cranelift_module/
data_context.rs

1//! Defines `DataContext`.
2
3use cranelift_codegen::binemit::{Addend, CodeOffset, Reloc};
4use cranelift_codegen::entity::PrimaryMap;
5use cranelift_codegen::ir;
6use std::borrow::ToOwned;
7use std::boxed::Box;
8use std::string::String;
9use std::vec::Vec;
10
11use crate::module::ModuleReloc;
12use crate::ModuleRelocTarget;
13
14/// This specifies how data is to be initialized.
15#[derive(Clone, PartialEq, Eq, Debug)]
16#[cfg_attr(
17    feature = "enable-serde",
18    derive(serde_derive::Serialize, serde_derive::Deserialize)
19)]
20pub enum Init {
21    /// This indicates that no initialization has been specified yet.
22    Uninitialized,
23    /// Initialize the data with all zeros.
24    Zeros {
25        /// The size of the data.
26        size: usize,
27    },
28    /// Initialize the data with the specified contents.
29    Bytes {
30        /// The contents, which also implies the size of the data.
31        contents: Box<[u8]>,
32    },
33}
34
35impl Init {
36    /// Return the size of the data to be initialized.
37    pub fn size(&self) -> usize {
38        match *self {
39            Self::Uninitialized => panic!("data size not initialized yet"),
40            Self::Zeros { size } => size,
41            Self::Bytes { ref contents } => contents.len(),
42        }
43    }
44}
45
46/// A description of a data object.
47#[derive(Clone, Debug)]
48#[cfg_attr(
49    feature = "enable-serde",
50    derive(serde_derive::Serialize, serde_derive::Deserialize)
51)]
52pub struct DataDescription {
53    /// How the data should be initialized.
54    pub init: Init,
55    /// External function declarations.
56    pub function_decls: PrimaryMap<ir::FuncRef, ModuleRelocTarget>,
57    /// External data object declarations.
58    pub data_decls: PrimaryMap<ir::GlobalValue, ModuleRelocTarget>,
59    /// Function addresses to write at specified offsets.
60    pub function_relocs: Vec<(CodeOffset, ir::FuncRef)>,
61    /// Data addresses to write at specified offsets.
62    pub data_relocs: Vec<(CodeOffset, ir::GlobalValue, Addend)>,
63    /// Object file section
64    pub custom_segment_section: Option<(String, String)>,
65    /// Alignment in bytes. `None` means that the default alignment of the respective module should
66    /// be used.
67    pub align: Option<u64>,
68}
69
70impl DataDescription {
71    /// Allocate a new `DataDescription`.
72    pub fn new() -> Self {
73        Self {
74            init: Init::Uninitialized,
75            function_decls: PrimaryMap::new(),
76            data_decls: PrimaryMap::new(),
77            function_relocs: vec![],
78            data_relocs: vec![],
79            custom_segment_section: None,
80            align: None,
81        }
82    }
83
84    /// Clear all data structures in this `DataDescription`.
85    pub fn clear(&mut self) {
86        self.init = Init::Uninitialized;
87        self.function_decls.clear();
88        self.data_decls.clear();
89        self.function_relocs.clear();
90        self.data_relocs.clear();
91        self.custom_segment_section = None;
92        self.align = None;
93    }
94
95    /// Define a zero-initialized object with the given size.
96    pub fn define_zeroinit(&mut self, size: usize) {
97        debug_assert_eq!(self.init, Init::Uninitialized);
98        self.init = Init::Zeros { size };
99    }
100
101    /// Define an object initialized with the given contents.
102    ///
103    /// TODO: Can we avoid a Box here?
104    pub fn define(&mut self, contents: Box<[u8]>) {
105        debug_assert_eq!(self.init, Init::Uninitialized);
106        self.init = Init::Bytes { contents };
107    }
108
109    /// Override the segment/section for data, only supported on Object backend
110    pub fn set_segment_section(&mut self, seg: &str, sec: &str) {
111        self.custom_segment_section = Some((seg.to_owned(), sec.to_owned()))
112    }
113
114    /// Set the alignment for data. The alignment must be a power of two.
115    pub fn set_align(&mut self, align: u64) {
116        assert!(align.is_power_of_two());
117        self.align = Some(align);
118    }
119
120    /// Declare an external function import.
121    ///
122    /// Users of the `Module` API generally should call
123    /// `Module::declare_func_in_data` instead, as it takes care of generating
124    /// the appropriate `ExternalName`.
125    pub fn import_function(&mut self, name: ModuleRelocTarget) -> ir::FuncRef {
126        self.function_decls.push(name)
127    }
128
129    /// Declares a global value import.
130    ///
131    /// TODO: Rename to import_data?
132    ///
133    /// Users of the `Module` API generally should call
134    /// `Module::declare_data_in_data` instead, as it takes care of generating
135    /// the appropriate `ExternalName`.
136    pub fn import_global_value(&mut self, name: ModuleRelocTarget) -> ir::GlobalValue {
137        self.data_decls.push(name)
138    }
139
140    /// Write the address of `func` into the data at offset `offset`.
141    pub fn write_function_addr(&mut self, offset: CodeOffset, func: ir::FuncRef) {
142        self.function_relocs.push((offset, func))
143    }
144
145    /// Write the address of `data` into the data at offset `offset`.
146    pub fn write_data_addr(&mut self, offset: CodeOffset, data: ir::GlobalValue, addend: Addend) {
147        self.data_relocs.push((offset, data, addend))
148    }
149
150    /// An iterator over all relocations of the data object.
151    pub fn all_relocs<'a>(
152        &'a self,
153        pointer_reloc: Reloc,
154    ) -> impl Iterator<Item = ModuleReloc> + 'a {
155        let func_relocs = self
156            .function_relocs
157            .iter()
158            .map(move |&(offset, id)| ModuleReloc {
159                kind: pointer_reloc,
160                offset,
161                name: self.function_decls[id].clone(),
162                addend: 0,
163            });
164        let data_relocs = self
165            .data_relocs
166            .iter()
167            .map(move |&(offset, id, addend)| ModuleReloc {
168                kind: pointer_reloc,
169                offset,
170                name: self.data_decls[id].clone(),
171                addend,
172            });
173        func_relocs.chain(data_relocs)
174    }
175}
176
177#[cfg(test)]
178mod tests {
179    use crate::ModuleRelocTarget;
180
181    use super::{DataDescription, Init};
182
183    #[test]
184    fn basic_data_context() {
185        let mut data = DataDescription::new();
186        assert_eq!(data.init, Init::Uninitialized);
187        assert!(data.function_decls.is_empty());
188        assert!(data.data_decls.is_empty());
189        assert!(data.function_relocs.is_empty());
190        assert!(data.data_relocs.is_empty());
191
192        data.define_zeroinit(256);
193
194        let _func_a = data.import_function(ModuleRelocTarget::user(0, 0));
195        let func_b = data.import_function(ModuleRelocTarget::user(0, 1));
196        let func_c = data.import_function(ModuleRelocTarget::user(0, 2));
197        let _data_a = data.import_global_value(ModuleRelocTarget::user(0, 3));
198        let data_b = data.import_global_value(ModuleRelocTarget::user(0, 4));
199
200        data.write_function_addr(8, func_b);
201        data.write_function_addr(16, func_c);
202        data.write_data_addr(32, data_b, 27);
203
204        assert_eq!(data.init, Init::Zeros { size: 256 });
205        assert_eq!(data.function_decls.len(), 3);
206        assert_eq!(data.data_decls.len(), 2);
207        assert_eq!(data.function_relocs.len(), 2);
208        assert_eq!(data.data_relocs.len(), 1);
209
210        data.clear();
211
212        assert_eq!(data.init, Init::Uninitialized);
213        assert!(data.function_decls.is_empty());
214        assert!(data.data_decls.is_empty());
215        assert!(data.function_relocs.is_empty());
216        assert!(data.data_relocs.is_empty());
217
218        let contents = vec![33, 34, 35, 36];
219        let contents_clone = contents.clone();
220        data.define(contents.into_boxed_slice());
221
222        assert_eq!(
223            data.init,
224            Init::Bytes {
225                contents: contents_clone.into_boxed_slice()
226            }
227        );
228        assert_eq!(data.function_decls.len(), 0);
229        assert_eq!(data.data_decls.len(), 0);
230        assert_eq!(data.function_relocs.len(), 0);
231        assert_eq!(data.data_relocs.len(), 0);
232    }
233}
cranelift_module/data_context.rs

cranelift_module/
data_context.rs
