From 47ac2a4b5cd8f0cb826f6368c2fc0eeb97e5d55f Mon Sep 17 00:00:00 2001 From: Shivam Kalra Date: Mon, 16 Feb 2026 19:39:55 +0530 Subject: rust: kvec: implement shrink_to for KVVec Implement shrink_to method specifically for `KVVec` (i.e., `Vec`). `shrink_to` reduces the vector's capacity to a specified minimum. For kmalloc-backed allocations, the method delegates to realloc(), letting the allocator decide whether shrinking is worthwhile. For vmalloc-backed allocations (detected via is_vmalloc_addr), shrinking only occurs if at least one page of memory can be freed, using an explicit alloc+copy+free since vrealloc does not yet support in-place shrinking. A TODO note marks this for future replacement with a generic shrink_to for all allocators that uses A::realloc() once the underlying allocators properly support shrinking via realloc. Suggested-by: Alice Ryhl Suggested-by: Danilo Krummrich Reviewed-by: Alice Ryhl Acked-by: Danilo Krummrich Signed-off-by: Shivam Kalra Link: https://patch.msgid.link/20260216-binder-shrink-vec-v3-v6-1-ece8e8593e53@zohomail.in Signed-off-by: Greg Kroah-Hartman --- rust/kernel/alloc/kvec.rs | 114 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 113 insertions(+), 1 deletion(-) (limited to 'rust/kernel') diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs index ac8d6f763ae8..e7bc439538e4 100644 --- a/rust/kernel/alloc/kvec.rs +++ b/rust/kernel/alloc/kvec.rs @@ -9,7 +9,10 @@ use super::{ }; use crate::{ fmt, - page::AsPageIter, // + page::{ + AsPageIter, + PAGE_SIZE, // + }, }; use core::{ borrow::{Borrow, BorrowMut}, @@ -734,6 +737,115 @@ where self.truncate(num_kept); } } +// TODO: This is a temporary KVVec-specific implementation. It should be replaced with a generic +// `shrink_to()` for `impl Vec` that uses `A::realloc()` once the +// underlying allocators properly support shrinking via realloc. +impl Vec { + /// Shrinks the capacity of the vector with a lower bound. + /// + /// The capacity will remain at least as large as both the length and the supplied value. + /// If the current capacity is less than the lower limit, this is a no-op. + /// + /// For `kmalloc` allocations, this delegates to `realloc()`, which decides whether + /// shrinking is worthwhile. For `vmalloc` allocations, shrinking only occurs if the + /// operation would free at least one page of memory, and performs a deep copy since + /// `vrealloc` does not yet support in-place shrinking. + /// + /// # Examples + /// + /// ``` + /// // Allocate enough capacity to span multiple pages. + /// let elements_per_page = kernel::page::PAGE_SIZE / core::mem::size_of::(); + /// let mut v = KVVec::with_capacity(elements_per_page * 4, GFP_KERNEL)?; + /// v.push(1, GFP_KERNEL)?; + /// v.push(2, GFP_KERNEL)?; + /// + /// v.shrink_to(0, GFP_KERNEL)?; + /// # Ok::<(), Error>(()) + /// ``` + pub fn shrink_to(&mut self, min_capacity: usize, flags: Flags) -> Result<(), AllocError> { + let target_cap = core::cmp::max(self.len(), min_capacity); + + if self.capacity() <= target_cap { + return Ok(()); + } + + if Self::is_zst() { + return Ok(()); + } + + // For kmalloc allocations, delegate to realloc() and let the allocator decide + // whether shrinking is worthwhile. + // + // SAFETY: `self.ptr` points to a valid `KVmalloc` allocation. + if !unsafe { bindings::is_vmalloc_addr(self.ptr.as_ptr().cast()) } { + let new_layout = ArrayLayout::::new(target_cap).map_err(|_| AllocError)?; + + // SAFETY: + // - `self.ptr` is valid and was previously allocated with `KVmalloc`. + // - `self.layout` matches the `ArrayLayout` of the preceding allocation. + let ptr = unsafe { + KVmalloc::realloc( + Some(self.ptr.cast()), + new_layout.into(), + self.layout.into(), + flags, + NumaNode::NO_NODE, + )? + }; + + self.ptr = ptr.cast(); + self.layout = new_layout; + return Ok(()); + } + + // Only shrink if we would free at least one page. + let current_size = self.capacity() * core::mem::size_of::(); + let target_size = target_cap * core::mem::size_of::(); + let current_pages = current_size.div_ceil(PAGE_SIZE); + let target_pages = target_size.div_ceil(PAGE_SIZE); + + if current_pages <= target_pages { + return Ok(()); + } + + if target_cap == 0 { + if !self.layout.is_empty() { + // SAFETY: + // - `self.ptr` was previously allocated with `KVmalloc`. + // - `self.layout` matches the `ArrayLayout` of the preceding allocation. + unsafe { KVmalloc::free(self.ptr.cast(), self.layout.into()) }; + } + self.ptr = NonNull::dangling(); + self.layout = ArrayLayout::empty(); + return Ok(()); + } + + // SAFETY: `target_cap <= self.capacity()` and original capacity was valid. + let new_layout = unsafe { ArrayLayout::::new_unchecked(target_cap) }; + + let new_ptr = KVmalloc::alloc(new_layout.into(), flags, NumaNode::NO_NODE)?; + + // SAFETY: + // - `self.as_ptr()` is valid for reads of `self.len()` elements of `T`. + // - `new_ptr` is valid for writes of at least `target_cap >= self.len()` elements. + // - The two allocations do not overlap since `new_ptr` is freshly allocated. + // - Both pointers are properly aligned for `T`. + unsafe { + ptr::copy_nonoverlapping(self.as_ptr(), new_ptr.as_ptr().cast::(), self.len()) + }; + + // SAFETY: + // - `self.ptr` was previously allocated with `KVmalloc`. + // - `self.layout` matches the `ArrayLayout` of the preceding allocation. + unsafe { KVmalloc::free(self.ptr.cast(), self.layout.into()) }; + + self.ptr = new_ptr.cast::(); + self.layout = new_layout; + + Ok(()) + } +} impl Vec { /// Extend the vector by `n` clones of `value`. -- cgit v1.2.3 From fbfc0d615368ddf71899dbea2205e741c79b23e8 Mon Sep 17 00:00:00 2001 From: Shivam Kalra Date: Mon, 16 Feb 2026 19:39:56 +0530 Subject: rust: alloc: add KUnit tests for KVVec shrink_to Add comprehensive KUnit tests for the shrink_to method for KVVec. The tests verify: - Basic shrinking from multiple pages to fewer pages with data integrity preservation - Empty vector shrinking to zero capacity - No-op behavior when shrinking to a larger capacity than current - Respect for min_capacity parameter when larger than vector length These tests ensure that the shrinking logic correctly identifies when memory can be reclaimed (by freeing at least one page) and that data integrity is maintained throughout shrink operations. Reviewed-by: Alice Ryhl Acked-by: Danilo Krummrich Signed-off-by: Shivam Kalra Link: https://patch.msgid.link/20260216-binder-shrink-vec-v3-v6-2-ece8e8593e53@zohomail.in Signed-off-by: Greg Kroah-Hartman --- rust/kernel/alloc/kvec.rs | 102 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 102 insertions(+) (limited to 'rust/kernel') diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs index e7bc439538e4..6438385e4322 100644 --- a/rust/kernel/alloc/kvec.rs +++ b/rust/kernel/alloc/kvec.rs @@ -1510,4 +1510,106 @@ mod tests { func.push_within_capacity(false).unwrap(); } } + + #[test] + fn test_kvvec_shrink_to() { + use crate::page::PAGE_SIZE; + + // Create a vector with capacity spanning multiple pages. + let mut v = KVVec::::with_capacity(PAGE_SIZE * 4, GFP_KERNEL).unwrap(); + + // Add a few elements. + v.push(1, GFP_KERNEL).unwrap(); + v.push(2, GFP_KERNEL).unwrap(); + v.push(3, GFP_KERNEL).unwrap(); + + let initial_capacity = v.capacity(); + assert!(initial_capacity >= PAGE_SIZE * 4); + + // Shrink to a capacity that would free at least one page. + v.shrink_to(PAGE_SIZE, GFP_KERNEL).unwrap(); + + // Capacity should have been reduced. + assert!(v.capacity() < initial_capacity); + assert!(v.capacity() >= PAGE_SIZE); + + // Elements should be preserved. + assert_eq!(v.len(), 3); + assert_eq!(v[0], 1); + assert_eq!(v[1], 2); + assert_eq!(v[2], 3); + + // Shrink to zero (should shrink to len). + v.shrink_to(0, GFP_KERNEL).unwrap(); + + // Capacity should be at least the length. + assert!(v.capacity() >= v.len()); + + // Elements should still be preserved. + assert_eq!(v.len(), 3); + assert_eq!(v[0], 1); + assert_eq!(v[1], 2); + assert_eq!(v[2], 3); + } + + #[test] + fn test_kvvec_shrink_to_empty() { + use crate::page::PAGE_SIZE; + + // Create a vector with large capacity but no elements. + let mut v = KVVec::::with_capacity(PAGE_SIZE * 4, GFP_KERNEL).unwrap(); + + assert!(v.is_empty()); + + // Shrink empty vector to zero. + v.shrink_to(0, GFP_KERNEL).unwrap(); + + // Should have freed the allocation. + assert_eq!(v.capacity(), 0); + assert!(v.is_empty()); + } + + #[test] + fn test_kvvec_shrink_to_no_op() { + use crate::page::PAGE_SIZE; + + // Create a small vector. + let mut v = KVVec::::with_capacity(PAGE_SIZE, GFP_KERNEL).unwrap(); + v.push(1, GFP_KERNEL).unwrap(); + + let capacity_before = v.capacity(); + + // Try to shrink to a capacity larger than current - should be no-op. + v.shrink_to(capacity_before + 100, GFP_KERNEL).unwrap(); + + assert_eq!(v.capacity(), capacity_before); + assert_eq!(v.len(), 1); + assert_eq!(v[0], 1); + } + + #[test] + fn test_kvvec_shrink_to_respects_min_capacity() { + use crate::page::PAGE_SIZE; + + // Create a vector with large capacity. + let mut v = KVVec::::with_capacity(PAGE_SIZE * 4, GFP_KERNEL).unwrap(); + + // Add some elements. + for i in 0..10u8 { + v.push(i, GFP_KERNEL).unwrap(); + } + + // Shrink to a min_capacity larger than length. + let min_cap = PAGE_SIZE * 2; + v.shrink_to(min_cap, GFP_KERNEL).unwrap(); + + // Capacity should be at least min_capacity. + assert!(v.capacity() >= min_cap); + + // All elements preserved. + assert_eq!(v.len(), 10); + for i in 0..10u8 { + assert_eq!(v[i as usize], i); + } + } } -- cgit v1.2.3 From 5326a18e3e640061ca4b65c1b732feaeace61c39 Mon Sep 17 00:00:00 2001 From: Alice Ryhl Date: Fri, 6 Mar 2026 11:28:46 +0000 Subject: rust_binder: introduce TransactionInfo Rust Binder exposes information about transactions that are sent in various ways: printing to the kernel log, tracepoints, files in binderfs, and the upcoming netlink support. Currently all these mechanisms use disparate ways of obtaining the same information, so let's introduce a single Info struct that collects all the required information in a single place, so that all of these different mechanisms can operate in a more uniform way. For now, the new info struct is only used to replace a few things: * The BinderTransactionDataSg struct that is passed as an argument to several methods is removed as the information is moved into the new info struct and passed down that way. * The oneway spam detection fields on Transaction and Allocation can be removed, as the information can be returned to the caller via the mutable info struct instead. But several other uses of the info struct are planned in follow-up patches. Signed-off-by: Alice Ryhl Link: https://patch.msgid.link/20260306-transaction-info-v1-1-fda58fca558b@google.com Signed-off-by: Greg Kroah-Hartman --- rust/kernel/uaccess.rs | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'rust/kernel') diff --git a/rust/kernel/uaccess.rs b/rust/kernel/uaccess.rs index f989539a31b4..984c3ec03a7b 100644 --- a/rust/kernel/uaccess.rs +++ b/rust/kernel/uaccess.rs @@ -19,7 +19,7 @@ use core::mem::{size_of, MaybeUninit}; /// /// This is the Rust equivalent to C pointers tagged with `__user`. #[repr(transparent)] -#[derive(Copy, Clone)] +#[derive(Copy, Clone, Zeroable)] pub struct UserPtr(*mut c_void); impl UserPtr { -- cgit v1.2.3 From 18e9fafb2672cb976edfe51e899484c2ea892170 Mon Sep 17 00:00:00 2001 From: Alice Ryhl Date: Tue, 24 Mar 2026 20:02:35 +0000 Subject: rust: sync: implement == operator for ARef Rust Binder wants to perform a comparison between ARef and &Task, so define the == operator for ARef<_> when compared with another ARef<_> or just a reference. The operator is implemented in terms of the same operator applied to the inner type. Note that PartialEq cannot be implemented because it would overlap with the impl for ARef. Reviewed-by: Gary Guo Signed-off-by: Alice Ryhl Link: https://patch.msgid.link/20260324-close-fd-check-current-v3-1-b94274bedac7@google.com Signed-off-by: Greg Kroah-Hartman --- rust/kernel/sync/aref.rs | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'rust/kernel') diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs index 0616c0353c2b..9989f56d0605 100644 --- a/rust/kernel/sync/aref.rs +++ b/rust/kernel/sync/aref.rs @@ -170,3 +170,25 @@ impl Drop for ARef { unsafe { T::dec_ref(self.ptr) }; } } + +impl PartialEq> for ARef +where + T: AlwaysRefCounted + PartialEq, + U: AlwaysRefCounted, +{ + #[inline] + fn eq(&self, other: &ARef) -> bool { + T::eq(&**self, &**other) + } +} +impl Eq for ARef {} + +impl PartialEq<&'_ U> for ARef +where + T: AlwaysRefCounted + PartialEq, +{ + #[inline] + fn eq(&self, other: &&U) -> bool { + T::eq(&**self, other) + } +} -- cgit v1.2.3 From 12c688086f091c24e62504f5a26c009a6a8dd8bc Mon Sep 17 00:00:00 2001 From: Alice Ryhl Date: Tue, 24 Mar 2026 20:02:36 +0000 Subject: rust: task: implement == operator for Task It's useful to compare if two tasks are the same task or not. Rust Binder wants this to check if a certain task is equal to the group leader of current. Reviewed-by: Gary Guo Signed-off-by: Alice Ryhl Link: https://patch.msgid.link/20260324-close-fd-check-current-v3-2-b94274bedac7@google.com Signed-off-by: Greg Kroah-Hartman --- rust/kernel/task.rs | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'rust/kernel') diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs index cc907fb531bc..deb948d99921 100644 --- a/rust/kernel/task.rs +++ b/rust/kernel/task.rs @@ -362,6 +362,15 @@ unsafe impl crate::sync::aref::AlwaysRefCounted for Task { } } +impl PartialEq for Task { + #[inline] + fn eq(&self, other: &Self) -> bool { + ptr::eq(self.as_ptr(), other.as_ptr()) + } +} + +impl Eq for Task {} + impl Kuid { /// Get the current euid. #[inline] -- cgit v1.2.3