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