util/oslib-posix.c - qemu - Git at Google

 /*
  * os-posix-lib.c
  *
  * Copyright (c) 2003-2008 Fabrice Bellard
  * Copyright (c) 2010 Red Hat, Inc.
  *
  * QEMU library functions on POSIX which are shared between QEMU and
  * the QEMU tools.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */

 #include "qemu/osdep.h"
 #include <termios.h>

 #include <glib/gprintf.h>

 #include "sysemu/sysemu.h"
 #include "trace.h"
 #include "qapi/error.h"
 #include "qemu/sockets.h"
 #include <libgen.h>
 #include <sys/signal.h>
 #include "qemu/cutils.h"

 #ifdef CONFIG_LINUX
 #include <sys/syscall.h>
 #endif

 #ifdef __FreeBSD__
 #include <sys/sysctl.h>
 #include <sys/user.h>
 #include <libutil.h>
 #endif

 #include "qemu/mmap-alloc.h"

 #ifdef CONFIG_DEBUG_STACK_USAGE
 #include "qemu/error-report.h"
 #endif

 #define MAX_MEM_PREALLOC_THREAD_COUNT 16

 struct MemsetThread {
     char *addr;
     uint64_t numpages;
     uint64_t hpagesize;
     QemuThread pgthread;
     sigjmp_buf env;
 };
 typedef struct MemsetThread MemsetThread;

 static MemsetThread *memset_thread;
 static int memset_num_threads;
 static bool memset_thread_failed;

 int qemu_get_thread_id(void)
 {
 #if defined(__linux__)
     return syscall(SYS_gettid);
 #else
     return getpid();
 #endif
 }

 int qemu_daemon(int nochdir, int noclose)
 {
     return daemon(nochdir, noclose);
 }

 void *qemu_oom_check(void *ptr)
 {
     if (ptr == NULL) {
         fprintf(stderr, "Failed to allocate memory: %s\n", strerror(errno));
         abort();
     }
     return ptr;
 }

 void *qemu_try_memalign(size_t alignment, size_t size)
 {
     void *ptr;

     if (alignment < sizeof(void*)) {
         alignment = sizeof(void*);
     }

 #if defined(_POSIX_C_SOURCE) && !defined(__sun__)
     int ret;
     ret = posix_memalign(&ptr, alignment, size);
     if (ret != 0) {
         errno = ret;
         ptr = NULL;
     }
 #elif defined(CONFIG_BSD)
     ptr = valloc(size);
 #else
     ptr = memalign(alignment, size);
 #endif
     trace_qemu_memalign(alignment, size, ptr);
     return ptr;
 }

 void *qemu_memalign(size_t alignment, size_t size)
 {
     return qemu_oom_check(qemu_try_memalign(alignment, size));
 }

 /* alloc shared memory pages */
 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment)
 {
     size_t align = QEMU_VMALLOC_ALIGN;
     void *ptr = qemu_ram_mmap(-1, size, align, false);

     if (ptr == MAP_FAILED) {
         return NULL;
     }

     if (alignment) {
         *alignment = align;
     }

     trace_qemu_anon_ram_alloc(size, ptr);
     return ptr;
 }

 void qemu_vfree(void *ptr)
 {
     trace_qemu_vfree(ptr);
     free(ptr);
 }

 void qemu_anon_ram_free(void *ptr, size_t size)
 {
     trace_qemu_anon_ram_free(ptr, size);
     qemu_ram_munmap(ptr, size);
 }

 void qemu_set_block(int fd)
 {
     int f;
     f = fcntl(fd, F_GETFL);
     fcntl(fd, F_SETFL, f & ~O_NONBLOCK);
 }

 void qemu_set_nonblock(int fd)
 {
     int f;
     f = fcntl(fd, F_GETFL);
     fcntl(fd, F_SETFL, f | O_NONBLOCK);
 }

 int socket_set_fast_reuse(int fd)
 {
     int val = 1, ret;

     ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
                      (const char *)&val, sizeof(val));

     assert(ret == 0);

     return ret;
 }

 void qemu_set_cloexec(int fd)
 {
     int f;
     f = fcntl(fd, F_GETFD);
     assert(f != -1);
     f = fcntl(fd, F_SETFD, f | FD_CLOEXEC);
     assert(f != -1);
 }

 /*
  * Creates a pipe with FD_CLOEXEC set on both file descriptors
  */
 int qemu_pipe(int pipefd[2])
 {
     int ret;

 #ifdef CONFIG_PIPE2
     ret = pipe2(pipefd, O_CLOEXEC);
     if (ret != -1 || errno != ENOSYS) {
         return ret;
     }
 #endif
     ret = pipe(pipefd);
     if (ret == 0) {
         qemu_set_cloexec(pipefd[0]);
         qemu_set_cloexec(pipefd[1]);
     }

     return ret;
 }

 char *
 qemu_get_local_state_pathname(const char *relative_pathname)
 {
     return g_strdup_printf("%s/%s", CONFIG_QEMU_LOCALSTATEDIR,
                            relative_pathname);
 }

 void qemu_set_tty_echo(int fd, bool echo)
 {
     struct termios tty;

     tcgetattr(fd, &tty);

     if (echo) {
         tty.c_lflag |= ECHO | ECHONL | ICANON | IEXTEN;
     } else {
         tty.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
     }

     tcsetattr(fd, TCSANOW, &tty);
 }

 static char exec_dir[PATH_MAX];

 void qemu_init_exec_dir(const char *argv0)
 {
     char *dir;
     char *p = NULL;
     char buf[PATH_MAX];

     assert(!exec_dir[0]);

 #if defined(__linux__)
     {
         int len;
         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
         if (len > 0) {
             buf[len] = 0;
             p = buf;
         }
     }
 #elif defined(__FreeBSD__)
     {
         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
         size_t len = sizeof(buf) - 1;

         *buf = '\0';
         if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
             *buf) {
             buf[sizeof(buf) - 1] = '\0';
             p = buf;
         }
     }
 #endif
     /* If we don't have any way of figuring out the actual executable
        location then try argv[0].  */
     if (!p) {
         if (!argv0) {
             return;
         }
         p = realpath(argv0, buf);
         if (!p) {
             return;
         }
     }
     dir = g_path_get_dirname(p);

     pstrcpy(exec_dir, sizeof(exec_dir), dir);

     g_free(dir);
 }

 char *qemu_get_exec_dir(void)
 {
     return g_strdup(exec_dir);
 }

 static void sigbus_handler(int signal)
 {
     int i;
     if (memset_thread) {
         for (i = 0; i < memset_num_threads; i++) {
             if (qemu_thread_is_self(&memset_thread[i].pgthread)) {
                 siglongjmp(memset_thread[i].env, 1);
             }
         }
     }
 }

 static void *do_touch_pages(void *arg)
 {
     MemsetThread *memset_args = (MemsetThread *)arg;
     char *addr = memset_args->addr;
     uint64_t numpages = memset_args->numpages;
     uint64_t hpagesize = memset_args->hpagesize;
     sigset_t set, oldset;
     int i = 0;

     /* unblock SIGBUS */
     sigemptyset(&set);
     sigaddset(&set, SIGBUS);
     pthread_sigmask(SIG_UNBLOCK, &set, &oldset);

     if (sigsetjmp(memset_args->env, 1)) {
         memset_thread_failed = true;
     } else {
         for (i = 0; i < numpages; i++) {
             /*
              * Read & write back the same value, so we don't
              * corrupt existing user/app data that might be
              * stored.
              *
              * 'volatile' to stop compiler optimizing this away
              * to a no-op
              *
              * TODO: get a better solution from kernel so we
              * don't need to write at all so we don't cause
              * wear on the storage backing the region...
              */
             *(volatile char *)addr = *addr;
             addr += hpagesize;
         }
     }
     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
     return NULL;
 }

 static inline int get_memset_num_threads(int smp_cpus)
 {
     long host_procs = sysconf(_SC_NPROCESSORS_ONLN);
     int ret = 1;

     if (host_procs > 0) {
         ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus);
     }
     /* In case sysconf() fails, we fall back to single threaded */
     return ret;
 }

 static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages,
                             int smp_cpus)
 {
     uint64_t numpages_per_thread, size_per_thread;
     char *addr = area;
     int i = 0;

     memset_thread_failed = false;
     memset_num_threads = get_memset_num_threads(smp_cpus);
     memset_thread = g_new0(MemsetThread, memset_num_threads);
     numpages_per_thread = (numpages / memset_num_threads);
     size_per_thread = (hpagesize * numpages_per_thread);
     for (i = 0; i < memset_num_threads; i++) {
         memset_thread[i].addr = addr;
         memset_thread[i].numpages = (i == (memset_num_threads - 1)) ?
                                     numpages : numpages_per_thread;
         memset_thread[i].hpagesize = hpagesize;
         qemu_thread_create(&memset_thread[i].pgthread, "touch_pages",
                            do_touch_pages, &memset_thread[i],
                            QEMU_THREAD_JOINABLE);
         addr += size_per_thread;
         numpages -= numpages_per_thread;
     }
     for (i = 0; i < memset_num_threads; i++) {
         qemu_thread_join(&memset_thread[i].pgthread);
     }
     g_free(memset_thread);
     memset_thread = NULL;

     return memset_thread_failed;
 }

 void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
                      Error **errp)
 {
     int ret;
     struct sigaction act, oldact;
     size_t hpagesize = qemu_fd_getpagesize(fd);
     size_t numpages = DIV_ROUND_UP(memory, hpagesize);

     memset(&act, 0, sizeof(act));
     act.sa_handler = &sigbus_handler;
     act.sa_flags = 0;

     ret = sigaction(SIGBUS, &act, &oldact);
     if (ret) {
         error_setg_errno(errp, errno,
             "os_mem_prealloc: failed to install signal handler");
         return;
     }

     /* touch pages simultaneously */
     if (touch_all_pages(area, hpagesize, numpages, smp_cpus)) {
         error_setg(errp, "os_mem_prealloc: Insufficient free host memory "
             "pages available to allocate guest RAM");
     }

     ret = sigaction(SIGBUS, &oldact, NULL);
     if (ret) {
         /* Terminate QEMU since it can't recover from error */
         perror("os_mem_prealloc: failed to reinstall signal handler");
         exit(1);
     }
 }


 char *qemu_get_pid_name(pid_t pid)
 {
     char *name = NULL;

 #if defined(__FreeBSD__)
     /* BSDs don't have /proc, but they provide a nice substitute */
     struct kinfo_proc *proc = kinfo_getproc(pid);

     if (proc) {
         name = g_strdup(proc->ki_comm);
         free(proc);
     }
 #else
     /* Assume a system with reasonable procfs */
     char *pid_path;
     size_t len;

     pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
     g_file_get_contents(pid_path, &name, &len, NULL);
     g_free(pid_path);
 #endif

     return name;
 }


 pid_t qemu_fork(Error **errp)
 {
     sigset_t oldmask, newmask;
     struct sigaction sig_action;
     int saved_errno;
     pid_t pid;

     /*
      * Need to block signals now, so that child process can safely
      * kill off caller's signal handlers without a race.
      */
     sigfillset(&newmask);
     if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
         error_setg_errno(errp, errno,
                          "cannot block signals");
         return -1;
     }

     pid = fork();
     saved_errno = errno;

     if (pid < 0) {
         /* attempt to restore signal mask, but ignore failure, to
          * avoid obscuring the fork failure */
         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
         error_setg_errno(errp, saved_errno,
                          "cannot fork child process");
         errno = saved_errno;
         return -1;
     } else if (pid) {
         /* parent process */

         /* Restore our original signal mask now that the child is
          * safely running. Only documented failures are EFAULT (not
          * possible, since we are using just-grabbed mask) or EINVAL
          * (not possible, since we are using correct arguments).  */
         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
     } else {
         /* child process */
         size_t i;

         /* Clear out all signal handlers from parent so nothing
          * unexpected can happen in our child once we unblock
          * signals */
         sig_action.sa_handler = SIG_DFL;
         sig_action.sa_flags = 0;
         sigemptyset(&sig_action.sa_mask);

         for (i = 1; i < NSIG; i++) {
             /* Only possible errors are EFAULT or EINVAL The former
              * won't happen, the latter we expect, so no need to check
              * return value */
             (void)sigaction(i, &sig_action, NULL);
         }

         /* Unmask all signals in child, since we've no idea what the
          * caller's done with their signal mask and don't want to
          * propagate that to children */
         sigemptyset(&newmask);
         if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) {
             Error *local_err = NULL;
             error_setg_errno(&local_err, errno,
                              "cannot unblock signals");
             error_report_err(local_err);
             _exit(1);
         }
     }
     return pid;
 }

 void *qemu_alloc_stack(size_t *sz)
 {
     void *ptr, *guardpage;
 #ifdef CONFIG_DEBUG_STACK_USAGE
     void *ptr2;
 #endif
     size_t pagesz = getpagesize();
 #ifdef _SC_THREAD_STACK_MIN
     /* avoid stacks smaller than _SC_THREAD_STACK_MIN */
     long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
     *sz = MAX(MAX(min_stack_sz, 0), *sz);
 #endif
     /* adjust stack size to a multiple of the page size */
     *sz = ROUND_UP(*sz, pagesz);
     /* allocate one extra page for the guard page */
     *sz += pagesz;

     ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE,
                MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
     if (ptr == MAP_FAILED) {
         perror("failed to allocate memory for stack");
         abort();
     }

 #if defined(HOST_IA64)
     /* separate register stack */
     guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
 #elif defined(HOST_HPPA)
     /* stack grows up */
     guardpage = ptr + *sz - pagesz;
 #else
     /* stack grows down */
     guardpage = ptr;
 #endif
     if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
         perror("failed to set up stack guard page");
         abort();
     }

 #ifdef CONFIG_DEBUG_STACK_USAGE
     for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) {
         *(uint32_t *)ptr2 = 0xdeadbeaf;
     }
 #endif

     return ptr;
 }

 #ifdef CONFIG_DEBUG_STACK_USAGE
 static __thread unsigned int max_stack_usage;
 #endif

 void qemu_free_stack(void *stack, size_t sz)
 {
 #ifdef CONFIG_DEBUG_STACK_USAGE
     unsigned int usage;
     void *ptr;

     for (ptr = stack + getpagesize(); ptr < stack + sz;
          ptr += sizeof(uint32_t)) {
         if (*(uint32_t *)ptr != 0xdeadbeaf) {
             break;
         }
     }
     usage = sz - (uintptr_t) (ptr - stack);
     if (usage > max_stack_usage) {
         error_report("thread %d max stack usage increased from %u to %u",
                      qemu_get_thread_id(), max_stack_usage, usage);
         max_stack_usage = usage;
     }
 #endif

     munmap(stack, sz);
 }

 void sigaction_invoke(struct sigaction *action,
                       struct qemu_signalfd_siginfo *info)
 {
     siginfo_t si = {};
     si.si_signo = info->ssi_signo;
     si.si_errno = info->ssi_errno;
     si.si_code = info->ssi_code;

     /* Convert the minimal set of fields defined by POSIX.
      * Positive si_code values are reserved for kernel-generated
      * signals, where the valid siginfo fields are determined by
      * the signal number.  But according to POSIX, it is unspecified
      * whether SI_USER and SI_QUEUE have values less than or equal to
      * zero.
      */
     if (info->ssi_code == SI_USER || info->ssi_code == SI_QUEUE ||
         info->ssi_code <= 0) {
         /* SIGTERM, etc.  */
         si.si_pid = info->ssi_pid;
         si.si_uid = info->ssi_uid;
     } else if (info->ssi_signo == SIGILL || info->ssi_signo == SIGFPE ||
                info->ssi_signo == SIGSEGV || info->ssi_signo == SIGBUS) {
         si.si_addr = (void *)(uintptr_t)info->ssi_addr;
     } else if (info->ssi_signo == SIGCHLD) {
         si.si_pid = info->ssi_pid;
         si.si_status = info->ssi_status;
         si.si_uid = info->ssi_uid;
     }
     action->sa_sigaction(info->ssi_signo, &si, NULL);
 }
	/*
	* os-posix-lib.c
	*
	* Copyright (c) 2003-2008 Fabrice Bellard
	* Copyright (c) 2010 Red Hat, Inc.
	*
	* QEMU library functions on POSIX which are shared between QEMU and
	* the QEMU tools.
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*/

	#include "qemu/osdep.h"
	#include <termios.h>

	#include <glib/gprintf.h>

	#include "sysemu/sysemu.h"
	#include "trace.h"
	#include "qapi/error.h"
	#include "qemu/sockets.h"
	#include <libgen.h>
	#include <sys/signal.h>
	#include "qemu/cutils.h"

	#ifdef CONFIG_LINUX
	#include <sys/syscall.h>
	#endif

	#ifdef __FreeBSD__
	#include <sys/sysctl.h>
	#include <sys/user.h>
	#include <libutil.h>
	#endif

	#include "qemu/mmap-alloc.h"

	#ifdef CONFIG_DEBUG_STACK_USAGE
	#include "qemu/error-report.h"
	#endif

	#define MAX_MEM_PREALLOC_THREAD_COUNT 16

	struct MemsetThread {
	char *addr;
	uint64_t numpages;
	uint64_t hpagesize;
	QemuThread pgthread;
	sigjmp_buf env;
	};
	typedef struct MemsetThread MemsetThread;

	static MemsetThread *memset_thread;
	static int memset_num_threads;
	static bool memset_thread_failed;

	int qemu_get_thread_id(void)
	{
	#if defined(__linux__)
	return syscall(SYS_gettid);
	#else
	return getpid();
	#endif
	}

	int qemu_daemon(int nochdir, int noclose)
	{
	return daemon(nochdir, noclose);
	}

	void qemu_oom_check(void ptr)
	{
	if (ptr == NULL) {
	fprintf(stderr, "Failed to allocate memory: %s\n", strerror(errno));
	abort();
	}
	return ptr;
	}

	void *qemu_try_memalign(size_t alignment, size_t size)
	{
	void *ptr;

	if (alignment < sizeof(void*)) {
	alignment = sizeof(void*);
	}

	#if defined(_POSIX_C_SOURCE) && !defined(__sun__)
	int ret;
	ret = posix_memalign(&ptr, alignment, size);
	if (ret != 0) {
	errno = ret;
	ptr = NULL;
	}
	#elif defined(CONFIG_BSD)
	ptr = valloc(size);
	#else
	ptr = memalign(alignment, size);
	#endif
	trace_qemu_memalign(alignment, size, ptr);
	return ptr;
	}

	void *qemu_memalign(size_t alignment, size_t size)
	{
	return qemu_oom_check(qemu_try_memalign(alignment, size));
	}

	/* alloc shared memory pages */
	void qemu_anon_ram_alloc(size_t size, uint64_t alignment)
	{
	size_t align = QEMU_VMALLOC_ALIGN;
	void *ptr = qemu_ram_mmap(-1, size, align, false);

	if (ptr == MAP_FAILED) {
	return NULL;
	}

	if (alignment) {
	*alignment = align;
	}

	trace_qemu_anon_ram_alloc(size, ptr);
	return ptr;
	}

	void qemu_vfree(void *ptr)
	{
	trace_qemu_vfree(ptr);
	free(ptr);
	}

	void qemu_anon_ram_free(void *ptr, size_t size)
	{
	trace_qemu_anon_ram_free(ptr, size);
	qemu_ram_munmap(ptr, size);
	}

	void qemu_set_block(int fd)
	{
	int f;
	f = fcntl(fd, F_GETFL);
	fcntl(fd, F_SETFL, f & ~O_NONBLOCK);
	}

	void qemu_set_nonblock(int fd)
	{
	int f;
	f = fcntl(fd, F_GETFL);
	fcntl(fd, F_SETFL, f \| O_NONBLOCK);
	}

	int socket_set_fast_reuse(int fd)
	{
	int val = 1, ret;

	ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
	(const char *)&val, sizeof(val));

	assert(ret == 0);

	return ret;
	}

	void qemu_set_cloexec(int fd)
	{
	int f;
	f = fcntl(fd, F_GETFD);
	assert(f != -1);
	f = fcntl(fd, F_SETFD, f \| FD_CLOEXEC);
	assert(f != -1);
	}

	/*
	* Creates a pipe with FD_CLOEXEC set on both file descriptors
	*/
	int qemu_pipe(int pipefd[2])
	{
	int ret;

	#ifdef CONFIG_PIPE2
	ret = pipe2(pipefd, O_CLOEXEC);
	if (ret != -1 \|\| errno != ENOSYS) {
	return ret;
	}
	#endif
	ret = pipe(pipefd);
	if (ret == 0) {
	qemu_set_cloexec(pipefd[0]);
	qemu_set_cloexec(pipefd[1]);
	}

	return ret;
	}

	char *
	qemu_get_local_state_pathname(const char *relative_pathname)
	{
	return g_strdup_printf("%s/%s", CONFIG_QEMU_LOCALSTATEDIR,
	relative_pathname);
	}

	void qemu_set_tty_echo(int fd, bool echo)
	{
	struct termios tty;

	tcgetattr(fd, &tty);

	if (echo) {
	tty.c_lflag \|= ECHO \| ECHONL \| ICANON \| IEXTEN;
	} else {
	tty.c_lflag &= ~(ECHO \| ECHONL \| ICANON \| IEXTEN);
	}

	tcsetattr(fd, TCSANOW, &tty);
	}

	static char exec_dir[PATH_MAX];

	void qemu_init_exec_dir(const char *argv0)
	{
	char *dir;
	char *p = NULL;
	char buf[PATH_MAX];

	assert(!exec_dir[0]);

	#if defined(__linux__)
	{
	int len;
	len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
	if (len > 0) {
	buf[len] = 0;
	p = buf;
	}
	}
	#elif defined(__FreeBSD__)
	{
	static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
	size_t len = sizeof(buf) - 1;

	*buf = '\0';
	if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
	*buf) {
	buf[sizeof(buf) - 1] = '\0';
	p = buf;
	}
	}
	#endif
	/* If we don't have any way of figuring out the actual executable
	location then try argv[0]. */
	if (!p) {
	if (!argv0) {
	return;
	}
	p = realpath(argv0, buf);
	if (!p) {
	return;
	}
	}
	dir = g_path_get_dirname(p);

	pstrcpy(exec_dir, sizeof(exec_dir), dir);

	g_free(dir);
	}

	char *qemu_get_exec_dir(void)
	{
	return g_strdup(exec_dir);
	}

	static void sigbus_handler(int signal)
	{
	int i;
	if (memset_thread) {
	for (i = 0; i < memset_num_threads; i++) {
	if (qemu_thread_is_self(&memset_thread[i].pgthread)) {
	siglongjmp(memset_thread[i].env, 1);
	}
	}
	}
	}

	static void do_touch_pages(void arg)
	{
	MemsetThread memset_args = (MemsetThread )arg;
	char *addr = memset_args->addr;
	uint64_t numpages = memset_args->numpages;
	uint64_t hpagesize = memset_args->hpagesize;
	sigset_t set, oldset;
	int i = 0;

	/* unblock SIGBUS */
	sigemptyset(&set);
	sigaddset(&set, SIGBUS);
	pthread_sigmask(SIG_UNBLOCK, &set, &oldset);

	if (sigsetjmp(memset_args->env, 1)) {
	memset_thread_failed = true;
	} else {
	for (i = 0; i < numpages; i++) {
	/*
	* Read & write back the same value, so we don't
	* corrupt existing user/app data that might be
	* stored.
	*
	* 'volatile' to stop compiler optimizing this away
	* to a no-op
	*
	* TODO: get a better solution from kernel so we
	* don't need to write at all so we don't cause
	* wear on the storage backing the region...
	*/
	(volatile char )addr = *addr;
	addr += hpagesize;
	}
	}
	pthread_sigmask(SIG_SETMASK, &oldset, NULL);
	return NULL;
	}

	static inline int get_memset_num_threads(int smp_cpus)
	{
	long host_procs = sysconf(_SC_NPROCESSORS_ONLN);
	int ret = 1;

	if (host_procs > 0) {
	ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus);
	}
	/* In case sysconf() fails, we fall back to single threaded */
	return ret;
	}

	static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages,
	int smp_cpus)
	{
	uint64_t numpages_per_thread, size_per_thread;
	char *addr = area;
	int i = 0;

	memset_thread_failed = false;
	memset_num_threads = get_memset_num_threads(smp_cpus);
	memset_thread = g_new0(MemsetThread, memset_num_threads);
	numpages_per_thread = (numpages / memset_num_threads);
	size_per_thread = (hpagesize * numpages_per_thread);
	for (i = 0; i < memset_num_threads; i++) {
	memset_thread[i].addr = addr;
	memset_thread[i].numpages = (i == (memset_num_threads - 1)) ?
	numpages : numpages_per_thread;
	memset_thread[i].hpagesize = hpagesize;
	qemu_thread_create(&memset_thread[i].pgthread, "touch_pages",
	do_touch_pages, &memset_thread[i],
	QEMU_THREAD_JOINABLE);
	addr += size_per_thread;
	numpages -= numpages_per_thread;
	}
	for (i = 0; i < memset_num_threads; i++) {
	qemu_thread_join(&memset_thread[i].pgthread);
	}
	g_free(memset_thread);
	memset_thread = NULL;

	return memset_thread_failed;
	}

	void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
	Error **errp)
	{
	int ret;
	struct sigaction act, oldact;
	size_t hpagesize = qemu_fd_getpagesize(fd);
	size_t numpages = DIV_ROUND_UP(memory, hpagesize);

	memset(&act, 0, sizeof(act));
	act.sa_handler = &sigbus_handler;
	act.sa_flags = 0;

	ret = sigaction(SIGBUS, &act, &oldact);
	if (ret) {
	error_setg_errno(errp, errno,
	"os_mem_prealloc: failed to install signal handler");
	return;
	}

	/* touch pages simultaneously */
	if (touch_all_pages(area, hpagesize, numpages, smp_cpus)) {
	error_setg(errp, "os_mem_prealloc: Insufficient free host memory "
	"pages available to allocate guest RAM");
	}

	ret = sigaction(SIGBUS, &oldact, NULL);
	if (ret) {
	/* Terminate QEMU since it can't recover from error */
	perror("os_mem_prealloc: failed to reinstall signal handler");
	exit(1);
	}
	}


	char *qemu_get_pid_name(pid_t pid)
	{
	char *name = NULL;

	#if defined(__FreeBSD__)
	/* BSDs don't have /proc, but they provide a nice substitute */
	struct kinfo_proc *proc = kinfo_getproc(pid);

	if (proc) {
	name = g_strdup(proc->ki_comm);
	free(proc);
	}
	#else
	/* Assume a system with reasonable procfs */
	char *pid_path;
	size_t len;

	pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
	g_file_get_contents(pid_path, &name, &len, NULL);
	g_free(pid_path);
	#endif

	return name;
	}


	pid_t qemu_fork(Error **errp)
	{
	sigset_t oldmask, newmask;
	struct sigaction sig_action;
	int saved_errno;
	pid_t pid;

	/*
	* Need to block signals now, so that child process can safely
	* kill off caller's signal handlers without a race.
	*/
	sigfillset(&newmask);
	if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
	error_setg_errno(errp, errno,
	"cannot block signals");
	return -1;
	}

	pid = fork();
	saved_errno = errno;

	if (pid < 0) {
	/* attempt to restore signal mask, but ignore failure, to
	* avoid obscuring the fork failure */
	(void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	error_setg_errno(errp, saved_errno,
	"cannot fork child process");
	errno = saved_errno;
	return -1;
	} else if (pid) {
	/* parent process */

	/* Restore our original signal mask now that the child is
	* safely running. Only documented failures are EFAULT (not
	* possible, since we are using just-grabbed mask) or EINVAL
	* (not possible, since we are using correct arguments). */
	(void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	} else {
	/* child process */
	size_t i;

	/* Clear out all signal handlers from parent so nothing
	* unexpected can happen in our child once we unblock
	* signals */
	sig_action.sa_handler = SIG_DFL;
	sig_action.sa_flags = 0;
	sigemptyset(&sig_action.sa_mask);

	for (i = 1; i < NSIG; i++) {
	/* Only possible errors are EFAULT or EINVAL The former
	* won't happen, the latter we expect, so no need to check
	* return value */
	(void)sigaction(i, &sig_action, NULL);
	}

	/* Unmask all signals in child, since we've no idea what the
	* caller's done with their signal mask and don't want to
	* propagate that to children */
	sigemptyset(&newmask);
	if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) {
	Error *local_err = NULL;
	error_setg_errno(&local_err, errno,
	"cannot unblock signals");
	error_report_err(local_err);
	_exit(1);
	}
	}
	return pid;
	}

	void qemu_alloc_stack(size_t sz)
	{
	void ptr, guardpage;
	#ifdef CONFIG_DEBUG_STACK_USAGE
	void *ptr2;
	#endif
	size_t pagesz = getpagesize();
	#ifdef _SC_THREAD_STACK_MIN
	/* avoid stacks smaller than _SC_THREAD_STACK_MIN */
	long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
	sz = MAX(MAX(min_stack_sz, 0), sz);
	#endif
	/* adjust stack size to a multiple of the page size */
	sz = ROUND_UP(sz, pagesz);
	/* allocate one extra page for the guard page */
	*sz += pagesz;

	ptr = mmap(NULL, *sz, PROT_READ \| PROT_WRITE,
	MAP_PRIVATE \| MAP_ANONYMOUS, -1, 0);
	if (ptr == MAP_FAILED) {
	perror("failed to allocate memory for stack");
	abort();
	}

	#if defined(HOST_IA64)
	/* separate register stack */
	guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
	#elif defined(HOST_HPPA)
	/* stack grows up */
	guardpage = ptr + *sz - pagesz;
	#else
	/* stack grows down */
	guardpage = ptr;
	#endif
	if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
	perror("failed to set up stack guard page");
	abort();
	}

	#ifdef CONFIG_DEBUG_STACK_USAGE
	for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) {
	(uint32_t )ptr2 = 0xdeadbeaf;
	}
	#endif

	return ptr;
	}

	#ifdef CONFIG_DEBUG_STACK_USAGE
	static __thread unsigned int max_stack_usage;
	#endif

	void qemu_free_stack(void *stack, size_t sz)
	{
	#ifdef CONFIG_DEBUG_STACK_USAGE
	unsigned int usage;
	void *ptr;

	for (ptr = stack + getpagesize(); ptr < stack + sz;
	ptr += sizeof(uint32_t)) {
	if ((uint32_t )ptr != 0xdeadbeaf) {
	break;
	}
	}
	usage = sz - (uintptr_t) (ptr - stack);
	if (usage > max_stack_usage) {
	error_report("thread %d max stack usage increased from %u to %u",
	qemu_get_thread_id(), max_stack_usage, usage);
	max_stack_usage = usage;
	}
	#endif

	munmap(stack, sz);
	}

	void sigaction_invoke(struct sigaction *action,
	struct qemu_signalfd_siginfo *info)
	{
	siginfo_t si = {};
	si.si_signo = info->ssi_signo;
	si.si_errno = info->ssi_errno;
	si.si_code = info->ssi_code;

	/* Convert the minimal set of fields defined by POSIX.
	* Positive si_code values are reserved for kernel-generated
	* signals, where the valid siginfo fields are determined by
	* the signal number. But according to POSIX, it is unspecified
	* whether SI_USER and SI_QUEUE have values less than or equal to
	* zero.
	*/
	if (info->ssi_code == SI_USER \|\| info->ssi_code == SI_QUEUE \|\|
	info->ssi_code <= 0) {
	/* SIGTERM, etc. */
	si.si_pid = info->ssi_pid;
	si.si_uid = info->ssi_uid;
	} else if (info->ssi_signo == SIGILL \|\| info->ssi_signo == SIGFPE \|\|
	info->ssi_signo == SIGSEGV \|\| info->ssi_signo == SIGBUS) {
	si.si_addr = (void *)(uintptr_t)info->ssi_addr;
	} else if (info->ssi_signo == SIGCHLD) {
	si.si_pid = info->ssi_pid;
	si.si_status = info->ssi_status;
	si.si_uid = info->ssi_uid;
	}
	action->sa_sigaction(info->ssi_signo, &si, NULL);
	}