xref: /openbmc/qemu/util/oslib-posix.c (revision e0091133)
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 "sysemu/sysemu.h"
35 #include "trace.h"
36 #include "qapi/error.h"
37 #include "qemu/error-report.h"
38 #include "qemu/madvise.h"
39 #include "qemu/sockets.h"
40 #include "qemu/thread.h"
41 #include <libgen.h>
42 #include "qemu/cutils.h"
43 #include "qemu/compiler.h"
44 #include "qemu/units.h"
45 #include "qemu/thread-context.h"
46 
47 #ifdef CONFIG_LINUX
48 #include <sys/syscall.h>
49 #endif
50 
51 #ifdef __FreeBSD__
52 #include <sys/thr.h>
53 #include <sys/types.h>
54 #include <sys/user.h>
55 #include <libutil.h>
56 #endif
57 
58 #ifdef __NetBSD__
59 #include <lwp.h>
60 #endif
61 
62 #include "qemu/mmap-alloc.h"
63 
64 #ifdef CONFIG_DEBUG_STACK_USAGE
65 #include "qemu/error-report.h"
66 #endif
67 
68 #define MAX_MEM_PREALLOC_THREAD_COUNT 16
69 
70 struct MemsetThread;
71 
72 typedef struct MemsetContext {
73     bool all_threads_created;
74     bool any_thread_failed;
75     struct MemsetThread *threads;
76     int num_threads;
77 } MemsetContext;
78 
79 struct MemsetThread {
80     char *addr;
81     size_t numpages;
82     size_t hpagesize;
83     QemuThread pgthread;
84     sigjmp_buf env;
85     MemsetContext *context;
86 };
87 typedef struct MemsetThread MemsetThread;
88 
89 /* used by sigbus_handler() */
90 static MemsetContext *sigbus_memset_context;
91 struct sigaction sigbus_oldact;
92 static QemuMutex sigbus_mutex;
93 
94 static QemuMutex page_mutex;
95 static QemuCond page_cond;
96 
97 int qemu_get_thread_id(void)
98 {
99 #if defined(__linux__)
100     return syscall(SYS_gettid);
101 #elif defined(__FreeBSD__)
102     /* thread id is up to INT_MAX */
103     long tid;
104     thr_self(&tid);
105     return (int)tid;
106 #elif defined(__NetBSD__)
107     return _lwp_self();
108 #elif defined(__OpenBSD__)
109     return getthrid();
110 #else
111     return getpid();
112 #endif
113 }
114 
115 int qemu_daemon(int nochdir, int noclose)
116 {
117     return daemon(nochdir, noclose);
118 }
119 
120 bool qemu_write_pidfile(const char *path, Error **errp)
121 {
122     int fd;
123     char pidstr[32];
124 
125     while (1) {
126         struct stat a, b;
127         struct flock lock = {
128             .l_type = F_WRLCK,
129             .l_whence = SEEK_SET,
130             .l_len = 0,
131         };
132 
133         fd = qemu_create(path, O_WRONLY, S_IRUSR | S_IWUSR, errp);
134         if (fd == -1) {
135             return false;
136         }
137 
138         if (fstat(fd, &b) < 0) {
139             error_setg_errno(errp, errno, "Cannot stat file");
140             goto fail_close;
141         }
142 
143         if (fcntl(fd, F_SETLK, &lock)) {
144             error_setg_errno(errp, errno, "Cannot lock pid file");
145             goto fail_close;
146         }
147 
148         /*
149          * Now make sure the path we locked is the same one that now
150          * exists on the filesystem.
151          */
152         if (stat(path, &a) < 0) {
153             /*
154              * PID file disappeared, someone else must be racing with
155              * us, so try again.
156              */
157             close(fd);
158             continue;
159         }
160 
161         if (a.st_ino == b.st_ino) {
162             break;
163         }
164 
165         /*
166          * PID file was recreated, someone else must be racing with
167          * us, so try again.
168          */
169         close(fd);
170     }
171 
172     if (ftruncate(fd, 0) < 0) {
173         error_setg_errno(errp, errno, "Failed to truncate pid file");
174         goto fail_unlink;
175     }
176 
177     snprintf(pidstr, sizeof(pidstr), FMT_pid "\n", getpid());
178     if (qemu_write_full(fd, pidstr, strlen(pidstr)) != strlen(pidstr)) {
179         error_setg(errp, "Failed to write pid file");
180         goto fail_unlink;
181     }
182 
183     return true;
184 
185 fail_unlink:
186     unlink(path);
187 fail_close:
188     close(fd);
189     return false;
190 }
191 
192 /* alloc shared memory pages */
193 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared,
194                           bool noreserve)
195 {
196     const uint32_t qemu_map_flags = (shared ? QEMU_MAP_SHARED : 0) |
197                                     (noreserve ? QEMU_MAP_NORESERVE : 0);
198     size_t align = QEMU_VMALLOC_ALIGN;
199     void *ptr = qemu_ram_mmap(-1, size, align, qemu_map_flags, 0);
200 
201     if (ptr == MAP_FAILED) {
202         return NULL;
203     }
204 
205     if (alignment) {
206         *alignment = align;
207     }
208 
209     trace_qemu_anon_ram_alloc(size, ptr);
210     return ptr;
211 }
212 
213 void qemu_anon_ram_free(void *ptr, size_t size)
214 {
215     trace_qemu_anon_ram_free(ptr, size);
216     qemu_ram_munmap(-1, ptr, size);
217 }
218 
219 void qemu_socket_set_block(int fd)
220 {
221     g_unix_set_fd_nonblocking(fd, false, NULL);
222 }
223 
224 int qemu_socket_try_set_nonblock(int fd)
225 {
226     return g_unix_set_fd_nonblocking(fd, true, NULL) ? 0 : -errno;
227 }
228 
229 void qemu_socket_set_nonblock(int fd)
230 {
231     int f;
232     f = qemu_socket_try_set_nonblock(fd);
233     assert(f == 0);
234 }
235 
236 int socket_set_fast_reuse(int fd)
237 {
238     int val = 1, ret;
239 
240     ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
241                      (const char *)&val, sizeof(val));
242 
243     assert(ret == 0);
244 
245     return ret;
246 }
247 
248 void qemu_set_cloexec(int fd)
249 {
250     int f;
251     f = fcntl(fd, F_GETFD);
252     assert(f != -1);
253     f = fcntl(fd, F_SETFD, f | FD_CLOEXEC);
254     assert(f != -1);
255 }
256 
257 int qemu_socketpair(int domain, int type, int protocol, int sv[2])
258 {
259     int ret;
260 
261 #ifdef SOCK_CLOEXEC
262     ret = socketpair(domain, type | SOCK_CLOEXEC, protocol, sv);
263     if (ret != -1 || errno != EINVAL) {
264         return ret;
265     }
266 #endif
267     ret = socketpair(domain, type, protocol, sv);;
268     if (ret == 0) {
269         qemu_set_cloexec(sv[0]);
270         qemu_set_cloexec(sv[1]);
271     }
272 
273     return ret;
274 }
275 
276 char *
277 qemu_get_local_state_dir(void)
278 {
279     return get_relocated_path(CONFIG_QEMU_LOCALSTATEDIR);
280 }
281 
282 void qemu_set_tty_echo(int fd, bool echo)
283 {
284     struct termios tty;
285 
286     tcgetattr(fd, &tty);
287 
288     if (echo) {
289         tty.c_lflag |= ECHO | ECHONL | ICANON | IEXTEN;
290     } else {
291         tty.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
292     }
293 
294     tcsetattr(fd, TCSANOW, &tty);
295 }
296 
297 #ifdef CONFIG_LINUX
298 static void sigbus_handler(int signal, siginfo_t *siginfo, void *ctx)
299 #else /* CONFIG_LINUX */
300 static void sigbus_handler(int signal)
301 #endif /* CONFIG_LINUX */
302 {
303     int i;
304 
305     if (sigbus_memset_context) {
306         for (i = 0; i < sigbus_memset_context->num_threads; i++) {
307             MemsetThread *thread = &sigbus_memset_context->threads[i];
308 
309             if (qemu_thread_is_self(&thread->pgthread)) {
310                 siglongjmp(thread->env, 1);
311             }
312         }
313     }
314 
315 #ifdef CONFIG_LINUX
316     /*
317      * We assume that the MCE SIGBUS handler could have been registered. We
318      * should never receive BUS_MCEERR_AO on any of our threads, but only on
319      * the main thread registered for PR_MCE_KILL_EARLY. Further, we should not
320      * receive BUS_MCEERR_AR triggered by action of other threads on one of
321      * our threads. So, no need to check for unrelated SIGBUS when seeing one
322      * for our threads.
323      *
324      * We will forward to the MCE handler, which will either handle the SIGBUS
325      * or reinstall the default SIGBUS handler and reraise the SIGBUS. The
326      * default SIGBUS handler will crash the process, so we don't care.
327      */
328     if (sigbus_oldact.sa_flags & SA_SIGINFO) {
329         sigbus_oldact.sa_sigaction(signal, siginfo, ctx);
330         return;
331     }
332 #endif /* CONFIG_LINUX */
333     warn_report("qemu_prealloc_mem: unrelated SIGBUS detected and ignored");
334 }
335 
336 static void *do_touch_pages(void *arg)
337 {
338     MemsetThread *memset_args = (MemsetThread *)arg;
339     sigset_t set, oldset;
340     int ret = 0;
341 
342     /*
343      * On Linux, the page faults from the loop below can cause mmap_sem
344      * contention with allocation of the thread stacks.  Do not start
345      * clearing until all threads have been created.
346      */
347     qemu_mutex_lock(&page_mutex);
348     while (!memset_args->context->all_threads_created) {
349         qemu_cond_wait(&page_cond, &page_mutex);
350     }
351     qemu_mutex_unlock(&page_mutex);
352 
353     /* unblock SIGBUS */
354     sigemptyset(&set);
355     sigaddset(&set, SIGBUS);
356     pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
357 
358     if (sigsetjmp(memset_args->env, 1)) {
359         ret = -EFAULT;
360     } else {
361         char *addr = memset_args->addr;
362         size_t numpages = memset_args->numpages;
363         size_t hpagesize = memset_args->hpagesize;
364         size_t i;
365         for (i = 0; i < numpages; i++) {
366             /*
367              * Read & write back the same value, so we don't
368              * corrupt existing user/app data that might be
369              * stored.
370              *
371              * 'volatile' to stop compiler optimizing this away
372              * to a no-op
373              */
374             *(volatile char *)addr = *addr;
375             addr += hpagesize;
376         }
377     }
378     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
379     return (void *)(uintptr_t)ret;
380 }
381 
382 static void *do_madv_populate_write_pages(void *arg)
383 {
384     MemsetThread *memset_args = (MemsetThread *)arg;
385     const size_t size = memset_args->numpages * memset_args->hpagesize;
386     char * const addr = memset_args->addr;
387     int ret = 0;
388 
389     /* See do_touch_pages(). */
390     qemu_mutex_lock(&page_mutex);
391     while (!memset_args->context->all_threads_created) {
392         qemu_cond_wait(&page_cond, &page_mutex);
393     }
394     qemu_mutex_unlock(&page_mutex);
395 
396     if (size && qemu_madvise(addr, size, QEMU_MADV_POPULATE_WRITE)) {
397         ret = -errno;
398     }
399     return (void *)(uintptr_t)ret;
400 }
401 
402 static inline int get_memset_num_threads(size_t hpagesize, size_t numpages,
403                                          int max_threads)
404 {
405     long host_procs = sysconf(_SC_NPROCESSORS_ONLN);
406     int ret = 1;
407 
408     if (host_procs > 0) {
409         ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), max_threads);
410     }
411 
412     /* Especially with gigantic pages, don't create more threads than pages. */
413     ret = MIN(ret, numpages);
414     /* Don't start threads to prealloc comparatively little memory. */
415     ret = MIN(ret, MAX(1, hpagesize * numpages / (64 * MiB)));
416 
417     /* In case sysconf() fails, we fall back to single threaded */
418     return ret;
419 }
420 
421 static int touch_all_pages(char *area, size_t hpagesize, size_t numpages,
422                            int max_threads, ThreadContext *tc,
423                            bool use_madv_populate_write)
424 {
425     static gsize initialized = 0;
426     MemsetContext context = {
427         .num_threads = get_memset_num_threads(hpagesize, numpages, max_threads),
428     };
429     size_t numpages_per_thread, leftover;
430     void *(*touch_fn)(void *);
431     int ret = 0, i = 0;
432     char *addr = area;
433 
434     if (g_once_init_enter(&initialized)) {
435         qemu_mutex_init(&page_mutex);
436         qemu_cond_init(&page_cond);
437         g_once_init_leave(&initialized, 1);
438     }
439 
440     if (use_madv_populate_write) {
441         /* Avoid creating a single thread for MADV_POPULATE_WRITE */
442         if (context.num_threads == 1) {
443             if (qemu_madvise(area, hpagesize * numpages,
444                              QEMU_MADV_POPULATE_WRITE)) {
445                 return -errno;
446             }
447             return 0;
448         }
449         touch_fn = do_madv_populate_write_pages;
450     } else {
451         touch_fn = do_touch_pages;
452     }
453 
454     context.threads = g_new0(MemsetThread, context.num_threads);
455     numpages_per_thread = numpages / context.num_threads;
456     leftover = numpages % context.num_threads;
457     for (i = 0; i < context.num_threads; i++) {
458         context.threads[i].addr = addr;
459         context.threads[i].numpages = numpages_per_thread + (i < leftover);
460         context.threads[i].hpagesize = hpagesize;
461         context.threads[i].context = &context;
462         if (tc) {
463             thread_context_create_thread(tc, &context.threads[i].pgthread,
464                                          "touch_pages",
465                                          touch_fn, &context.threads[i],
466                                          QEMU_THREAD_JOINABLE);
467         } else {
468             qemu_thread_create(&context.threads[i].pgthread, "touch_pages",
469                                touch_fn, &context.threads[i],
470                                QEMU_THREAD_JOINABLE);
471         }
472         addr += context.threads[i].numpages * hpagesize;
473     }
474 
475     if (!use_madv_populate_write) {
476         sigbus_memset_context = &context;
477     }
478 
479     qemu_mutex_lock(&page_mutex);
480     context.all_threads_created = true;
481     qemu_cond_broadcast(&page_cond);
482     qemu_mutex_unlock(&page_mutex);
483 
484     for (i = 0; i < context.num_threads; i++) {
485         int tmp = (uintptr_t)qemu_thread_join(&context.threads[i].pgthread);
486 
487         if (tmp) {
488             ret = tmp;
489         }
490     }
491 
492     if (!use_madv_populate_write) {
493         sigbus_memset_context = NULL;
494     }
495     g_free(context.threads);
496 
497     return ret;
498 }
499 
500 static bool madv_populate_write_possible(char *area, size_t pagesize)
501 {
502     return !qemu_madvise(area, pagesize, QEMU_MADV_POPULATE_WRITE) ||
503            errno != EINVAL;
504 }
505 
506 void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
507                        ThreadContext *tc, Error **errp)
508 {
509     static gsize initialized;
510     int ret;
511     size_t hpagesize = qemu_fd_getpagesize(fd);
512     size_t numpages = DIV_ROUND_UP(sz, hpagesize);
513     bool use_madv_populate_write;
514     struct sigaction act;
515 
516     /*
517      * Sense on every invocation, as MADV_POPULATE_WRITE cannot be used for
518      * some special mappings, such as mapping /dev/mem.
519      */
520     use_madv_populate_write = madv_populate_write_possible(area, hpagesize);
521 
522     if (!use_madv_populate_write) {
523         if (g_once_init_enter(&initialized)) {
524             qemu_mutex_init(&sigbus_mutex);
525             g_once_init_leave(&initialized, 1);
526         }
527 
528         qemu_mutex_lock(&sigbus_mutex);
529         memset(&act, 0, sizeof(act));
530 #ifdef CONFIG_LINUX
531         act.sa_sigaction = &sigbus_handler;
532         act.sa_flags = SA_SIGINFO;
533 #else /* CONFIG_LINUX */
534         act.sa_handler = &sigbus_handler;
535         act.sa_flags = 0;
536 #endif /* CONFIG_LINUX */
537 
538         ret = sigaction(SIGBUS, &act, &sigbus_oldact);
539         if (ret) {
540             qemu_mutex_unlock(&sigbus_mutex);
541             error_setg_errno(errp, errno,
542                 "qemu_prealloc_mem: failed to install signal handler");
543             return;
544         }
545     }
546 
547     /* touch pages simultaneously */
548     ret = touch_all_pages(area, hpagesize, numpages, max_threads, tc,
549                           use_madv_populate_write);
550     if (ret) {
551         error_setg_errno(errp, -ret,
552                          "qemu_prealloc_mem: preallocating memory failed");
553     }
554 
555     if (!use_madv_populate_write) {
556         ret = sigaction(SIGBUS, &sigbus_oldact, NULL);
557         if (ret) {
558             /* Terminate QEMU since it can't recover from error */
559             perror("qemu_prealloc_mem: failed to reinstall signal handler");
560             exit(1);
561         }
562         qemu_mutex_unlock(&sigbus_mutex);
563     }
564 }
565 
566 char *qemu_get_pid_name(pid_t pid)
567 {
568     char *name = NULL;
569 
570 #if defined(__FreeBSD__)
571     /* BSDs don't have /proc, but they provide a nice substitute */
572     struct kinfo_proc *proc = kinfo_getproc(pid);
573 
574     if (proc) {
575         name = g_strdup(proc->ki_comm);
576         free(proc);
577     }
578 #else
579     /* Assume a system with reasonable procfs */
580     char *pid_path;
581     size_t len;
582 
583     pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
584     g_file_get_contents(pid_path, &name, &len, NULL);
585     g_free(pid_path);
586 #endif
587 
588     return name;
589 }
590 
591 
592 pid_t qemu_fork(Error **errp)
593 {
594     sigset_t oldmask, newmask;
595     struct sigaction sig_action;
596     int saved_errno;
597     pid_t pid;
598 
599     /*
600      * Need to block signals now, so that child process can safely
601      * kill off caller's signal handlers without a race.
602      */
603     sigfillset(&newmask);
604     if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
605         error_setg_errno(errp, errno,
606                          "cannot block signals");
607         return -1;
608     }
609 
610     pid = fork();
611     saved_errno = errno;
612 
613     if (pid < 0) {
614         /* attempt to restore signal mask, but ignore failure, to
615          * avoid obscuring the fork failure */
616         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
617         error_setg_errno(errp, saved_errno,
618                          "cannot fork child process");
619         errno = saved_errno;
620         return -1;
621     } else if (pid) {
622         /* parent process */
623 
624         /* Restore our original signal mask now that the child is
625          * safely running. Only documented failures are EFAULT (not
626          * possible, since we are using just-grabbed mask) or EINVAL
627          * (not possible, since we are using correct arguments).  */
628         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
629     } else {
630         /* child process */
631         size_t i;
632 
633         /* Clear out all signal handlers from parent so nothing
634          * unexpected can happen in our child once we unblock
635          * signals */
636         sig_action.sa_handler = SIG_DFL;
637         sig_action.sa_flags = 0;
638         sigemptyset(&sig_action.sa_mask);
639 
640         for (i = 1; i < NSIG; i++) {
641             /* Only possible errors are EFAULT or EINVAL The former
642              * won't happen, the latter we expect, so no need to check
643              * return value */
644             (void)sigaction(i, &sig_action, NULL);
645         }
646 
647         /* Unmask all signals in child, since we've no idea what the
648          * caller's done with their signal mask and don't want to
649          * propagate that to children */
650         sigemptyset(&newmask);
651         if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) {
652             Error *local_err = NULL;
653             error_setg_errno(&local_err, errno,
654                              "cannot unblock signals");
655             error_report_err(local_err);
656             _exit(1);
657         }
658     }
659     return pid;
660 }
661 
662 void *qemu_alloc_stack(size_t *sz)
663 {
664     void *ptr, *guardpage;
665     int flags;
666 #ifdef CONFIG_DEBUG_STACK_USAGE
667     void *ptr2;
668 #endif
669     size_t pagesz = qemu_real_host_page_size();
670 #ifdef _SC_THREAD_STACK_MIN
671     /* avoid stacks smaller than _SC_THREAD_STACK_MIN */
672     long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
673     *sz = MAX(MAX(min_stack_sz, 0), *sz);
674 #endif
675     /* adjust stack size to a multiple of the page size */
676     *sz = ROUND_UP(*sz, pagesz);
677     /* allocate one extra page for the guard page */
678     *sz += pagesz;
679 
680     flags = MAP_PRIVATE | MAP_ANONYMOUS;
681 #if defined(MAP_STACK) && defined(__OpenBSD__)
682     /* Only enable MAP_STACK on OpenBSD. Other OS's such as
683      * Linux/FreeBSD/NetBSD have a flag with the same name
684      * but have differing functionality. OpenBSD will SEGV
685      * if it spots execution with a stack pointer pointing
686      * at memory that was not allocated with MAP_STACK.
687      */
688     flags |= MAP_STACK;
689 #endif
690 
691     ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -1, 0);
692     if (ptr == MAP_FAILED) {
693         perror("failed to allocate memory for stack");
694         abort();
695     }
696 
697 #if defined(HOST_IA64)
698     /* separate register stack */
699     guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
700 #elif defined(HOST_HPPA)
701     /* stack grows up */
702     guardpage = ptr + *sz - pagesz;
703 #else
704     /* stack grows down */
705     guardpage = ptr;
706 #endif
707     if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
708         perror("failed to set up stack guard page");
709         abort();
710     }
711 
712 #ifdef CONFIG_DEBUG_STACK_USAGE
713     for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) {
714         *(uint32_t *)ptr2 = 0xdeadbeaf;
715     }
716 #endif
717 
718     return ptr;
719 }
720 
721 #ifdef CONFIG_DEBUG_STACK_USAGE
722 static __thread unsigned int max_stack_usage;
723 #endif
724 
725 void qemu_free_stack(void *stack, size_t sz)
726 {
727 #ifdef CONFIG_DEBUG_STACK_USAGE
728     unsigned int usage;
729     void *ptr;
730 
731     for (ptr = stack + qemu_real_host_page_size(); ptr < stack + sz;
732          ptr += sizeof(uint32_t)) {
733         if (*(uint32_t *)ptr != 0xdeadbeaf) {
734             break;
735         }
736     }
737     usage = sz - (uintptr_t) (ptr - stack);
738     if (usage > max_stack_usage) {
739         error_report("thread %d max stack usage increased from %u to %u",
740                      qemu_get_thread_id(), max_stack_usage, usage);
741         max_stack_usage = usage;
742     }
743 #endif
744 
745     munmap(stack, sz);
746 }
747 
748 /*
749  * Disable CFI checks.
750  * We are going to call a signal hander directly. Such handler may or may not
751  * have been defined in our binary, so there's no guarantee that the pointer
752  * used to set the handler is a cfi-valid pointer. Since the handlers are
753  * stored in kernel memory, changing the handler to an attacker-defined
754  * function requires being able to call a sigaction() syscall,
755  * which is not as easy as overwriting a pointer in memory.
756  */
757 QEMU_DISABLE_CFI
758 void sigaction_invoke(struct sigaction *action,
759                       struct qemu_signalfd_siginfo *info)
760 {
761     siginfo_t si = {};
762     si.si_signo = info->ssi_signo;
763     si.si_errno = info->ssi_errno;
764     si.si_code = info->ssi_code;
765 
766     /* Convert the minimal set of fields defined by POSIX.
767      * Positive si_code values are reserved for kernel-generated
768      * signals, where the valid siginfo fields are determined by
769      * the signal number.  But according to POSIX, it is unspecified
770      * whether SI_USER and SI_QUEUE have values less than or equal to
771      * zero.
772      */
773     if (info->ssi_code == SI_USER || info->ssi_code == SI_QUEUE ||
774         info->ssi_code <= 0) {
775         /* SIGTERM, etc.  */
776         si.si_pid = info->ssi_pid;
777         si.si_uid = info->ssi_uid;
778     } else if (info->ssi_signo == SIGILL || info->ssi_signo == SIGFPE ||
779                info->ssi_signo == SIGSEGV || info->ssi_signo == SIGBUS) {
780         si.si_addr = (void *)(uintptr_t)info->ssi_addr;
781     } else if (info->ssi_signo == SIGCHLD) {
782         si.si_pid = info->ssi_pid;
783         si.si_status = info->ssi_status;
784         si.si_uid = info->ssi_uid;
785     }
786     action->sa_sigaction(info->ssi_signo, &si, NULL);
787 }
788 
789 size_t qemu_get_host_physmem(void)
790 {
791 #ifdef _SC_PHYS_PAGES
792     long pages = sysconf(_SC_PHYS_PAGES);
793     if (pages > 0) {
794         if (pages > SIZE_MAX / qemu_real_host_page_size()) {
795             return SIZE_MAX;
796         } else {
797             return pages * qemu_real_host_page_size();
798         }
799     }
800 #endif
801     return 0;
802 }
803 
804 int qemu_msync(void *addr, size_t length, int fd)
805 {
806     size_t align_mask = ~(qemu_real_host_page_size() - 1);
807 
808     /**
809      * There are no strict reqs as per the length of mapping
810      * to be synced. Still the length needs to follow the address
811      * alignment changes. Additionally - round the size to the multiple
812      * of PAGE_SIZE
813      */
814     length += ((uintptr_t)addr & (qemu_real_host_page_size() - 1));
815     length = (length + ~align_mask) & align_mask;
816 
817     addr = (void *)((uintptr_t)addr & align_mask);
818 
819     return msync(addr, length, MS_SYNC);
820 }
821