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thread.rs
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thread.rs
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use crate::cmp;
use crate::ffi::{CStr, CString};
use crate::io;
use crate::mem;
use crate::num::NonZero;
use crate::ptr;
use crate::sys::{os, stack_overflow};
use crate::time::Duration;
#[cfg(all(target_os = "linux", target_env = "gnu"))]
use crate::sys::weak::dlsym;
#[cfg(any(target_os = "solaris", target_os = "illumos", target_os = "nto"))]
use crate::sys::weak::weak;
#[cfg(not(any(target_os = "l4re", target_os = "vxworks", target_os = "espidf")))]
pub const DEFAULT_MIN_STACK_SIZE: usize = 2 * 1024 * 1024;
#[cfg(target_os = "l4re")]
pub const DEFAULT_MIN_STACK_SIZE: usize = 1024 * 1024;
#[cfg(target_os = "vxworks")]
pub const DEFAULT_MIN_STACK_SIZE: usize = 256 * 1024;
#[cfg(target_os = "espidf")]
pub const DEFAULT_MIN_STACK_SIZE: usize = 0; // 0 indicates that the stack size configured in the ESP-IDF menuconfig system should be used
#[cfg(target_os = "fuchsia")]
mod zircon {
type zx_handle_t = u32;
type zx_status_t = i32;
pub const ZX_PROP_NAME: u32 = 3;
extern "C" {
pub fn zx_object_set_property(
handle: zx_handle_t,
property: u32,
value: *const libc::c_void,
value_size: libc::size_t,
) -> zx_status_t;
pub fn zx_thread_self() -> zx_handle_t;
}
}
pub struct Thread {
id: libc::pthread_t,
}
// Some platforms may have pthread_t as a pointer in which case we still want
// a thread to be Send/Sync
unsafe impl Send for Thread {}
unsafe impl Sync for Thread {}
impl Thread {
// unsafe: see thread::Builder::spawn_unchecked for safety requirements
pub unsafe fn new(stack: usize, p: Box<dyn FnOnce()>) -> io::Result<Thread> {
let p = Box::into_raw(Box::new(p));
let mut native: libc::pthread_t = mem::zeroed();
let mut attr: libc::pthread_attr_t = mem::zeroed();
assert_eq!(libc::pthread_attr_init(&mut attr), 0);
#[cfg(target_os = "espidf")]
if stack > 0 {
// Only set the stack if a non-zero value is passed
// 0 is used as an indication that the default stack size configured in the ESP-IDF menuconfig system should be used
assert_eq!(
libc::pthread_attr_setstacksize(&mut attr, cmp::max(stack, min_stack_size(&attr))),
0
);
}
#[cfg(not(target_os = "espidf"))]
{
let stack_size = cmp::max(stack, min_stack_size(&attr));
match libc::pthread_attr_setstacksize(&mut attr, stack_size) {
0 => {}
n => {
assert_eq!(n, libc::EINVAL);
// EINVAL means |stack_size| is either too small or not a
// multiple of the system page size. Because it's definitely
// >= PTHREAD_STACK_MIN, it must be an alignment issue.
// Round up to the nearest page and try again.
let page_size = os::page_size();
let stack_size =
(stack_size + page_size - 1) & (-(page_size as isize - 1) as usize - 1);
assert_eq!(libc::pthread_attr_setstacksize(&mut attr, stack_size), 0);
}
};
}
let ret = libc::pthread_create(&mut native, &attr, thread_start, p as *mut _);
// Note: if the thread creation fails and this assert fails, then p will
// be leaked. However, an alternative design could cause double-free
// which is clearly worse.
assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
return if ret != 0 {
// The thread failed to start and as a result p was not consumed. Therefore, it is
// safe to reconstruct the box so that it gets deallocated.
drop(Box::from_raw(p));
Err(io::Error::from_raw_os_error(ret))
} else {
Ok(Thread { id: native })
};
extern "C" fn thread_start(main: *mut libc::c_void) -> *mut libc::c_void {
unsafe {
// Next, set up our stack overflow handler which may get triggered if we run
// out of stack.
let _handler = stack_overflow::Handler::new();
// Finally, let's run some code.
Box::from_raw(main as *mut Box<dyn FnOnce()>)();
}
ptr::null_mut()
}
}
pub fn yield_now() {
let ret = unsafe { libc::sched_yield() };
debug_assert_eq!(ret, 0);
}
#[cfg(target_os = "android")]
pub fn set_name(name: &CStr) {
const PR_SET_NAME: libc::c_int = 15;
unsafe {
libc::prctl(
PR_SET_NAME,
name.as_ptr(),
0 as libc::c_ulong,
0 as libc::c_ulong,
0 as libc::c_ulong,
);
}
}
#[cfg(target_os = "linux")]
pub fn set_name(name: &CStr) {
const TASK_COMM_LEN: usize = 16;
unsafe {
// Available since glibc 2.12, musl 1.1.16, and uClibc 1.0.20.
let name = truncate_cstr::<{ TASK_COMM_LEN }>(name);
let res = libc::pthread_setname_np(libc::pthread_self(), name.as_ptr());
// We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
debug_assert_eq!(res, 0);
}
}
#[cfg(any(target_os = "freebsd", target_os = "dragonfly", target_os = "openbsd"))]
pub fn set_name(name: &CStr) {
unsafe {
libc::pthread_set_name_np(libc::pthread_self(), name.as_ptr());
}
}
#[cfg(any(target_os = "macos", target_os = "ios", target_os = "tvos", target_os = "watchos"))]
pub fn set_name(name: &CStr) {
unsafe {
let name = truncate_cstr::<{ libc::MAXTHREADNAMESIZE }>(name);
let res = libc::pthread_setname_np(name.as_ptr());
// We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
debug_assert_eq!(res, 0);
}
}
#[cfg(target_os = "netbsd")]
pub fn set_name(name: &CStr) {
unsafe {
let res = libc::pthread_setname_np(
libc::pthread_self(),
c"%s".as_ptr(),
name.as_ptr() as *mut libc::c_void,
);
debug_assert_eq!(res, 0);
}
}
#[cfg(any(target_os = "solaris", target_os = "illumos", target_os = "nto"))]
pub fn set_name(name: &CStr) {
weak! {
fn pthread_setname_np(
libc::pthread_t, *const libc::c_char
) -> libc::c_int
}
if let Some(f) = pthread_setname_np.get() {
#[cfg(target_os = "nto")]
let name = truncate_cstr::<{ libc::_NTO_THREAD_NAME_MAX as usize }>(name);
let res = unsafe { f(libc::pthread_self(), name.as_ptr()) };
debug_assert_eq!(res, 0);
}
}
#[cfg(target_os = "fuchsia")]
pub fn set_name(name: &CStr) {
use self::zircon::*;
unsafe {
zx_object_set_property(
zx_thread_self(),
ZX_PROP_NAME,
name.as_ptr() as *const libc::c_void,
name.to_bytes().len(),
);
}
}
#[cfg(target_os = "haiku")]
pub fn set_name(name: &CStr) {
unsafe {
let thread_self = libc::find_thread(ptr::null_mut());
let res = libc::rename_thread(thread_self, name.as_ptr());
// We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
debug_assert_eq!(res, libc::B_OK);
}
}
#[cfg(any(
target_env = "newlib",
target_os = "l4re",
target_os = "emscripten",
target_os = "redox",
target_os = "vxworks",
target_os = "hurd",
target_os = "aix",
))]
pub fn set_name(_name: &CStr) {
// Newlib, Emscripten, and VxWorks have no way to set a thread name.
}
#[cfg(target_os = "linux")]
pub fn get_name() -> Option<CString> {
const TASK_COMM_LEN: usize = 16;
let mut name = vec![0u8; TASK_COMM_LEN];
let res = unsafe {
libc::pthread_getname_np(libc::pthread_self(), name.as_mut_ptr().cast(), name.len())
};
if res != 0 {
return None;
}
name.truncate(name.iter().position(|&c| c == 0)?);
CString::new(name).ok()
}
#[cfg(any(target_os = "macos", target_os = "ios", target_os = "tvos", target_os = "watchos"))]
pub fn get_name() -> Option<CString> {
let mut name = vec![0u8; libc::MAXTHREADNAMESIZE];
let res = unsafe {
libc::pthread_getname_np(libc::pthread_self(), name.as_mut_ptr().cast(), name.len())
};
if res != 0 {
return None;
}
name.truncate(name.iter().position(|&c| c == 0)?);
CString::new(name).ok()
}
#[cfg(not(any(
target_os = "linux",
target_os = "macos",
target_os = "ios",
target_os = "tvos",
target_os = "watchos"
)))]
pub fn get_name() -> Option<CString> {
None
}
#[cfg(not(target_os = "espidf"))]
pub fn sleep(dur: Duration) {
let mut secs = dur.as_secs();
let mut nsecs = dur.subsec_nanos() as _;
// If we're awoken with a signal then the return value will be -1 and
// nanosleep will fill in `ts` with the remaining time.
unsafe {
while secs > 0 || nsecs > 0 {
let mut ts = libc::timespec {
tv_sec: cmp::min(libc::time_t::MAX as u64, secs) as libc::time_t,
tv_nsec: nsecs,
};
secs -= ts.tv_sec as u64;
let ts_ptr = core::ptr::addr_of_mut!(ts);
if libc::nanosleep(ts_ptr, ts_ptr) == -1 {
assert_eq!(os::errno(), libc::EINTR);
secs += ts.tv_sec as u64;
nsecs = ts.tv_nsec;
} else {
nsecs = 0;
}
}
}
}
#[cfg(target_os = "espidf")]
pub fn sleep(dur: Duration) {
let mut micros = dur.as_micros();
unsafe {
while micros > 0 {
let st = if micros > u32::MAX as u128 { u32::MAX } else { micros as u32 };
libc::usleep(st);
micros -= st as u128;
}
}
}
pub fn join(self) {
unsafe {
let ret = libc::pthread_join(self.id, ptr::null_mut());
mem::forget(self);
assert!(ret == 0, "failed to join thread: {}", io::Error::from_raw_os_error(ret));
}
}
pub fn id(&self) -> libc::pthread_t {
self.id
}
pub fn into_id(self) -> libc::pthread_t {
let id = self.id;
mem::forget(self);
id
}
}
impl Drop for Thread {
fn drop(&mut self) {
let ret = unsafe { libc::pthread_detach(self.id) };
debug_assert_eq!(ret, 0);
}
}
#[cfg(any(
target_os = "linux",
target_os = "macos",
target_os = "ios",
target_os = "tvos",
target_os = "watchos",
target_os = "nto",
))]
fn truncate_cstr<const MAX_WITH_NUL: usize>(cstr: &CStr) -> [libc::c_char; MAX_WITH_NUL] {
let mut result = [0; MAX_WITH_NUL];
for (src, dst) in cstr.to_bytes().iter().zip(&mut result[..MAX_WITH_NUL - 1]) {
*dst = *src as libc::c_char;
}
result
}
pub fn available_parallelism() -> io::Result<NonZero<usize>> {
cfg_if::cfg_if! {
if #[cfg(any(
target_os = "android",
target_os = "emscripten",
target_os = "fuchsia",
target_os = "hurd",
target_os = "ios",
target_os = "tvos",
target_os = "linux",
target_os = "macos",
target_os = "solaris",
target_os = "illumos",
target_os = "aix",
))] {
#[allow(unused_assignments)]
#[allow(unused_mut)]
let mut quota = usize::MAX;
#[cfg(any(target_os = "android", target_os = "linux"))]
{
quota = cgroups::quota().max(1);
let mut set: libc::cpu_set_t = unsafe { mem::zeroed() };
unsafe {
if libc::sched_getaffinity(0, mem::size_of::<libc::cpu_set_t>(), &mut set) == 0 {
let count = libc::CPU_COUNT(&set) as usize;
let count = count.min(quota);
// According to sched_getaffinity's API it should always be non-zero, but
// some old MIPS kernels were buggy and zero-initialized the mask if
// none was explicitly set.
// In that case we use the sysconf fallback.
if let Some(count) = NonZero::new(count) {
return Ok(count)
}
}
}
}
match unsafe { libc::sysconf(libc::_SC_NPROCESSORS_ONLN) } {
-1 => Err(io::Error::last_os_error()),
0 => Err(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")),
cpus => {
let count = cpus as usize;
// Cover the unusual situation where we were able to get the quota but not the affinity mask
let count = count.min(quota);
Ok(unsafe { NonZero::new_unchecked(count) })
}
}
} else if #[cfg(any(
target_os = "freebsd",
target_os = "dragonfly",
target_os = "openbsd",
target_os = "netbsd",
))] {
use crate::ptr;
#[cfg(target_os = "freebsd")]
{
let mut set: libc::cpuset_t = unsafe { mem::zeroed() };
unsafe {
if libc::cpuset_getaffinity(
libc::CPU_LEVEL_WHICH,
libc::CPU_WHICH_PID,
-1,
mem::size_of::<libc::cpuset_t>(),
&mut set,
) == 0 {
let count = libc::CPU_COUNT(&set) as usize;
if count > 0 {
return Ok(NonZero::new_unchecked(count));
}
}
}
}
#[cfg(target_os = "netbsd")]
{
unsafe {
let set = libc::_cpuset_create();
if !set.is_null() {
let mut count: usize = 0;
if libc::pthread_getaffinity_np(libc::pthread_self(), libc::_cpuset_size(set), set) == 0 {
for i in 0..u64::MAX {
match libc::_cpuset_isset(i, set) {
-1 => break,
0 => continue,
_ => count = count + 1,
}
}
}
libc::_cpuset_destroy(set);
if let Some(count) = NonZero::new(count) {
return Ok(count);
}
}
}
}
let mut cpus: libc::c_uint = 0;
let mut cpus_size = crate::mem::size_of_val(&cpus);
unsafe {
cpus = libc::sysconf(libc::_SC_NPROCESSORS_ONLN) as libc::c_uint;
}
// Fallback approach in case of errors or no hardware threads.
if cpus < 1 {
let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0];
let res = unsafe {
libc::sysctl(
mib.as_mut_ptr(),
2,
core::ptr::addr_of_mut!(cpus) as *mut _,
core::ptr::addr_of_mut!(cpus_size) as *mut _,
ptr::null_mut(),
0,
)
};
// Handle errors if any.
if res == -1 {
return Err(io::Error::last_os_error());
} else if cpus == 0 {
return Err(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform"));
}
}
Ok(unsafe { NonZero::new_unchecked(cpus as usize) })
} else if #[cfg(target_os = "nto")] {
unsafe {
use libc::_syspage_ptr;
if _syspage_ptr.is_null() {
Err(io::const_io_error!(io::ErrorKind::NotFound, "No syspage available"))
} else {
let cpus = (*_syspage_ptr).num_cpu;
NonZero::new(cpus as usize)
.ok_or(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform"))
}
}
} else if #[cfg(target_os = "haiku")] {
// system_info cpu_count field gets the static data set at boot time with `smp_set_num_cpus`
// `get_system_info` calls then `smp_get_num_cpus`
unsafe {
let mut sinfo: libc::system_info = crate::mem::zeroed();
let res = libc::get_system_info(&mut sinfo);
if res != libc::B_OK {
return Err(io::const_io_error!(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform"));
}
Ok(NonZero::new_unchecked(sinfo.cpu_count as usize))
}
} else {
// FIXME: implement on vxWorks, Redox, l4re
Err(io::const_io_error!(io::ErrorKind::Unsupported, "Getting the number of hardware threads is not supported on the target platform"))
}
}
}
#[cfg(any(target_os = "android", target_os = "linux"))]
mod cgroups {
//! Currently not covered
//! * cgroup v2 in non-standard mountpoints
//! * paths containing control characters or spaces, since those would be escaped in procfs
//! output and we don't unescape
use crate::borrow::Cow;
use crate::ffi::OsString;
use crate::fs::{try_exists, File};
use crate::io::Read;
use crate::io::{BufRead, BufReader};
use crate::os::unix::ffi::OsStringExt;
use crate::path::Path;
use crate::path::PathBuf;
use crate::str::from_utf8;
#[derive(PartialEq)]
enum Cgroup {
V1,
V2,
}
/// Returns cgroup CPU quota in core-equivalents, rounded down or usize::MAX if the quota cannot
/// be determined or is not set.
pub(super) fn quota() -> usize {
let mut quota = usize::MAX;
if cfg!(miri) {
// Attempting to open a file fails under default flags due to isolation.
// And Miri does not have parallelism anyway.
return quota;
}
let _: Option<()> = try {
let mut buf = Vec::with_capacity(128);
// find our place in the cgroup hierarchy
File::open("/proc/self/cgroup").ok()?.read_to_end(&mut buf).ok()?;
let (cgroup_path, version) =
buf.split(|&c| c == b'\n').fold(None, |previous, line| {
let mut fields = line.splitn(3, |&c| c == b':');
// 2nd field is a list of controllers for v1 or empty for v2
let version = match fields.nth(1) {
Some(b"") => Cgroup::V2,
Some(controllers)
if from_utf8(controllers)
.is_ok_and(|c| c.split(',').any(|c| c == "cpu")) =>
{
Cgroup::V1
}
_ => return previous,
};
// already-found v1 trumps v2 since it explicitly specifies its controllers
if previous.is_some() && version == Cgroup::V2 {
return previous;
}
let path = fields.last()?;
// skip leading slash
Some((path[1..].to_owned(), version))
})?;
let cgroup_path = PathBuf::from(OsString::from_vec(cgroup_path));
quota = match version {
Cgroup::V1 => quota_v1(cgroup_path),
Cgroup::V2 => quota_v2(cgroup_path),
};
};
quota
}
fn quota_v2(group_path: PathBuf) -> usize {
let mut quota = usize::MAX;
let mut path = PathBuf::with_capacity(128);
let mut read_buf = String::with_capacity(20);
// standard mount location defined in file-hierarchy(7) manpage
let cgroup_mount = "/sys/fs/cgroup";
path.push(cgroup_mount);
path.push(&group_path);
path.push("cgroup.controllers");
// skip if we're not looking at cgroup2
if matches!(try_exists(&path), Err(_) | Ok(false)) {
return usize::MAX;
};
path.pop();
let _: Option<()> = try {
while path.starts_with(cgroup_mount) {
path.push("cpu.max");
read_buf.clear();
if File::open(&path).and_then(|mut f| f.read_to_string(&mut read_buf)).is_ok() {
let raw_quota = read_buf.lines().next()?;
let mut raw_quota = raw_quota.split(' ');
let limit = raw_quota.next()?;
let period = raw_quota.next()?;
match (limit.parse::<usize>(), period.parse::<usize>()) {
(Ok(limit), Ok(period)) if period > 0 => {
quota = quota.min(limit / period);
}
_ => {}
}
}
path.pop(); // pop filename
path.pop(); // pop dir
}
};
quota
}
fn quota_v1(group_path: PathBuf) -> usize {
let mut quota = usize::MAX;
let mut path = PathBuf::with_capacity(128);
let mut read_buf = String::with_capacity(20);
// Hardcode commonly used locations mentioned in the cgroups(7) manpage
// if that doesn't work scan mountinfo and adjust `group_path` for bind-mounts
let mounts: &[fn(&Path) -> Option<(_, &Path)>] = &[
|p| Some((Cow::Borrowed("/sys/fs/cgroup/cpu"), p)),
|p| Some((Cow::Borrowed("/sys/fs/cgroup/cpu,cpuacct"), p)),
// this can be expensive on systems with tons of mountpoints
// but we only get to this point when /proc/self/cgroups explicitly indicated
// this process belongs to a cpu-controller cgroup v1 and the defaults didn't work
find_mountpoint,
];
for mount in mounts {
let Some((mount, group_path)) = mount(&group_path) else { continue };
path.clear();
path.push(mount.as_ref());
path.push(&group_path);
// skip if we guessed the mount incorrectly
if matches!(try_exists(&path), Err(_) | Ok(false)) {
continue;
}
while path.starts_with(mount.as_ref()) {
let mut parse_file = |name| {
path.push(name);
read_buf.clear();
let f = File::open(&path);
path.pop(); // restore buffer before any early returns
f.ok()?.read_to_string(&mut read_buf).ok()?;
let parsed = read_buf.trim().parse::<usize>().ok()?;
Some(parsed)
};
let limit = parse_file("cpu.cfs_quota_us");
let period = parse_file("cpu.cfs_period_us");
match (limit, period) {
(Some(limit), Some(period)) if period > 0 => quota = quota.min(limit / period),
_ => {}
}
path.pop();
}
// we passed the try_exists above so we should have traversed the correct hierarchy
// when reaching this line
break;
}
quota
}
/// Scan mountinfo for cgroup v1 mountpoint with a cpu controller
///
/// If the cgroupfs is a bind mount then `group_path` is adjusted to skip
/// over the already-included prefix
fn find_mountpoint(group_path: &Path) -> Option<(Cow<'static, str>, &Path)> {
let mut reader = BufReader::new(File::open("/proc/self/mountinfo").ok()?);
let mut line = String::with_capacity(256);
loop {
line.clear();
if reader.read_line(&mut line).ok()? == 0 {
break;
}
let line = line.trim();
let mut items = line.split(' ');
let sub_path = items.nth(3)?;
let mount_point = items.next()?;
let mount_opts = items.next_back()?;
let filesystem_type = items.nth_back(1)?;
if filesystem_type != "cgroup" || !mount_opts.split(',').any(|opt| opt == "cpu") {
// not a cgroup / not a cpu-controller
continue;
}
let sub_path = Path::new(sub_path).strip_prefix("/").ok()?;
if !group_path.starts_with(sub_path) {
// this is a bind-mount and the bound subdirectory
// does not contain the cgroup this process belongs to
continue;
}
let trimmed_group_path = group_path.strip_prefix(sub_path).ok()?;
return Some((Cow::Owned(mount_point.to_owned()), trimmed_group_path));
}
None
}
}
#[cfg(all(
not(target_os = "linux"),
not(target_os = "freebsd"),
not(target_os = "hurd"),
not(target_os = "macos"),
not(target_os = "netbsd"),
not(target_os = "openbsd"),
not(target_os = "solaris")
))]
#[cfg_attr(test, allow(dead_code))]
pub mod guard {
use crate::ops::Range;
pub type Guard = Range<usize>;
pub unsafe fn current() -> Option<Guard> {
None
}
pub unsafe fn init() -> Option<Guard> {
None
}
}
#[cfg(any(
target_os = "linux",
target_os = "freebsd",
target_os = "hurd",
target_os = "macos",
target_os = "netbsd",
target_os = "openbsd",
target_os = "solaris"
))]
#[cfg_attr(test, allow(dead_code))]
pub mod guard {
#[cfg(not(all(target_os = "linux", target_env = "gnu")))]
use libc::{mmap as mmap64, mprotect};
#[cfg(all(target_os = "linux", target_env = "gnu"))]
use libc::{mmap64, mprotect};
use libc::{MAP_ANON, MAP_FAILED, MAP_FIXED, MAP_PRIVATE, PROT_NONE, PROT_READ, PROT_WRITE};
use crate::io;
use crate::ops::Range;
use crate::sync::atomic::{AtomicUsize, Ordering};
use crate::sys::os;
// This is initialized in init() and only read from after
static PAGE_SIZE: AtomicUsize = AtomicUsize::new(0);
pub type Guard = Range<usize>;
#[cfg(target_os = "solaris")]
unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
let mut current_stack: libc::stack_t = crate::mem::zeroed();
assert_eq!(libc::stack_getbounds(&mut current_stack), 0);
Some(current_stack.ss_sp)
}
#[cfg(target_os = "macos")]
unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
let th = libc::pthread_self();
let stackptr = libc::pthread_get_stackaddr_np(th);
Some(stackptr.map_addr(|addr| addr - libc::pthread_get_stacksize_np(th)))
}
#[cfg(target_os = "openbsd")]
unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
let mut current_stack: libc::stack_t = crate::mem::zeroed();
assert_eq!(libc::pthread_stackseg_np(libc::pthread_self(), &mut current_stack), 0);
let stack_ptr = current_stack.ss_sp;
let stackaddr = if libc::pthread_main_np() == 1 {
// main thread
stack_ptr.addr() - current_stack.ss_size + PAGE_SIZE.load(Ordering::Relaxed)
} else {
// new thread
stack_ptr.addr() - current_stack.ss_size
};
Some(stack_ptr.with_addr(stackaddr))
}
#[cfg(any(
target_os = "android",
target_os = "freebsd",
target_os = "hurd",
target_os = "linux",
target_os = "netbsd",
target_os = "l4re"
))]
unsafe fn get_stack_start() -> Option<*mut libc::c_void> {
let mut ret = None;
let mut attr: libc::pthread_attr_t = crate::mem::zeroed();
#[cfg(target_os = "freebsd")]
assert_eq!(libc::pthread_attr_init(&mut attr), 0);
#[cfg(target_os = "freebsd")]
let e = libc::pthread_attr_get_np(libc::pthread_self(), &mut attr);
#[cfg(not(target_os = "freebsd"))]
let e = libc::pthread_getattr_np(libc::pthread_self(), &mut attr);
if e == 0 {
let mut stackaddr = crate::ptr::null_mut();
let mut stacksize = 0;
assert_eq!(libc::pthread_attr_getstack(&attr, &mut stackaddr, &mut stacksize), 0);
ret = Some(stackaddr);
}
if e == 0 || cfg!(target_os = "freebsd") {
assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
}
ret
}
// Precondition: PAGE_SIZE is initialized.
unsafe fn get_stack_start_aligned() -> Option<*mut libc::c_void> {
let page_size = PAGE_SIZE.load(Ordering::Relaxed);
assert!(page_size != 0);
let stackptr = get_stack_start()?;
let stackaddr = stackptr.addr();
// Ensure stackaddr is page aligned! A parent process might
// have reset RLIMIT_STACK to be non-page aligned. The
// pthread_attr_getstack() reports the usable stack area
// stackaddr < stackaddr + stacksize, so if stackaddr is not
// page-aligned, calculate the fix such that stackaddr <
// new_page_aligned_stackaddr < stackaddr + stacksize
let remainder = stackaddr % page_size;
Some(if remainder == 0 {
stackptr
} else {
stackptr.with_addr(stackaddr + page_size - remainder)
})
}
pub unsafe fn init() -> Option<Guard> {
let page_size = os::page_size();
PAGE_SIZE.store(page_size, Ordering::Relaxed);
if cfg!(all(target_os = "linux", not(target_env = "musl"))) {
// Linux doesn't allocate the whole stack right away, and
// the kernel has its own stack-guard mechanism to fault
// when growing too close to an existing mapping. If we map
// our own guard, then the kernel starts enforcing a rather
// large gap above that, rendering much of the possible
// stack space useless. See #43052.
//
// Instead, we'll just note where we expect rlimit to start
// faulting, so our handler can report "stack overflow", and
// trust that the kernel's own stack guard will work.
let stackptr = get_stack_start_aligned()?;
let stackaddr = stackptr.addr();
Some(stackaddr - page_size..stackaddr)
} else if cfg!(all(target_os = "linux", target_env = "musl")) {
// For the main thread, the musl's pthread_attr_getstack
// returns the current stack size, rather than maximum size
// it can eventually grow to. It cannot be used to determine
// the position of kernel's stack guard.
None
} else if cfg!(target_os = "freebsd") {
// FreeBSD's stack autogrows, and optionally includes a guard page
// at the bottom. If we try to remap the bottom of the stack
// ourselves, FreeBSD's guard page moves upwards. So we'll just use
// the builtin guard page.
let stackptr = get_stack_start_aligned()?;
let guardaddr = stackptr.addr();
// Technically the number of guard pages is tunable and controlled
// by the security.bsd.stack_guard_page sysctl.
// By default it is 1, checking once is enough since it is
// a boot time config value.
static LOCK: crate::sync::OnceLock<usize> = crate::sync::OnceLock::new();
let guard = guardaddr
..guardaddr
+ *LOCK.get_or_init(|| {
use crate::sys::weak::dlsym;
dlsym!(fn sysctlbyname(*const libc::c_char, *mut libc::c_void, *mut libc::size_t, *const libc::c_void, libc::size_t) -> libc::c_int);
let mut guard: usize = 0;
let mut size = crate::mem::size_of_val(&guard);
let oid = crate::ffi::CStr::from_bytes_with_nul(
b"security.bsd.stack_guard_page\0",
)
.unwrap();
match sysctlbyname.get() {
Some(fcn) => {
if fcn(oid.as_ptr(), core::ptr::addr_of_mut!(guard) as *mut _, core::ptr::addr_of_mut!(size) as *mut _, crate::ptr::null_mut(), 0) == 0 {
return guard;
}
return 1;
},
_ => { return 1; }
}
}) * page_size;
Some(guard)
} else if cfg!(target_os = "openbsd") {
// OpenBSD stack already includes a guard page, and stack is
// immutable.
//
// We'll just note where we expect rlimit to start
// faulting, so our handler can report "stack overflow", and
// trust that the kernel's own stack guard will work.
let stackptr = get_stack_start_aligned()?;
let stackaddr = stackptr.addr();
Some(stackaddr - page_size..stackaddr)
} else {
// Reallocate the last page of the stack.
// This ensures SIGBUS will be raised on
// stack overflow.
// Systems which enforce strict PAX MPROTECT do not allow
// to mprotect() a mapping with less restrictive permissions
// than the initial mmap() used, so we mmap() here with
// read/write permissions and only then mprotect() it to
// no permissions at all. See issue #50313.
let stackptr = get_stack_start_aligned()?;
let result = mmap64(
stackptr,
page_size,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANON | MAP_FIXED,
-1,
0,
);
if result != stackptr || result == MAP_FAILED {
panic!("failed to allocate a guard page: {}", io::Error::last_os_error());
}
let result = mprotect(stackptr, page_size, PROT_NONE);
if result != 0 {
panic!("failed to protect the guard page: {}", io::Error::last_os_error());
}
let guardaddr = stackptr.addr();
Some(guardaddr..guardaddr + page_size)
}
}
#[cfg(any(target_os = "macos", target_os = "openbsd", target_os = "solaris"))]
pub unsafe fn current() -> Option<Guard> {
let stackptr = get_stack_start()?;
let stackaddr = stackptr.addr();
Some(stackaddr - PAGE_SIZE.load(Ordering::Relaxed)..stackaddr)
}
#[cfg(any(
target_os = "android",
target_os = "freebsd",
target_os = "hurd",
target_os = "linux",
target_os = "netbsd",
target_os = "l4re"
))]
pub unsafe fn current() -> Option<Guard> {
let mut ret = None;
let mut attr: libc::pthread_attr_t = crate::mem::zeroed();
#[cfg(target_os = "freebsd")]
assert_eq!(libc::pthread_attr_init(&mut attr), 0);
#[cfg(target_os = "freebsd")]
let e = libc::pthread_attr_get_np(libc::pthread_self(), &mut attr);
#[cfg(not(target_os = "freebsd"))]
let e = libc::pthread_getattr_np(libc::pthread_self(), &mut attr);
if e == 0 {
let mut guardsize = 0;
assert_eq!(libc::pthread_attr_getguardsize(&attr, &mut guardsize), 0);
if guardsize == 0 {
if cfg!(all(target_os = "linux", target_env = "musl")) {
// musl versions before 1.1.19 always reported guard
// size obtained from pthread_attr_get_np as zero.
// Use page size as a fallback.
guardsize = PAGE_SIZE.load(Ordering::Relaxed);
} else {
panic!("there is no guard page");
}
}
let mut stackptr = crate::ptr::null_mut::<libc::c_void>();
let mut size = 0;
assert_eq!(libc::pthread_attr_getstack(&attr, &mut stackptr, &mut size), 0);
let stackaddr = stackptr.addr();
ret = if cfg!(any(target_os = "freebsd", target_os = "netbsd", target_os = "hurd")) {
Some(stackaddr - guardsize..stackaddr)