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// SPDX-License-Identifier: GPL-2.0
//! So far the kernel's `Box` and `Vec` types can't be used by userspace test cases, since all users
//! of those types (e.g. `CString`) use kernel allocators for instantiation.
//!
//! In order to allow userspace test cases to make use of such types as well, implement the
//! `Cmalloc` allocator within the allocator_test module and type alias all kernel allocators to
//! `Cmalloc`. The `Cmalloc` allocator uses libc's `realloc()` function as allocator backend.
#![allow(missing_docs)]
use super::{flags::*, AllocError, Allocator, Flags};
use core::alloc::Layout;
use core::cmp;
use core::ptr;
use core::ptr::NonNull;
/// The userspace allocator based on libc.
pub struct Cmalloc;
pub type Kmalloc = Cmalloc;
pub type Vmalloc = Kmalloc;
pub type KVmalloc = Kmalloc;
extern "C" {
#[link_name = "aligned_alloc"]
fn libc_aligned_alloc(align: usize, size: usize) -> *mut core::ffi::c_void;
#[link_name = "free"]
fn libc_free(ptr: *mut core::ffi::c_void);
}
// SAFETY:
// - memory remains valid until it is explicitly freed,
// - passing a pointer to a valid memory allocation created by this `Allocator` is always OK,
// - `realloc` provides the guarantees as provided in the `# Guarantees` section.
unsafe impl Allocator for Cmalloc {
unsafe fn realloc(
ptr: Option<NonNull<u8>>,
layout: Layout,
old_layout: Layout,
flags: Flags,
) -> Result<NonNull<[u8]>, AllocError> {
let src = match ptr {
Some(src) => {
if old_layout.size() == 0 {
ptr::null_mut()
} else {
src.as_ptr()
}
}
None => ptr::null_mut(),
};
if layout.size() == 0 {
// SAFETY: `src` is either NULL or was previously allocated with this `Allocator`
unsafe { libc_free(src.cast()) };
return Ok(NonNull::slice_from_raw_parts(
crate::alloc::dangling_from_layout(layout),
0,
));
}
// SAFETY: Returns either NULL or a pointer to a memory allocation that satisfies or
// exceeds the given size and alignment requirements.
let dst = unsafe { libc_aligned_alloc(layout.align(), layout.size()) } as *mut u8;
let dst = NonNull::new(dst).ok_or(AllocError)?;
if flags.contains(__GFP_ZERO) {
// SAFETY: The preceding calls to `libc_aligned_alloc` and `NonNull::new`
// guarantee that `dst` points to memory of at least `layout.size()` bytes.
unsafe { dst.as_ptr().write_bytes(0, layout.size()) };
}
if !src.is_null() {
// SAFETY:
// - `src` has previously been allocated with this `Allocator`; `dst` has just been
// newly allocated, hence the memory regions do not overlap.
// - both` src` and `dst` are properly aligned and valid for reads and writes
unsafe {
ptr::copy_nonoverlapping(
src,
dst.as_ptr(),
cmp::min(layout.size(), old_layout.size()),
)
};
}
// SAFETY: `src` is either NULL or was previously allocated with this `Allocator`
unsafe { libc_free(src.cast()) };
Ok(NonNull::slice_from_raw_parts(dst, layout.size()))
}
}
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