1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
use crate::cmp;
use crate::ffi::CStr;
use crate::io;
use crate::mem;
use crate::ptr;
use crate::sys::{os, stack_overflow};
use crate::time::Duration;

#[cfg(not(target_os = "l4re"))]
pub const DEFAULT_MIN_STACK_SIZE: usize = 2 * 1024 * 1024;
#[cfg(target_os = "l4re")]
pub const DEFAULT_MIN_STACK_SIZE: usize = 1024 * 1024;

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 {}

// The pthread_attr_setstacksize symbol doesn't exist in the emscripten libc,
// so we have to not link to it to satisfy emcc's ERROR_ON_UNDEFINED_SYMBOLS.
#[cfg(not(target_os = "emscripten"))]
unsafe fn pthread_attr_setstacksize(
    attr: *mut libc::pthread_attr_t,
    stack_size: libc::size_t,
) -> libc::c_int {
    libc::pthread_attr_setstacksize(attr, stack_size)
}

#[cfg(target_os = "emscripten")]
unsafe fn pthread_attr_setstacksize(
    _attr: *mut libc::pthread_attr_t,
    _stack_size: libc::size_t,
) -> libc::c_int {
    panic!()
}

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 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);

        let stack_size = cmp::max(stack, min_stack_size(&attr));

        match 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(any(target_os = "linux", target_os = "android"))]
    pub fn set_name(name: &CStr) {
        const PR_SET_NAME: libc::c_int = 15;
        // pthread wrapper only appeared in glibc 2.12, so we use syscall
        // directly.
        unsafe {
            libc::prctl(PR_SET_NAME, name.as_ptr() as libc::c_ulong, 0, 0, 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"))]
    pub fn set_name(name: &CStr) {
        unsafe {
            libc::pthread_setname_np(name.as_ptr());
        }
    }

    #[cfg(target_os = "netbsd")]
    pub fn set_name(name: &CStr) {
        use crate::ffi::CString;
        let cname = CString::new(&b"%s"[..]).unwrap();
        unsafe {
            libc::pthread_setname_np(
                libc::pthread_self(),
                cname.as_ptr(),
                name.as_ptr() as *mut libc::c_void,
            );
        }
    }

    #[cfg(any(target_os = "solaris", target_os = "illumos"))]
    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() {
            unsafe {
                f(libc::pthread_self(), name.as_ptr());
            }
        }
    }

    #[cfg(any(
        target_env = "newlib",
        target_os = "haiku",
        target_os = "l4re",
        target_os = "emscripten",
        target_os = "redox"
    ))]
    pub fn set_name(_name: &CStr) {
        // Newlib, Haiku, and Emscripten have no way to set a thread name.
    }
    #[cfg(target_os = "fuchsia")]
    pub fn set_name(_name: &CStr) {
        // FIXME: determine whether Fuchsia has a way to set a thread name.
    }

    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;
                if libc::nanosleep(&ts, &mut ts) == -1 {
                    assert_eq!(os::errno(), libc::EINTR);
                    secs += ts.tv_sec as u64;
                    nsecs = ts.tv_nsec;
                } else {
                    nsecs = 0;
                }
            }
        }
    }

    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(all(
    not(all(target_os = "linux", not(target_env = "musl"))),
    not(target_os = "freebsd"),
    not(target_os = "macos"),
    not(all(target_os = "netbsd", not(target_vendor = "rumprun"))),
    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(
    all(target_os = "linux", not(target_env = "musl")),
    target_os = "freebsd",
    target_os = "macos",
    all(target_os = "netbsd", not(target_vendor = "rumprun")),
    target_os = "openbsd",
    target_os = "solaris"
))]
#[cfg_attr(test, allow(dead_code))]
pub mod guard {
    use libc::{mmap, mprotect};
    use libc::{MAP_ANON, MAP_FAILED, MAP_FIXED, MAP_PRIVATE, PROT_NONE, PROT_READ, PROT_WRITE};

    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 stackaddr =
            libc::pthread_get_stackaddr_np(th) as usize - libc::pthread_get_stacksize_np(th);
        Some(stackaddr as *mut libc::c_void)
    }

    #[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 stackaddr = if libc::pthread_main_np() == 1 {
            // main thread
            current_stack.ss_sp as usize - current_stack.ss_size + PAGE_SIZE.load(Ordering::Relaxed)
        } else {
            // new thread
            current_stack.ss_sp as usize - current_stack.ss_size
        };
        Some(stackaddr as *mut libc::c_void)
    }

    #[cfg(any(
        target_os = "android",
        target_os = "freebsd",
        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();
        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);
        }
        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 stackaddr = get_stack_start()?;

        // 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 as usize) % page_size;
        Some(if remainder == 0 {
            stackaddr
        } else {
            ((stackaddr as usize) + page_size - remainder) as *mut libc::c_void
        })
    }

    pub unsafe fn init() -> Option<Guard> {
        let page_size = os::page_size();
        PAGE_SIZE.store(page_size, Ordering::Relaxed);

        let stackaddr = get_stack_start_aligned()?;

        if cfg!(target_os = "linux") {
            // 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 stackaddr = stackaddr as usize;
            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 result = mmap(
                stackaddr,
                page_size,
                PROT_READ | PROT_WRITE,
                MAP_PRIVATE | MAP_ANON | MAP_FIXED,
                -1,
                0,
            );
            if result != stackaddr || result == MAP_FAILED {
                panic!("failed to allocate a guard page");
            }

            let result = mprotect(stackaddr, page_size, PROT_NONE);
            if result != 0 {
                panic!("failed to protect the guard page");
            }

            let guardaddr = stackaddr as usize;
            let offset = if cfg!(target_os = "freebsd") { 2 } else { 1 };

            Some(guardaddr..guardaddr + offset * page_size)
        }
    }

    #[cfg(any(target_os = "macos", target_os = "openbsd", target_os = "solaris"))]
    pub unsafe fn current() -> Option<Guard> {
        let stackaddr = get_stack_start()? as usize;
        Some(stackaddr - PAGE_SIZE.load(Ordering::Relaxed)..stackaddr)
    }

    #[cfg(any(
        target_os = "android",
        target_os = "freebsd",
        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();
        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 {
                panic!("there is no guard page");
            }
            let mut stackaddr = crate::ptr::null_mut();
            let mut size = 0;
            assert_eq!(libc::pthread_attr_getstack(&attr, &mut stackaddr, &mut size), 0);

            let stackaddr = stackaddr as usize;
            ret = if cfg!(target_os = "freebsd") {
                // FIXME does freebsd really fault *below* the guard addr?
                let guardaddr = stackaddr - guardsize;
                Some(guardaddr - PAGE_SIZE.load(Ordering::Relaxed)..guardaddr)
            } else if cfg!(target_os = "netbsd") {
                Some(stackaddr - guardsize..stackaddr)
            } else if cfg!(all(target_os = "linux", target_env = "gnu")) {
                // glibc used to include the guard area within the stack, as noted in the BUGS
                // section of `man pthread_attr_getguardsize`.  This has been corrected starting
                // with glibc 2.27, and in some distro backports, so the guard is now placed at the
                // end (below) the stack.  There's no easy way for us to know which we have at
                // runtime, so we'll just match any fault in the range right above or below the
                // stack base to call that fault a stack overflow.
                Some(stackaddr - guardsize..stackaddr + guardsize)
            } else {
                Some(stackaddr..stackaddr + guardsize)
            };
        }
        assert_eq!(libc::pthread_attr_destroy(&mut attr), 0);
        ret
    }
}

// glibc >= 2.15 has a __pthread_get_minstack() function that returns
// PTHREAD_STACK_MIN plus bytes needed for thread-local storage.
// We need that information to avoid blowing up when a small stack
// is created in an application with big thread-local storage requirements.
// See #6233 for rationale and details.
#[cfg(target_os = "linux")]
#[allow(deprecated)]
fn min_stack_size(attr: *const libc::pthread_attr_t) -> usize {
    weak!(fn __pthread_get_minstack(*const libc::pthread_attr_t) -> libc::size_t);

    match __pthread_get_minstack.get() {
        None => libc::PTHREAD_STACK_MIN,
        Some(f) => unsafe { f(attr) },
    }
}

// No point in looking up __pthread_get_minstack() on non-glibc
// platforms.
#[cfg(all(not(target_os = "linux"), not(target_os = "netbsd")))]
fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
    libc::PTHREAD_STACK_MIN
}

#[cfg(target_os = "netbsd")]
fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
    2048 // just a guess
}