5 use crate::num::NonZeroUsize;
7 use crate::sys::{os, stack_overflow};
8 use crate::time::Duration;
10 #[cfg(all(target_os = "linux", target_env = "gnu"))]
11 use crate::sys::weak::dlsym;
12 #[cfg(any(target_os = "solaris", target_os = "illumos"))]
13 use crate::sys::weak::weak;
14 #[cfg(not(any(target_os = "l4re", target_os = "vxworks", target_os = "espidf")))]
15 pub const DEFAULT_MIN_STACK_SIZE: usize = 2 * 1024 * 1024;
16 #[cfg(target_os = "l4re")]
17 pub const DEFAULT_MIN_STACK_SIZE: usize = 1024 * 1024;
18 #[cfg(target_os = "vxworks")]
19 pub const DEFAULT_MIN_STACK_SIZE: usize = 256 * 1024;
20 #[cfg(target_os = "espidf")]
21 pub const DEFAULT_MIN_STACK_SIZE: usize = 0; // 0 indicates that the stack size configured in the ESP-IDF menuconfig system should be used
23 #[cfg(target_os = "fuchsia")]
25 type zx_handle_t = u32;
26 type zx_status_t = i32;
27 pub const ZX_PROP_NAME: u32 = 3;
30 pub fn zx_object_set_property(
33 value: *const libc::c_void,
34 value_size: libc::size_t,
36 pub fn zx_thread_self() -> zx_handle_t;
44 // Some platforms may have pthread_t as a pointer in which case we still want
45 // a thread to be Send/Sync
46 unsafe impl Send for Thread {}
47 unsafe impl Sync for Thread {}
50 // unsafe: see thread::Builder::spawn_unchecked for safety requirements
51 pub unsafe fn new(stack: usize, p: Box<dyn FnOnce()>) -> io::Result<Thread> {
52 let p = Box::into_raw(box p);
53 let mut native: libc::pthread_t = mem::zeroed();
54 let mut attr: libc::pthread_attr_t = mem::zeroed();
55 assert_eq!(libc::pthread_attr_init(&mut attr), 0);
57 #[cfg(target_os = "espidf")]
59 // Only set the stack if a non-zero value is passed
60 // 0 is used as an indication that the default stack size configured in the ESP-IDF menuconfig system should be used
62 libc::pthread_attr_setstacksize(&mut attr, cmp::max(stack, min_stack_size(&attr))),
67 #[cfg(not(target_os = "espidf"))]
69 let stack_size = cmp::max(stack, min_stack_size(&attr));
71 match libc::pthread_attr_setstacksize(&mut attr, stack_size) {
74 assert_eq!(n, libc::EINVAL);
75 // EINVAL means |stack_size| is either too small or not a
76 // multiple of the system page size. Because it's definitely
77 // >= PTHREAD_STACK_MIN, it must be an alignment issue.
78 // Round up to the nearest page and try again.
79 let page_size = os::page_size();
81 (stack_size + page_size - 1) & (-(page_size as isize - 1) as usize - 1);
82 assert_eq!(libc::pthread_attr_setstacksize(&mut attr, stack_size), 0);
87 let ret = libc::pthread_create(&mut native, &attr, thread_start, p as *mut _);
88 // Note: if the thread creation fails and this assert fails, then p will
89 // be leaked. However, an alternative design could cause double-free
90 // which is clearly worse.
91 assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
94 // The thread failed to start and as a result p was not consumed. Therefore, it is
95 // safe to reconstruct the box so that it gets deallocated.
96 drop(Box::from_raw(p));
97 Err(io::Error::from_raw_os_error(ret))
99 Ok(Thread { id: native })
102 extern "C" fn thread_start(main: *mut libc::c_void) -> *mut libc::c_void {
104 // Next, set up our stack overflow handler which may get triggered if we run
106 let _handler = stack_overflow::Handler::new();
107 // Finally, let's run some code.
108 Box::from_raw(main as *mut Box<dyn FnOnce()>)();
115 let ret = unsafe { libc::sched_yield() };
116 debug_assert_eq!(ret, 0);
119 #[cfg(target_os = "android")]
120 pub fn set_name(name: &CStr) {
121 const PR_SET_NAME: libc::c_int = 15;
133 #[cfg(target_os = "linux")]
134 pub fn set_name(name: &CStr) {
135 const TASK_COMM_LEN: usize = 16;
138 // Available since glibc 2.12, musl 1.1.16, and uClibc 1.0.20.
139 let name = truncate_cstr(name, TASK_COMM_LEN);
140 libc::pthread_setname_np(libc::pthread_self(), name.as_ptr());
144 #[cfg(any(target_os = "freebsd", target_os = "dragonfly", target_os = "openbsd"))]
145 pub fn set_name(name: &CStr) {
147 libc::pthread_set_name_np(libc::pthread_self(), name.as_ptr());
151 #[cfg(any(target_os = "macos", target_os = "ios", target_os = "watchos"))]
152 pub fn set_name(name: &CStr) {
154 let name = truncate_cstr(name, libc::MAXTHREADNAMESIZE);
155 libc::pthread_setname_np(name.as_ptr());
159 #[cfg(target_os = "netbsd")]
160 pub fn set_name(name: &CStr) {
162 let cname = CStr::from_bytes_with_nul_unchecked(b"%s\0".as_slice());
163 libc::pthread_setname_np(
164 libc::pthread_self(),
166 name.as_ptr() as *mut libc::c_void,
171 #[cfg(any(target_os = "solaris", target_os = "illumos"))]
172 pub fn set_name(name: &CStr) {
174 fn pthread_setname_np(
175 libc::pthread_t, *const libc::c_char
179 if let Some(f) = pthread_setname_np.get() {
181 f(libc::pthread_self(), name.as_ptr());
186 #[cfg(target_os = "fuchsia")]
187 pub fn set_name(name: &CStr) {
190 zx_object_set_property(
193 name.as_ptr() as *const libc::c_void,
194 name.to_bytes().len(),
199 #[cfg(target_os = "haiku")]
200 pub fn set_name(name: &CStr) {
202 let thread_self = libc::find_thread(ptr::null_mut());
203 libc::rename_thread(thread_self, name.as_ptr());
208 target_env = "newlib",
210 target_os = "emscripten",
212 target_os = "vxworks"
214 pub fn set_name(_name: &CStr) {
215 // Newlib, Emscripten, and VxWorks have no way to set a thread name.
218 #[cfg(not(target_os = "espidf"))]
219 pub fn sleep(dur: Duration) {
220 let mut secs = dur.as_secs();
221 let mut nsecs = dur.subsec_nanos() as _;
223 // If we're awoken with a signal then the return value will be -1 and
224 // nanosleep will fill in `ts` with the remaining time.
226 while secs > 0 || nsecs > 0 {
227 let mut ts = libc::timespec {
228 tv_sec: cmp::min(libc::time_t::MAX as u64, secs) as libc::time_t,
231 secs -= ts.tv_sec as u64;
232 let ts_ptr = &mut ts as *mut _;
233 if libc::nanosleep(ts_ptr, ts_ptr) == -1 {
234 assert_eq!(os::errno(), libc::EINTR);
235 secs += ts.tv_sec as u64;
244 #[cfg(target_os = "espidf")]
245 pub fn sleep(dur: Duration) {
246 let mut micros = dur.as_micros();
249 let st = if micros > u32::MAX as u128 { u32::MAX } else { micros as u32 };
252 micros -= st as u128;
259 let ret = libc::pthread_join(self.id, ptr::null_mut());
261 assert!(ret == 0, "failed to join thread: {}", io::Error::from_raw_os_error(ret));
265 pub fn id(&self) -> libc::pthread_t {
269 pub fn into_id(self) -> libc::pthread_t {
276 impl Drop for Thread {
278 let ret = unsafe { libc::pthread_detach(self.id) };
279 debug_assert_eq!(ret, 0);
283 #[cfg(any(target_os = "linux", target_os = "macos", target_os = "ios", target_os = "watchos"))]
284 fn truncate_cstr(cstr: &CStr, max_with_nul: usize) -> crate::borrow::Cow<'_, CStr> {
285 use crate::{borrow::Cow, ffi::CString};
287 if cstr.to_bytes_with_nul().len() > max_with_nul {
288 let bytes = cstr.to_bytes()[..max_with_nul - 1].to_vec();
289 // SAFETY: the non-nul bytes came straight from a CStr.
290 // (CString will add the terminating nul.)
291 Cow::Owned(unsafe { CString::from_vec_unchecked(bytes) })
297 pub fn available_parallelism() -> io::Result<NonZeroUsize> {
300 target_os = "android",
301 target_os = "emscripten",
302 target_os = "fuchsia",
306 target_os = "solaris",
307 target_os = "illumos",
309 #[cfg(any(target_os = "android", target_os = "linux"))]
311 let quota = cgroups::quota().max(1);
312 let mut set: libc::cpu_set_t = unsafe { mem::zeroed() };
314 if libc::sched_getaffinity(0, mem::size_of::<libc::cpu_set_t>(), &mut set) == 0 {
315 let count = libc::CPU_COUNT(&set) as usize;
316 let count = count.min(quota);
317 // SAFETY: affinity mask can't be empty and the quota gets clamped to a minimum of 1
318 return Ok(NonZeroUsize::new_unchecked(count));
322 match unsafe { libc::sysconf(libc::_SC_NPROCESSORS_ONLN) } {
323 -1 => Err(io::Error::last_os_error()),
324 0 => Err(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")),
325 cpus => Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) }),
327 } else if #[cfg(any(target_os = "freebsd", target_os = "dragonfly", target_os = "netbsd"))] {
330 let mut cpus: libc::c_uint = 0;
331 let mut cpus_size = crate::mem::size_of_val(&cpus);
334 cpus = libc::sysconf(libc::_SC_NPROCESSORS_ONLN) as libc::c_uint;
337 // Fallback approach in case of errors or no hardware threads.
339 let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0];
344 &mut cpus as *mut _ as *mut _,
345 &mut cpus_size as *mut _ as *mut _,
351 // Handle errors if any.
353 return Err(io::Error::last_os_error());
354 } else if cpus == 0 {
355 return Err(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform"));
358 Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) })
359 } else if #[cfg(target_os = "openbsd")] {
362 let mut cpus: libc::c_uint = 0;
363 let mut cpus_size = crate::mem::size_of_val(&cpus);
364 let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0];
370 &mut cpus as *mut _ as *mut _,
371 &mut cpus_size as *mut _ as *mut _,
377 // Handle errors if any.
379 return Err(io::Error::last_os_error());
380 } else if cpus == 0 {
381 return Err(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform"));
384 Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) })
385 } else if #[cfg(target_os = "haiku")] {
386 // system_info cpu_count field gets the static data set at boot time with `smp_set_num_cpus`
387 // `get_system_info` calls then `smp_get_num_cpus`
389 let mut sinfo: libc::system_info = crate::mem::zeroed();
390 let res = libc::get_system_info(&mut sinfo);
392 if res != libc::B_OK {
393 return Err(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform"));
396 Ok(NonZeroUsize::new_unchecked(sinfo.cpu_count as usize))
399 // FIXME: implement on vxWorks, Redox, l4re
400 Err(io::const_io_error!(io::ErrorKind::Unsupported, "Getting the number of hardware threads is not supported on the target platform"))
405 #[cfg(any(target_os = "android", target_os = "linux"))]
407 //! Currently not covered
408 //! * cgroup v2 in non-standard mountpoints
409 //! * paths containing control characters or spaces, since those would be escaped in procfs
410 //! output and we don't unescape
411 use crate::borrow::Cow;
412 use crate::ffi::OsString;
413 use crate::fs::{try_exists, File};
415 use crate::io::{BufRead, BufReader};
416 use crate::os::unix::ffi::OsStringExt;
417 use crate::path::Path;
418 use crate::path::PathBuf;
419 use crate::str::from_utf8;
427 /// Returns cgroup CPU quota in core-equivalents, rounded down or usize::MAX if the quota cannot
428 /// be determined or is not set.
429 pub(super) fn quota() -> usize {
430 let mut quota = usize::MAX;
432 // Attempting to open a file fails under default flags due to isolation.
433 // And Miri does not have parallelism anyway.
437 let _: Option<()> = try {
438 let mut buf = Vec::with_capacity(128);
439 // find our place in the cgroup hierarchy
440 File::open("/proc/self/cgroup").ok()?.read_to_end(&mut buf).ok()?;
441 let (cgroup_path, version) =
442 buf.split(|&c| c == b'\n').fold(None, |previous, line| {
443 let mut fields = line.splitn(3, |&c| c == b':');
444 // 2nd field is a list of controllers for v1 or empty for v2
445 let version = match fields.nth(1) {
446 Some(b"") => Cgroup::V2,
448 if from_utf8(controllers)
449 .is_ok_and(|c| c.split(',').any(|c| c == "cpu")) =>
453 _ => return previous,
456 // already-found v1 trumps v2 since it explicitly specifies its controllers
457 if previous.is_some() && version == Cgroup::V2 {
461 let path = fields.last()?;
462 // skip leading slash
463 Some((path[1..].to_owned(), version))
465 let cgroup_path = PathBuf::from(OsString::from_vec(cgroup_path));
467 quota = match version {
468 Cgroup::V1 => quota_v1(cgroup_path),
469 Cgroup::V2 => quota_v2(cgroup_path),
476 fn quota_v2(group_path: PathBuf) -> usize {
477 let mut quota = usize::MAX;
479 let mut path = PathBuf::with_capacity(128);
480 let mut read_buf = String::with_capacity(20);
482 // standard mount location defined in file-hierarchy(7) manpage
483 let cgroup_mount = "/sys/fs/cgroup";
485 path.push(cgroup_mount);
486 path.push(&group_path);
488 path.push("cgroup.controllers");
490 // skip if we're not looking at cgroup2
491 if matches!(try_exists(&path), Err(_) | Ok(false)) {
497 let _: Option<()> = try {
498 while path.starts_with(cgroup_mount) {
499 path.push("cpu.max");
503 if File::open(&path).and_then(|mut f| f.read_to_string(&mut read_buf)).is_ok() {
504 let raw_quota = read_buf.lines().next()?;
505 let mut raw_quota = raw_quota.split(' ');
506 let limit = raw_quota.next()?;
507 let period = raw_quota.next()?;
508 match (limit.parse::<usize>(), period.parse::<usize>()) {
509 (Ok(limit), Ok(period)) => {
510 quota = quota.min(limit / period);
516 path.pop(); // pop filename
517 path.pop(); // pop dir
524 fn quota_v1(group_path: PathBuf) -> usize {
525 let mut quota = usize::MAX;
526 let mut path = PathBuf::with_capacity(128);
527 let mut read_buf = String::with_capacity(20);
529 // Hardcode commonly used locations mentioned in the cgroups(7) manpage
530 // if that doesn't work scan mountinfo and adjust `group_path` for bind-mounts
531 let mounts: &[fn(&Path) -> Option<(_, &Path)>] = &[
532 |p| Some((Cow::Borrowed("/sys/fs/cgroup/cpu"), p)),
533 |p| Some((Cow::Borrowed("/sys/fs/cgroup/cpu,cpuacct"), p)),
534 // this can be expensive on systems with tons of mountpoints
535 // but we only get to this point when /proc/self/cgroups explicitly indicated
536 // this process belongs to a cpu-controller cgroup v1 and the defaults didn't work
540 for mount in mounts {
541 let Some((mount, group_path)) = mount(&group_path) else { continue };
544 path.push(mount.as_ref());
545 path.push(&group_path);
547 // skip if we guessed the mount incorrectly
548 if matches!(try_exists(&path), Err(_) | Ok(false)) {
552 while path.starts_with(mount.as_ref()) {
553 let mut parse_file = |name| {
557 let f = File::open(&path);
558 path.pop(); // restore buffer before any early returns
559 f.ok()?.read_to_string(&mut read_buf).ok()?;
560 let parsed = read_buf.trim().parse::<usize>().ok()?;
565 let limit = parse_file("cpu.cfs_quota_us");
566 let period = parse_file("cpu.cfs_period_us");
568 match (limit, period) {
569 (Some(limit), Some(period)) => quota = quota.min(limit / period),
576 // we passed the try_exists above so we should have traversed the correct hierarchy
577 // when reaching this line
584 /// Scan mountinfo for cgroup v1 mountpoint with a cpu controller
586 /// If the cgroupfs is a bind mount then `group_path` is adjusted to skip
587 /// over the already-included prefix
588 fn find_mountpoint(group_path: &Path) -> Option<(Cow<'static, str>, &Path)> {
589 let mut reader = BufReader::new(File::open("/proc/self/mountinfo").ok()?);
590 let mut line = String::with_capacity(256);
593 if reader.read_line(&mut line).ok()? == 0 {
597 let line = line.trim();
598 let mut items = line.split(' ');
600 let sub_path = items.nth(3)?;
601 let mount_point = items.next()?;
602 let mount_opts = items.next_back()?;
603 let filesystem_type = items.nth_back(1)?;
605 if filesystem_type != "cgroup" || !mount_opts.split(',').any(|opt| opt == "cpu") {
606 // not a cgroup / not a cpu-controller
610 let sub_path = Path::new(sub_path).strip_prefix("/").ok()?;
612 if !group_path.starts_with(sub_path) {
613 // this is a bind-mount and the bound subdirectory
614 // does not contain the cgroup this process belongs to
618 let trimmed_group_path = group_path.strip_prefix(sub_path).ok()?;
620 return Some((Cow::Owned(mount_point.to_owned()), trimmed_group_path));
628 not(target_os = "linux"),
629 not(target_os = "freebsd"),
630 not(target_os = "macos"),
631 not(target_os = "netbsd"),
632 not(target_os = "openbsd"),
633 not(target_os = "solaris")
635 #[cfg_attr(test, allow(dead_code))]
637 use crate::ops::Range;
638 pub type Guard = Range<usize>;
639 pub unsafe fn current() -> Option<Guard> {
642 pub unsafe fn init() -> Option<Guard> {
649 target_os = "freebsd",
651 target_os = "netbsd",
652 target_os = "openbsd",
653 target_os = "solaris"
655 #[cfg_attr(test, allow(dead_code))]
657 use libc::{mmap, mprotect};
658 use libc::{MAP_ANON, MAP_FAILED, MAP_FIXED, MAP_PRIVATE, PROT_NONE, PROT_READ, PROT_WRITE};
661 use crate::ops::Range;
662 use crate::sync::atomic::{AtomicUsize, Ordering};
665 // This is initialized in init() and only read from after
666 static PAGE_SIZE: AtomicUsize = AtomicUsize::new(0);
668 pub type Guard = Range<usize>;
670 #[cfg(target_os = "solaris")]
671 unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
672 let mut current_stack: libc::stack_t = crate::mem::zeroed();
673 assert_eq!(libc::stack_getbounds(&mut current_stack), 0);
674 Some(current_stack.ss_sp)
677 #[cfg(target_os = "macos")]
678 unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
679 let th = libc::pthread_self();
680 let stackptr = libc::pthread_get_stackaddr_np(th);
681 Some(stackptr.map_addr(|addr| addr - libc::pthread_get_stacksize_np(th)))
684 #[cfg(target_os = "openbsd")]
685 unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
686 let mut current_stack: libc::stack_t = crate::mem::zeroed();
687 assert_eq!(libc::pthread_stackseg_np(libc::pthread_self(), &mut current_stack), 0);
689 let stack_ptr = current_stack.ss_sp;
690 let stackaddr = if libc::pthread_main_np() == 1 {
692 stack_ptr.addr() - current_stack.ss_size + PAGE_SIZE.load(Ordering::Relaxed)
695 stack_ptr.addr() - current_stack.ss_size
697 Some(stack_ptr.with_addr(stackaddr))
701 target_os = "android",
702 target_os = "freebsd",
704 target_os = "netbsd",
707 unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
709 let mut attr: libc::pthread_attr_t = crate::mem::zeroed();
710 #[cfg(target_os = "freebsd")]
711 assert_eq!(libc::pthread_attr_init(&mut attr), 0);
712 #[cfg(target_os = "freebsd")]
713 let e = libc::pthread_attr_get_np(libc::pthread_self(), &mut attr);
714 #[cfg(not(target_os = "freebsd"))]
715 let e = libc::pthread_getattr_np(libc::pthread_self(), &mut attr);
717 let mut stackaddr = crate::ptr::null_mut();
718 let mut stacksize = 0;
719 assert_eq!(libc::pthread_attr_getstack(&attr, &mut stackaddr, &mut stacksize), 0);
720 ret = Some(stackaddr);
722 if e == 0 || cfg!(target_os = "freebsd") {
723 assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
728 // Precondition: PAGE_SIZE is initialized.
729 unsafe fn get_stack_start_aligned() -> Option<*mut libc::c_void> {
730 let page_size = PAGE_SIZE.load(Ordering::Relaxed);
731 assert!(page_size != 0);
732 let stackptr = get_stack_start()?;
733 let stackaddr = stackptr.addr();
735 // Ensure stackaddr is page aligned! A parent process might
736 // have reset RLIMIT_STACK to be non-page aligned. The
737 // pthread_attr_getstack() reports the usable stack area
738 // stackaddr < stackaddr + stacksize, so if stackaddr is not
739 // page-aligned, calculate the fix such that stackaddr <
740 // new_page_aligned_stackaddr < stackaddr + stacksize
741 let remainder = stackaddr % page_size;
742 Some(if remainder == 0 {
745 stackptr.with_addr(stackaddr + page_size - remainder)
749 pub unsafe fn init() -> Option<Guard> {
750 let page_size = os::page_size();
751 PAGE_SIZE.store(page_size, Ordering::Relaxed);
753 if cfg!(all(target_os = "linux", not(target_env = "musl"))) {
754 // Linux doesn't allocate the whole stack right away, and
755 // the kernel has its own stack-guard mechanism to fault
756 // when growing too close to an existing mapping. If we map
757 // our own guard, then the kernel starts enforcing a rather
758 // large gap above that, rendering much of the possible
759 // stack space useless. See #43052.
761 // Instead, we'll just note where we expect rlimit to start
762 // faulting, so our handler can report "stack overflow", and
763 // trust that the kernel's own stack guard will work.
764 let stackptr = get_stack_start_aligned()?;
765 let stackaddr = stackptr.addr();
766 Some(stackaddr - page_size..stackaddr)
767 } else if cfg!(all(target_os = "linux", target_env = "musl")) {
768 // For the main thread, the musl's pthread_attr_getstack
769 // returns the current stack size, rather than maximum size
770 // it can eventually grow to. It cannot be used to determine
771 // the position of kernel's stack guard.
773 } else if cfg!(target_os = "freebsd") {
774 // FreeBSD's stack autogrows, and optionally includes a guard page
775 // at the bottom. If we try to remap the bottom of the stack
776 // ourselves, FreeBSD's guard page moves upwards. So we'll just use
777 // the builtin guard page.
778 let stackptr = get_stack_start_aligned()?;
779 let guardaddr = stackptr.addr();
780 // Technically the number of guard pages is tunable and controlled
781 // by the security.bsd.stack_guard_page sysctl, but there are
782 // few reasons to change it from the default. The default value has
783 // been 1 ever since FreeBSD 11.1 and 10.4.
784 const GUARD_PAGES: usize = 1;
785 let guard = guardaddr..guardaddr + GUARD_PAGES * page_size;
787 } else if cfg!(target_os = "openbsd") {
788 // OpenBSD stack already includes a guard page, and stack is
791 // We'll just note where we expect rlimit to start
792 // faulting, so our handler can report "stack overflow", and
793 // trust that the kernel's own stack guard will work.
794 let stackptr = get_stack_start_aligned()?;
795 let stackaddr = stackptr.addr();
796 Some(stackaddr - page_size..stackaddr)
798 // Reallocate the last page of the stack.
799 // This ensures SIGBUS will be raised on
801 // Systems which enforce strict PAX MPROTECT do not allow
802 // to mprotect() a mapping with less restrictive permissions
803 // than the initial mmap() used, so we mmap() here with
804 // read/write permissions and only then mprotect() it to
805 // no permissions at all. See issue #50313.
806 let stackptr = get_stack_start_aligned()?;
810 PROT_READ | PROT_WRITE,
811 MAP_PRIVATE | MAP_ANON | MAP_FIXED,
815 if result != stackptr || result == MAP_FAILED {
816 panic!("failed to allocate a guard page: {}", io::Error::last_os_error());
819 let result = mprotect(stackptr, page_size, PROT_NONE);
821 panic!("failed to protect the guard page: {}", io::Error::last_os_error());
824 let guardaddr = stackptr.addr();
826 Some(guardaddr..guardaddr + page_size)
830 #[cfg(any(target_os = "macos", target_os = "openbsd", target_os = "solaris"))]
831 pub unsafe fn current() -> Option<Guard> {
832 let stackptr = get_stack_start()?;
833 let stackaddr = stackptr.addr();
834 Some(stackaddr - PAGE_SIZE.load(Ordering::Relaxed)..stackaddr)
838 target_os = "android",
839 target_os = "freebsd",
841 target_os = "netbsd",
844 pub unsafe fn current() -> Option<Guard> {
846 let mut attr: libc::pthread_attr_t = crate::mem::zeroed();
847 #[cfg(target_os = "freebsd")]
848 assert_eq!(libc::pthread_attr_init(&mut attr), 0);
849 #[cfg(target_os = "freebsd")]
850 let e = libc::pthread_attr_get_np(libc::pthread_self(), &mut attr);
851 #[cfg(not(target_os = "freebsd"))]
852 let e = libc::pthread_getattr_np(libc::pthread_self(), &mut attr);
854 let mut guardsize = 0;
855 assert_eq!(libc::pthread_attr_getguardsize(&attr, &mut guardsize), 0);
857 if cfg!(all(target_os = "linux", target_env = "musl")) {
858 // musl versions before 1.1.19 always reported guard
859 // size obtained from pthread_attr_get_np as zero.
860 // Use page size as a fallback.
861 guardsize = PAGE_SIZE.load(Ordering::Relaxed);
863 panic!("there is no guard page");
866 let mut stackptr = crate::ptr::null_mut::<libc::c_void>();
868 assert_eq!(libc::pthread_attr_getstack(&attr, &mut stackptr, &mut size), 0);
870 let stackaddr = stackptr.addr();
871 ret = if cfg!(any(target_os = "freebsd", target_os = "netbsd")) {
872 Some(stackaddr - guardsize..stackaddr)
873 } else if cfg!(all(target_os = "linux", target_env = "musl")) {
874 Some(stackaddr - guardsize..stackaddr)
875 } else if cfg!(all(target_os = "linux", any(target_env = "gnu", target_env = "uclibc")))
877 // glibc used to include the guard area within the stack, as noted in the BUGS
878 // section of `man pthread_attr_getguardsize`. This has been corrected starting
879 // with glibc 2.27, and in some distro backports, so the guard is now placed at the
880 // end (below) the stack. There's no easy way for us to know which we have at
881 // runtime, so we'll just match any fault in the range right above or below the
882 // stack base to call that fault a stack overflow.
883 Some(stackaddr - guardsize..stackaddr + guardsize)
885 Some(stackaddr..stackaddr + guardsize)
888 if e == 0 || cfg!(target_os = "freebsd") {
889 assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
895 // glibc >= 2.15 has a __pthread_get_minstack() function that returns
896 // PTHREAD_STACK_MIN plus bytes needed for thread-local storage.
897 // We need that information to avoid blowing up when a small stack
898 // is created in an application with big thread-local storage requirements.
899 // See #6233 for rationale and details.
900 #[cfg(all(target_os = "linux", target_env = "gnu"))]
901 fn min_stack_size(attr: *const libc::pthread_attr_t) -> usize {
902 // We use dlsym to avoid an ELF version dependency on GLIBC_PRIVATE. (#23628)
903 // We shouldn't really be using such an internal symbol, but there's currently
904 // no other way to account for the TLS size.
905 dlsym!(fn __pthread_get_minstack(*const libc::pthread_attr_t) -> libc::size_t);
907 match __pthread_get_minstack.get() {
908 None => libc::PTHREAD_STACK_MIN,
909 Some(f) => unsafe { f(attr) },
913 // No point in looking up __pthread_get_minstack() on non-glibc platforms.
914 #[cfg(all(not(all(target_os = "linux", target_env = "gnu")), not(target_os = "netbsd")))]
915 fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
916 libc::PTHREAD_STACK_MIN
919 #[cfg(target_os = "netbsd")]
920 fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {