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|
extern crate libc;
use core::ptr;
use Allocator;
/// System setting for Linux
pub struct System {
_priv: (),
}
impl System {
pub const fn new() -> System {
System { _priv: () }
}
}
#[cfg(feature = "global")]
static mut LOCK: libc::pthread_mutex_t = libc::PTHREAD_MUTEX_INITIALIZER;
unsafe impl Allocator for System {
fn alloc(&self, size: usize) -> (*mut u8, usize, u32) {
let addr = unsafe {
libc::mmap(
0 as *mut _,
size,
libc::PROT_WRITE | libc::PROT_READ,
libc::MAP_ANON | libc::MAP_PRIVATE,
-1,
0,
)
};
if addr == libc::MAP_FAILED {
(ptr::null_mut(), 0, 0)
} else {
(addr as *mut u8, size, 0)
}
}
#[cfg(target_os = "linux")]
fn remap(&self, ptr: *mut u8, oldsize: usize, newsize: usize, can_move: bool) -> *mut u8 {
let flags = if can_move { libc::MREMAP_MAYMOVE } else { 0 };
let ptr = unsafe { libc::mremap(ptr as *mut _, oldsize, newsize, flags) };
if ptr == libc::MAP_FAILED {
ptr::null_mut()
} else {
ptr as *mut u8
}
}
#[cfg(target_os = "macos")]
fn remap(&self, _ptr: *mut u8, _oldsize: usize, _newsize: usize, _can_move: bool) -> *mut u8 {
ptr::null_mut()
}
#[cfg(target_os = "linux")]
fn free_part(&self, ptr: *mut u8, oldsize: usize, newsize: usize) -> bool {
unsafe {
let rc = libc::mremap(ptr as *mut _, oldsize, newsize, 0);
if rc != libc::MAP_FAILED {
return true;
}
libc::munmap(ptr.offset(newsize as isize) as *mut _, oldsize - newsize) == 0
}
}
#[cfg(target_os = "macos")]
fn free_part(&self, ptr: *mut u8, oldsize: usize, newsize: usize) -> bool {
unsafe { libc::munmap(ptr.offset(newsize as isize) as *mut _, oldsize - newsize) == 0 }
}
fn free(&self, ptr: *mut u8, size: usize) -> bool {
unsafe { libc::munmap(ptr as *mut _, size) == 0 }
}
fn can_release_part(&self, _flags: u32) -> bool {
true
}
fn allocates_zeros(&self) -> bool {
true
}
fn page_size(&self) -> usize {
4096
}
}
#[cfg(feature = "global")]
pub fn acquire_global_lock() {
unsafe { assert_eq!(libc::pthread_mutex_lock(&mut LOCK), 0) }
}
#[cfg(feature = "global")]
pub fn release_global_lock() {
unsafe { assert_eq!(libc::pthread_mutex_unlock(&mut LOCK), 0) }
}
#[cfg(feature = "global")]
/// allows the allocator to remain unsable in the child process,
/// after a call to `fork(2)`
///
/// #Safety
///
/// if used, this function must be called,
/// before any allocations are made with the global allocator.
pub unsafe fn enable_alloc_after_fork() {
// atfork must only be called once, to avoid a deadlock,
// where the handler attempts to acquire the global lock twice
static mut FORK_PROTECTED: bool = false;
unsafe extern "C" fn _acquire_global_lock() {
acquire_global_lock()
}
unsafe extern "C" fn _release_global_lock() {
release_global_lock()
}
acquire_global_lock();
// if a process forks,
// it will acquire the lock before any other thread,
// protecting it from deadlock,
// due to the child being created with only the calling thread.
if !FORK_PROTECTED {
libc::pthread_atfork(
Some(_acquire_global_lock),
Some(_release_global_lock),
Some(_release_global_lock),
);
FORK_PROTECTED = true;
}
release_global_lock();
}
|
