cranelift_module/
data_context.rs

1//! Defines `DataDescription`.
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::ModuleRelocTarget;
12use crate::module::ModuleReloc;
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
66    /// respective module should be used.
67    pub align: Option<u64>,
68    /// Whether or not to request the linker to preserve this data object even
69    /// if not referenced.
70    pub used: bool,
71}
72
73impl DataDescription {
74    /// Allocate a new `DataDescription`.
75    pub fn new() -> Self {
76        Self {
77            init: Init::Uninitialized,
78            function_decls: PrimaryMap::new(),
79            data_decls: PrimaryMap::new(),
80            function_relocs: vec![],
81            data_relocs: vec![],
82            custom_segment_section: None,
83            align: None,
84            used: false,
85        }
86    }
87
88    /// Clear all data structures in this `DataDescription`.
89    pub fn clear(&mut self) {
90        self.init = Init::Uninitialized;
91        self.function_decls.clear();
92        self.data_decls.clear();
93        self.function_relocs.clear();
94        self.data_relocs.clear();
95        self.custom_segment_section = None;
96        self.align = None;
97        self.used = false;
98    }
99
100    /// Define a zero-initialized object with the given size.
101    pub fn define_zeroinit(&mut self, size: usize) {
102        debug_assert_eq!(self.init, Init::Uninitialized);
103        self.init = Init::Zeros { size };
104    }
105
106    /// Define an object initialized with the given contents.
107    ///
108    /// TODO: Can we avoid a Box here?
109    pub fn define(&mut self, contents: Box<[u8]>) {
110        debug_assert_eq!(self.init, Init::Uninitialized);
111        self.init = Init::Bytes { contents };
112    }
113
114    /// Override the segment/section for data, only supported on Object backend
115    pub fn set_segment_section(&mut self, seg: &str, sec: &str) {
116        self.custom_segment_section = Some((seg.to_owned(), sec.to_owned()))
117    }
118
119    /// Set the alignment for data. The alignment must be a power of two.
120    pub fn set_align(&mut self, align: u64) {
121        assert!(align.is_power_of_two());
122        self.align = Some(align);
123    }
124
125    /// Set whether or not the linker should preserve this data object even if
126    /// not referenced.
127    pub fn set_used(&mut self, used: bool) {
128        self.used = used;
129    }
130
131    /// Declare an external function import.
132    ///
133    /// Users of the `Module` API generally should call
134    /// `Module::declare_func_in_data` instead, as it takes care of generating
135    /// the appropriate `ExternalName`.
136    pub fn import_function(&mut self, name: ModuleRelocTarget) -> ir::FuncRef {
137        self.function_decls.push(name)
138    }
139
140    /// Declares a global value import.
141    ///
142    /// TODO: Rename to import_data?
143    ///
144    /// Users of the `Module` API generally should call
145    /// `Module::declare_data_in_data` instead, as it takes care of generating
146    /// the appropriate `ExternalName`.
147    pub fn import_global_value(&mut self, name: ModuleRelocTarget) -> ir::GlobalValue {
148        self.data_decls.push(name)
149    }
150
151    /// Write the address of `func` into the data at offset `offset`.
152    pub fn write_function_addr(&mut self, offset: CodeOffset, func: ir::FuncRef) {
153        self.function_relocs.push((offset, func))
154    }
155
156    /// Write the address of `data` into the data at offset `offset`.
157    pub fn write_data_addr(&mut self, offset: CodeOffset, data: ir::GlobalValue, addend: Addend) {
158        self.data_relocs.push((offset, data, addend))
159    }
160
161    /// An iterator over all relocations of the data object.
162    pub fn all_relocs<'a>(
163        &'a self,
164        pointer_reloc: Reloc,
165    ) -> impl Iterator<Item = ModuleReloc> + 'a {
166        let func_relocs = self
167            .function_relocs
168            .iter()
169            .map(move |&(offset, id)| ModuleReloc {
170                kind: pointer_reloc,
171                offset,
172                name: self.function_decls[id].clone(),
173                addend: 0,
174            });
175        let data_relocs = self
176            .data_relocs
177            .iter()
178            .map(move |&(offset, id, addend)| ModuleReloc {
179                kind: pointer_reloc,
180                offset,
181                name: self.data_decls[id].clone(),
182                addend,
183            });
184        func_relocs.chain(data_relocs)
185    }
186}
187
188#[cfg(test)]
189mod tests {
190    use crate::ModuleRelocTarget;
191
192    use super::{DataDescription, Init};
193
194    #[test]
195    fn basic_data_context() {
196        let mut data = DataDescription::new();
197        assert_eq!(data.init, Init::Uninitialized);
198        assert!(data.function_decls.is_empty());
199        assert!(data.data_decls.is_empty());
200        assert!(data.function_relocs.is_empty());
201        assert!(data.data_relocs.is_empty());
202
203        data.define_zeroinit(256);
204
205        let _func_a = data.import_function(ModuleRelocTarget::user(0, 0));
206        let func_b = data.import_function(ModuleRelocTarget::user(0, 1));
207        let func_c = data.import_function(ModuleRelocTarget::user(0, 2));
208        let _data_a = data.import_global_value(ModuleRelocTarget::user(0, 3));
209        let data_b = data.import_global_value(ModuleRelocTarget::user(0, 4));
210
211        data.write_function_addr(8, func_b);
212        data.write_function_addr(16, func_c);
213        data.write_data_addr(32, data_b, 27);
214
215        assert_eq!(data.init, Init::Zeros { size: 256 });
216        assert_eq!(data.function_decls.len(), 3);
217        assert_eq!(data.data_decls.len(), 2);
218        assert_eq!(data.function_relocs.len(), 2);
219        assert_eq!(data.data_relocs.len(), 1);
220
221        data.clear();
222
223        assert_eq!(data.init, Init::Uninitialized);
224        assert!(data.function_decls.is_empty());
225        assert!(data.data_decls.is_empty());
226        assert!(data.function_relocs.is_empty());
227        assert!(data.data_relocs.is_empty());
228
229        let contents = vec![33, 34, 35, 36];
230        let contents_clone = contents.clone();
231        data.define(contents.into_boxed_slice());
232
233        assert_eq!(
234            data.init,
235            Init::Bytes {
236                contents: contents_clone.into_boxed_slice()
237            }
238        );
239        assert_eq!(data.function_decls.len(), 0);
240        assert_eq!(data.data_decls.len(), 0);
241        assert_eq!(data.function_relocs.len(), 0);
242        assert_eq!(data.data_relocs.len(), 0);
243    }
244}
cranelift_module/data_context.rs

cranelift_module/
data_context.rs
