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 `vrealloc()`.
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
rust/helpers.c | 7 +++++++
rust/kernel/alloc/allocator.rs | 32 +++++++++++++++++++++++++++++
rust/kernel/alloc/allocator_test.rs | 1 +
3 files changed, 40 insertions(+)
diff --git a/rust/helpers.c b/rust/helpers.c
index 9f7275493365..7406943f887d 100644
--- a/rust/helpers.c
+++ b/rust/helpers.c
@@ -33,6 +33,7 @@
#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
+#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
@@ -199,6 +200,12 @@ void *rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags)
}
EXPORT_SYMBOL_GPL(rust_helper_krealloc);
+void *rust_helper_vrealloc(const void *p, size_t size, gfp_t flags)
+{
+ return vrealloc(p, size, flags);
+}
+EXPORT_SYMBOL_GPL(rust_helper_vrealloc);
+
/*
* `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can
* use it in contexts where Rust expects a `usize` like slice (array) indices.
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index c6ad1dd59dd0..bb55895cbd03 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -9,6 +9,7 @@
use crate::alloc::{AllocError, Allocator};
use crate::bindings;
+use crate::pr_warn;
/// The contiguous kernel allocator.
///
@@ -16,6 +17,12 @@
/// `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.
@@ -61,6 +68,11 @@ fn krealloc() -> Self {
Self(bindings::krealloc)
}
+ // INVARIANT: `vrealloc` satisfies the type invariants.
+ fn vrealloc() -> Self {
+ Self(bindings::vrealloc)
+ }
+
/// # Safety
///
/// This method has the exact same safety requirements as `Allocator::realloc`.
@@ -141,6 +153,26 @@ unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
}
}
+unsafe impl Allocator for Vmalloc {
+ unsafe fn realloc(
+ ptr: Option<NonNull<u8>>,
+ layout: Layout,
+ flags: Flags,
+ ) -> Result<NonNull<[u8]>, AllocError> {
+ let realloc = ReallocFunc::vrealloc();
+
+ // TODO: Support alignments larger than PAGE_SIZE.
+ if layout.align() > bindings::PAGE_SIZE {
+ pr_warn!("Vmalloc does not support alignments larger than PAGE_SIZE yet.\n");
+ return Err(AllocError);
+ }
+
+ // 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) }
+ }
+}
+
#[global_allocator]
static ALLOCATOR: Kmalloc = Kmalloc;
diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs
index 4785efc474a7..e7bf2982f68f 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(
--
2.45.2On 05.08.24 17:19, Danilo Krummrich wrote:
> 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 `vrealloc()`.
>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
> rust/helpers.c | 7 +++++++
> rust/kernel/alloc/allocator.rs | 32 +++++++++++++++++++++++++++++
> rust/kernel/alloc/allocator_test.rs | 1 +
> 3 files changed, 40 insertions(+)
>
> diff --git a/rust/helpers.c b/rust/helpers.c
> index 9f7275493365..7406943f887d 100644
> --- a/rust/helpers.c
> +++ b/rust/helpers.c
> @@ -33,6 +33,7 @@
> #include <linux/sched/signal.h>
> #include <linux/slab.h>
> #include <linux/spinlock.h>
> +#include <linux/vmalloc.h>
> #include <linux/wait.h>
> #include <linux/workqueue.h>
>
> @@ -199,6 +200,12 @@ void *rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags)
> }
> EXPORT_SYMBOL_GPL(rust_helper_krealloc);
>
> +void *rust_helper_vrealloc(const void *p, size_t size, gfp_t flags)
> +{
> + return vrealloc(p, size, flags);
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_vrealloc);
> +
> /*
> * `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can
> * use it in contexts where Rust expects a `usize` like slice (array) indices.
> diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
> index c6ad1dd59dd0..bb55895cbd03 100644
> --- a/rust/kernel/alloc/allocator.rs
> +++ b/rust/kernel/alloc/allocator.rs
> @@ -9,6 +9,7 @@
>
> use crate::alloc::{AllocError, Allocator};
> use crate::bindings;
> +use crate::pr_warn;
>
> /// The contiguous kernel allocator.
> ///
> @@ -16,6 +17,12 @@
> /// `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;
One thing that I should also have mentioned for `Kmalloc`, do we want
these types to also have values? I don't think that we need them to be,
so we could declare them as `pub enum 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.
> @@ -61,6 +68,11 @@ fn krealloc() -> Self {
> Self(bindings::krealloc)
> }
>
> + // INVARIANT: `vrealloc` satisfies the type invariants.
This should be moved down a line.
---
Cheers,
Benno
> + fn vrealloc() -> Self {
> + Self(bindings::vrealloc)
> + }
> +
> /// # Safety
> ///
> /// This method has the exact same safety requirements as `Allocator::realloc`.
> @@ -141,6 +153,26 @@ unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
> }
> }
>
> +unsafe impl Allocator for Vmalloc {
> + unsafe fn realloc(
> + ptr: Option<NonNull<u8>>,
> + layout: Layout,
> + flags: Flags,
> + ) -> Result<NonNull<[u8]>, AllocError> {
> + let realloc = ReallocFunc::vrealloc();
> +
> + // TODO: Support alignments larger than PAGE_SIZE.
> + if layout.align() > bindings::PAGE_SIZE {
> + pr_warn!("Vmalloc does not support alignments larger than PAGE_SIZE yet.\n");
> + return Err(AllocError);
> + }
> +
> + // 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) }
I am a bit confused, for `Kmalloc`, you manually returned
`NonNull::dangling` when allocating a zero-sized allocation, but here
you don't?
---
Cheers,
Benno
> + }
> +}
> +
> #[global_allocator]
> static ALLOCATOR: Kmalloc = Kmalloc;
>
> diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs
> index 4785efc474a7..e7bf2982f68f 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
>
On Tue, Aug 06, 2024 at 05:00:24PM +0000, Benno Lossin wrote:
> On 05.08.24 17:19, Danilo Krummrich wrote:
> > 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 `vrealloc()`.
> >
> > Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> > Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> > ---
> > rust/helpers.c | 7 +++++++
> > rust/kernel/alloc/allocator.rs | 32 +++++++++++++++++++++++++++++
> > rust/kernel/alloc/allocator_test.rs | 1 +
> > 3 files changed, 40 insertions(+)
> >
> > diff --git a/rust/helpers.c b/rust/helpers.c
> > index 9f7275493365..7406943f887d 100644
> > --- a/rust/helpers.c
> > +++ b/rust/helpers.c
> > @@ -33,6 +33,7 @@
> > #include <linux/sched/signal.h>
> > #include <linux/slab.h>
> > #include <linux/spinlock.h>
> > +#include <linux/vmalloc.h>
> > #include <linux/wait.h>
> > #include <linux/workqueue.h>
> >
> > @@ -199,6 +200,12 @@ void *rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags)
> > }
> > EXPORT_SYMBOL_GPL(rust_helper_krealloc);
> >
> > +void *rust_helper_vrealloc(const void *p, size_t size, gfp_t flags)
> > +{
> > + return vrealloc(p, size, flags);
> > +}
> > +EXPORT_SYMBOL_GPL(rust_helper_vrealloc);
> > +
> > /*
> > * `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can
> > * use it in contexts where Rust expects a `usize` like slice (array) indices.
> > diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
> > index c6ad1dd59dd0..bb55895cbd03 100644
> > --- a/rust/kernel/alloc/allocator.rs
> > +++ b/rust/kernel/alloc/allocator.rs
> > @@ -9,6 +9,7 @@
> >
> > use crate::alloc::{AllocError, Allocator};
> > use crate::bindings;
> > +use crate::pr_warn;
> >
> > /// The contiguous kernel allocator.
> > ///
> > @@ -16,6 +17,12 @@
> > /// `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;
>
> One thing that I should also have mentioned for `Kmalloc`, do we want
> these types to also have values? I don't think that we need them to be,
> so we could declare them as `pub enum Vmalloc {}`.
What the difference? Would `pub enum Vmalloc {}` be better for some reason?
>
> > +
> > /// 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.
> > @@ -61,6 +68,11 @@ fn krealloc() -> Self {
> > Self(bindings::krealloc)
> > }
> >
> > + // INVARIANT: `vrealloc` satisfies the type invariants.
>
> This should be moved down a line.
>
> ---
> Cheers,
> Benno
>
> > + fn vrealloc() -> Self {
> > + Self(bindings::vrealloc)
> > + }
> > +
> > /// # Safety
> > ///
> > /// This method has the exact same safety requirements as `Allocator::realloc`.
> > @@ -141,6 +153,26 @@ unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
> > }
> > }
> >
> > +unsafe impl Allocator for Vmalloc {
> > + unsafe fn realloc(
> > + ptr: Option<NonNull<u8>>,
> > + layout: Layout,
> > + flags: Flags,
> > + ) -> Result<NonNull<[u8]>, AllocError> {
> > + let realloc = ReallocFunc::vrealloc();
> > +
> > + // TODO: Support alignments larger than PAGE_SIZE.
> > + if layout.align() > bindings::PAGE_SIZE {
> > + pr_warn!("Vmalloc does not support alignments larger than PAGE_SIZE yet.\n");
> > + return Err(AllocError);
> > + }
> > +
> > + // 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) }
>
> I am a bit confused, for `Kmalloc`, you manually returned
> `NonNull::dangling` when allocating a zero-sized allocation, but here
> you don't?
>
I do, it's the exact same implementation for krealloc(), vrealloc() and
kvrealloc(). That why I added the `ReallocFunc` abstraction.
> ---
> Cheers,
> Benno
>
> > + }
> > +}
> > +
> > #[global_allocator]
> > static ALLOCATOR: Kmalloc = Kmalloc;
> >
> > diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs
> > index 4785efc474a7..e7bf2982f68f 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
> >
>
On 06.08.24 21:01, Danilo Krummrich wrote:
> On Tue, Aug 06, 2024 at 05:00:24PM +0000, Benno Lossin wrote:
>> On 05.08.24 17:19, Danilo Krummrich wrote:
>>> 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 `vrealloc()`.
>>>
>>> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
>>> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
>>> ---
>>> rust/helpers.c | 7 +++++++
>>> rust/kernel/alloc/allocator.rs | 32 +++++++++++++++++++++++++++++
>>> rust/kernel/alloc/allocator_test.rs | 1 +
>>> 3 files changed, 40 insertions(+)
>>>
>>> diff --git a/rust/helpers.c b/rust/helpers.c
>>> index 9f7275493365..7406943f887d 100644
>>> --- a/rust/helpers.c
>>> +++ b/rust/helpers.c
>>> @@ -33,6 +33,7 @@
>>> #include <linux/sched/signal.h>
>>> #include <linux/slab.h>
>>> #include <linux/spinlock.h>
>>> +#include <linux/vmalloc.h>
>>> #include <linux/wait.h>
>>> #include <linux/workqueue.h>
>>>
>>> @@ -199,6 +200,12 @@ void *rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags)
>>> }
>>> EXPORT_SYMBOL_GPL(rust_helper_krealloc);
>>>
>>> +void *rust_helper_vrealloc(const void *p, size_t size, gfp_t flags)
>>> +{
>>> + return vrealloc(p, size, flags);
>>> +}
>>> +EXPORT_SYMBOL_GPL(rust_helper_vrealloc);
>>> +
>>> /*
>>> * `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can
>>> * use it in contexts where Rust expects a `usize` like slice (array) indices.
>>> diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
>>> index c6ad1dd59dd0..bb55895cbd03 100644
>>> --- a/rust/kernel/alloc/allocator.rs
>>> +++ b/rust/kernel/alloc/allocator.rs
>>> @@ -9,6 +9,7 @@
>>>
>>> use crate::alloc::{AllocError, Allocator};
>>> use crate::bindings;
>>> +use crate::pr_warn;
>>>
>>> /// The contiguous kernel allocator.
>>> ///
>>> @@ -16,6 +17,12 @@
>>> /// `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;
>>
>> One thing that I should also have mentioned for `Kmalloc`, do we want
>> these types to also have values? I don't think that we need them to be,
>> so we could declare them as `pub enum Vmalloc {}`.
>
> What the difference? Would `pub enum Vmalloc {}` be better for some reason?
It doesn't make a huge difference, it doesn't allow you to create a
value of type `Vmalloc` (as there are no values of that type). So
you can't accidentally use the type where it shouldn't be used.
If we use `pub struct Vmalloc;`, then you can do this:
let a = Vmalloc;
you can't really do anything with it (as there are no methods on that
type), but it might be confusing for people.
>>> @@ -141,6 +153,26 @@ unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
>>> }
>>> }
>>>
>>> +unsafe impl Allocator for Vmalloc {
>>> + unsafe fn realloc(
>>> + ptr: Option<NonNull<u8>>,
>>> + layout: Layout,
>>> + flags: Flags,
>>> + ) -> Result<NonNull<[u8]>, AllocError> {
>>> + let realloc = ReallocFunc::vrealloc();
>>> +
>>> + // TODO: Support alignments larger than PAGE_SIZE.
>>> + if layout.align() > bindings::PAGE_SIZE {
>>> + pr_warn!("Vmalloc does not support alignments larger than PAGE_SIZE yet.\n");
>>> + return Err(AllocError);
>>> + }
>>> +
>>> + // 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) }
>>
>> I am a bit confused, for `Kmalloc`, you manually returned
>> `NonNull::dangling` when allocating a zero-sized allocation, but here
>> you don't?
>>
>
> I do, it's the exact same implementation for krealloc(), vrealloc() and
> kvrealloc(). That why I added the `ReallocFunc` abstraction.
Oh yeah, my bad.
---
Cheers
Benno
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