Commit 0beaf546 authored by Björn Roy Baron's avatar Björn Roy Baron Committed by Miguel Ojeda
Browse files

rust: alloc: Add realloc and alloc_zeroed to the GlobalAlloc impl 

While there are default impls for these methods, using the respective C
api's is faster. Currently neither the existing nor these new
GlobalAlloc method implementations are actually called. Instead the
__rust_* function defined below the GlobalAlloc impl are used. With
rustc 1.71 these functions will be gone and all allocation calls will go
through the GlobalAlloc implementation.

Link: https://github.com/Rust-for-Linux/linux/issues/68


Signed-off-by: default avatarBjörn Roy Baron <bjorn3_gh@protonmail.com>
[boqun: add size adjustment for alignment requirement]
Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Reviewed-by: default avatarAndreas Hindborg <a.hindborg@samsung.com>
Link: https://lore.kernel.org/r/20230730012905.643822-4-boqun.feng@gmail.com


Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent f39a97d0

rust/kernel/allocator.rs

+27 −0
Original line number Diff line number Diff line
@@ -51,6 +51,33 @@ unsafe impl GlobalAlloc for KernelAllocator { 
            bindings::kfree(ptr as *const core::ffi::c_void);

        }

    }



    unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {

        // SAFETY:

        // - `new_size`, when rounded up to the nearest multiple of `layout.align()`, will not

        //   overflow `isize` by the function safety requirement.

        // - `layout.align()` is a proper alignment (i.e. not zero and must be a power of two).

        let layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) };



        // SAFETY:

        // - `ptr` is either null or a pointer allocated by this allocator by the function safety

        //   requirement.

        // - the size of `layout` is not zero because `new_size` is not zero by the function safety

        //   requirement.

        unsafe { krealloc_aligned(ptr, layout, bindings::GFP_KERNEL) }

    }



    unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {

        // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety

        // requirement.

        unsafe {

            krealloc_aligned(

                ptr::null_mut(),

                layout,

                bindings::GFP_KERNEL | bindings::__GFP_ZERO,

            )

        }

    }

}



#[global_allocator]