80 lines
2.1 KiB
Rust
80 lines
2.1 KiB
Rust
// This file is part of libfringe, a low-level green threading library.
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// Copyright (c) edef <edef@edef.eu>
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// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
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// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
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// http://opensource.org/licenses/MIT>, at your option. This file may not be
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// copied, modified, or distributed except according to those terms.
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extern crate std;
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use self::std::io::Error as IoError;
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use stack::{Stack, GuardedStack};
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mod sys;
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/// OsStack holds a guarded stack allocated using the operating system's anonymous
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/// memory mapping facility.
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#[derive(Debug)]
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pub struct OsStack {
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ptr: *mut u8,
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len: usize,
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}
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unsafe impl Send for OsStack {}
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impl OsStack {
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/// Allocates a new stack with at least `size` accessible bytes.
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/// `size` is rounded up to an integral number of pages; `OsStack::new(0)` is legal
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/// and allocates the smallest possible stack, consisting of one data page and
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/// one guard page.
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pub fn new(size: usize) -> Result<OsStack, IoError> {
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let page_size = sys::page_size();
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// Stacks have to be at least one page long.
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let len = if size == 0 { page_size } else { size };
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// Round the length one page size up, using the fact that the page size
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// is a power of two.
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let len = (len + page_size - 1) & !(page_size - 1);
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// Increase the length to fit the guard page.
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let len = len + page_size;
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// Allocate a stack.
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let ptr = try!(unsafe { sys::map_stack(len) });
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let stack = OsStack {
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ptr: ptr,
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len: len,
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};
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// Mark the guard page. If this fails, `stack` will be dropped,
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// unmapping it.
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try!(unsafe { sys::protect_stack(stack.ptr) });
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Ok(stack)
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}
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}
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unsafe impl Stack for OsStack {
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#[inline(always)]
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fn base(&self) -> *mut u8 {
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unsafe {
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self.ptr.offset(self.len as isize)
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}
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}
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#[inline(always)]
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fn limit(&self) -> *mut u8 {
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unsafe {
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self.ptr.offset(sys::page_size() as isize)
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}
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}
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}
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unsafe impl GuardedStack for OsStack {}
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impl Drop for OsStack {
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fn drop(&mut self) {
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unsafe { sys::unmap_stack(self.ptr, self.len) }.expect("cannot unmap stack")
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}
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}
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