1 // SPDX-License-Identifier: GPL-2.0 2 3 //! Implementation of the kernel's memory allocation infrastructure. 4 5 pub mod allocator; 6 pub mod kbox; 7 pub mod kvec; 8 pub mod layout; 9 10 pub use self::kbox::Box; 11 pub use self::kbox::KBox; 12 pub use self::kbox::KVBox; 13 pub use self::kbox::VBox; 14 15 pub use self::kvec::IntoIter; 16 pub use self::kvec::KVVec; 17 pub use self::kvec::KVec; 18 pub use self::kvec::VVec; 19 pub use self::kvec::Vec; 20 21 /// Indicates an allocation error. 22 #[derive(Copy, Clone, PartialEq, Eq, Debug)] 23 pub struct AllocError; 24 25 use crate::prelude::*; 26 27 use core::{ 28 alloc::Layout, 29 ptr::NonNull, // 30 }; 31 32 /// Flags to be used when allocating memory. 33 /// 34 /// They can be combined with the operators `|`, `&`, and `!`. 35 /// 36 /// Values can be used from the [`flags`] module. 37 #[derive(Clone, Copy, PartialEq)] 38 pub struct Flags(u32); 39 40 impl Flags { 41 /// Get the raw representation of this flag. 42 pub(crate) fn as_raw(self) -> u32 { 43 self.0 44 } 45 46 /// Check whether `flags` is contained in `self`. 47 pub fn contains(self, flags: Flags) -> bool { 48 (self & flags) == flags 49 } 50 } 51 52 impl core::ops::BitOr for Flags { 53 type Output = Self; 54 fn bitor(self, rhs: Self) -> Self::Output { 55 Self(self.0 | rhs.0) 56 } 57 } 58 59 impl core::ops::BitAnd for Flags { 60 type Output = Self; 61 fn bitand(self, rhs: Self) -> Self::Output { 62 Self(self.0 & rhs.0) 63 } 64 } 65 66 impl core::ops::Not for Flags { 67 type Output = Self; 68 fn not(self) -> Self::Output { 69 Self(!self.0) 70 } 71 } 72 73 /// Allocation flags. 74 /// 75 /// These are meant to be used in functions that can allocate memory. 76 pub mod flags { 77 use super::Flags; 78 79 /// Zeroes out the allocated memory. 80 /// 81 /// This is normally or'd with other flags. 82 pub const __GFP_ZERO: Flags = Flags(bindings::__GFP_ZERO); 83 84 /// Allow the allocation to be in high memory. 85 /// 86 /// Allocations in high memory may not be mapped into the kernel's address space, so this can't 87 /// be used with `kmalloc` and other similar methods. 88 /// 89 /// This is normally or'd with other flags. 90 pub const __GFP_HIGHMEM: Flags = Flags(bindings::__GFP_HIGHMEM); 91 92 /// Users can not sleep and need the allocation to succeed. 93 /// 94 /// A lower watermark is applied to allow access to "atomic reserves". The current 95 /// implementation doesn't support NMI and few other strict non-preemptive contexts (e.g. 96 /// `raw_spin_lock`). The same applies to [`GFP_NOWAIT`]. 97 pub const GFP_ATOMIC: Flags = Flags(bindings::GFP_ATOMIC); 98 99 /// Typical for kernel-internal allocations. The caller requires `ZONE_NORMAL` or a lower zone 100 /// for direct access but can direct reclaim. 101 pub const GFP_KERNEL: Flags = Flags(bindings::GFP_KERNEL); 102 103 /// The same as [`GFP_KERNEL`], except the allocation is accounted to kmemcg. 104 pub const GFP_KERNEL_ACCOUNT: Flags = Flags(bindings::GFP_KERNEL_ACCOUNT); 105 106 /// For kernel allocations that should not stall for direct reclaim, start physical IO or 107 /// use any filesystem callback. It is very likely to fail to allocate memory, even for very 108 /// small allocations. 109 pub const GFP_NOWAIT: Flags = Flags(bindings::GFP_NOWAIT); 110 111 /// Suppresses allocation failure reports. 112 /// 113 /// This is normally or'd with other flags. 114 pub const __GFP_NOWARN: Flags = Flags(bindings::__GFP_NOWARN); 115 } 116 117 /// Non Uniform Memory Access (NUMA) node identifier. 118 #[derive(Clone, Copy, PartialEq)] 119 pub struct NumaNode(i32); 120 121 impl NumaNode { 122 /// Create a new NUMA node identifier (non-negative integer). 123 /// 124 /// Returns [`EINVAL`] if a negative id or an id exceeding [`bindings::MAX_NUMNODES`] is 125 /// specified. 126 pub fn new(node: i32) -> Result<Self> { 127 // MAX_NUMNODES never exceeds 2**10 because NODES_SHIFT is 0..10. 128 if node < 0 || node >= bindings::MAX_NUMNODES as i32 { 129 return Err(EINVAL); 130 } 131 Ok(Self(node)) 132 } 133 } 134 135 /// Specify necessary constant to pass the information to Allocator that the caller doesn't care 136 /// about the NUMA node to allocate memory from. 137 impl NumaNode { 138 /// No node preference. 139 pub const NO_NODE: NumaNode = NumaNode(bindings::NUMA_NO_NODE); 140 } 141 142 /// The kernel's [`Allocator`] trait. 143 /// 144 /// An implementation of [`Allocator`] can allocate, re-allocate and free memory buffers described 145 /// via [`Layout`]. 146 /// 147 /// [`Allocator`] is designed to be implemented as a ZST; [`Allocator`] functions do not operate on 148 /// an object instance. 149 /// 150 /// In order to be able to support `#[derive(CoercePointee)]` later on, we need to avoid a design 151 /// that requires an `Allocator` to be instantiated, hence its functions must not contain any kind 152 /// of `self` parameter. 153 /// 154 /// # Safety 155 /// 156 /// - A memory allocation returned from an allocator must remain valid until it is explicitly freed. 157 /// 158 /// - Any pointer to a valid memory allocation must be valid to be passed to any other [`Allocator`] 159 /// function of the same type. 160 /// 161 /// - Implementers must ensure that all trait functions abide by the guarantees documented in the 162 /// `# Guarantees` sections. 163 pub unsafe trait Allocator { 164 /// The minimum alignment satisfied by all allocations from this allocator. 165 /// 166 /// # Guarantees 167 /// 168 /// Any pointer allocated by this allocator is guaranteed to be aligned to `MIN_ALIGN` even if 169 /// the requested layout has a smaller alignment. 170 const MIN_ALIGN: usize; 171 172 /// Allocate memory based on `layout`, `flags` and `nid`. 173 /// 174 /// On success, returns a buffer represented as `NonNull<[u8]>` that satisfies the layout 175 /// constraints (i.e. minimum size and alignment as specified by `layout`). 176 /// 177 /// This function is equivalent to `realloc` when called with `None`. 178 /// 179 /// # Guarantees 180 /// 181 /// When the return value is `Ok(ptr)`, then `ptr` is 182 /// - valid for reads and writes for `layout.size()` bytes, until it is passed to 183 /// [`Allocator::free`] or [`Allocator::realloc`], 184 /// - aligned to `layout.align()`, 185 /// 186 /// Additionally, `Flags` are honored as documented in 187 /// <https://docs.kernel.org/core-api/mm-api.html#mm-api-gfp-flags>. 188 fn alloc(layout: Layout, flags: Flags, nid: NumaNode) -> Result<NonNull<[u8]>, AllocError> { 189 // SAFETY: Passing `None` to `realloc` is valid by its safety requirements and asks for a 190 // new memory allocation. 191 unsafe { Self::realloc(None, layout, Layout::new::<()>(), flags, nid) } 192 } 193 194 /// Re-allocate an existing memory allocation to satisfy the requested `layout` and 195 /// a specific NUMA node request to allocate the memory for. 196 /// 197 /// Systems employing a Non Uniform Memory Access (NUMA) architecture contain collections of 198 /// hardware resources including processors, memory, and I/O buses, that comprise what is 199 /// commonly known as a NUMA node. 200 /// 201 /// `nid` stands for NUMA id, i. e. NUMA node identifier, which is a non-negative integer 202 /// if a node needs to be specified, or [`NumaNode::NO_NODE`] if the caller doesn't care. 203 /// 204 /// If the requested size is zero, `realloc` behaves equivalent to `free`. 205 /// 206 /// If the requested size is larger than the size of the existing allocation, a successful call 207 /// to `realloc` guarantees that the new or grown buffer has at least `Layout::size` bytes, but 208 /// may also be larger. 209 /// 210 /// If the requested size is smaller than the size of the existing allocation, `realloc` may or 211 /// may not shrink the buffer; this is implementation specific to the allocator. 212 /// 213 /// On allocation failure, the existing buffer, if any, remains valid. 214 /// 215 /// The buffer is represented as `NonNull<[u8]>`. 216 /// 217 /// # Safety 218 /// 219 /// - If `ptr == Some(p)`, then `p` must point to an existing and valid memory allocation 220 /// created by this [`Allocator`]; if `old_layout` is zero-sized `p` does not need to be a 221 /// pointer returned by this [`Allocator`]. 222 /// - `ptr` is allowed to be `None`; in this case a new memory allocation is created and 223 /// `old_layout` is ignored. 224 /// - `old_layout` must match the `Layout` the allocation has been created with. 225 /// 226 /// # Guarantees 227 /// 228 /// This function has the same guarantees as [`Allocator::alloc`]. When `ptr == Some(p)`, then 229 /// it additionally guarantees that: 230 /// - the contents of the memory pointed to by `p` are preserved up to the lesser of the new 231 /// and old size, i.e. `ret_ptr[0..min(layout.size(), old_layout.size())] == 232 /// p[0..min(layout.size(), old_layout.size())]`. 233 /// - when the return value is `Err(AllocError)`, then `ptr` is still valid. 234 unsafe fn realloc( 235 ptr: Option<NonNull<u8>>, 236 layout: Layout, 237 old_layout: Layout, 238 flags: Flags, 239 nid: NumaNode, 240 ) -> Result<NonNull<[u8]>, AllocError>; 241 242 /// Free an existing memory allocation. 243 /// 244 /// # Safety 245 /// 246 /// - `ptr` must point to an existing and valid memory allocation created by this [`Allocator`]; 247 /// if `old_layout` is zero-sized `p` does not need to be a pointer returned by this 248 /// [`Allocator`]. 249 /// - `layout` must match the `Layout` the allocation has been created with. 250 /// - The memory allocation at `ptr` must never again be read from or written to. 251 unsafe fn free(ptr: NonNull<u8>, layout: Layout) { 252 // SAFETY: The caller guarantees that `ptr` points at a valid allocation created by this 253 // allocator. We are passing a `Layout` with the smallest possible alignment, so it is 254 // smaller than or equal to the alignment previously used with this allocation. 255 let _ = unsafe { 256 Self::realloc( 257 Some(ptr), 258 Layout::new::<()>(), 259 layout, 260 Flags(0), 261 NumaNode::NO_NODE, 262 ) 263 }; 264 } 265 } 266 267 /// Returns a properly aligned dangling pointer from the given `layout`. 268 pub(crate) fn dangling_from_layout(layout: Layout) -> NonNull<u8> { 269 let ptr = layout.align() as *mut u8; 270 271 // SAFETY: `layout.align()` (and hence `ptr`) is guaranteed to be non-zero. 272 unsafe { NonNull::new_unchecked(ptr) } 273 } 274