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) {
136 // Available since glibc 2.12, musl 1.1.16, and uClibc 1.0.20.
137 libc::pthread_setname_np(libc::pthread_self(), name.as_ptr());
141 #[cfg(any(target_os = "freebsd", target_os = "dragonfly", target_os = "openbsd"))]
142 pub fn set_name(name: &CStr) {
144 libc::pthread_set_name_np(libc::pthread_self(), name.as_ptr());
148 #[cfg(any(target_os = "macos", target_os = "ios", target_os = "watchos"))]
149 pub fn set_name(name: &CStr) {
151 libc::pthread_setname_np(name.as_ptr());
155 #[cfg(target_os = "netbsd")]
156 pub fn set_name(name: &CStr) {
157 use crate::ffi::CString;
158 let cname = CString::new(&b"%s"[..]).unwrap();
160 libc::pthread_setname_np(
161 libc::pthread_self(),
163 name.as_ptr() as *mut libc::c_void,
168 #[cfg(any(target_os = "solaris", target_os = "illumos"))]
169 pub fn set_name(name: &CStr) {
171 fn pthread_setname_np(
172 libc::pthread_t, *const libc::c_char
176 if let Some(f) = pthread_setname_np.get() {
178 f(libc::pthread_self(), name.as_ptr());
183 #[cfg(target_os = "fuchsia")]
184 pub fn set_name(name: &CStr) {
187 zx_object_set_property(
190 name.as_ptr() as *const libc::c_void,
191 name.to_bytes().len(),
196 #[cfg(target_os = "haiku")]
197 pub fn set_name(name: &CStr) {
199 let thread_self = libc::find_thread(ptr::null_mut());
200 libc::rename_thread(thread_self, name.as_ptr());
205 target_env = "newlib",
207 target_os = "emscripten",
209 target_os = "vxworks"
211 pub fn set_name(_name: &CStr) {
212 // Newlib, Emscripten, and VxWorks have no way to set a thread name.
215 #[cfg(not(target_os = "espidf"))]
216 pub fn sleep(dur: Duration) {
217 let mut secs = dur.as_secs();
218 let mut nsecs = dur.subsec_nanos() as _;
220 // If we're awoken with a signal then the return value will be -1 and
221 // nanosleep will fill in `ts` with the remaining time.
223 while secs > 0 || nsecs > 0 {
224 let mut ts = libc::timespec {
225 tv_sec: cmp::min(libc::time_t::MAX as u64, secs) as libc::time_t,
228 secs -= ts.tv_sec as u64;
229 let ts_ptr = &mut ts as *mut _;
230 if libc::nanosleep(ts_ptr, ts_ptr) == -1 {
231 assert_eq!(os::errno(), libc::EINTR);
232 secs += ts.tv_sec as u64;
241 #[cfg(target_os = "espidf")]
242 pub fn sleep(dur: Duration) {
243 let mut micros = dur.as_micros();
246 let st = if micros > u32::MAX as u128 { u32::MAX } else { micros as u32 };
249 micros -= st as u128;
256 let ret = libc::pthread_join(self.id, ptr::null_mut());
258 assert!(ret == 0, "failed to join thread: {}", io::Error::from_raw_os_error(ret));
262 pub fn id(&self) -> libc::pthread_t {
266 pub fn into_id(self) -> libc::pthread_t {
273 impl Drop for Thread {
275 let ret = unsafe { libc::pthread_detach(self.id) };
276 debug_assert_eq!(ret, 0);
280 pub fn available_parallelism() -> io::Result<NonZeroUsize> {
283 target_os = "android",
284 target_os = "emscripten",
285 target_os = "fuchsia",
289 target_os = "solaris",
290 target_os = "illumos",
292 #[cfg(any(target_os = "android", target_os = "linux"))]
294 let quota = cgroups::quota().max(1);
295 let mut set: libc::cpu_set_t = unsafe { mem::zeroed() };
297 if libc::sched_getaffinity(0, mem::size_of::<libc::cpu_set_t>(), &mut set) == 0 {
298 let count = libc::CPU_COUNT(&set) as usize;
299 let count = count.min(quota);
300 // SAFETY: affinity mask can't be empty and the quota gets clamped to a minimum of 1
301 return Ok(NonZeroUsize::new_unchecked(count));
305 match unsafe { libc::sysconf(libc::_SC_NPROCESSORS_ONLN) } {
306 -1 => Err(io::Error::last_os_error()),
307 0 => Err(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")),
308 cpus => Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) }),
310 } else if #[cfg(any(target_os = "freebsd", target_os = "dragonfly", target_os = "netbsd"))] {
313 let mut cpus: libc::c_uint = 0;
314 let mut cpus_size = crate::mem::size_of_val(&cpus);
317 cpus = libc::sysconf(libc::_SC_NPROCESSORS_ONLN) as libc::c_uint;
320 // Fallback approach in case of errors or no hardware threads.
322 let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0];
327 &mut cpus as *mut _ as *mut _,
328 &mut cpus_size as *mut _ as *mut _,
334 // Handle errors if any.
336 return Err(io::Error::last_os_error());
337 } else if cpus == 0 {
338 return Err(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform"));
341 Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) })
342 } else if #[cfg(target_os = "openbsd")] {
345 let mut cpus: libc::c_uint = 0;
346 let mut cpus_size = crate::mem::size_of_val(&cpus);
347 let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0];
353 &mut cpus as *mut _ as *mut _,
354 &mut cpus_size as *mut _ as *mut _,
360 // Handle errors if any.
362 return Err(io::Error::last_os_error());
363 } else if cpus == 0 {
364 return Err(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform"));
367 Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) })
368 } else if #[cfg(target_os = "haiku")] {
369 // system_info cpu_count field gets the static data set at boot time with `smp_set_num_cpus`
370 // `get_system_info` calls then `smp_get_num_cpus`
372 let mut sinfo: libc::system_info = crate::mem::zeroed();
373 let res = libc::get_system_info(&mut sinfo);
375 if res != libc::B_OK {
376 return Err(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform"));
379 Ok(NonZeroUsize::new_unchecked(sinfo.cpu_count as usize))
382 // FIXME: implement on vxWorks, Redox, l4re
383 Err(io::const_io_error!(io::ErrorKind::Unsupported, "Getting the number of hardware threads is not supported on the target platform"))
388 #[cfg(any(target_os = "android", target_os = "linux"))]
390 //! Currently not covered
391 //! * cgroup v2 in non-standard mountpoints
392 //! * paths containing control characters or spaces, since those would be escaped in procfs
393 //! output and we don't unescape
394 use crate::borrow::Cow;
395 use crate::ffi::OsString;
396 use crate::fs::{try_exists, File};
398 use crate::io::{BufRead, BufReader};
399 use crate::os::unix::ffi::OsStringExt;
400 use crate::path::Path;
401 use crate::path::PathBuf;
402 use crate::str::from_utf8;
410 /// Returns cgroup CPU quota in core-equivalents, rounded down or usize::MAX if the quota cannot
411 /// be determined or is not set.
412 pub(super) fn quota() -> usize {
413 let mut quota = usize::MAX;
415 // Attempting to open a file fails under default flags due to isolation.
416 // And Miri does not have parallelism anyway.
420 let _: Option<()> = try {
421 let mut buf = Vec::with_capacity(128);
422 // find our place in the cgroup hierarchy
423 File::open("/proc/self/cgroup").ok()?.read_to_end(&mut buf).ok()?;
424 let (cgroup_path, version) =
425 buf.split(|&c| c == b'\n').fold(None, |previous, line| {
426 let mut fields = line.splitn(3, |&c| c == b':');
427 // 2nd field is a list of controllers for v1 or empty for v2
428 let version = match fields.nth(1) {
429 Some(b"") => Cgroup::V2,
431 if from_utf8(controllers)
432 .is_ok_and(|c| c.split(",").any(|c| c == "cpu")) =>
436 _ => return previous,
439 // already-found v1 trumps v2 since it explicitly specifies its controllers
440 if previous.is_some() && version == Cgroup::V2 {
444 let path = fields.last()?;
445 // skip leading slash
446 Some((path[1..].to_owned(), version))
448 let cgroup_path = PathBuf::from(OsString::from_vec(cgroup_path));
450 quota = match version {
451 Cgroup::V1 => quota_v1(cgroup_path),
452 Cgroup::V2 => quota_v2(cgroup_path),
459 fn quota_v2(group_path: PathBuf) -> usize {
460 let mut quota = usize::MAX;
462 let mut path = PathBuf::with_capacity(128);
463 let mut read_buf = String::with_capacity(20);
465 // standard mount location defined in file-hierarchy(7) manpage
466 let cgroup_mount = "/sys/fs/cgroup";
468 path.push(cgroup_mount);
469 path.push(&group_path);
471 path.push("cgroup.controllers");
473 // skip if we're not looking at cgroup2
474 if matches!(try_exists(&path), Err(_) | Ok(false)) {
480 let _: Option<()> = try {
481 while path.starts_with(cgroup_mount) {
482 path.push("cpu.max");
486 if File::open(&path).and_then(|mut f| f.read_to_string(&mut read_buf)).is_ok() {
487 let raw_quota = read_buf.lines().next()?;
488 let mut raw_quota = raw_quota.split(' ');
489 let limit = raw_quota.next()?;
490 let period = raw_quota.next()?;
491 match (limit.parse::<usize>(), period.parse::<usize>()) {
492 (Ok(limit), Ok(period)) => {
493 quota = quota.min(limit / period);
499 path.pop(); // pop filename
500 path.pop(); // pop dir
507 fn quota_v1(group_path: PathBuf) -> usize {
508 let mut quota = usize::MAX;
509 let mut path = PathBuf::with_capacity(128);
510 let mut read_buf = String::with_capacity(20);
512 // Hardcode commonly used locations mentioned in the cgroups(7) manpage
513 // if that doesn't work scan mountinfo and adjust `group_path` for bind-mounts
514 let mounts: &[fn(&Path) -> Option<(_, &Path)>] = &[
515 |p| Some((Cow::Borrowed("/sys/fs/cgroup/cpu"), p)),
516 |p| Some((Cow::Borrowed("/sys/fs/cgroup/cpu,cpuacct"), p)),
517 // this can be expensive on systems with tons of mountpoints
518 // but we only get to this point when /proc/self/cgroups explicitly indicated
519 // this process belongs to a cpu-controller cgroup v1 and the defaults didn't work
523 for mount in mounts {
524 let Some((mount, group_path)) = mount(&group_path) else { continue };
527 path.push(mount.as_ref());
528 path.push(&group_path);
530 // skip if we guessed the mount incorrectly
531 if matches!(try_exists(&path), Err(_) | Ok(false)) {
535 while path.starts_with(mount.as_ref()) {
536 let mut parse_file = |name| {
540 let f = File::open(&path);
541 path.pop(); // restore buffer before any early returns
542 f.ok()?.read_to_string(&mut read_buf).ok()?;
543 let parsed = read_buf.trim().parse::<usize>().ok()?;
548 let limit = parse_file("cpu.cfs_quota_us");
549 let period = parse_file("cpu.cfs_period_us");
551 match (limit, period) {
552 (Some(limit), Some(period)) => quota = quota.min(limit / period),
559 // we passed the try_exists above so we should have traversed the correct hierarchy
560 // when reaching this line
567 /// Scan mountinfo for cgroup v1 mountpoint with a cpu controller
569 /// If the cgroupfs is a bind mount then `group_path` is adjusted to skip
570 /// over the already-included prefix
571 fn find_mountpoint(group_path: &Path) -> Option<(Cow<'static, str>, &Path)> {
572 let mut reader = BufReader::new(File::open("/proc/self/mountinfo").ok()?);
573 let mut line = String::with_capacity(256);
576 if reader.read_line(&mut line).ok()? == 0 {
580 let line = line.trim();
581 let mut items = line.split(' ');
583 let sub_path = items.nth(3)?;
584 let mount_point = items.next()?;
585 let mount_opts = items.next_back()?;
586 let filesystem_type = items.nth_back(1)?;
588 if filesystem_type != "cgroup" || !mount_opts.split(',').any(|opt| opt == "cpu") {
589 // not a cgroup / not a cpu-controller
593 let sub_path = Path::new(sub_path).strip_prefix("/").ok()?;
595 if !group_path.starts_with(sub_path) {
596 // this is a bind-mount and the bound subdirectory
597 // does not contain the cgroup this process belongs to
601 let trimmed_group_path = group_path.strip_prefix(sub_path).ok()?;
603 return Some((Cow::Owned(mount_point.to_owned()), trimmed_group_path));
611 not(target_os = "linux"),
612 not(target_os = "freebsd"),
613 not(target_os = "macos"),
614 not(target_os = "netbsd"),
615 not(target_os = "openbsd"),
616 not(target_os = "solaris")
618 #[cfg_attr(test, allow(dead_code))]
620 use crate::ops::Range;
621 pub type Guard = Range<usize>;
622 pub unsafe fn current() -> Option<Guard> {
625 pub unsafe fn init() -> Option<Guard> {
632 target_os = "freebsd",
634 target_os = "netbsd",
635 target_os = "openbsd",
636 target_os = "solaris"
638 #[cfg_attr(test, allow(dead_code))]
640 use libc::{mmap, mprotect};
641 use libc::{MAP_ANON, MAP_FAILED, MAP_FIXED, MAP_PRIVATE, PROT_NONE, PROT_READ, PROT_WRITE};
644 use crate::ops::Range;
645 use crate::sync::atomic::{AtomicUsize, Ordering};
648 // This is initialized in init() and only read from after
649 static PAGE_SIZE: AtomicUsize = AtomicUsize::new(0);
651 pub type Guard = Range<usize>;
653 #[cfg(target_os = "solaris")]
654 unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
655 let mut current_stack: libc::stack_t = crate::mem::zeroed();
656 assert_eq!(libc::stack_getbounds(&mut current_stack), 0);
657 Some(current_stack.ss_sp)
660 #[cfg(target_os = "macos")]
661 unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
662 let th = libc::pthread_self();
663 let stackptr = libc::pthread_get_stackaddr_np(th);
664 Some(stackptr.map_addr(|addr| addr - libc::pthread_get_stacksize_np(th)))
667 #[cfg(target_os = "openbsd")]
668 unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
669 let mut current_stack: libc::stack_t = crate::mem::zeroed();
670 assert_eq!(libc::pthread_stackseg_np(libc::pthread_self(), &mut current_stack), 0);
672 let stack_ptr = current_stack.ss_sp;
673 let stackaddr = if libc::pthread_main_np() == 1 {
675 stack_ptr.addr() - current_stack.ss_size + PAGE_SIZE.load(Ordering::Relaxed)
678 stack_ptr.addr() - current_stack.ss_size
680 Some(stack_ptr.with_addr(stackaddr))
684 target_os = "android",
685 target_os = "freebsd",
687 target_os = "netbsd",
690 unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
692 let mut attr: libc::pthread_attr_t = crate::mem::zeroed();
693 #[cfg(target_os = "freebsd")]
694 assert_eq!(libc::pthread_attr_init(&mut attr), 0);
695 #[cfg(target_os = "freebsd")]
696 let e = libc::pthread_attr_get_np(libc::pthread_self(), &mut attr);
697 #[cfg(not(target_os = "freebsd"))]
698 let e = libc::pthread_getattr_np(libc::pthread_self(), &mut attr);
700 let mut stackaddr = crate::ptr::null_mut();
701 let mut stacksize = 0;
702 assert_eq!(libc::pthread_attr_getstack(&attr, &mut stackaddr, &mut stacksize), 0);
703 ret = Some(stackaddr);
705 if e == 0 || cfg!(target_os = "freebsd") {
706 assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
711 // Precondition: PAGE_SIZE is initialized.
712 unsafe fn get_stack_start_aligned() -> Option<*mut libc::c_void> {
713 let page_size = PAGE_SIZE.load(Ordering::Relaxed);
714 assert!(page_size != 0);
715 let stackptr = get_stack_start()?;
716 let stackaddr = stackptr.addr();
718 // Ensure stackaddr is page aligned! A parent process might
719 // have reset RLIMIT_STACK to be non-page aligned. The
720 // pthread_attr_getstack() reports the usable stack area
721 // stackaddr < stackaddr + stacksize, so if stackaddr is not
722 // page-aligned, calculate the fix such that stackaddr <
723 // new_page_aligned_stackaddr < stackaddr + stacksize
724 let remainder = stackaddr % page_size;
725 Some(if remainder == 0 {
728 stackptr.with_addr(stackaddr + page_size - remainder)
732 pub unsafe fn init() -> Option<Guard> {
733 let page_size = os::page_size();
734 PAGE_SIZE.store(page_size, Ordering::Relaxed);
736 if cfg!(all(target_os = "linux", not(target_env = "musl"))) {
737 // Linux doesn't allocate the whole stack right away, and
738 // the kernel has its own stack-guard mechanism to fault
739 // when growing too close to an existing mapping. If we map
740 // our own guard, then the kernel starts enforcing a rather
741 // large gap above that, rendering much of the possible
742 // stack space useless. See #43052.
744 // Instead, we'll just note where we expect rlimit to start
745 // faulting, so our handler can report "stack overflow", and
746 // trust that the kernel's own stack guard will work.
747 let stackptr = get_stack_start_aligned()?;
748 let stackaddr = stackptr.addr();
749 Some(stackaddr - page_size..stackaddr)
750 } else if cfg!(all(target_os = "linux", target_env = "musl")) {
751 // For the main thread, the musl's pthread_attr_getstack
752 // returns the current stack size, rather than maximum size
753 // it can eventually grow to. It cannot be used to determine
754 // the position of kernel's stack guard.
756 } else if cfg!(target_os = "freebsd") {
757 // FreeBSD's stack autogrows, and optionally includes a guard page
758 // at the bottom. If we try to remap the bottom of the stack
759 // ourselves, FreeBSD's guard page moves upwards. So we'll just use
760 // the builtin guard page.
761 let stackptr = get_stack_start_aligned()?;
762 let guardaddr = stackptr.addr();
763 // Technically the number of guard pages is tunable and controlled
764 // by the security.bsd.stack_guard_page sysctl, but there are
765 // few reasons to change it from the default. The default value has
766 // been 1 ever since FreeBSD 11.1 and 10.4.
767 const GUARD_PAGES: usize = 1;
768 let guard = guardaddr..guardaddr + GUARD_PAGES * page_size;
771 // Reallocate the last page of the stack.
772 // This ensures SIGBUS will be raised on
774 // Systems which enforce strict PAX MPROTECT do not allow
775 // to mprotect() a mapping with less restrictive permissions
776 // than the initial mmap() used, so we mmap() here with
777 // read/write permissions and only then mprotect() it to
778 // no permissions at all. See issue #50313.
779 let stackptr = get_stack_start_aligned()?;
783 PROT_READ | PROT_WRITE,
784 MAP_PRIVATE | MAP_ANON | MAP_FIXED,
788 if result != stackptr || result == MAP_FAILED {
789 panic!("failed to allocate a guard page: {}", io::Error::last_os_error());
792 let result = mprotect(stackptr, page_size, PROT_NONE);
794 panic!("failed to protect the guard page: {}", io::Error::last_os_error());
797 let guardaddr = stackptr.addr();
799 Some(guardaddr..guardaddr + page_size)
803 #[cfg(any(target_os = "macos", target_os = "openbsd", target_os = "solaris"))]
804 pub unsafe fn current() -> Option<Guard> {
805 let stackptr = get_stack_start()?;
806 let stackaddr = stackptr.addr();
807 Some(stackaddr - PAGE_SIZE.load(Ordering::Relaxed)..stackaddr)
811 target_os = "android",
812 target_os = "freebsd",
814 target_os = "netbsd",
817 pub unsafe fn current() -> Option<Guard> {
819 let mut attr: libc::pthread_attr_t = crate::mem::zeroed();
820 #[cfg(target_os = "freebsd")]
821 assert_eq!(libc::pthread_attr_init(&mut attr), 0);
822 #[cfg(target_os = "freebsd")]
823 let e = libc::pthread_attr_get_np(libc::pthread_self(), &mut attr);
824 #[cfg(not(target_os = "freebsd"))]
825 let e = libc::pthread_getattr_np(libc::pthread_self(), &mut attr);
827 let mut guardsize = 0;
828 assert_eq!(libc::pthread_attr_getguardsize(&attr, &mut guardsize), 0);
830 if cfg!(all(target_os = "linux", target_env = "musl")) {
831 // musl versions before 1.1.19 always reported guard
832 // size obtained from pthread_attr_get_np as zero.
833 // Use page size as a fallback.
834 guardsize = PAGE_SIZE.load(Ordering::Relaxed);
836 panic!("there is no guard page");
839 let mut stackptr = crate::ptr::null_mut::<libc::c_void>();
841 assert_eq!(libc::pthread_attr_getstack(&attr, &mut stackptr, &mut size), 0);
843 let stackaddr = stackptr.addr();
844 ret = if cfg!(any(target_os = "freebsd", target_os = "netbsd")) {
845 Some(stackaddr - guardsize..stackaddr)
846 } else if cfg!(all(target_os = "linux", target_env = "musl")) {
847 Some(stackaddr - guardsize..stackaddr)
848 } else if cfg!(all(target_os = "linux", any(target_env = "gnu", target_env = "uclibc")))
850 // glibc used to include the guard area within the stack, as noted in the BUGS
851 // section of `man pthread_attr_getguardsize`. This has been corrected starting
852 // with glibc 2.27, and in some distro backports, so the guard is now placed at the
853 // end (below) the stack. There's no easy way for us to know which we have at
854 // runtime, so we'll just match any fault in the range right above or below the
855 // stack base to call that fault a stack overflow.
856 Some(stackaddr - guardsize..stackaddr + guardsize)
858 Some(stackaddr..stackaddr + guardsize)
861 if e == 0 || cfg!(target_os = "freebsd") {
862 assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
868 // glibc >= 2.15 has a __pthread_get_minstack() function that returns
869 // PTHREAD_STACK_MIN plus bytes needed for thread-local storage.
870 // We need that information to avoid blowing up when a small stack
871 // is created in an application with big thread-local storage requirements.
872 // See #6233 for rationale and details.
873 #[cfg(all(target_os = "linux", target_env = "gnu"))]
874 fn min_stack_size(attr: *const libc::pthread_attr_t) -> usize {
875 // We use dlsym to avoid an ELF version dependency on GLIBC_PRIVATE. (#23628)
876 // We shouldn't really be using such an internal symbol, but there's currently
877 // no other way to account for the TLS size.
878 dlsym!(fn __pthread_get_minstack(*const libc::pthread_attr_t) -> libc::size_t);
880 match __pthread_get_minstack.get() {
881 None => libc::PTHREAD_STACK_MIN,
882 Some(f) => unsafe { f(attr) },
886 // No point in looking up __pthread_get_minstack() on non-glibc platforms.
887 #[cfg(all(not(all(target_os = "linux", target_env = "gnu")), not(target_os = "netbsd")))]
888 fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
889 libc::PTHREAD_STACK_MIN
892 #[cfg(target_os = "netbsd")]
893 fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {