Auto merge of #3957 - YohDeadfall:macos-thread-name, r=RalfJung

Fixed get/set thread name implementations for macOS and FreeBSD

So, the story of fixing `pthread_getname_np` and `pthread_setname_np` continues, but this time I fixed the macOS implementation.

### [`pthread_getname_np`](https://github.com/apple-oss-distributions/libpthread/blob/c032e0b076700a0a47db75528a282b8d3a06531a/src/pthread.c#L1160-L1175)

The function never fails except for an invalid thread. Miri never verifies thread identifiers and uses them as indices when accessing a vector of threads. Therefore, the only possible result is `0` and a possibly trimmed output.

```c
int
pthread_getname_np(pthread_t thread, char *threadname, size_t len)
{
	if (thread == pthread_self()) {
		strlcpy(threadname, thread->pthread_name, len);
		return 0;
	}

	if (!_pthread_validate_thread_and_list_lock(thread)) {
		return ESRCH;
	}

	strlcpy(threadname, thread->pthread_name, len);
	_pthread_lock_unlock(&_pthread_list_lock);
	return 0;
}
```

#### [`strcpy`](https://www.man7.org/linux/man-pages/man7/strlcpy.7.html)

```
strlcpy(3bsd)
strlcat(3bsd)
      Copy and catenate the input string into a destination
      string.  If the destination buffer, limited by its size,
      isn't large enough to hold the copy, the resulting string
      is truncated (but it is guaranteed to be null-terminated).
      They return the length of the total string they tried to
      create.
```

### [`pthread_setname_np`](https://github.com/apple-oss-distributions/libpthread/blob/c032e0b076700a0a47db75528a282b8d3a06531a/src/pthread.c#L1178-L1200)

```c
pthread_setname_np(const char *name)
{
	int res;
	pthread_t self = pthread_self();

	size_t len = 0;
	if (name != NULL) {
		len = strlen(name);
	}

	_pthread_validate_signature(self);

	res = __proc_info(5, getpid(), 2, (uint64_t)0, (void*)name, (int)len);
	if (res == 0) {
		if (len > 0) {
			strlcpy(self->pthread_name, name, MAXTHREADNAMESIZE);
		} else {
			bzero(self->pthread_name, MAXTHREADNAMESIZE);
		}
	}
	return res;

}
```

Where `5` is [`PROC_INFO_CALL_SETCONTROL`](https://github.com/apple-oss-distributions/xnu/blob/8d741a5de7ff4191bf97d57b9f54c2f6d4a15585/bsd/sys/proc_info_private.h#L274), and `2` is [`PROC_INFO_CALL_SETCONTROL`](https://github.com/apple-oss-distributions/xnu/blob/8d741a5de7ff4191bf97d57b9f54c2f6d4a15585/bsd/sys/proc_info.h#L821). And `__proc_info` is a syscall handled by the XNU kernel by [`proc_info_internal`](https://github.com/apple-oss-distributions/xnu/blob/8d741a5de7ff4191bf97d57b9f54c2f6d4a15585/bsd/kern/proc_info.c#L300-L314):

```c
int
proc_info_internal(int callnum, int pid, uint32_t flags, uint64_t ext_id, int flavor, uint64_t arg, user_addr_t buffer, uint32_t  buffersize, int32_t * retval)
{
	switch (callnum) {
	// ...
	case PROC_INFO_CALL_SETCONTROL:
		return proc_setcontrol(pid, flavor, arg, buffer, buffersize, retval);
```

And the actual logic from [`proc_setcontrol`](https://github.com/apple-oss-distributions/xnu/blob/8d741a5de7ff4191bf97d57b9f54c2f6d4a15585/bsd/kern/proc_info.c#L3218-L3227):
```c
	case PROC_SELFSET_THREADNAME: {
		/*
		 * This is a bit ugly, as it copies the name into the kernel, and then
		 * invokes bsd_setthreadname again to copy it into the uthread name
		 * buffer.  Hopefully this isn't such a hot codepath that an additional
		 * MAXTHREADNAMESIZE copy is a big issue.
		 */
		if (buffersize > (MAXTHREADNAMESIZE - 1)) {
			return ENAMETOOLONG;
		}
```

Unrelated to the current pull request, but perhaps, there's a very ugly thing in the kernel/libc because the last thing happening in `PROC_SELFSET_THREADNAME` is `bsd_setthreadname` which sets the name in the user space. But we just saw that `pthread_setname_np` sets the name in the user space too. Guess, I need to open a ticket in one of Apple's repositories at least to clarify that :D

0 files changed, 0 insertions, 0 deletions