[PATCH v2] rust: generalize userSliceReader to support any Vec

Filipe Xavier
2025-01-07T19:25:55Z

The UserSliceReader::read_all function is currently restricted to use
only Vec with the kmalloc allocator.
However, there is no reason for this limitation.
This patch generalizes the function to accept any Vec regardless of the
allocator used.
There's a use-case for a KVVec in Binder to avoid maximum
sizes for a certain array.

Link: https://github.com/Rust-for-Linux/linux/issues/1136
Signed-off-by: Filipe Xavier <felipeaggger@gmail.com>
---
Changes in v2:
- Commit description: added use case on description and send to memorymanagment on copy.
- Link to v1: https://lore.kernel.org/r/20241222-gen-userslice-readall-alloc-v1-1-c57b7d4972f0@gmail.com
---
rust/kernel/uaccess.rs | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/rust/kernel/uaccess.rs b/rust/kernel/uaccess.rs
index cc044924867b89f6116c7f9ec216d8cea2b3f8d7..719b0a48ff5550acc19f2e607c0a09f818145def 100644
--- a/rust/kernel/uaccess.rs
+++ b/rust/kernel/uaccess.rs
@@ -5,7 +5,7 @@
//! C header: [`include/linux/uaccess.h`](srctree/include/linux/uaccess.h)

use crate::{
- alloc::Flags,
+ alloc::{Allocator, Flags},
bindings,
error::Result,
ffi::c_void,
@@ -127,7 +127,7 @@ pub fn new(ptr: UserPtr, length: usize) -> Self {
/// Reads the entirety of the user slice, appending it to the end of the provided buffer.
///
/// Fails with [`EFAULT`] if the read happens on a bad address.
- pub fn read_all(self, buf: &mut KVec<u8>, flags: Flags) -> Result {
+ pub fn read_all<A: Allocator>(self, buf: &mut Vec<u8, A>, flags: Flags) -> Result {
self.reader().read_all(buf, flags)
}

@@ -281,7 +281,7 @@ pub fn read<T: FromBytes>(&mut self) -> Result<T> {
/// Reads the entirety of the user slice, appending it to the end of the provided buffer.
///
/// Fails with [`EFAULT`] if the read happens on a bad address.
- pub fn read_all(mut self, buf: &mut KVec<u8>, flags: Flags) -> Result {
+ pub fn read_all<A: Allocator>(mut self, buf: &mut Vec<u8, A>, flags: Flags) -> Result {
let len = self.length;
buf.reserve(len, flags)?;

---
base-commit: 0c5928deada15a8d075516e6e0d9ee19011bb000
change-id: 20241222-gen-userslice-readall-alloc-8049c668e65e

Best regards,
--
Filipe Xavier <felipeaggger@gmail.com>