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qemu-e2k/util/oslib-posix.c
Marc-André Lureau 06680b15b4 include: move qemu_*_exec_dir() to cutils 
The function is required by get_relocated_path() (already in cutils),
and used by qemu-ga and may be generally useful.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20220525144140.591926-2-marcandre.lureau@redhat.com>
2022-05-28 11:42:56 +02:00

801 lines
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/*
* 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/error-report.h"
#include "qemu/madvise.h"
#include "qemu/sockets.h"
#include "qemu/thread.h"
#include <libgen.h>
#include "qemu/cutils.h"
#include "qemu/compiler.h"
#include "qemu/units.h"
#ifdef CONFIG_LINUX
#include <sys/syscall.h>
#endif
#ifdef __FreeBSD__
#include <sys/thr.h>
#include <sys/types.h>
#include <sys/user.h>
#include <libutil.h>
#endif
#ifdef __NetBSD__
#include <lwp.h>
#endif
#ifdef __APPLE__
#include <mach-o/dyld.h>
#endif
#ifdef __HAIKU__
#include <kernel/image.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;
typedef struct MemsetContext {
bool all_threads_created;
bool any_thread_failed;
struct MemsetThread *threads;
int num_threads;
} MemsetContext;
struct MemsetThread {
char *addr;
size_t numpages;
size_t hpagesize;
QemuThread pgthread;
sigjmp_buf env;
MemsetContext *context;
};
typedef struct MemsetThread MemsetThread;
/* used by sigbus_handler() */
static MemsetContext *sigbus_memset_context;
struct sigaction sigbus_oldact;
static QemuMutex sigbus_mutex;
static QemuMutex page_mutex;
static QemuCond page_cond;
int qemu_get_thread_id(void)
{
#if defined(__linux__)
return syscall(SYS_gettid);
#elif defined(__FreeBSD__)
/* thread id is up to INT_MAX */
long tid;
thr_self(&tid);
return (int)tid;
#elif defined(__NetBSD__)
return _lwp_self();
#elif defined(__OpenBSD__)
return getthrid();
#else
return getpid();
#endif
}
int qemu_daemon(int nochdir, int noclose)
{
return daemon(nochdir, noclose);
}
bool qemu_write_pidfile(const char *path, Error **errp)
{
int fd;
char pidstr[32];
while (1) {
struct stat a, b;
struct flock lock = {
.l_type = F_WRLCK,
.l_whence = SEEK_SET,
.l_len = 0,
};
fd = qemu_create(path, O_WRONLY, S_IRUSR | S_IWUSR, errp);
if (fd == -1) {
return false;
}
if (fstat(fd, &b) < 0) {
error_setg_errno(errp, errno, "Cannot stat file");
goto fail_close;
}
if (fcntl(fd, F_SETLK, &lock)) {
error_setg_errno(errp, errno, "Cannot lock pid file");
goto fail_close;
}
/*
* Now make sure the path we locked is the same one that now
* exists on the filesystem.
*/
if (stat(path, &a) < 0) {
/*
* PID file disappeared, someone else must be racing with
* us, so try again.
*/
close(fd);
continue;
}
if (a.st_ino == b.st_ino) {
break;
}
/*
* PID file was recreated, someone else must be racing with
* us, so try again.
*/
close(fd);
}
if (ftruncate(fd, 0) < 0) {
error_setg_errno(errp, errno, "Failed to truncate pid file");
goto fail_unlink;
}
snprintf(pidstr, sizeof(pidstr), FMT_pid "\n", getpid());
if (qemu_write_full(fd, pidstr, strlen(pidstr)) != strlen(pidstr)) {
error_setg(errp, "Failed to write pid file");
goto fail_unlink;
}
return true;
fail_unlink:
unlink(path);
fail_close:
close(fd);
return false;
}
/* alloc shared memory pages */
void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared,
bool noreserve)
{
const uint32_t qemu_map_flags = (shared ? QEMU_MAP_SHARED : 0) |
(noreserve ? QEMU_MAP_NORESERVE : 0);
size_t align = QEMU_VMALLOC_ALIGN;
void *ptr = qemu_ram_mmap(-1, size, align, qemu_map_flags, 0);
if (ptr == MAP_FAILED) {
return NULL;
}
if (alignment) {
*alignment = align;
}
trace_qemu_anon_ram_alloc(size, ptr);
return ptr;
}
void qemu_anon_ram_free(void *ptr, size_t size)
{
trace_qemu_anon_ram_free(ptr, size);
qemu_ram_munmap(-1, ptr, size);
}
void qemu_socket_set_block(int fd)
{
g_unix_set_fd_nonblocking(fd, false, NULL);
}
int qemu_socket_try_set_nonblock(int fd)
{
return g_unix_set_fd_nonblocking(fd, true, NULL) ? 0 : -errno;
}
void qemu_socket_set_nonblock(int fd)
{
int f;
f = qemu_socket_try_set_nonblock(fd);
assert(f == 0);
}
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);
}
char *
qemu_get_local_state_dir(void)
{
return get_relocated_path(CONFIG_QEMU_LOCALSTATEDIR);
}
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);
}
#ifdef CONFIG_LINUX
static void sigbus_handler(int signal, siginfo_t *siginfo, void *ctx)
#else /* CONFIG_LINUX */
static void sigbus_handler(int signal)
#endif /* CONFIG_LINUX */
{
int i;
if (sigbus_memset_context) {
for (i = 0; i < sigbus_memset_context->num_threads; i++) {
MemsetThread *thread = &sigbus_memset_context->threads[i];
if (qemu_thread_is_self(&thread->pgthread)) {
siglongjmp(thread->env, 1);
}
}
}
#ifdef CONFIG_LINUX
/*
* We assume that the MCE SIGBUS handler could have been registered. We
* should never receive BUS_MCEERR_AO on any of our threads, but only on
* the main thread registered for PR_MCE_KILL_EARLY. Further, we should not
* receive BUS_MCEERR_AR triggered by action of other threads on one of
* our threads. So, no need to check for unrelated SIGBUS when seeing one
* for our threads.
*
* We will forward to the MCE handler, which will either handle the SIGBUS
* or reinstall the default SIGBUS handler and reraise the SIGBUS. The
* default SIGBUS handler will crash the process, so we don't care.
*/
if (sigbus_oldact.sa_flags & SA_SIGINFO) {
sigbus_oldact.sa_sigaction(signal, siginfo, ctx);
return;
}
#endif /* CONFIG_LINUX */
warn_report("os_mem_prealloc: unrelated SIGBUS detected and ignored");
}
static void *do_touch_pages(void *arg)
{
MemsetThread *memset_args = (MemsetThread *)arg;
sigset_t set, oldset;
int ret = 0;
/*
* On Linux, the page faults from the loop below can cause mmap_sem
* contention with allocation of the thread stacks. Do not start
* clearing until all threads have been created.
*/
qemu_mutex_lock(&page_mutex);
while (!memset_args->context->all_threads_created) {
qemu_cond_wait(&page_cond, &page_mutex);
}
qemu_mutex_unlock(&page_mutex);
/* unblock SIGBUS */
sigemptyset(&set);
sigaddset(&set, SIGBUS);
pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
if (sigsetjmp(memset_args->env, 1)) {
ret = -EFAULT;
} else {
char *addr = memset_args->addr;
size_t numpages = memset_args->numpages;
size_t hpagesize = memset_args->hpagesize;
size_t i;
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
*/
*(volatile char *)addr = *addr;
addr += hpagesize;
}
}
pthread_sigmask(SIG_SETMASK, &oldset, NULL);
return (void *)(uintptr_t)ret;
}
static void *do_madv_populate_write_pages(void *arg)
{
MemsetThread *memset_args = (MemsetThread *)arg;
const size_t size = memset_args->numpages * memset_args->hpagesize;
char * const addr = memset_args->addr;
int ret = 0;
/* See do_touch_pages(). */
qemu_mutex_lock(&page_mutex);
while (!memset_args->context->all_threads_created) {
qemu_cond_wait(&page_cond, &page_mutex);
}
qemu_mutex_unlock(&page_mutex);
if (size && qemu_madvise(addr, size, QEMU_MADV_POPULATE_WRITE)) {
ret = -errno;
}
return (void *)(uintptr_t)ret;
}
static inline int get_memset_num_threads(size_t hpagesize, size_t numpages,
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);
}
/* Especially with gigantic pages, don't create more threads than pages. */
ret = MIN(ret, numpages);
/* Don't start threads to prealloc comparatively little memory. */
ret = MIN(ret, MAX(1, hpagesize * numpages / (64 * MiB)));
/* In case sysconf() fails, we fall back to single threaded */
return ret;
}
static int touch_all_pages(char *area, size_t hpagesize, size_t numpages,
int smp_cpus, bool use_madv_populate_write)
{
static gsize initialized = 0;
MemsetContext context = {
.num_threads = get_memset_num_threads(hpagesize, numpages, smp_cpus),
};
size_t numpages_per_thread, leftover;
void *(*touch_fn)(void *);
int ret = 0, i = 0;
char *addr = area;
if (g_once_init_enter(&initialized)) {
qemu_mutex_init(&page_mutex);
qemu_cond_init(&page_cond);
g_once_init_leave(&initialized, 1);
}
if (use_madv_populate_write) {
/* Avoid creating a single thread for MADV_POPULATE_WRITE */
if (context.num_threads == 1) {
if (qemu_madvise(area, hpagesize * numpages,
QEMU_MADV_POPULATE_WRITE)) {
return -errno;
}
return 0;
}
touch_fn = do_madv_populate_write_pages;
} else {
touch_fn = do_touch_pages;
}
context.threads = g_new0(MemsetThread, context.num_threads);
numpages_per_thread = numpages / context.num_threads;
leftover = numpages % context.num_threads;
for (i = 0; i < context.num_threads; i++) {
context.threads[i].addr = addr;
context.threads[i].numpages = numpages_per_thread + (i < leftover);
context.threads[i].hpagesize = hpagesize;
context.threads[i].context = &context;
qemu_thread_create(&context.threads[i].pgthread, "touch_pages",
touch_fn, &context.threads[i],
QEMU_THREAD_JOINABLE);
addr += context.threads[i].numpages * hpagesize;
}
if (!use_madv_populate_write) {
sigbus_memset_context = &context;
}
qemu_mutex_lock(&page_mutex);
context.all_threads_created = true;
qemu_cond_broadcast(&page_cond);
qemu_mutex_unlock(&page_mutex);
for (i = 0; i < context.num_threads; i++) {
int tmp = (uintptr_t)qemu_thread_join(&context.threads[i].pgthread);
if (tmp) {
ret = tmp;
}
}
if (!use_madv_populate_write) {
sigbus_memset_context = NULL;
}
g_free(context.threads);
return ret;
}
static bool madv_populate_write_possible(char *area, size_t pagesize)
{
return !qemu_madvise(area, pagesize, QEMU_MADV_POPULATE_WRITE) ||
errno != EINVAL;
}
void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
Error **errp)
{
static gsize initialized;
int ret;
size_t hpagesize = qemu_fd_getpagesize(fd);
size_t numpages = DIV_ROUND_UP(memory, hpagesize);
bool use_madv_populate_write;
struct sigaction act;
/*
* Sense on every invocation, as MADV_POPULATE_WRITE cannot be used for
* some special mappings, such as mapping /dev/mem.
*/
use_madv_populate_write = madv_populate_write_possible(area, hpagesize);
if (!use_madv_populate_write) {
if (g_once_init_enter(&initialized)) {
qemu_mutex_init(&sigbus_mutex);
g_once_init_leave(&initialized, 1);
}
qemu_mutex_lock(&sigbus_mutex);
memset(&act, 0, sizeof(act));
#ifdef CONFIG_LINUX
act.sa_sigaction = &sigbus_handler;
act.sa_flags = SA_SIGINFO;
#else /* CONFIG_LINUX */
act.sa_handler = &sigbus_handler;
act.sa_flags = 0;
#endif /* CONFIG_LINUX */
ret = sigaction(SIGBUS, &act, &sigbus_oldact);
if (ret) {
qemu_mutex_unlock(&sigbus_mutex);
error_setg_errno(errp, errno,
"os_mem_prealloc: failed to install signal handler");
return;
}
}
/* touch pages simultaneously */
ret = touch_all_pages(area, hpagesize, numpages, smp_cpus,
use_madv_populate_write);
if (ret) {
error_setg_errno(errp, -ret,
"os_mem_prealloc: preallocating memory failed");
}
if (!use_madv_populate_write) {
ret = sigaction(SIGBUS, &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);
}
qemu_mutex_unlock(&sigbus_mutex);
}
}
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;
int flags;
#ifdef CONFIG_DEBUG_STACK_USAGE
void *ptr2;
#endif
size_t pagesz = qemu_real_host_page_size();
#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;
flags = MAP_PRIVATE | MAP_ANONYMOUS;
#if defined(MAP_STACK) && defined(__OpenBSD__)
/* Only enable MAP_STACK on OpenBSD. Other OS's such as
* Linux/FreeBSD/NetBSD have a flag with the same name
* but have differing functionality. OpenBSD will SEGV
* if it spots execution with a stack pointer pointing
* at memory that was not allocated with MAP_STACK.
*/
flags |= MAP_STACK;
#endif
ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -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 + qemu_real_host_page_size(); 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);
}
/*
* Disable CFI checks.
* We are going to call a signal hander directly. Such handler may or may not
* have been defined in our binary, so there's no guarantee that the pointer
* used to set the handler is a cfi-valid pointer. Since the handlers are
* stored in kernel memory, changing the handler to an attacker-defined
* function requires being able to call a sigaction() syscall,
* which is not as easy as overwriting a pointer in memory.
*/
QEMU_DISABLE_CFI
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);
}
size_t qemu_get_host_physmem(void)
{
#ifdef _SC_PHYS_PAGES
long pages = sysconf(_SC_PHYS_PAGES);
if (pages > 0) {
if (pages > SIZE_MAX / qemu_real_host_page_size()) {
return SIZE_MAX;
} else {
return pages * qemu_real_host_page_size();
}
}
#endif
return 0;
}
int qemu_msync(void *addr, size_t length, int fd)
{
size_t align_mask = ~(qemu_real_host_page_size() - 1);
/**
* There are no strict reqs as per the length of mapping
* to be synced. Still the length needs to follow the address
* alignment changes. Additionally - round the size to the multiple
* of PAGE_SIZE
*/
length += ((uintptr_t)addr & (qemu_real_host_page_size() - 1));
length = (length + ~align_mask) & align_mask;
addr = (void *)((uintptr_t)addr & align_mask);
return msync(addr, length, MS_SYNC);
}
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