1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466
use std::fmt::Debug; use num_traits::{Num,WrappingAdd}; /// Trait that the field types defined in CompressedCapability (Length, Offset, Addr) have to implement. /// This asserts that a) they're numeric, b) they support Default/Copy/Clone/Debug so that CcxCap can derive these. pub trait NumType: Default + Num + WrappingAdd + Copy + Clone + Debug + PartialOrd + Ord {} impl NumType for u32 {} impl NumType for u64 {} impl NumType for u128 {} impl NumType for i32 {} impl NumType for i64 {} impl NumType for i128 {} /// Value which can be converted to T (a NumType). /// Must also be Default/Copy/Clone/Debug, so CcxCap can derive these. pub trait FfiNumType<T>: Default + Copy + Clone + Debug + Into<T> + From<T> {} impl FfiNumType<u64> for u64 {} impl FfiNumType<i64> for i64 {} /// We assume the C representation of `u128` is identical to the Rust representation. /// See [crate::c_funcs] documentation. impl FfiNumType<u128> for u128 {} /// We assume the C representation of `i128` is identical to the Rust representation. /// See [crate::c_funcs] documentation. impl FfiNumType<i128> for i128 {} /// Trait defining an Rust version of the public API for a specific capability type. /// A type X implementing CompressedCapability is equivalent to the API provided by `cheri_compressed_cap_X.h` in C, /// where `ccx_cap_t` is equivalent to [CcxCap]. /// /// It is not recommended to call the trait functions directly. /// Instead, use one of the [crate::wrappers]. pub trait CompressedCapability: Sized + Copy + Clone { /// ccx_length_t Rust-land equivalent - should be a superset of Addr type Length: NumType + From<Self::Addr>; /// ccx_offset_t Rust-land equivalent - should be a superset of Addr type Offset: NumType + From<Self::Addr>; /// ccx_addr_t equivalent type Addr: NumType + Into<Self::Offset> + Into<Self::Length>; /// ccx_length_t C-land equivalent - should have a memory layout identical to the C ccx_length_t. /// This is separate from Length because for 128-bit types the Rust and C versions may not look the same. /// In practice, we just assume they are the same (see [crate::c_funcs] documentation). type FfiLength: FfiNumType<Self::Length>; /// ccx_offset_t C-land equivalent - should have a memory layout identical to the C ccx_offset_t. /// See [Self::FfiLength] for an explanation. type FfiOffset: FfiNumType<Self::Offset>; /// CCX_PERM_GLOBAL equivalent /// These are the same for 64 and 128bit, but should be overridden for Morello-128 const PERM_GLOBAL: u32 = (1 << 0); const PERM_EXECUTE: u32 = (1 << 1); const PERM_LOAD: u32 = (1 << 2); const PERM_STORE: u32 = (1 << 3); const PERM_LOAD_CAP: u32 = (1 << 4); const PERM_STORE_CAP: u32 = (1 << 5); const PERM_STORE_LOCAL: u32 = (1 << 6); const PERM_SEAL: u32 = (1 << 7); const PERM_CINVOKE: u32 = (1 << 8); const PERM_UNSEAL: u32 = (1 << 9); const PERM_ACCESS_SYS_REGS: u32 = (1 << 10); const PERM_SETCID: u32 = (1 << 11); const MAX_REPRESENTABLE_OTYPE: u32; /// CCX_OTYPE_UNSEALED equivalent const OTYPE_UNSEALED: u32; const OTYPE_SENTRY: u32; const OTYPE_RESERVED2: u32; const OTYPE_RESERVED3: u32; const MAX_UNRESERVED_OTYPE: u32; // Adapted, Rust-safe version of the C API // Should be defined by building a wrapper around a linked C function /// Generate the `pesbt` bits for a capability (the top bits, which encode permissions, object type, compressed bounds, etc.) /// This transformation can be undone with [Self::decompress_raw]. /// /// This is presumably intended for storing compressed capabilities in e.g. registers. /// Its counterpart for storing compressed capabilities in memory is [Self::compress_mem]. fn compress_raw(src_cap: &CcxCap<Self>) -> Self::Addr; /// Decompress a (pesbt, cursor) pair into a capability. /// This transformation can be undone with [Self::compress_raw]. fn decompress_raw(pesbt: Self::Addr, cursor: Self::Addr, tag: bool) -> CcxCap<Self>; /// Generate the `pesbt` bits for a capability (the top bits, which encode permissions, object type, compressed bounds, etc.) /// This transformation can be undone with [Self::decompress_mem]. /// /// This is presumably intended for storing compressed capabilities in memory. /// It is equivalent to calling [Self::compress_raw] and XOR-ing the result with a "null mask". /// Presumably this transformation prevents all-zero data from being interpreted as a capability? fn compress_mem(src_cap: &CcxCap<Self>) -> Self::Addr; /// Decompress a (pesbt, cursor) pair into a capability. /// This transformation can be undone with [Self::compress_mem]. /// /// This is equivalent to XOR-ing the pesbt with a "null mask" and calling [Self::decompress_raw]. /// Presumably the null mask prevents all-zero data from being interpreted as a capability? fn decompress_mem(pesbt: Self::Addr, cursor: Self::Addr, tag: bool) -> CcxCap<Self>; /* Getters */ /// Gets the user/software-defined permissions from the [CcxCap::cr_pesbt] field /// /// Counterpart: [Self::update_uperms] fn get_uperms(cap: &CcxCap<Self>) -> u32; /// Gets the hardware-defined permissions from the [CcxCap::cr_pesbt] field /// /// Counterpart: [Self::update_perms] fn get_perms(cap: &CcxCap<Self>) -> u32; /// Gets the object type from the [CcxCap::cr_pesbt] field /// /// Counterpart: [Self::update_otype] fn get_otype(cap: &CcxCap<Self>) -> u32; /// Gets the reserved bits from the [CcxCap::cr_pesbt] field /// /// Counterpart: [Self::update_reserved] fn get_reserved(cap: &CcxCap<Self>) -> u8; /// Gets the flags from the [CcxCap::cr_pesbt] field /// /// Counterpart: [Self::update_flags] fn get_flags(cap: &CcxCap<Self>) -> u8; /* Updaters The C API updaters all use Self::Addr for the type of `value`. I've changed these to use the types from corresponding `get` functions. */ /// Updates the user/software-defined permissions field in [CcxCap::cr_pesbt] /// /// Counterpart: [Self::get_uperms] fn update_uperms(cap: &mut CcxCap<Self>, value: u32); /// Updates the hardware-defined permissions field in [CcxCap::cr_pesbt] /// /// Counterpart: [Self::get_perms] fn update_perms(cap: &mut CcxCap<Self>, value: u32); /// Updates the object type field in [CcxCap::cr_pesbt] /// /// Counterpart: [Self::get_otype] fn update_otype(cap: &mut CcxCap<Self>, value: u32); /// Updates the reserved field in [CcxCap::cr_pesbt] /// /// Counterpart: [Self::get_reserved] fn update_reserved(cap: &mut CcxCap<Self>, value: u8); /// Updates the flags field in [CcxCap::cr_pesbt] /// /// Counterpart: [Self::get_flags] fn update_flags(cap: &mut CcxCap<Self>, value: u8); /* Misc */ /// Extracts the floating-point encoded bounds from [CcxCap::cr_pesbt] fn extract_bounds_bits(pesbt: Self::Addr) -> CcxBoundsBits; /// Sets the capability bounds to bounds that encompass (req_base, req_top). /// Because a floating-point representation is used for bounds, it may not be able to set (req_base, req_top) exactly. /// In this case it will return False. /// /// Updates [CcxCap::cr_pesbt], [CcxCap::_cr_top], [CcxCap::cr_base] fn set_bounds(cap: &mut CcxCap<Self>, req_base: Self::Addr, req_top: Self::Length) -> bool; /// Check if the range ([CcxCap::cr_base], [CcxCap::_cr_top]) can be encoded exactly with the floating-point encoding fn is_representable_cap_exact(cap: &CcxCap<Self>) -> bool; /// Check if a capability with the parameters `sealed, base, length, cursor` would be representable if the cursor were updated to `new_cursor`. fn is_representable_new_addr(sealed: bool, base: Self::Addr, length: Self::Length, cursor: Self::Addr, new_cursor: Self::Addr) -> bool; /// Generate a capability for `base, top, cursor` with the maximum available permissions fn make_max_perms_cap(base: Self::Addr, cursor: Self::Addr, top: Self::Length) -> CcxCap<Self>; /// Get the minimum representable length greater than or equal to `length`. /// /// If `get_representable_length(l) == l` then bounds of length `l` are exactly representable (if properly aligned). /// /// See also [Self::get_required_alignment], [Self::get_alignment_mask]. fn get_representable_length(length: Self::Length) -> Self::Length; /// Get the alignment required for bounds of some `length` to be exactly represented. /// /// See also [Self::get_representable_length], [Self::get_alignment_mask]. fn get_required_alignment(length: Self::Length) -> Self::Length; /// Get a mask which aligns a bounds of some `length` to be exactly representable. /// /// See also [Self::get_representable_length], [Self::get_required_alignment]. fn get_alignment_mask(length: Self::Length) -> Self::Length; } #[repr(C, align(16))] #[derive(Copy,Clone)] /// Structure matching the C type `_cc_N(cap)`. /// Field order and layout is binary-compatible with the C version, /// assuming the C preprocessor macro `_CC_REVERSE_PESBT_CURSOR_ORDER` is *not* defined. /// /// This is a plain-old-data type. It only supplies getters and setters, and does *not* guarantee any safety/correctness. /// For example, there are no added assertions or checks if you set the cursor to a value outside the bounds. /// However, the C FFI functions from [CompressedCapability] may have their own asserts. /// These are documented where possible. /// /// *For a safe interface, use one of the [crate::wrappers]* pub struct CcxCap<T: CompressedCapability> { /// The bottom half of the capability as stored in memory. /// /// If [Self::cr_tag] is 1, this is the capability's "cursor" i.e. the address it's actually pointing to. _cr_cursor: T::Addr, /// The top half of the capability as stored in memory. /// /// If [Self::cr_tag] is 1, this is the compressed capability metadata (permissions, otype, bounds, etc.). cr_pesbt: T::Addr, /// The top of this capability's valid address range. /// Derived from [Self::cr_pesbt]. /// As long as [Self::cr_tag] is 1, the getter/setter will ensure it matches. _cr_top: T::FfiLength, /// The base of this capability's valid address range. /// Derived from [Self::cr_pesbt]. /// As long as [Self::cr_tag] is 1, the getter/setter will ensure it matches. cr_base: T::Addr, /// Tag - if 1, this is a valid capability, 0 it's just plain data cr_tag: u8, /// 0 (false) if the bounds decode step was given an invalid capability. /// Should be 1 (true) for all non-Morello capabilities. cr_bounds_valid: u8, /// The exponent used for storing the bounds. /// Stored from various places, only used in Morello-exclusive function cap_bounds_uses_value(). cr_exp: u8, /// "Additional data stored by the caller." /// Seemingly completely unused, essentially padding. cr_extra: u8, } /// Implements getters and setters similar to the C++-only member functions in the header. impl<T: CompressedCapability> CcxCap<T> { /// Returns a `(tag, [cursor, pesbt])` tuple that represents all data required to /// store a capability in a register. /// /// To store capabilities in memory, see [Self::mem_representation] pub fn reg_representation(&self) -> (bool, [T::Addr; 2]) { // This should be equal to self.cr_pesbt, the compress_raw function just returns that. // We use this function in case that behaviour changes in the future, and for consistency with mem_representation. let compressed_pesbt = T::compress_raw(self); (self.tag(), [self._cr_cursor, compressed_pesbt]) } /// Returns a `(tag, [cursor, pesbt])` tuple that represents all data required to /// store a capability in memory. /// /// To store capabilities in a register, see [Self::reg_representation] pub fn mem_representation(&self) -> (bool, [T::Addr; 2]) { // This should be equal to (self.cr_pesbt ^ SOME_XOR_MASK) let compressed_pesbt = T::compress_mem(self); (self.tag(), [self._cr_cursor, compressed_pesbt]) } pub fn tag(&self) -> bool { // cr_tag is interpreted as a boolean with C rules self.cr_tag != 0 } pub fn set_tag(&mut self, tag: bool) { self.cr_tag = if tag { 1 } else { 0 }; } pub fn base(&self) -> T::Addr { self.cr_base } pub fn top(&self) -> T::Length { self._cr_top.into() } pub fn bounds(&self) -> (T::Addr, T::Length) { (self.base(), self.top()) } /// Sets the base and top of this capability using C FFI function [CompressedCapability::set_bounds]. /// Updates the PESBT field correspondingly. /// On non-Morello platforms, will fail with an assertion error if [Self::tag()] is not set. pub fn set_bounds_unchecked(&mut self, req_base: T::Addr, req_top: T::Length) -> bool { T::set_bounds(self, req_base, req_top) } pub fn address(&self) -> T::Addr { self._cr_cursor } pub fn set_address_unchecked(&mut self, addr: T::Addr) { self._cr_cursor = addr; } pub fn offset(&self) -> T::Offset { let cursor: T::Offset = self._cr_cursor.into(); let base: T::Offset = self.cr_base.into(); (cursor - base).into() } // TODO top64 pub fn length(&self) -> T::Length { let top: T::Length = self._cr_top.into(); let base: T::Length = self.cr_base.into(); (top - base).into() } // TODO length64 pub fn software_permissions(&self) -> u32 { T::get_uperms(self) } pub fn set_software_permissions(&mut self, uperms: u32) { T::update_uperms(self, uperms) } pub fn permissions(&self) -> u32 { T::get_perms(self) } pub fn set_permissions(&mut self, perms: u32) { T::update_perms(self, perms) } pub fn otype(&self) -> u32 { T::get_otype(self) } pub fn is_sealed(&self) -> bool { self.otype() != T::OTYPE_UNSEALED } pub fn set_otype(&mut self, otype: u32) { T::update_otype(self, otype) } pub fn reserved_bits(&self) -> u8 { T::get_reserved(self) } pub fn set_reserved_bits(&mut self, bits: u8) { T::update_reserved(self, bits) } pub fn flags(&self) -> u8 { T::get_flags(self) } pub fn set_flags(&mut self, flags: u8) { T::update_flags(self, flags) } /// Helper function for easily calling FFI function [CompressedCapability::is_representable_cap_exact] /// on this capability. /// Assertions are present in the C code, but should never be triggered. pub fn is_exact(&self) -> bool { T::is_representable_cap_exact(self) } /// Helper function for easily calling FFI function [CompressedCapability::is_representable_new_addr] /// on this capability. /// Assertions are present in the C code, but should never be triggered. pub fn is_representable_with_new_addr(&self, new_addr: T::Addr) -> bool { T::is_representable_new_addr(self.is_sealed(), self.base(), self.length(), self.address(), new_addr) } } /// Implements `operator==` from cheri_compressed_cap_common.h impl<T: CompressedCapability> PartialEq for CcxCap<T> { fn eq(&self, other: &Self) -> bool { self.cr_tag == other.cr_tag && self._cr_cursor == other._cr_cursor && self.cr_pesbt == other.cr_pesbt } } impl<T: CompressedCapability> Eq for CcxCap<T> {} /// Equivalent to initialization pattern used in tests: /// ``` /// ccx_cap_t value; /// memset(&value, 0, sizeof(value)); /// ``` /// /// cc64.rs doesn't pick it up when it was automatically #[derive]-d, so it's manually implemented here impl<T: CompressedCapability> Default for CcxCap<T> { fn default() -> Self { CcxCap { // Use Default::default for the associated types (Addr, Length, Offset) // Rust doesn't have enough information to know they are numbers _cr_cursor: Default::default(), cr_pesbt: Default::default(), _cr_top: Default::default(), cr_base: Default::default(), cr_tag: 0, cr_bounds_valid: 0, cr_exp: 0, cr_extra: 0, } } } /// Debug printer for capabilities that decodes the PESBT field instead of printing it raw. impl<T: CompressedCapability> Debug for CcxCap<T> { fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { f.debug_struct("CcxCap") .field("cr_cursor", &self._cr_cursor) .field("cr_base", &self.cr_base) .field("cr_top", &self._cr_top) .field("cr_tag", &self.cr_tag) .field("cr_bounds_valid", &self.cr_bounds_valid) .field("cr_exp", &self.cr_exp) .field("cr_extra", &self.cr_extra) .field("permissions", &self.permissions()) .field("software_permissions", &self.software_permissions()) .field("otype", &self.otype()) .field("reserved_bits", &self.reserved_bits()) .field("flags", &self.flags()) .finish() } } /// Structure matching the C type `_cc_N(bounds_bits)`. /// Represents a floating-point encoded capability bounds. #[repr(C)] pub struct CcxBoundsBits { b: u16, t: u16, e: u8, ie: bool, } // Link the C functions mod c_funcs; // Include cc64 definitions mod cc64; // Export the CC64 instance of CompressedCapability, and the associated CcxCap type pub use cc64::{Cc64,Cc64Cap}; // Include cc128 definitions mod cc128; // Export the CC128 instance of CompressedCapability, and the associated CcxCap type pub use cc128::{Cc128,Cc128Cap}; pub mod wrappers; #[cfg(test)] mod tests { use crate::CompressedCapability; // TODO port some tests from the C tests? #[test] fn test_printing() { let cap = crate::Cc64::decompress_raw(0, 0, false); println!("{:?}", cap); let cap = crate::Cc128::decompress_raw(0, 0, false); println!("{:?}", cap); dbg!(cap.is_exact()); } #[test] fn test_cc128_u128_conversion() { // Generate a capability between 0, 0x1_0000_0000_0000_0000 with the current cursor/address at 0x100 // When we get the 128-bit top(), it should be the same as the one we specified. // If it isn't, the memory representation of FfiU128 and the C u128 may be different let base: u64 = 0x1000_0000_0000; let top: u128 = 0x2000_0000_0000; let cap = crate::Cc128::make_max_perms_cap(base, base, top); assert_eq!(cap.top(), top); assert_eq!(cap._cr_top, top); // cr_base is stored directly after _cr_top, so if the sizes for FfiU128 and C u128 are different it will have been overwritten assert_eq!(cap.cr_base, base); } }