Implement `Allocator` for `Kmalloc`, the kernel's default allocator,
typically used for objects smaller than page size.
All memory allocations made with `Kmalloc` end up in `krealloc()`.
It serves as allocator for the subsequently introduced types `KBox` and
`KVec`.
Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
---
rust/helpers.c | 3 +-
rust/kernel/alloc.rs | 2 +-
rust/kernel/alloc/allocator.rs | 68 +++++++++++++++++++++++++++++++++-
3 files changed, 69 insertions(+), 4 deletions(-)
diff --git a/rust/helpers.c b/rust/helpers.c
index 92d3c03ae1bd..9f7275493365 100644
--- a/rust/helpers.c
+++ b/rust/helpers.c
@@ -193,8 +193,7 @@ void rust_helper_init_work_with_key(struct work_struct *work, work_func_t func,
}
EXPORT_SYMBOL_GPL(rust_helper_init_work_with_key);
-void * __must_check __realloc_size(2)
-rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags)
+void *rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags)
{
return krealloc(objp, new_size, flags);
}
diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
index 8a71a589469d..bc01a17df5e0 100644
--- a/rust/kernel/alloc.rs
+++ b/rust/kernel/alloc.rs
@@ -4,7 +4,7 @@
#[cfg(not(test))]
#[cfg(not(testlib))]
-mod allocator;
+pub mod allocator;
pub mod box_ext;
pub mod vec_ext;
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index 2c1eae25da84..c6ad1dd59dd0 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -5,8 +5,16 @@
use super::{flags::*, Flags};
use core::alloc::{GlobalAlloc, Layout};
use core::ptr;
+use core::ptr::NonNull;
-struct Kmalloc;
+use crate::alloc::{AllocError, Allocator};
+use crate::bindings;
+
+/// The contiguous kernel allocator.
+///
+/// The contiguous kernel allocator only ever allocates physically contiguous memory through
+/// `bindings::krealloc`.
+pub struct Kmalloc;
/// Returns a proper size to alloc a new object aligned to `new_layout`'s alignment.
fn aligned_size(new_layout: Layout) -> usize {
@@ -40,6 +48,64 @@ pub(crate) unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: F
}
}
+/// # Invariants
+///
+/// One of the following `krealloc`, `vrealloc`, `kvrealloc`.
+struct ReallocFunc(
+ unsafe extern "C" fn(*const core::ffi::c_void, usize, u32) -> *mut core::ffi::c_void,
+);
+
+impl ReallocFunc {
+ // INVARIANT: `krealloc` satisfies the type invariants.
+ fn krealloc() -> Self {
+ Self(bindings::krealloc)
+ }
+
+ /// # Safety
+ ///
+ /// This method has the exact same safety requirements as `Allocator::realloc`.
+ unsafe fn call(
+ &self,
+ ptr: Option<NonNull<u8>>,
+ layout: Layout,
+ flags: Flags,
+ ) -> Result<NonNull<[u8]>, AllocError> {
+ let size = aligned_size(layout);
+ let ptr = match ptr {
+ Some(ptr) => ptr.as_ptr(),
+ None => ptr::null(),
+ };
+
+ // SAFETY: `ptr` is valid by the safety requirements of this function.
+ let raw_ptr = unsafe {
+ // If `size == 0` and `ptr != NULL` the memory behind the pointer is freed.
+ self.0(ptr.cast(), size, flags.0).cast()
+ };
+
+ let ptr = if size == 0 {
+ NonNull::dangling()
+ } else {
+ NonNull::new(raw_ptr).ok_or(AllocError)?
+ };
+
+ Ok(NonNull::slice_from_raw_parts(ptr, size))
+ }
+}
+
+unsafe impl Allocator for Kmalloc {
+ unsafe fn realloc(
+ ptr: Option<NonNull<u8>>,
+ layout: Layout,
+ flags: Flags,
+ ) -> Result<NonNull<[u8]>, AllocError> {
+ let realloc = ReallocFunc::krealloc();
+
+ // SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously
+ // allocated with this `Allocator`.
+ unsafe { realloc.call(ptr, layout, flags) }
+ }
+}
+
unsafe impl GlobalAlloc for Kmalloc {
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
// SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
--
2.45.2
