1 // SPDX-License-Identifier: GPL-2.0 2 3 //! Implementation of the kernel's memory allocation infrastructure. 4 5 #[cfg(not(any(test, testlib)))] 6 pub mod allocator; 7 pub mod kbox; 8 pub mod kvec; 9 pub mod layout; 10 11 #[cfg(any(test, testlib))] 12 pub mod allocator_test; 13 14 #[cfg(any(test, testlib))] 15 pub use self::allocator_test as allocator; 16 17 pub use self::kbox::Box; 18 pub use self::kbox::KBox; 19 pub use self::kbox::KVBox; 20 pub use self::kbox::VBox; 21 22 pub use self::kvec::IntoIter; 23 pub use self::kvec::KVVec; 24 pub use self::kvec::KVec; 25 pub use self::kvec::VVec; 26 pub use self::kvec::Vec; 27 28 /// Indicates an allocation error. 29 #[derive(Copy, Clone, PartialEq, Eq, Debug)] 30 pub struct AllocError; 31 32 use crate::error::{code::EINVAL, Result}; 33 use core::{alloc::Layout, ptr::NonNull}; 34 35 /// Flags to be used when allocating memory. 36 /// 37 /// They can be combined with the operators `|`, `&`, and `!`. 38 /// 39 /// Values can be used from the [`flags`] module. 40 #[derive(Clone, Copy, PartialEq)] 41 pub struct Flags(u32); 42 43 impl Flags { 44 /// Get the raw representation of this flag. 45 pub(crate) fn as_raw(self) -> u32 { 46 self.0 47 } 48 49 /// Check whether `flags` is contained in `self`. 50 pub fn contains(self, flags: Flags) -> bool { 51 (self & flags) == flags 52 } 53 } 54 55 impl core::ops::BitOr for Flags { 56 type Output = Self; 57 fn bitor(self, rhs: Self) -> Self::Output { 58 Self(self.0 | rhs.0) 59 } 60 } 61 62 impl core::ops::BitAnd for Flags { 63 type Output = Self; 64 fn bitand(self, rhs: Self) -> Self::Output { 65 Self(self.0 & rhs.0) 66 } 67 } 68 69 impl core::ops::Not for Flags { 70 type Output = Self; 71 fn not(self) -> Self::Output { 72 Self(!self.0) 73 } 74 } 75 76 /// Allocation flags. 77 /// 78 /// These are meant to be used in functions that can allocate memory. 79 pub mod flags { 80 use super::Flags; 81 82 /// Zeroes out the allocated memory. 83 /// 84 /// This is normally or'd with other flags. 85 pub const __GFP_ZERO: Flags = Flags(bindings::__GFP_ZERO); 86 87 /// Allow the allocation to be in high memory. 88 /// 89 /// Allocations in high memory may not be mapped into the kernel's address space, so this can't 90 /// be used with `kmalloc` and other similar methods. 91 /// 92 /// This is normally or'd with other flags. 93 pub const __GFP_HIGHMEM: Flags = Flags(bindings::__GFP_HIGHMEM); 94 95 /// Users can not sleep and need the allocation to succeed. 96 /// 97 /// A lower watermark is applied to allow access to "atomic reserves". The current 98 /// implementation doesn't support NMI and few other strict non-preemptive contexts (e.g. 99 /// `raw_spin_lock`). The same applies to [`GFP_NOWAIT`]. 100 pub const GFP_ATOMIC: Flags = Flags(bindings::GFP_ATOMIC); 101 102 /// Typical for kernel-internal allocations. The caller requires `ZONE_NORMAL` or a lower zone 103 /// for direct access but can direct reclaim. 104 pub const GFP_KERNEL: Flags = Flags(bindings::GFP_KERNEL); 105 106 /// The same as [`GFP_KERNEL`], except the allocation is accounted to kmemcg. 107 pub const GFP_KERNEL_ACCOUNT: Flags = Flags(bindings::GFP_KERNEL_ACCOUNT); 108 109 /// For kernel allocations that should not stall for direct reclaim, start physical IO or 110 /// use any filesystem callback. It is very likely to fail to allocate memory, even for very 111 /// small allocations. 112 pub const GFP_NOWAIT: Flags = Flags(bindings::GFP_NOWAIT); 113 114 /// Suppresses allocation failure reports. 115 /// 116 /// This is normally or'd with other flags. 117 pub const __GFP_NOWARN: Flags = Flags(bindings::__GFP_NOWARN); 118 } 119 120 /// Non Uniform Memory Access (NUMA) node identifier. 121 #[derive(Clone, Copy, PartialEq)] 122 pub struct NumaNode(i32); 123 124 impl NumaNode { 125 /// Create a new NUMA node identifier (non-negative integer). 126 /// 127 /// Returns [`EINVAL`] if a negative id or an id exceeding [`bindings::MAX_NUMNODES`] is 128 /// specified. 129 pub fn new(node: i32) -> Result<Self> { 130 // MAX_NUMNODES never exceeds 2**10 because NODES_SHIFT is 0..10. 131 if node < 0 || node >= bindings::MAX_NUMNODES as i32 { 132 return Err(EINVAL); 133 } 134 Ok(Self(node)) 135 } 136 } 137 138 /// Specify necessary constant to pass the information to Allocator that the caller doesn't care 139 /// about the NUMA node to allocate memory from. 140 impl NumaNode { 141 /// No node preference. 142 pub const NO_NODE: NumaNode = NumaNode(bindings::NUMA_NO_NODE); 143 } 144 145 /// The kernel's [`Allocator`] trait. 146 /// 147 /// An implementation of [`Allocator`] can allocate, re-allocate and free memory buffers described 148 /// via [`Layout`]. 149 /// 150 /// [`Allocator`] is designed to be implemented as a ZST; [`Allocator`] functions do not operate on 151 /// an object instance. 152 /// 153 /// In order to be able to support `#[derive(CoercePointee)]` later on, we need to avoid a design 154 /// that requires an `Allocator` to be instantiated, hence its functions must not contain any kind 155 /// of `self` parameter. 156 /// 157 /// # Safety 158 /// 159 /// - A memory allocation returned from an allocator must remain valid until it is explicitly freed. 160 /// 161 /// - Any pointer to a valid memory allocation must be valid to be passed to any other [`Allocator`] 162 /// function of the same type. 163 /// 164 /// - Implementers must ensure that all trait functions abide by the guarantees documented in the 165 /// `# Guarantees` sections. 166 pub unsafe trait Allocator { 167 /// Allocate memory based on `layout`, `flags` and `nid`. 168 /// 169 /// On success, returns a buffer represented as `NonNull<[u8]>` that satisfies the layout 170 /// constraints (i.e. minimum size and alignment as specified by `layout`). 171 /// 172 /// This function is equivalent to `realloc` when called with `None`. 173 /// 174 /// # Guarantees 175 /// 176 /// When the return value is `Ok(ptr)`, then `ptr` is 177 /// - valid for reads and writes for `layout.size()` bytes, until it is passed to 178 /// [`Allocator::free`] or [`Allocator::realloc`], 179 /// - aligned to `layout.align()`, 180 /// 181 /// Additionally, `Flags` are honored as documented in 182 /// <https://docs.kernel.org/core-api/mm-api.html#mm-api-gfp-flags>. 183 fn alloc(layout: Layout, flags: Flags, nid: NumaNode) -> Result<NonNull<[u8]>, AllocError> { 184 // SAFETY: Passing `None` to `realloc` is valid by its safety requirements and asks for a 185 // new memory allocation. 186 unsafe { Self::realloc(None, layout, Layout::new::<()>(), flags, nid) } 187 } 188 189 /// Re-allocate an existing memory allocation to satisfy the requested `layout` and 190 /// a specific NUMA node request to allocate the memory for. 191 /// 192 /// Systems employing a Non Uniform Memory Access (NUMA) architecture contain collections of 193 /// hardware resources including processors, memory, and I/O buses, that comprise what is 194 /// commonly known as a NUMA node. 195 /// 196 /// `nid` stands for NUMA id, i. e. NUMA node identifier, which is a non-negative integer 197 /// if a node needs to be specified, or [`NumaNode::NO_NODE`] if the caller doesn't care. 198 /// 199 /// If the requested size is zero, `realloc` behaves equivalent to `free`. 200 /// 201 /// If the requested size is larger than the size of the existing allocation, a successful call 202 /// to `realloc` guarantees that the new or grown buffer has at least `Layout::size` bytes, but 203 /// may also be larger. 204 /// 205 /// If the requested size is smaller than the size of the existing allocation, `realloc` may or 206 /// may not shrink the buffer; this is implementation specific to the allocator. 207 /// 208 /// On allocation failure, the existing buffer, if any, remains valid. 209 /// 210 /// The buffer is represented as `NonNull<[u8]>`. 211 /// 212 /// # Safety 213 /// 214 /// - If `ptr == Some(p)`, then `p` must point to an existing and valid memory allocation 215 /// created by this [`Allocator`]; if `old_layout` is zero-sized `p` does not need to be a 216 /// pointer returned by this [`Allocator`]. 217 /// - `ptr` is allowed to be `None`; in this case a new memory allocation is created and 218 /// `old_layout` is ignored. 219 /// - `old_layout` must match the `Layout` the allocation has been created with. 220 /// 221 /// # Guarantees 222 /// 223 /// This function has the same guarantees as [`Allocator::alloc`]. When `ptr == Some(p)`, then 224 /// it additionally guarantees that: 225 /// - the contents of the memory pointed to by `p` are preserved up to the lesser of the new 226 /// and old size, i.e. `ret_ptr[0..min(layout.size(), old_layout.size())] == 227 /// p[0..min(layout.size(), old_layout.size())]`. 228 /// - when the return value is `Err(AllocError)`, then `ptr` is still valid. 229 unsafe fn realloc( 230 ptr: Option<NonNull<u8>>, 231 layout: Layout, 232 old_layout: Layout, 233 flags: Flags, 234 nid: NumaNode, 235 ) -> Result<NonNull<[u8]>, AllocError>; 236 237 /// Free an existing memory allocation. 238 /// 239 /// # Safety 240 /// 241 /// - `ptr` must point to an existing and valid memory allocation created by this [`Allocator`]; 242 /// if `old_layout` is zero-sized `p` does not need to be a pointer returned by this 243 /// [`Allocator`]. 244 /// - `layout` must match the `Layout` the allocation has been created with. 245 /// - The memory allocation at `ptr` must never again be read from or written to. 246 unsafe fn free(ptr: NonNull<u8>, layout: Layout) { 247 // SAFETY: The caller guarantees that `ptr` points at a valid allocation created by this 248 // allocator. We are passing a `Layout` with the smallest possible alignment, so it is 249 // smaller than or equal to the alignment previously used with this allocation. 250 let _ = unsafe { 251 Self::realloc( 252 Some(ptr), 253 Layout::new::<()>(), 254 layout, 255 Flags(0), 256 NumaNode::NO_NODE, 257 ) 258 }; 259 } 260 } 261 262 /// Returns a properly aligned dangling pointer from the given `layout`. 263 pub(crate) fn dangling_from_layout(layout: Layout) -> NonNull<u8> { 264 let ptr = layout.align() as *mut u8; 265 266 // SAFETY: `layout.align()` (and hence `ptr`) is guaranteed to be non-zero. 267 unsafe { NonNull::new_unchecked(ptr) } 268 } 269