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.
Reviewed-by: Benno Lossin <benno.lossin@xxxxxxxxx>
Reviewed-by: Gary Guo <gary@xxxxxxxxxxx>
Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
---
rust/kernel/alloc/allocator_test.rs | 88 ++++++++++++++++++++++++++---
1 file changed, 81 insertions(+), 7 deletions(-)
diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs
index 1b2642c547ec..47c2b509898e 100644
--- a/rust/kernel/alloc/allocator_test.rs
+++ b/rust/kernel/alloc/allocator_test.rs
@@ -1,21 +1,95 @@
// 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::{AllocError, Allocator, Flags};
+use super::{flags::*, AllocError, Allocator, Flags};
use core::alloc::Layout;
+use core::cmp;
+use core::ptr;
use core::ptr::NonNull;
-pub struct Kmalloc;
+/// The userspace allocator based on libc.
+pub struct Cmalloc;
+
+pub type Kmalloc = Cmalloc;
pub type Vmalloc = Kmalloc;
pub type KVmalloc = Kmalloc;
-unsafe impl Allocator for 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,
- _flags: Flags,
+ ptr: Option<NonNull<u8>>,
+ layout: Layout,
+ old_layout: Layout,
+ flags: Flags,
) -> Result<NonNull<[u8]>, AllocError> {
- panic!();
+ 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 preceeding 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()))
}
}
--
2.46.1
