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Message-ID: <20240704170738.3621-8-dakr@redhat.com>
Date: Thu, 4 Jul 2024 19:06:35 +0200
From: Danilo Krummrich <dakr@...hat.com>
To: ojeda@...nel.org,
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Danilo Krummrich <dakr@...hat.com>
Subject: [PATCH 07/20] rust: alloc: implement `Vmalloc` allocator
Implement `Allocator` for `Vmalloc`, the kernel's virtually contiguous
allocator, typically used for larger objects, (much) larger than page
size.
All memory allocations made with `Vmalloc` end up in
`__vmalloc_noprof()`; all frees in `vfree()`.
Signed-off-by: Danilo Krummrich <dakr@...hat.com>
---
rust/bindings/bindings_helper.h | 1 +
rust/kernel/alloc/allocator.rs | 55 +++++++++++++++++++++++++++++
rust/kernel/alloc/allocator_test.rs | 1 +
3 files changed, 57 insertions(+)
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index ddb5644d4fd9..f10518045c16 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -15,6 +15,7 @@
#include <linux/refcount.h>
#include <linux/sched.h>
#include <linux/slab.h>
+#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index 1860cb79b875..0a4f27c5c3a6 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -16,6 +16,12 @@
/// `bindings::krealloc`.
pub struct Kmalloc;
+/// The virtually contiguous kernel allocator.
+///
+/// The vmalloc allocator allocates pages from the page level allocator and maps them into the
+/// contiguous kernel virtual space.
+pub struct Vmalloc;
+
/// Returns a proper size to alloc a new object aligned to `new_layout`'s alignment.
fn aligned_size(new_layout: Layout) -> usize {
// Customized layouts from `Layout::from_size_align()` can have size < align, so pad first.
@@ -112,6 +118,55 @@ unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
}
}
+unsafe impl Allocator for Vmalloc {
+ unsafe fn realloc(
+ &self,
+ src: *mut u8,
+ old_size: usize,
+ layout: Layout,
+ flags: Flags,
+ ) -> Result<NonNull<[u8]>, AllocError> {
+ let mut size = aligned_size(layout);
+
+ let dst = if size == 0 {
+ // SAFETY: `src` is guaranteed to be previously allocated with this `Allocator` or NULL.
+ unsafe { bindings::vfree(src.cast()) };
+ NonNull::dangling()
+ } else if size <= old_size {
+ size = old_size;
+ NonNull::new(src).ok_or(AllocError)?
+ } else {
+ // SAFETY: `src` is guaranteed to point to valid memory with a size of at least
+ // `old_size`, which was previously allocated with this `Allocator` or NULL.
+ let dst = unsafe { bindings::__vmalloc_noprof(size as u64, flags.0) };
+
+ // Validate that we actually allocated the requested memory.
+ let dst = NonNull::new(dst.cast()).ok_or(AllocError)?;
+
+ if !src.is_null() {
+ // SAFETY: `src` is guaranteed to point to valid memory with a size of at least
+ // `old_size`; `dst` is guaranteed to point to valid memory with a size of at least
+ // `size`.
+ unsafe {
+ core::ptr::copy_nonoverlapping(
+ src,
+ dst.as_ptr(),
+ core::cmp::min(old_size, size),
+ )
+ };
+
+ // SAFETY: `src` is guaranteed to be previously allocated with this `Allocator` or
+ // NULL.
+ unsafe { bindings::vfree(src.cast()) }
+ }
+
+ dst
+ };
+
+ Ok(NonNull::slice_from_raw_parts(dst, size))
+ }
+}
+
#[global_allocator]
static ALLOCATOR: Kmalloc = Kmalloc;
diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs
index 3a0abe65491d..b2d7db492ba6 100644
--- a/rust/kernel/alloc/allocator_test.rs
+++ b/rust/kernel/alloc/allocator_test.rs
@@ -7,6 +7,7 @@
use core::ptr::NonNull;
pub struct Kmalloc;
+pub type Vmalloc = Kmalloc;
unsafe impl Allocator for Kmalloc {
unsafe fn realloc(
--
2.45.2
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