xref: /openbmc/qemu/util/oslib-posix.c (revision 438c78da)
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/sockets.h"
38 #include <libgen.h>
39 #include <sys/signal.h>
40 #include "qemu/cutils.h"
41 
42 #ifdef CONFIG_LINUX
43 #include <sys/syscall.h>
44 #endif
45 
46 #ifdef __FreeBSD__
47 #include <sys/sysctl.h>
48 #include <sys/user.h>
49 #include <libutil.h>
50 #endif
51 
52 #ifdef __NetBSD__
53 #include <sys/sysctl.h>
54 #endif
55 
56 #include "qemu/mmap-alloc.h"
57 
58 #ifdef CONFIG_DEBUG_STACK_USAGE
59 #include "qemu/error-report.h"
60 #endif
61 
62 #define MAX_MEM_PREALLOC_THREAD_COUNT 16
63 
64 struct MemsetThread {
65     char *addr;
66     size_t numpages;
67     size_t hpagesize;
68     QemuThread pgthread;
69     sigjmp_buf env;
70 };
71 typedef struct MemsetThread MemsetThread;
72 
73 static MemsetThread *memset_thread;
74 static int memset_num_threads;
75 static bool memset_thread_failed;
76 
77 int qemu_get_thread_id(void)
78 {
79 #if defined(__linux__)
80     return syscall(SYS_gettid);
81 #else
82     return getpid();
83 #endif
84 }
85 
86 int qemu_daemon(int nochdir, int noclose)
87 {
88     return daemon(nochdir, noclose);
89 }
90 
91 bool qemu_write_pidfile(const char *path, Error **errp)
92 {
93     int fd;
94     char pidstr[32];
95 
96     while (1) {
97         struct stat a, b;
98         struct flock lock = {
99             .l_type = F_WRLCK,
100             .l_whence = SEEK_SET,
101             .l_len = 0,
102         };
103 
104         fd = qemu_open(path, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR);
105         if (fd == -1) {
106             error_setg_errno(errp, errno, "Cannot open pid file");
107             return false;
108         }
109 
110         if (fstat(fd, &b) < 0) {
111             error_setg_errno(errp, errno, "Cannot stat file");
112             goto fail_close;
113         }
114 
115         if (fcntl(fd, F_SETLK, &lock)) {
116             error_setg_errno(errp, errno, "Cannot lock pid file");
117             goto fail_close;
118         }
119 
120         /*
121          * Now make sure the path we locked is the same one that now
122          * exists on the filesystem.
123          */
124         if (stat(path, &a) < 0) {
125             /*
126              * PID file disappeared, someone else must be racing with
127              * us, so try again.
128              */
129             close(fd);
130             continue;
131         }
132 
133         if (a.st_ino == b.st_ino) {
134             break;
135         }
136 
137         /*
138          * PID file was recreated, someone else must be racing with
139          * us, so try again.
140          */
141         close(fd);
142     }
143 
144     if (ftruncate(fd, 0) < 0) {
145         error_setg_errno(errp, errno, "Failed to truncate pid file");
146         goto fail_unlink;
147     }
148 
149     snprintf(pidstr, sizeof(pidstr), FMT_pid "\n", getpid());
150     if (write(fd, pidstr, strlen(pidstr)) != strlen(pidstr)) {
151         error_setg(errp, "Failed to write pid file");
152         goto fail_unlink;
153     }
154 
155     return true;
156 
157 fail_unlink:
158     unlink(path);
159 fail_close:
160     close(fd);
161     return false;
162 }
163 
164 void *qemu_oom_check(void *ptr)
165 {
166     if (ptr == NULL) {
167         fprintf(stderr, "Failed to allocate memory: %s\n", strerror(errno));
168         abort();
169     }
170     return ptr;
171 }
172 
173 void *qemu_try_memalign(size_t alignment, size_t size)
174 {
175     void *ptr;
176 
177     if (alignment < sizeof(void*)) {
178         alignment = sizeof(void*);
179     }
180 
181 #if defined(CONFIG_POSIX_MEMALIGN)
182     int ret;
183     ret = posix_memalign(&ptr, alignment, size);
184     if (ret != 0) {
185         errno = ret;
186         ptr = NULL;
187     }
188 #elif defined(CONFIG_BSD)
189     ptr = valloc(size);
190 #else
191     ptr = memalign(alignment, size);
192 #endif
193     trace_qemu_memalign(alignment, size, ptr);
194     return ptr;
195 }
196 
197 void *qemu_memalign(size_t alignment, size_t size)
198 {
199     return qemu_oom_check(qemu_try_memalign(alignment, size));
200 }
201 
202 /* alloc shared memory pages */
203 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared)
204 {
205     size_t align = QEMU_VMALLOC_ALIGN;
206     void *ptr = qemu_ram_mmap(-1, size, align, shared);
207 
208     if (ptr == MAP_FAILED) {
209         return NULL;
210     }
211 
212     if (alignment) {
213         *alignment = align;
214     }
215 
216     trace_qemu_anon_ram_alloc(size, ptr);
217     return ptr;
218 }
219 
220 void qemu_vfree(void *ptr)
221 {
222     trace_qemu_vfree(ptr);
223     free(ptr);
224 }
225 
226 void qemu_anon_ram_free(void *ptr, size_t size)
227 {
228     trace_qemu_anon_ram_free(ptr, size);
229     qemu_ram_munmap(ptr, size);
230 }
231 
232 void qemu_set_block(int fd)
233 {
234     int f;
235     f = fcntl(fd, F_GETFL);
236     fcntl(fd, F_SETFL, f & ~O_NONBLOCK);
237 }
238 
239 void qemu_set_nonblock(int fd)
240 {
241     int f;
242     f = fcntl(fd, F_GETFL);
243     fcntl(fd, F_SETFL, f | O_NONBLOCK);
244 }
245 
246 int socket_set_fast_reuse(int fd)
247 {
248     int val = 1, ret;
249 
250     ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
251                      (const char *)&val, sizeof(val));
252 
253     assert(ret == 0);
254 
255     return ret;
256 }
257 
258 void qemu_set_cloexec(int fd)
259 {
260     int f;
261     f = fcntl(fd, F_GETFD);
262     assert(f != -1);
263     f = fcntl(fd, F_SETFD, f | FD_CLOEXEC);
264     assert(f != -1);
265 }
266 
267 /*
268  * Creates a pipe with FD_CLOEXEC set on both file descriptors
269  */
270 int qemu_pipe(int pipefd[2])
271 {
272     int ret;
273 
274 #ifdef CONFIG_PIPE2
275     ret = pipe2(pipefd, O_CLOEXEC);
276     if (ret != -1 || errno != ENOSYS) {
277         return ret;
278     }
279 #endif
280     ret = pipe(pipefd);
281     if (ret == 0) {
282         qemu_set_cloexec(pipefd[0]);
283         qemu_set_cloexec(pipefd[1]);
284     }
285 
286     return ret;
287 }
288 
289 char *
290 qemu_get_local_state_pathname(const char *relative_pathname)
291 {
292     return g_strdup_printf("%s/%s", CONFIG_QEMU_LOCALSTATEDIR,
293                            relative_pathname);
294 }
295 
296 void qemu_set_tty_echo(int fd, bool echo)
297 {
298     struct termios tty;
299 
300     tcgetattr(fd, &tty);
301 
302     if (echo) {
303         tty.c_lflag |= ECHO | ECHONL | ICANON | IEXTEN;
304     } else {
305         tty.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
306     }
307 
308     tcsetattr(fd, TCSANOW, &tty);
309 }
310 
311 static char exec_dir[PATH_MAX];
312 
313 void qemu_init_exec_dir(const char *argv0)
314 {
315     char *dir;
316     char *p = NULL;
317     char buf[PATH_MAX];
318 
319     assert(!exec_dir[0]);
320 
321 #if defined(__linux__)
322     {
323         int len;
324         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
325         if (len > 0) {
326             buf[len] = 0;
327             p = buf;
328         }
329     }
330 #elif defined(__FreeBSD__) \
331       || (defined(__NetBSD__) && defined(KERN_PROC_PATHNAME))
332     {
333 #if defined(__FreeBSD__)
334         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
335 #else
336         static int mib[4] = {CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME};
337 #endif
338         size_t len = sizeof(buf) - 1;
339 
340         *buf = '\0';
341         if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
342             *buf) {
343             buf[sizeof(buf) - 1] = '\0';
344             p = buf;
345         }
346     }
347 #endif
348     /* If we don't have any way of figuring out the actual executable
349        location then try argv[0].  */
350     if (!p) {
351         if (!argv0) {
352             return;
353         }
354         p = realpath(argv0, buf);
355         if (!p) {
356             return;
357         }
358     }
359     dir = g_path_get_dirname(p);
360 
361     pstrcpy(exec_dir, sizeof(exec_dir), dir);
362 
363     g_free(dir);
364 }
365 
366 char *qemu_get_exec_dir(void)
367 {
368     return g_strdup(exec_dir);
369 }
370 
371 static void sigbus_handler(int signal)
372 {
373     int i;
374     if (memset_thread) {
375         for (i = 0; i < memset_num_threads; i++) {
376             if (qemu_thread_is_self(&memset_thread[i].pgthread)) {
377                 siglongjmp(memset_thread[i].env, 1);
378             }
379         }
380     }
381 }
382 
383 static void *do_touch_pages(void *arg)
384 {
385     MemsetThread *memset_args = (MemsetThread *)arg;
386     sigset_t set, oldset;
387 
388     /* unblock SIGBUS */
389     sigemptyset(&set);
390     sigaddset(&set, SIGBUS);
391     pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
392 
393     if (sigsetjmp(memset_args->env, 1)) {
394         memset_thread_failed = true;
395     } else {
396         char *addr = memset_args->addr;
397         size_t numpages = memset_args->numpages;
398         size_t hpagesize = memset_args->hpagesize;
399         size_t i;
400         for (i = 0; i < numpages; i++) {
401             /*
402              * Read & write back the same value, so we don't
403              * corrupt existing user/app data that might be
404              * stored.
405              *
406              * 'volatile' to stop compiler optimizing this away
407              * to a no-op
408              *
409              * TODO: get a better solution from kernel so we
410              * don't need to write at all so we don't cause
411              * wear on the storage backing the region...
412              */
413             *(volatile char *)addr = *addr;
414             addr += hpagesize;
415         }
416     }
417     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
418     return NULL;
419 }
420 
421 static inline int get_memset_num_threads(int smp_cpus)
422 {
423     long host_procs = sysconf(_SC_NPROCESSORS_ONLN);
424     int ret = 1;
425 
426     if (host_procs > 0) {
427         ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus);
428     }
429     /* In case sysconf() fails, we fall back to single threaded */
430     return ret;
431 }
432 
433 static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages,
434                             int smp_cpus)
435 {
436     size_t numpages_per_thread;
437     size_t size_per_thread;
438     char *addr = area;
439     int i = 0;
440 
441     memset_thread_failed = false;
442     memset_num_threads = get_memset_num_threads(smp_cpus);
443     memset_thread = g_new0(MemsetThread, memset_num_threads);
444     numpages_per_thread = (numpages / memset_num_threads);
445     size_per_thread = (hpagesize * numpages_per_thread);
446     for (i = 0; i < memset_num_threads; i++) {
447         memset_thread[i].addr = addr;
448         memset_thread[i].numpages = (i == (memset_num_threads - 1)) ?
449                                     numpages : numpages_per_thread;
450         memset_thread[i].hpagesize = hpagesize;
451         qemu_thread_create(&memset_thread[i].pgthread, "touch_pages",
452                            do_touch_pages, &memset_thread[i],
453                            QEMU_THREAD_JOINABLE);
454         addr += size_per_thread;
455         numpages -= numpages_per_thread;
456     }
457     for (i = 0; i < memset_num_threads; i++) {
458         qemu_thread_join(&memset_thread[i].pgthread);
459     }
460     g_free(memset_thread);
461     memset_thread = NULL;
462 
463     return memset_thread_failed;
464 }
465 
466 void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
467                      Error **errp)
468 {
469     int ret;
470     struct sigaction act, oldact;
471     size_t hpagesize = qemu_fd_getpagesize(fd);
472     size_t numpages = DIV_ROUND_UP(memory, hpagesize);
473 
474     memset(&act, 0, sizeof(act));
475     act.sa_handler = &sigbus_handler;
476     act.sa_flags = 0;
477 
478     ret = sigaction(SIGBUS, &act, &oldact);
479     if (ret) {
480         error_setg_errno(errp, errno,
481             "os_mem_prealloc: failed to install signal handler");
482         return;
483     }
484 
485     /* touch pages simultaneously */
486     if (touch_all_pages(area, hpagesize, numpages, smp_cpus)) {
487         error_setg(errp, "os_mem_prealloc: Insufficient free host memory "
488             "pages available to allocate guest RAM");
489     }
490 
491     ret = sigaction(SIGBUS, &oldact, NULL);
492     if (ret) {
493         /* Terminate QEMU since it can't recover from error */
494         perror("os_mem_prealloc: failed to reinstall signal handler");
495         exit(1);
496     }
497 }
498 
499 
500 char *qemu_get_pid_name(pid_t pid)
501 {
502     char *name = NULL;
503 
504 #if defined(__FreeBSD__)
505     /* BSDs don't have /proc, but they provide a nice substitute */
506     struct kinfo_proc *proc = kinfo_getproc(pid);
507 
508     if (proc) {
509         name = g_strdup(proc->ki_comm);
510         free(proc);
511     }
512 #else
513     /* Assume a system with reasonable procfs */
514     char *pid_path;
515     size_t len;
516 
517     pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
518     g_file_get_contents(pid_path, &name, &len, NULL);
519     g_free(pid_path);
520 #endif
521 
522     return name;
523 }
524 
525 
526 pid_t qemu_fork(Error **errp)
527 {
528     sigset_t oldmask, newmask;
529     struct sigaction sig_action;
530     int saved_errno;
531     pid_t pid;
532 
533     /*
534      * Need to block signals now, so that child process can safely
535      * kill off caller's signal handlers without a race.
536      */
537     sigfillset(&newmask);
538     if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
539         error_setg_errno(errp, errno,
540                          "cannot block signals");
541         return -1;
542     }
543 
544     pid = fork();
545     saved_errno = errno;
546 
547     if (pid < 0) {
548         /* attempt to restore signal mask, but ignore failure, to
549          * avoid obscuring the fork failure */
550         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
551         error_setg_errno(errp, saved_errno,
552                          "cannot fork child process");
553         errno = saved_errno;
554         return -1;
555     } else if (pid) {
556         /* parent process */
557 
558         /* Restore our original signal mask now that the child is
559          * safely running. Only documented failures are EFAULT (not
560          * possible, since we are using just-grabbed mask) or EINVAL
561          * (not possible, since we are using correct arguments).  */
562         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
563     } else {
564         /* child process */
565         size_t i;
566 
567         /* Clear out all signal handlers from parent so nothing
568          * unexpected can happen in our child once we unblock
569          * signals */
570         sig_action.sa_handler = SIG_DFL;
571         sig_action.sa_flags = 0;
572         sigemptyset(&sig_action.sa_mask);
573 
574         for (i = 1; i < NSIG; i++) {
575             /* Only possible errors are EFAULT or EINVAL The former
576              * won't happen, the latter we expect, so no need to check
577              * return value */
578             (void)sigaction(i, &sig_action, NULL);
579         }
580 
581         /* Unmask all signals in child, since we've no idea what the
582          * caller's done with their signal mask and don't want to
583          * propagate that to children */
584         sigemptyset(&newmask);
585         if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) {
586             Error *local_err = NULL;
587             error_setg_errno(&local_err, errno,
588                              "cannot unblock signals");
589             error_report_err(local_err);
590             _exit(1);
591         }
592     }
593     return pid;
594 }
595 
596 void *qemu_alloc_stack(size_t *sz)
597 {
598     void *ptr, *guardpage;
599 #ifdef CONFIG_DEBUG_STACK_USAGE
600     void *ptr2;
601 #endif
602     size_t pagesz = getpagesize();
603 #ifdef _SC_THREAD_STACK_MIN
604     /* avoid stacks smaller than _SC_THREAD_STACK_MIN */
605     long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
606     *sz = MAX(MAX(min_stack_sz, 0), *sz);
607 #endif
608     /* adjust stack size to a multiple of the page size */
609     *sz = ROUND_UP(*sz, pagesz);
610     /* allocate one extra page for the guard page */
611     *sz += pagesz;
612 
613     ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE,
614                MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
615     if (ptr == MAP_FAILED) {
616         perror("failed to allocate memory for stack");
617         abort();
618     }
619 
620 #if defined(HOST_IA64)
621     /* separate register stack */
622     guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
623 #elif defined(HOST_HPPA)
624     /* stack grows up */
625     guardpage = ptr + *sz - pagesz;
626 #else
627     /* stack grows down */
628     guardpage = ptr;
629 #endif
630     if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
631         perror("failed to set up stack guard page");
632         abort();
633     }
634 
635 #ifdef CONFIG_DEBUG_STACK_USAGE
636     for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) {
637         *(uint32_t *)ptr2 = 0xdeadbeaf;
638     }
639 #endif
640 
641     return ptr;
642 }
643 
644 #ifdef CONFIG_DEBUG_STACK_USAGE
645 static __thread unsigned int max_stack_usage;
646 #endif
647 
648 void qemu_free_stack(void *stack, size_t sz)
649 {
650 #ifdef CONFIG_DEBUG_STACK_USAGE
651     unsigned int usage;
652     void *ptr;
653 
654     for (ptr = stack + getpagesize(); ptr < stack + sz;
655          ptr += sizeof(uint32_t)) {
656         if (*(uint32_t *)ptr != 0xdeadbeaf) {
657             break;
658         }
659     }
660     usage = sz - (uintptr_t) (ptr - stack);
661     if (usage > max_stack_usage) {
662         error_report("thread %d max stack usage increased from %u to %u",
663                      qemu_get_thread_id(), max_stack_usage, usage);
664         max_stack_usage = usage;
665     }
666 #endif
667 
668     munmap(stack, sz);
669 }
670 
671 void sigaction_invoke(struct sigaction *action,
672                       struct qemu_signalfd_siginfo *info)
673 {
674     siginfo_t si = {};
675     si.si_signo = info->ssi_signo;
676     si.si_errno = info->ssi_errno;
677     si.si_code = info->ssi_code;
678 
679     /* Convert the minimal set of fields defined by POSIX.
680      * Positive si_code values are reserved for kernel-generated
681      * signals, where the valid siginfo fields are determined by
682      * the signal number.  But according to POSIX, it is unspecified
683      * whether SI_USER and SI_QUEUE have values less than or equal to
684      * zero.
685      */
686     if (info->ssi_code == SI_USER || info->ssi_code == SI_QUEUE ||
687         info->ssi_code <= 0) {
688         /* SIGTERM, etc.  */
689         si.si_pid = info->ssi_pid;
690         si.si_uid = info->ssi_uid;
691     } else if (info->ssi_signo == SIGILL || info->ssi_signo == SIGFPE ||
692                info->ssi_signo == SIGSEGV || info->ssi_signo == SIGBUS) {
693         si.si_addr = (void *)(uintptr_t)info->ssi_addr;
694     } else if (info->ssi_signo == SIGCHLD) {
695         si.si_pid = info->ssi_pid;
696         si.si_status = info->ssi_status;
697         si.si_uid = info->ssi_uid;
698     }
699     action->sa_sigaction(info->ssi_signo, &si, NULL);
700 }
701