1 // Copyright 2022, The Android Open Source Project
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 //     http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
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11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 
15 //! Page table management.
16 
17 use crate::read_sysreg;
18 use aarch64_paging::idmap::IdMap;
19 use aarch64_paging::paging::{Attributes, Constraints, Descriptor, MemoryRegion};
20 use aarch64_paging::MapError;
21 use core::result;
22 
23 /// Software bit used to indicate a device that should be lazily mapped.
24 pub(super) const MMIO_LAZY_MAP_FLAG: Attributes = Attributes::SWFLAG_0;
25 
26 // We assume that:
27 // - MAIR_EL1.Attr0 = "Device-nGnRE memory" (0b0000_0100)
28 // - MAIR_EL1.Attr1 = "Normal memory, Outer & Inner WB Non-transient, R/W-Allocate" (0b1111_1111)
29 const MEMORY: Attributes =
30     Attributes::VALID.union(Attributes::NORMAL).union(Attributes::NON_GLOBAL);
31 const DEVICE_LAZY: Attributes =
32     MMIO_LAZY_MAP_FLAG.union(Attributes::DEVICE_NGNRE).union(Attributes::EXECUTE_NEVER);
33 const DEVICE: Attributes = DEVICE_LAZY.union(Attributes::VALID);
34 const CODE: Attributes = MEMORY.union(Attributes::READ_ONLY);
35 const DATA: Attributes = MEMORY.union(Attributes::EXECUTE_NEVER);
36 const RODATA: Attributes = DATA.union(Attributes::READ_ONLY);
37 const DATA_DBM: Attributes = RODATA.union(Attributes::DBM);
38 
39 type Result<T> = result::Result<T, MapError>;
40 
41 /// High-level API for managing MMU mappings.
42 pub struct PageTable {
43     idmap: IdMap,
44 }
45 
46 impl From<IdMap> for PageTable {
from(idmap: IdMap) -> Self47     fn from(idmap: IdMap) -> Self {
48         Self { idmap }
49     }
50 }
51 
52 impl Default for PageTable {
default() -> Self53     fn default() -> Self {
54         const TCR_EL1_TG0_MASK: usize = 0x3;
55         const TCR_EL1_TG0_SHIFT: u32 = 14;
56         const TCR_EL1_TG0_SIZE_4KB: usize = 0b00;
57 
58         const TCR_EL1_T0SZ_MASK: usize = 0x3f;
59         const TCR_EL1_T0SZ_SHIFT: u32 = 0;
60         const TCR_EL1_T0SZ_39_VA_BITS: usize = 64 - 39;
61 
62         // Ensure that entry.S wasn't changed without updating the assumptions about TCR_EL1 here.
63         let tcr_el1 = read_sysreg!("tcr_el1");
64         assert_eq!((tcr_el1 >> TCR_EL1_TG0_SHIFT) & TCR_EL1_TG0_MASK, TCR_EL1_TG0_SIZE_4KB);
65         assert_eq!((tcr_el1 >> TCR_EL1_T0SZ_SHIFT) & TCR_EL1_T0SZ_MASK, TCR_EL1_T0SZ_39_VA_BITS);
66 
67         IdMap::new(Self::ASID, Self::ROOT_LEVEL).into()
68     }
69 }
70 
71 impl PageTable {
72     /// ASID used for the underlying page table.
73     pub const ASID: usize = 1;
74 
75     /// Level of the underlying page table's root page.
76     const ROOT_LEVEL: usize = 1;
77 
78     /// Activates the page table.
79     ///
80     /// # Safety
81     ///
82     /// The caller must ensure that the PageTable instance has valid and identical mappings for the
83     /// code being currently executed. Otherwise, the Rust execution model (on which the borrow
84     /// checker relies) would be violated.
activate(&mut self)85     pub unsafe fn activate(&mut self) {
86         // SAFETY: the caller of this unsafe function asserts that switching to a different
87         // translation is safe
88         unsafe { self.idmap.activate() }
89     }
90 
91     /// Maps the given range of virtual addresses to the physical addresses as lazily mapped
92     /// nGnRE device memory.
map_device_lazy(&mut self, range: &MemoryRegion) -> Result<()>93     pub fn map_device_lazy(&mut self, range: &MemoryRegion) -> Result<()> {
94         self.idmap.map_range(range, DEVICE_LAZY)
95     }
96 
97     /// Maps the given range of virtual addresses to the physical addresses as valid device
98     /// nGnRE device memory.
map_device(&mut self, range: &MemoryRegion) -> Result<()>99     pub fn map_device(&mut self, range: &MemoryRegion) -> Result<()> {
100         self.idmap.map_range(range, DEVICE)
101     }
102 
103     /// Maps the given range of virtual addresses to the physical addresses as non-executable
104     /// and writable normal memory.
map_data(&mut self, range: &MemoryRegion) -> Result<()>105     pub fn map_data(&mut self, range: &MemoryRegion) -> Result<()> {
106         self.idmap.map_range(range, DATA)
107     }
108 
109     /// Maps the given range of virtual addresses to the physical addresses as non-executable,
110     /// read-only and writable-clean normal memory.
map_data_dbm(&mut self, range: &MemoryRegion) -> Result<()>111     pub fn map_data_dbm(&mut self, range: &MemoryRegion) -> Result<()> {
112         // Map the region down to pages to minimize the size of the regions that will be marked
113         // dirty once a store hits them, but also to ensure that we can clear the read-only
114         // attribute while the mapping is live without causing break-before-make (BBM) violations.
115         // The latter implies that we must avoid the use of the contiguous hint as well.
116         self.idmap.map_range_with_constraints(
117             range,
118             DATA_DBM,
119             Constraints::NO_BLOCK_MAPPINGS | Constraints::NO_CONTIGUOUS_HINT,
120         )
121     }
122 
123     /// Maps the given range of virtual addresses to the physical addresses as read-only
124     /// normal memory.
map_code(&mut self, range: &MemoryRegion) -> Result<()>125     pub fn map_code(&mut self, range: &MemoryRegion) -> Result<()> {
126         self.idmap.map_range(range, CODE)
127     }
128 
129     /// Maps the given range of virtual addresses to the physical addresses as non-executable
130     /// and read-only normal memory.
map_rodata(&mut self, range: &MemoryRegion) -> Result<()>131     pub fn map_rodata(&mut self, range: &MemoryRegion) -> Result<()> {
132         self.idmap.map_range(range, RODATA)
133     }
134 
135     /// Applies the provided updater function to a number of PTEs corresponding to a given memory
136     /// range.
modify_range<F>(&mut self, range: &MemoryRegion, f: &F) -> Result<()> where F: Fn(&MemoryRegion, &mut Descriptor, usize) -> result::Result<(), ()>,137     pub fn modify_range<F>(&mut self, range: &MemoryRegion, f: &F) -> Result<()>
138     where
139         F: Fn(&MemoryRegion, &mut Descriptor, usize) -> result::Result<(), ()>,
140     {
141         self.idmap.modify_range(range, f)
142     }
143 
144     /// Applies the provided callback function to a number of PTEs corresponding to a given memory
145     /// range.
walk_range<F>(&self, range: &MemoryRegion, f: &F) -> Result<()> where F: Fn(&MemoryRegion, &Descriptor, usize) -> result::Result<(), ()>,146     pub fn walk_range<F>(&self, range: &MemoryRegion, f: &F) -> Result<()>
147     where
148         F: Fn(&MemoryRegion, &Descriptor, usize) -> result::Result<(), ()>,
149     {
150         let mut callback = |mr: &MemoryRegion, d: &Descriptor, l: usize| f(mr, d, l);
151         self.idmap.walk_range(range, &mut callback)
152     }
153 }
154