summaryrefslogtreecommitdiffstats
path: root/vendor/rustix/src/runtime.rs
blob: 3c754a62f6a67e3aa203c2b285b9fb8105d943fd (plain)
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
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
//! Experimental low-level implementation details for libc-like runtime
//! libraries such as [Origin].
//!
//! Do not use the functions in this module unless you've read all of their
//! code. They don't always behave the same way as functions with similar names
//! in `libc`. Sometimes information about the differences is included in the
//! Linux documentation under “C library/kernel differences” sections. And, if
//! there is a libc in the process, these functions may have surprising
//! interactions with it.
//!
//! These functions are for implementing thread-local storage (TLS), managing
//! threads, loaded libraries, and other process-wide resources. Most of
//! `rustix` doesn't care about what other libraries are linked into the
//! program or what they're doing, but the features in this module generally
//! can only be used by one entity within a process.
//!
//! The API for these functions is not stable, and this module is
//! `doc(hidden)`.
//!
//! [Origin]: https://github.com/sunfishcode/origin#readme
//!
//! # Safety
//!
//! This module is intended to be used for implementing a runtime library such
//! as libc. Use of these features for any other purpose is likely to create
//! serious problems.
#![allow(unsafe_code)]

use crate::backend;
#[cfg(linux_raw)]
use crate::ffi::CStr;
#[cfg(linux_raw)]
#[cfg(feature = "fs")]
use crate::fs::AtFlags;
#[cfg(linux_raw)]
use crate::io;
#[cfg(linux_raw)]
use crate::pid::Pid;
#[cfg(linux_raw)]
#[cfg(feature = "fs")]
use backend::fd::AsFd;
#[cfg(linux_raw)]
use core::ffi::c_void;

#[cfg(linux_raw)]
pub use crate::signal::Signal;

/// `sigaction`
#[cfg(linux_raw)]
pub type Sigaction = linux_raw_sys::general::kernel_sigaction;

/// `stack_t`
#[cfg(linux_raw)]
pub type Stack = linux_raw_sys::general::stack_t;

/// `sigset_t`
#[cfg(linux_raw)]
pub type Sigset = linux_raw_sys::general::kernel_sigset_t;

/// `siginfo_t`
#[cfg(linux_raw)]
pub type Siginfo = linux_raw_sys::general::siginfo_t;

pub use crate::timespec::{Nsecs, Secs, Timespec};

/// `SIG_*` constants for use with [`sigprocmask`].
#[cfg(linux_raw)]
#[repr(u32)]
pub enum How {
    /// `SIG_BLOCK`
    BLOCK = linux_raw_sys::general::SIG_BLOCK,

    /// `SIG_UNBLOCK`
    UNBLOCK = linux_raw_sys::general::SIG_UNBLOCK,

    /// `SIG_SETMASK`
    SETMASK = linux_raw_sys::general::SIG_SETMASK,
}

#[cfg(target_arch = "x86")]
#[inline]
pub unsafe fn set_thread_area(u_info: &mut UserDesc) -> io::Result<()> {
    backend::runtime::syscalls::tls::set_thread_area(u_info)
}

#[cfg(target_arch = "arm")]
#[inline]
pub unsafe fn arm_set_tls(data: *mut c_void) -> io::Result<()> {
    backend::runtime::syscalls::tls::arm_set_tls(data)
}

/// `prctl(PR_SET_FS, data)`—Set the x86-64 `fs` register.
///
/// # Safety
///
/// This is a very low-level feature for implementing threading libraries.
/// See the references links above.
#[cfg(target_arch = "x86_64")]
#[inline]
pub unsafe fn set_fs(data: *mut c_void) {
    backend::runtime::syscalls::tls::set_fs(data)
}

/// Set the x86-64 thread ID address.
///
/// # Safety
///
/// This is a very low-level feature for implementing threading libraries.
/// See the references links above.
#[inline]
pub unsafe fn set_tid_address(data: *mut c_void) -> Pid {
    backend::runtime::syscalls::tls::set_tid_address(data)
}

/// `prctl(PR_SET_NAME, name)`
///
/// # References
///  - [Linux]
///
/// # Safety
///
/// This is a very low-level feature for implementing threading libraries.
/// See the references links above.
///
/// [Linux]: https://man7.org/linux/man-pages/man2/prctl.2.html
#[inline]
pub unsafe fn set_thread_name(name: &CStr) -> io::Result<()> {
    backend::runtime::syscalls::tls::set_thread_name(name)
}

#[cfg(linux_raw)]
#[cfg(target_arch = "x86")]
pub use backend::runtime::tls::UserDesc;

/// `syscall(SYS_exit, status)`—Exit the current thread.
///
/// # Safety
///
/// This is a very low-level feature for implementing threading libraries.
#[inline]
pub unsafe fn exit_thread(status: i32) -> ! {
    backend::runtime::syscalls::tls::exit_thread(status)
}

/// Exit all the threads in the current process' thread group.
///
/// This is equivalent to `_exit` and `_Exit` in libc.
///
/// This does not call any `__cxa_atexit`, `atexit`, or any other destructors.
/// Most programs should use [`std::process::exit`] instead of calling this
/// directly.
///
/// # References
///  - [POSIX `_Exit`]
///  - [Linux `exit_group`]
///  - [Linux `_Exit`]
///
/// [POSIX `_Exit`]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/_Exit.html
/// [Linux `exit_group`]: https://man7.org/linux/man-pages/man2/exit_group.2.html
/// [Linux `_Exit`]: https://man7.org/linux/man-pages/man2/_Exit.2.html
#[doc(alias = "_exit")]
#[doc(alias = "_Exit")]
#[inline]
pub fn exit_group(status: i32) -> ! {
    backend::runtime::syscalls::exit_group(status)
}

/// `EXIT_SUCCESS` for use with [`exit_group`].
///
/// # References
///  - [POSIX]
///  - [Linux]
///
/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stdlib.h.html
/// [Linux]: https://man7.org/linux/man-pages/man3/exit.3.html
pub const EXIT_SUCCESS: i32 = backend::c::EXIT_SUCCESS;

/// `EXIT_FAILURE` for use with [`exit_group`].
///
/// # References
///  - [POSIX]
///  - [Linux]
///
/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stdlib.h.html
/// [Linux]: https://man7.org/linux/man-pages/man3/exit.3.html
pub const EXIT_FAILURE: i32 = backend::c::EXIT_FAILURE;

/// Return fields from the main executable segment headers ("phdrs") relevant
/// to initializing TLS provided to the program at startup.
///
/// `addr` will always be non-null, even when the TLS data is absent, so that
/// the `addr` and `file_size` parameters are suitable for creating a slice
/// with `slice::from_raw_parts`.
#[inline]
pub fn startup_tls_info() -> StartupTlsInfo {
    backend::runtime::tls::startup_tls_info()
}

/// `(getauxval(AT_PHDR), getauxval(AT_PHENT), getauxval(AT_PHNUM))`—Returns
/// the address, ELF segment header size, and number of ELF segment headers for
/// the main executable.
///
/// # References
///  - [Linux]
///
/// [Linux]: https://man7.org/linux/man-pages/man3/getauxval.3.html
#[inline]
pub fn exe_phdrs() -> (*const c_void, usize, usize) {
    backend::param::auxv::exe_phdrs()
}

/// `getauxval(AT_ENTRY)`—Returns the address of the program entrypoint.
///
/// Most code interested in the program entrypoint address should instead use a
/// symbol reference to `_start`. That will be properly PC-relative or
/// relocated if needed, and will come with appropriate pointer type and
/// pointer provenance.
///
/// This function is intended only for use in code that implements those
/// relocations, to compute the ASLR offset. It has type `usize`, so it doesn't
/// carry any provenance, and it shouldn't be used to dereference memory.
///
/// # References
///  - [Linux]
///
/// [Linux]: https://man7.org/linux/man-pages/man3/getauxval.3.html
#[inline]
pub fn entry() -> usize {
    backend::param::auxv::entry()
}

#[cfg(linux_raw)]
pub use backend::runtime::tls::StartupTlsInfo;

/// `fork()`—Creates a new process by duplicating the calling process.
///
/// On success, the pid of the child process is returned in the parent, and
/// `None` is returned in the child.
///
/// Unlike its POSIX and libc counterparts, this `fork` does not invoke any
/// handlers (such as those registered with `pthread_atfork`).
///
/// The program environment in the child after a `fork` and before an `execve`
/// is very special. All code that executes in this environment must avoid:
///
///  - Acquiring any other locks that are held in other threads on the parent
///    at the time of the `fork`, as the child only contains one thread, and
///    attempting to acquire such locks will deadlock (though this is [not
///    considered unsafe]).
///
///  - Performing any dynamic allocation using the global allocator, since
///    global allocators may use locks to ensure thread safety, and their locks
///    may not be released in the child process, so attempts to allocate may
///    deadlock (as described in the previous point).
///
///  - Accessing any external state which the parent assumes it has exclusive
///    access to, such as a file protected by a file lock, as this could
///    corrupt the external state.
///
///  - Accessing any random-number-generator state inherited from the parent,
///    as the parent may have the same state and generate the same random
///    numbers, which may violate security invariants.
///
///  - Accessing any thread runtime state, since this function does not update
///    the thread id in the thread runtime, so thread runtime functions could
///    cause undefined behavior.
///
///  - Accessing any memory shared with the parent, such as a [`MAP_SHARED`]
///    mapping, even with anonymous or [`memfd_create`] mappings, as this could
///    cause undefined behavior.
///
///  - Calling any C function which isn't known to be [async-signal-safe], as
///    that could cause undefined behavior. The extent to which this also
///    applies to Rust functions is unclear at this time.
///
///  - And more.
///
/// # Safety
///
/// The child must avoid accessing any memory shared with the parent in a
/// way that invokes undefined behavior. It must avoid accessing any threading
/// runtime functions in a way that invokes undefined behavior. And it must
/// avoid invoking any undefined behavior through any function that is not
/// guaranteed to be async-signal-safe. But, what does async-signal-safe even
/// mean in a Rust program? This documentation does not have all the answers.
///
/// So you're on your own. And on top of all the troubles with `fork` in
/// general, this wrapper implementation is highly experimental.
///
/// # References
///  - [POSIX]
///  - [Linux]
///
/// # Literary interlude
///
/// > Do not jump on ancient uncles.
/// > Do not yell at average mice.
/// > Do not wear a broom to breakfast.
/// > Do not ask a snake’s advice.
/// > Do not bathe in chocolate pudding.
/// > Do not talk to bearded bears.
/// > Do not smoke cigars on sofas.
/// > Do not dance on velvet chairs.
/// > Do not take a whale to visit
/// > Russell’s mother’s cousin’s yacht.
/// > And whatever else you do do
/// > It is better you
/// > Do not.
///
/// - “Rules”, by Karla Kuskin
///
/// [`MAP_SHARED`]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/mmap.html
/// [not considered unsafe]: https://doc.rust-lang.org/reference/behavior-not-considered-unsafe.html#deadlocks
/// [`memfd_create`]: https://man7.org/linux/man-pages/man2/memfd_create.2.html
/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/fork.html
/// [Linux]: https://man7.org/linux/man-pages/man2/fork.2.html
/// [async-signal-safe]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04_03
pub unsafe fn fork() -> io::Result<Option<Pid>> {
    backend::runtime::syscalls::fork()
}

/// `execveat(dirfd, path.as_c_str(), argv, envp, flags)`—Execute a new
/// command using the current process.
///
/// # Safety
///
/// The `argv` and `envp` pointers must point to NUL-terminated arrays, and
/// their contents must be pointers to NUL-terminated byte arrays.
///
/// # References
///  - [Linux]
///
/// [Linux]: https://man7.org/linux/man-pages/man2/execveat.2.html
#[inline]
#[cfg(feature = "fs")]
#[cfg_attr(doc_cfg, doc(cfg(feature = "fs")))]
pub unsafe fn execveat<Fd: AsFd>(
    dirfd: Fd,
    path: &CStr,
    argv: *const *const u8,
    envp: *const *const u8,
    flags: AtFlags,
) -> io::Errno {
    backend::runtime::syscalls::execveat(dirfd.as_fd(), path, argv, envp, flags)
}

/// `execve(path.as_c_str(), argv, envp)`—Execute a new command using the
/// current process.
///
/// # Safety
///
/// The `argv` and `envp` pointers must point to NUL-terminated arrays, and
/// their contents must be pointers to NUL-terminated byte arrays.
///
/// # References
///  - [Linux]
///
/// [Linux]: https://man7.org/linux/man-pages/man2/execve.2.html
#[inline]
pub unsafe fn execve(path: &CStr, argv: *const *const u8, envp: *const *const u8) -> io::Errno {
    backend::runtime::syscalls::execve(path, argv, envp)
}

/// `sigaction(signal, &new, &old)`—Modify or query a signal handler.
///
/// # Safety
///
/// You're on your own. And on top of all the troubles with signal handlers,
/// this implementation is highly experimental. Even further, it differs from
/// the libc `sigaction` in several non-obvious and unsafe ways.
///
/// # References
///  - [POSIX]
///  - [Linux]
///
/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigaction.html
/// [Linux]: https://man7.org/linux/man-pages/man2/sigaction.2.html
#[inline]
pub unsafe fn sigaction(signal: Signal, new: Option<Sigaction>) -> io::Result<Sigaction> {
    backend::runtime::syscalls::sigaction(signal, new)
}

/// `sigaltstack(new, old)`—Modify or query a signal stack.
///
/// # Safety
///
/// You're on your own. And on top of all the troubles with signal handlers,
/// this implementation is highly experimental.
///
/// # References
///  - [POSIX]
///  - [Linux]
///
/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigaltstack.html
/// [Linux]: https://man7.org/linux/man-pages/man2/sigaltstack.2.html
#[inline]
pub unsafe fn sigaltstack(new: Option<Stack>) -> io::Result<Stack> {
    backend::runtime::syscalls::sigaltstack(new)
}

/// `tkill(tid, sig)`—Send a signal to a thread.
///
/// # Safety
///
/// You're on your own. And on top of all the troubles with signal handlers,
/// this implementation is highly experimental. The warning about the hazard
/// of recycled thread ID's applies.
///
/// # References
///  - [Linux]
///
/// [Linux]: https://man7.org/linux/man-pages/man2/tkill.2.html
#[inline]
pub unsafe fn tkill(tid: Pid, sig: Signal) -> io::Result<()> {
    backend::runtime::syscalls::tkill(tid, sig)
}

/// `sigprocmask(how, set, oldset)`—Adjust the process signal mask.
///
/// # Safety
///
/// You're on your own. And on top of all the troubles with signal handlers,
/// this implementation is highly experimental. Even further, it differs from
/// the libc `sigprocmask` in several non-obvious and unsafe ways.
///
/// # References
///  - [Linux `sigprocmask`]
///  - [Linux `pthread_sigmask`]
///
/// [Linux `sigprocmask`]: https://man7.org/linux/man-pages/man2/sigprocmask.2.html
/// [Linux `pthread_sigmask`]: https://man7.org/linux/man-pages/man3/pthread_sigmask.3.html
#[inline]
#[doc(alias = "pthread_sigmask")]
pub unsafe fn sigprocmask(how: How, set: Option<&Sigset>) -> io::Result<Sigset> {
    backend::runtime::syscalls::sigprocmask(how, set)
}

/// `sigwait(set)`—Wait for signals.
///
/// # Safety
///
/// If code elsewhere in the process is depending on delivery of a signal to
/// prevent it from executing some code, this could cause it to miss that
/// signal and execute that code.
///
/// # References
///  - [Linux]
///
/// [Linux]: https://man7.org/linux/man-pages/man3/sigwait.3.html
#[inline]
pub unsafe fn sigwait(set: &Sigset) -> io::Result<Signal> {
    backend::runtime::syscalls::sigwait(set)
}

/// `sigwait(set)`—Wait for signals, returning a [`Siginfo`].
///
/// # Safety
///
/// If code elsewhere in the process is depending on delivery of a signal to
/// prevent it from executing some code, this could cause it to miss that
/// signal and execute that code.
///
/// # References
///  - [Linux]
///
/// [Linux]: https://man7.org/linux/man-pages/man2/sigwaitinfo.2.html
#[inline]
pub unsafe fn sigwaitinfo(set: &Sigset) -> io::Result<Siginfo> {
    backend::runtime::syscalls::sigwaitinfo(set)
}

/// `sigtimedwait(set)`—Wait for signals, optionally with a timeout.
///
/// # Safety
///
/// If code elsewhere in the process is depending on delivery of a signal to
/// prevent it from executing some code, this could cause it to miss that
/// signal and execute that code.
///
/// # References
///  - [Linux]
///
/// [Linux]: https://man7.org/linux/man-pages/man2/sigtimedwait.2.html
#[inline]
pub unsafe fn sigtimedwait(set: &Sigset, timeout: Option<Timespec>) -> io::Result<Siginfo> {
    backend::runtime::syscalls::sigtimedwait(set, timeout)
}

/// `getauxval(AT_SECURE)`—Returns the Linux “secure execution” mode.
///
/// Return a boolean value indicating whether “secure execution” mode was
/// requested, due to the process having elevated privileges. This includes
/// whether the `AT_SECURE` AUX value is set, and whether the initial real UID
/// and GID differ from the initial effective UID and GID.
///
/// The meaning of “secure execution” mode is beyond the scope of this comment.
///
/// # References
///  - [Linux]
///
/// [Linux]: https://man7.org/linux/man-pages/man3/getauxval.3.html
#[cfg(any(
    linux_raw,
    any(
        all(target_os = "android", target_pointer_width = "64"),
        target_os = "linux",
    )
))]
#[inline]
pub fn linux_secure() -> bool {
    backend::param::auxv::linux_secure()
}

/// `brk(addr)`—Change the location of the “program break”.
///
/// # Safety
///
/// This is not identical to `brk` in libc. libc `brk` may have bookkeeping
/// that needs to be kept up to date that this doesn't keep up to date, so
/// don't use it unless you are implementing libc.
#[cfg(linux_raw)]
#[inline]
pub unsafe fn brk(addr: *mut c_void) -> io::Result<*mut c_void> {
    backend::runtime::syscalls::brk(addr)
}