sgx_alloc/src/lib.rs

// Copyright (C) 2017-2018 Baidu, Inc. All Rights Reserved.
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//! # liballoc crate for Rust SGX SDK
//!
//! This crate equals to the `liballoc_system` crate in Rust.
//! It connects Rust memory allocation to Intel SGX's sgx_tstd library.
//! It is essential, because we depends on Intel SGX's SDK.
//! 2018-06-22 Add liballoc components here

#![no_std]

#![feature(allocator_api)]

extern crate sgx_trts;

use core::alloc::{GlobalAlloc, Alloc, AllocErr, Layout};
use core::ptr::NonNull;

// The minimum alignment guaranteed by the architecture. This value is used to
// add fast paths for low alignment values. In practice, the alignment is a
// constant at the call site and the branch will be optimized out.
#[cfg(target_arch = "x86")]
const MIN_ALIGN: usize = 8;
#[cfg(target_arch = "x86_64")]
const MIN_ALIGN: usize = 16;

pub struct System;

unsafe impl Alloc for System {
    #[inline]
    unsafe fn alloc(&mut self, layout: Layout) -> Result<NonNull<u8>, AllocErr> {
        NonNull::new(GlobalAlloc::alloc(self, layout)).ok_or(AllocErr)
    }

    #[inline]
    unsafe fn alloc_zeroed(&mut self, layout: Layout)
        -> Result<NonNull<u8>, AllocErr>
    {
        NonNull::new(GlobalAlloc::alloc_zeroed(self, layout)).ok_or(AllocErr)
    }

    #[inline]
    unsafe fn dealloc(&mut self, ptr: core::ptr::NonNull<u8>, layout: Layout) {
        GlobalAlloc::dealloc(self, ptr.as_ptr(), layout)
    }

    #[inline]
    unsafe fn realloc(&mut self,
                      ptr: core::ptr::NonNull<u8>,
                      layout: Layout,
                      new_size: usize) -> Result<NonNull<u8>, AllocErr> {
        NonNull::new(GlobalAlloc::realloc(self, ptr.as_ptr(), layout, new_size)).ok_or(AllocErr)
    }
}


mod realloc_fallback {
    use core::alloc::{GlobalAlloc, Layout};
    use core::cmp;
    use core::ptr;

    impl super::System {
        pub(crate) unsafe fn realloc_fallback(&self, ptr: *mut u8, old_layout: Layout,
                                              new_size: usize) -> *mut u8 {
            // Docs for GlobalAlloc::realloc require this to be valid:
            let new_layout = Layout::from_size_align_unchecked(new_size, old_layout.align());

            let new_ptr = GlobalAlloc::alloc(self, new_layout);
            if !new_ptr.is_null() {
                let size = cmp::min(old_layout.size(), new_size);
                ptr::copy_nonoverlapping(ptr, new_ptr, size);
                GlobalAlloc::dealloc(self, ptr, old_layout);
            }
            new_ptr
        }
    }
}

mod platform {

    use sgx_trts::libc::{self, c_void};
    use core::ptr;

    use MIN_ALIGN;
    use System;
    use core::alloc::{GlobalAlloc, Layout};

    unsafe impl GlobalAlloc for System {
        #[inline]
        unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
            if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
                libc::malloc(layout.size()) as *mut u8
            } else {
                aligned_malloc(&layout)
            }
        }

        #[inline]
        unsafe fn alloc_zeroed(&self, layout: Layout)
            -> *mut u8
        {
            if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
                libc::calloc(layout.size(), 1) as *mut u8
            } else {
                let ptr = self.alloc(layout);
                if !ptr.is_null() {
                    ptr::write_bytes(ptr, 0, layout.size());
                }
                ptr
            }
        }

        #[inline]
        unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
            libc::free(ptr as *mut c_void)
        }

        #[inline]
        unsafe fn realloc(&self,
                          ptr: *mut u8,
                          layout: Layout,
                          new_size: usize) -> *mut u8 {
            if layout.align() <= MIN_ALIGN && layout.align() <= new_size {
                libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8
            } else {
                self.realloc_fallback(ptr, layout, new_size)
            }
        }
    }

    #[inline]
    unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 {
        let mut out = ptr::null_mut();
        let ret = libc::posix_memalign(&mut out, layout.align(), layout.size());
        if ret != 0 {
            ptr::null_mut()
        } else {
            out as *mut u8
        }
    }
}