_write_pidfile(const char *path, Error **errp)
117 {
118     int fd;
119     char pidstr[32];
120 
121     while (1) {
122         struct stat a, b;
123         struct flock lock = {
124             .l_type = F_WRLCK,
125             .l_whence = SEEK_SET,
126             .l_len = 0,
127         };
128 
129         fd = qemu_open_old(path, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR);
130         if (fd == -1) {
131             error_setg_errno(errp, errno, "Cannot open pid file");
132             return false;
133         }
134 
135         if (fstat(fd, &b) < 0) {
136             error_setg_errno(errp, errno, "Cannot stat file");
137             goto fail_close;
138         }
139 
140         if (fcntl(fd, F_SETLK, &lock)) {
141             error_setg_errno(errp, errno, "Cannot lock pid file");
142             goto fail_close;
143         }
144 
145         /*
146          * Now make sure the path we locked is the same one that now
147          * exists on the filesystem.
148          */
149         if (stat(path, &a) < 0) {
150             /*
151              * PID file disappeared, someone else must be racing with
152              * us, so try again.
153              */
154             close(fd);
155             continue;
156         }
157 
158         if (a.st_ino == b.st_ino) {
159             break;
160         }
161 
162         /*
163          * PID file was recreated, someone else must be racing with
164          * us, so try again.
165          */
166         close(fd);
167     }
168 
169     if (ftruncate(fd, 0) < 0) {
170         error_setg_errno(errp, errno, "Failed to truncate pid file");
171         goto fail_unlink;
172     }
173 
174     snprintf(pidstr, sizeof(pidstr), FMT_pid "\n", getpid());
175     if (write(fd, pidstr, strlen(pidstr)) != strlen(pidstr)) {
176         error_setg(errp, "Failed to write pid file");
177         goto fail_unlink;
178     }
179 
180     return true;
181 
182 fail_unlink:
183     unlink(path);
184 fail_close:
185     close(fd);
186     return false;
187 }
188 
189 void *qemu_oom_check(void *ptr)
190 {
191     if (ptr == NULL) {
192         fprintf(stderr, "Failed to allocate memory: %s\n", strerror(errno));
193         abort();
194     }
195     return ptr;
196 }
197 
198 void *qemu_try_memalign(size_t alignment, size_t size)
199 {
200     void *ptr;
201 
202     if (alignment < sizeof(void*)) {
203         alignment = sizeof(void*);
204     } else {
205         g_assert(is_power_of_2(alignment));
206     }
207 
208 #if defined(CONFIG_POSIX_MEMALIGN)
209     int ret;
210     ret = posix_memalign(&ptr, alignment, size);
211     if (ret != 0) {
212         errno = ret;
213         ptr = NULL;
214     }
215 #elif defined(CONFIG_BSD)
216     ptr = valloc(size);
217 #else
218     ptr = memalign(alignment, size);
219 #endif
220     trace_qemu_memalign(alignment, size, ptr);
221     return ptr;
222 }
223 
224 void *qemu_memalign(size_t alignment, size_t size)
225 {
226     return qemu_oom_check(qemu_try_memalign(alignment, size));
227 }
228 
229 /* alloc shared memory pages */
230 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared)
231 {
232     size_t align = QEMU_VMALLOC_ALIGN;
233     void *ptr = qemu_ram_mmap(-1, size, align, false, shared, false, 0);
234 
235     if (ptr == MAP_FAILED) {
236         return NULL;
237     }
238 
239     if (alignment) {
240         *alignment = align;
241     }
242 
243     trace_qemu_anon_ram_alloc(size, ptr);
244     return ptr;
245 }
246 
247 void qemu_vfree(void *ptr)
248 {
249     trace_qemu_vfree(ptr);
250     free(ptr);
251 }
252 
253 void qemu_anon_ram_free(void *ptr, size_t size)
254 {
255     trace_qemu_anon_ram_free(ptr, size);
256     qemu_ram_munmap(-1, ptr, size);
257 }
258 
259 void qemu_set_block(int fd)
260 {
261     int f;
262     f = fcntl(fd, F_GETFL);
263     assert(f != -1);
264     f = fcntl(fd, F_SETFL, f & ~O_NONBLOCK);
265     assert(f != -1);
266 }
267 
268 int qemu_try_set_nonblock(int fd)
269 {
270     int f;
271     f = fcntl(fd, F_GETFL);
272     if (f == -1) {
273         return -errno;
274     }
275     if (fcntl(fd, F_SETFL, f | O_NONBLOCK) == -1) {
276 #ifdef __OpenBSD__
277         /*
278          * Previous to OpenBSD 6.3, fcntl(F_SETFL) is not permitted on
279          * memory devices and sets errno to ENODEV.
280          * It's OK if we fail to set O_NONBLOCK on devices like /dev/null,
281          * because they will never block anyway.
282          */
283         if (errno == ENODEV) {
284             return 0;
285         }
286 #endif
287         return -errno;
288     }
289     return 0;
290 }
291 
292 void qemu_set_nonblock(int fd)
293 {
294     int f;
295     f = qemu_try_set_nonblock(fd);
296     assert(f == 0);
297 }
298 
299 int socket_set_fast_reuse(int fd)
300 {
301     int val = 1, ret;
302 
303     ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
304                      (const char *)&val, sizeof(val));
305 
306     assert(ret == 0);
307 
308     return ret;
309 }
310 
311 void qemu_set_cloexec(int fd)
312 {
313     int f;
314     f = fcntl(fd, F_GETFD);
315     assert(f != -1);
316     f = fcntl(fd, F_SETFD, f | FD_CLOEXEC);
317     assert(f != -1);
318 }
319 
320 /*
321  * Creates a pipe with FD_CLOEXEC set on both file descriptors
322  */
323 int qemu_pipe(int pipefd[2])
324 {
325     int ret;
326 
327 #ifdef CONFIG_PIPE2
328     ret = pipe2(pipefd, O_CLOEXEC);
329     if (ret != -1 || errno != ENOSYS) {
330         return ret;
331     }
332 #endif
333     ret = pipe(pipefd);
334     if (ret == 0) {
335         qemu_set_cloexec(pipefd[0]);
336         qemu_set_cloexec(pipefd[1]);
337     }
338 
339     return ret;
340 }
341 
342 char *
343 qemu_get_local_state_pathname(const char *relative_pathname)
344 {
345     g_autofree char *dir = g_strdup_printf("%s/%s",
346                                            CONFIG_QEMU_LOCALSTATEDIR,
347                                            relative_pathname);
348     return get_relocated_path(dir);
349 }
350 
351 void qemu_set_tty_echo(int fd, bool echo)
352 {
353     struct termios tty;
354 
355     tcgetattr(fd, &tty);
356 
357     if (echo) {
358         tty.c_lflag |= ECHO | ECHONL | ICANON | IEXTEN;
359     } else {
360         tty.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
361     }
362 
363     tcsetattr(fd, TCSANOW, &tty);
364 }
365 
366 static const char *exec_dir;
367 
368 void qemu_init_exec_dir(const char *argv0)
369 {
370     char *p = NULL;
371     char buf[PATH_MAX];
372 
373     if (exec_dir) {
374         return;
375     }
376 
377 #if defined(__linux__)
378     {
379         int len;
380         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
381         if (len > 0) {
382             buf[len] = 0;
383             p = buf;
384         }
385     }
386 #elif defined(__FreeBSD__) \
387       || (defined(__NetBSD__) && defined(KERN_PROC_PATHNAME))
388     {
389 #if defined(__FreeBSD__)
390         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
391 #else
392         static int mib[4] = {CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME};
393 #endif
394         size_t len = sizeof(buf) - 1;
395 
396         *buf = '\0';
397         if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
398             *buf) {
399             buf[sizeof(buf) - 1] = '\0';
400             p = buf;
401         }
402     }
403 #elif defined(__APPLE__)
404     {
405         char fpath[PATH_MAX];
406         uint32_t len = sizeof(fpath);
407         if (_NSGetExecutablePath(fpath, &len) == 0) {
408             p = realpath(fpath, buf);
409             if (!p) {
410                 return;
411             }
412         }
413     }
414 #elif defined(__HAIKU__)
415     {
416         image_info ii;
417         int32_t c = 0;
418 
419         *buf = '\0';
420         while (get_next_image_info(0, &c, &ii) == B_OK) {
421             if (ii.type == B_APP_IMAGE) {
422                 strncpy(buf, ii.name, sizeof(buf));
423                 buf[sizeof(buf) - 1] = 0;
424                 p = buf;
425                 break;
426             }
427         }
428     }
429 #endif
430     /* If we don't have any way of figuring out the actual executable
431        location then try argv[0].  */
432     if (!p && argv0) {
433         p = realpath(argv0, buf);
434     }
435     if (p) {
436         exec_dir = g_path_get_dirname(p);
437     } else {
438         exec_dir = CONFIG_BINDIR;
439     }
440 }
441 
442 const char *qemu_get_exec_dir(void)
443 {
444     return exec_dir;
445 }
446 
447 static void sigbus_handler(int signal)
448 {
449     int i;
450     if (memset_thread) {
451         for (i = 0; i < memset_num_threads; i++) {
452             if (qemu_thread_is_self(&memset_thread[i].pgthread)) {
453                 siglongjmp(memset_thread[i].env, 1);
454             }
455         }
456     }
457 }
458 
459 static void *do_touch_pages(void *arg)
460 {
461     MemsetThread *memset_args = (MemsetThread *)arg;
462     sigset_t set, oldset;
463 
464     /*
465      * On Linux, the page faults from the loop below can cause mmap_sem
466      * contention with allocation of the thread stacks.  Do not start
467      * clearing until all threads have been created.
468      */
469     qemu_mutex_lock(&page_mutex);
470     while(!threads_created_flag){
471         qemu_cond_wait(&page_cond, &page_mutex);
472     }
473     qemu_mutex_unlock(&page_mutex);
474 
475     /* unblock SIGBUS */
476     sigemptyset(&set);
477     sigaddset(&set, SIGBUS);
478     pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
479 
480     if (sigsetjmp(memset_args->env, 1)) {
481         memset_thread_failed = true;
482     } else {
483         char *addr = memset_args->addr;
484         size_t numpages = memset_args->numpages;
485         size_t hpagesize = memset_args->hpagesize;
486         size_t i;
487         for (i = 0; i < numpages; i++) {
488             /*
489              * Read & write back the same value, so we don't
490              * corrupt existing user/app data that might be
491              * stored.
492              *
493              * 'volatile' to stop compiler optimizing this away
494              * to a no-op
495              *
496              * TODO: get a better solution from kernel so we
497              * don't need to write at all so we don't cause
498              * wear on the storage backing the region...
499              */
500             *(volatile char *)addr = *addr;
501             addr += hpagesize;
502         }
503     }
504     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
505     return NULL;
506 }
507 
508 static inline int get_memset_num_threads(int smp_cpus)
509 {
510     long host_procs = sysconf(_SC_NPROCESSORS_ONLN);
511     int ret = 1;
512 
513     if (host_procs > 0) {
514         ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus);
515     }
516     /* In case sysconf() fails, we fall back to single threaded */
517     return ret;
518 }
519 
520 static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages,
521                             int smp_cpus)
522 {
523     static gsize initialized = 0;
524     size_t numpages_per_thread, leftover;
525     char *addr = area;
526     int i = 0;
527 
528     if (g_once_init_enter(&initialized)) {
529         qemu_mutex_init(&page_mutex);
530         qemu_cond_init(&page_cond);
531         g_once_init_leave(&initialized, 1);
532     }
533 
534     memset_thread_failed = false;
535     threads_created_flag = false;
536     memset_num_threads = get_memset_num_threads(smp_cpus);
537     memset_thread = g_new0(MemsetThread, memset_num_threads);
538     numpages_per_thread = numpages / memset_num_threads;
539     leftover = numpages % memset_num_threads;
540     for (i = 0; i < memset_num_threads; i++) {
541         memset_thread[i].addr = addr;
542         memset_thread[i].numpages = numpages_per_thread + (i < leftover);
543         memset_thread[i].hpagesize = hpagesize;
544         qemu_thread_create(&memset_thread[i].pgthread, "touch_pages",
545                            do_touch_pages, &memset_thread[i],
546                            QEMU_THREAD_JOINABLE);
547         addr += memset_thread[i].numpages * hpagesize;
548     }
549 
550     qemu_mutex_lock(&page_mutex);
551     threads_created_flag = true;
552     qemu_cond_broadcast(&page_cond);
553     qemu_mutex_unlock(&page_mutex);
554 
555     for (i = 0; i < memset_num_threads; i++) {
556         qemu_thread_join(&memset_thread[i].pgthread);
557     }
558     g_free(memset_thread);
559     memset_thread = NULL;
560 
561     return memset_thread_failed;
562 }
563 
564 void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
565                      Error **errp)
566 {
567     int ret;
568     struct sigaction act, oldact;
569     size_t hpagesize = qemu_fd_getpagesize(fd);
570     size_t numpages = DIV_ROUND_UP(memory, hpagesize);
571 
572     memset(&act, 0, sizeof(act));
573     act.sa_handler = &sigbus_handler;
574     act.sa_flags = 0;
575 
576     ret = sigaction(SIGBUS, &act, &oldact);
577     if (ret) {
578         error_setg_errno(errp, errno,
579             "os_mem_prealloc: failed to install signal handler");
580         return;
581     }
582 
583     /* touch pages simultaneously */
584     if (touch_all_pages(area, hpagesize, numpages, smp_cpus)) {
585         error_setg(errp, "os_mem_prealloc: Insufficient free host memory "
586             "pages available to allocate guest RAM");
587     }
588 
589     ret = sigaction(SIGBUS, &oldact, NULL);
590     if (ret) {
591         /* Terminate QEMU since it can't recover from error */
592         perror("os_mem_prealloc: failed to reinstall signal handler");
593         exit(1);
594     }
595 }
596 
597 char *qemu_get_pid_name(pid_t pid)
598 {
599     char *name = NULL;
600 
601 #if defined(__FreeBSD__)
602     /* BSDs don't have /proc, but they provide a nice substitute */
603     struct kinfo_proc *proc = kinfo_getproc(pid);
604 
605     if (proc) {
606         name = g_strdup(proc->ki_comm);
607         free(proc);
608     }
609 #else
610     /* Assume a system with reasonable procfs */
611     char *pid_path;
612     size_t len;
613 
614     pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
615     g_file_get_contents(pid_path, &name, &len, NULL);
616     g_free(pid_path);
617 #endif
618 
619     return name;
620 }
621 
622 
623 pid_t qemu_fork(Error **errp)
624 {
625     sigset_t oldmask, newmask;
626     struct sigaction sig_action;
627     int saved_errno;
628     pid_t pid;
629 
630     /*
631      * Need to block signals now, so that child process can safely
632      * kill off caller's signal handlers without a race.
633      */
634     sigfillset(&newmask);
635     if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
636         error_setg_errno(errp, errno,
637                          "cannot block signals");
638         return -1;
639     }
640 
641     pid = fork();
642     saved_errno = errno;
643 
644     if (pid < 0) {
645         /* attempt to restore signal mask, but ignore failure, to
646          * avoid obscuring the fork failure */
647         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
648         error_setg_errno(errp, saved_errno,
649                          "cannot fork child process");
650         errno = saved_errno;
651         return -1;
652     } else if (pid) {
653         /* parent process */
654 
655         /* Restore our original signal mask now that the child is
656          * safely running. Only documented failures are EFAULT (not
657          * possible, since we are using just-grabbed mask) or EINVAL
658          * (not possible, since we are using correct arguments).  */
659         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
660     } else {
661         /* child process */
662         size_t i;
663 
664         /* Clear out all signal handlers from parent so nothing
665          * unexpected can happen in our child once we unblock
666          * signals */
667         sig_action.sa_handler = SIG_DFL;
668         sig_action.sa_flags = 0;
669         sigemptyset(&sig_action.sa_mask);
670 
671         for (i = 1; i < NSIG; i++) {
672             /* Only possible errors are EFAULT or EINVAL The former
673              * won't happen, the latter we expect, so no need to check
674              * return value */
675             (void)sigaction(i, &sig_action, NULL);
676         }
677 
678         /* Unmask all signals in child, since we've no idea what the
679          * caller's done with their signal mask and don't want to
680          * propagate that to children */
681         sigemptyset(&newmask);
682         if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) {
683             Error *local_err = NULL;
684             error_setg_errno(&local_err, errno,
685                              "cannot unblock signals");
686             error_report_err(local_err);
687             _exit(1);
688         }
689     }
690     return pid;
691 }
692 
693 void *qemu_alloc_stack(size_t *sz)
694 {
695     void *ptr, *guardpage;
696     int flags;
697 #ifdef CONFIG_DEBUG_STACK_USAGE
698     void *ptr2;
699 #endif
700     size_t pagesz = qemu_real_host_page_size;
701 #ifdef _SC_THREAD_STACK_MIN
702     /* avoid stacks smaller than _SC_THREAD_STACK_MIN */
703     long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
704     *sz = MAX(MAX(min_stack_sz, 0), *sz);
705 #endif
706     /* adjust stack size to a multiple of the page size */
707     *sz = ROUND_UP(*sz, pagesz);
708     /* allocate one extra page for the guard page */
709     *sz += pagesz;
710 
711     flags = MAP_PRIVATE | MAP_ANONYMOUS;
712 #if defined(MAP_STACK) && defined(__OpenBSD__)
713     /* Only enable MAP_STACK on OpenBSD. Other OS's such as
714      * Linux/FreeBSD/NetBSD have a flag with the same name
715      * but have differing functionality. OpenBSD will SEGV
716      * if it spots execution with a stack pointer pointing
717      * at memory that was not allocated with MAP_STACK.
718      */
719     flags |= MAP_STACK;
720 #endif
721 
722     ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -1, 0);
723     if (ptr == MAP_FAILED) {
724         perror("failed to allocate memory for stack");
725         abort();
726     }
727 
728 #if defined(HOST_IA64)
729     /* separate register stack */
730     guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
731 #elif defined(HOST_HPPA)
732     /* stack grows up */
733     guardpage = ptr + *sz - pagesz;
734 #else
735     /* stack grows down */
736     guardpage = ptr;
737 #endif
738     if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
739         perror("failed to set up stack guard page");
740         abort();
741     }
742 
743 #ifdef CONFIG_DEBUG_STACK_USAGE
744     for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) {
745         *(uint32_t *)ptr2 = 0xdeadbeaf;
746     }
747 #endif
748 
749     return ptr;
750 }
751 
752 #ifdef CONFIG_DEBUG_STACK_USAGE
753 static __thread unsigned int max_stack_usage;
754 #endif
755 
756 void qemu_free_stack(void *stack, size_t sz)
757 {
758 #ifdef CONFIG_DEBUG_STACK_USAGE
759     unsigned int usage;
760     void *ptr;
761 
762     for (ptr = stack + qemu_real_host_page_size; ptr < stack + sz;
763          ptr += sizeof(uint32_t)) {
764         if (*(uint32_t *)ptr != 0xdeadbeaf) {
765             break;
766         }
767     }
768     usage = sz - (uintptr_t) (ptr - stack);
769     if (usage > max_stack_usage) {
770         error_report("thread %d max stack usage increased from %u to %u",
771                      qemu_get_thread_id(), max_stack_usage, usage);
772         max_stack_usage = usage;
773     }
774 #endif
775 
776     munmap(stack, sz);
777 }
778 
779 /*
780  * Disable CFI checks.
781  * We are going to call a signal hander directly. Such handler may or may not
782  * have been defined in our binary, so there's no guarantee that the pointer
783  * used to set the handler is a cfi-valid pointer. Since the handlers are
784  * stored in kernel memory, changing the handler to an attacker-defined
785  * function requires being able to call a sigaction() syscall,
786  * which is not as easy as overwriting a pointer in memory.
787  */
788 QEMU_DISABLE_CFI
789 void sigaction_invoke(struct sigaction *action,
790                       struct qemu_signalfd_siginfo *info)
791 {
792     siginfo_t si = {};
793     si.si_signo = info->ssi_signo;
794     si.si_errno = info->ssi_errno;
795     si.si_code = info->ssi_code;
796 
797     /* Convert the minimal set of fields defined by POSIX.
798      * Positive si_code values are reserved for kernel-generated
799      * signals, where the valid siginfo fields are determined by
800      * the signal number.  But according to POSIX, it is unspecified
801      * whether SI_USER and SI_QUEUE have values less than or equal to
802      * zero.
803      */
804     if (info->ssi_code == SI_USER || info->ssi_code == SI_QUEUE ||
805         info->ssi_code <= 0) {
806         /* SIGTERM, etc.  */
807         si.si_pid = info->ssi_pid;
808         si.si_uid = info->ssi_uid;
809     } else if (info->ssi_signo == SIGILL || info->ssi_signo == SIGFPE ||
810                info->ssi_signo == SIGSEGV || info->ssi_signo == SIGBUS) {
811         si.si_addr = (void *)(uintptr_t)info->ssi_addr;
812     } else if (info->ssi_signo == SIGCHLD) {
813         si.si_pid = info->ssi_pid;
814         si.si_status = info->ssi_status;
815         si.si_uid = info->ssi_uid;
816     }
817     action->sa_sigaction(info->ssi_signo, &si, NULL);
818 }
819 
820 #ifndef HOST_NAME_MAX
821 # ifdef _POSIX_HOST_NAME_MAX
822 #  define HOST_NAME_MAX _POSIX_HOST_NAME_MAX
823 # else
824 #  define HOST_NAME_MAX 255
825 # endif
826 #endif
827 
828 char *qemu_get_host_name(Error **errp)
829 {
830     long len = -1;
831     g_autofree char *hostname = NULL;
832 
833 #ifdef _SC_HOST_NAME_MAX
834     len = sysconf(_SC_HOST_NAME_MAX);
835 #endif /* _SC_HOST_NAME_MAX */
836 
837     if (len < 0) {
838         len = HOST_NAME_MAX;
839     }
840 
841     /* Unfortunately, gethostname() below does not guarantee a
842      * NULL terminated string. Therefore, allocate one byte more
843      * to be sure. */
844     hostname = g_new0(char, len + 1);
845 
846     if (gethostname(hostname, len) < 0) {
847         error_setg_errno(errp, errno,
848                          "cannot get hostname");
849         return NULL;
850     }
851 
852     return g_steal_pointer(&hostname);
853 }
854 
855 size_t qemu_get_host_physmem(void)
856 {
857 #ifdef _SC_PHYS_PAGES
858     long pages = sysconf(_SC_PHYS_PAGES);
859     if (pages > 0) {
860         if (pages > SIZE_MAX / qemu_real_host_page_size) {
861             return SIZE_MAX;
862         } else {
863             return pages * qemu_real_host_page_size;
864         }
865     }
866 #endif
867     return 0;
868 }
869