wasmtime_environ/component/
vmcomponent_offsets.rs

1// Currently the `VMComponentContext` allocation by field looks like this:
2//
3// struct VMComponentContext {
4//      magic: u32,
5//      builtins: &'static VMComponentBuiltins,
6//      limits: *const VMStoreContext,
7//      flags: [VMGlobalDefinition; component.num_runtime_component_instances],
8//      trampoline_func_refs: [VMFuncRef; component.num_trampolines],
9//      lowerings: [VMLowering; component.num_lowerings],
10//      memories: [*mut VMMemoryDefinition; component.num_runtime_memories],
11//      tables: [VMTable; component.num_runtime_tables],
12//      reallocs: [*mut VMFuncRef; component.num_runtime_reallocs],
13//      post_returns: [*mut VMFuncRef; component.num_runtime_post_returns],
14//      resource_destructors: [*mut VMFuncRef; component.num_resources],
15// }
16
17use crate::PtrSize;
18use crate::component::*;
19
20/// Equivalent of `VMCONTEXT_MAGIC` except for components.
21///
22/// This is stored at the start of all `VMComponentContext` structures and
23/// double-checked on `VMComponentContext::from_opaque`.
24pub const VMCOMPONENT_MAGIC: u32 = u32::from_le_bytes(*b"comp");
25
26/// Flag for the `VMComponentContext::flags` field which corresponds to the
27/// canonical ABI flag `may_leave`
28pub const FLAG_MAY_LEAVE: i32 = 1 << 0;
29
30/// Flag for the `VMComponentContext::flags` field which corresponds to the
31/// canonical ABI flag `may_enter`
32pub const FLAG_MAY_ENTER: i32 = 1 << 1;
33
34/// Flag for the `VMComponentContext::flags` field which is set whenever a
35/// function is called to indicate that `post_return` must be called next.
36pub const FLAG_NEEDS_POST_RETURN: i32 = 1 << 2;
37
38/// Runtime offsets within a `VMComponentContext` for a specific component.
39#[derive(Debug, Clone, Copy)]
40pub struct VMComponentOffsets<P> {
41    /// The host pointer size
42    pub ptr: P,
43
44    /// The number of lowered functions this component will be creating.
45    pub num_lowerings: u32,
46    /// The number of memories which are recorded in this component for options.
47    pub num_runtime_memories: u32,
48    /// The number of tables which are recorded in this component for options.
49    pub num_runtime_tables: u32,
50    /// The number of reallocs which are recorded in this component for options.
51    pub num_runtime_reallocs: u32,
52    /// The number of callbacks which are recorded in this component for options.
53    pub num_runtime_callbacks: u32,
54    /// The number of post-returns which are recorded in this component for options.
55    pub num_runtime_post_returns: u32,
56    /// Number of component instances internally in the component (always at
57    /// least 1).
58    pub num_runtime_component_instances: u32,
59    /// Number of cranelift-compiled trampolines required for this component.
60    pub num_trampolines: u32,
61    /// Number of resources within a component which need destructors stored.
62    pub num_resources: u32,
63
64    // precalculated offsets of various member fields
65    magic: u32,
66    builtins: u32,
67    vm_store_context: u32,
68    flags: u32,
69    trampoline_func_refs: u32,
70    lowerings: u32,
71    memories: u32,
72    tables: u32,
73    reallocs: u32,
74    callbacks: u32,
75    post_returns: u32,
76    resource_destructors: u32,
77    size: u32,
78}
79
80#[inline]
81fn align(offset: u32, align: u32) -> u32 {
82    assert!(align.is_power_of_two());
83    (offset + (align - 1)) & !(align - 1)
84}
85
86impl<P: PtrSize> VMComponentOffsets<P> {
87    /// Creates a new set of offsets for the `component` specified configured
88    /// additionally for the `ptr` size specified.
89    pub fn new(ptr: P, component: &Component) -> Self {
90        let mut ret = Self {
91            ptr,
92            num_lowerings: component.num_lowerings,
93            num_runtime_memories: component.num_runtime_memories,
94            num_runtime_tables: component.num_runtime_tables,
95            num_runtime_reallocs: component.num_runtime_reallocs,
96            num_runtime_callbacks: component.num_runtime_callbacks,
97            num_runtime_post_returns: component.num_runtime_post_returns,
98            num_runtime_component_instances: component.num_runtime_component_instances,
99            num_trampolines: component.trampolines.len().try_into().unwrap(),
100            num_resources: component.num_resources,
101            magic: 0,
102            builtins: 0,
103            vm_store_context: 0,
104            flags: 0,
105            trampoline_func_refs: 0,
106            lowerings: 0,
107            memories: 0,
108            tables: 0,
109            reallocs: 0,
110            callbacks: 0,
111            post_returns: 0,
112            resource_destructors: 0,
113            size: 0,
114        };
115
116        // Convenience functions for checked addition and multiplication.
117        // As side effect this reduces binary size by using only a single
118        // `#[track_caller]` location for each function instead of one for
119        // each individual invocation.
120        #[inline]
121        fn cmul(count: u32, size: u8) -> u32 {
122            count.checked_mul(u32::from(size)).unwrap()
123        }
124
125        let mut next_field_offset = 0;
126
127        macro_rules! fields {
128            (size($field:ident) = $size:expr, $($rest:tt)*) => {
129                ret.$field = next_field_offset;
130                next_field_offset = next_field_offset.checked_add(u32::from($size)).unwrap();
131                fields!($($rest)*);
132            };
133            (align($align:expr), $($rest:tt)*) => {
134                next_field_offset = align(next_field_offset, $align);
135                fields!($($rest)*);
136            };
137            () => {};
138        }
139
140        fields! {
141            size(magic) = 4u32,
142            align(u32::from(ret.ptr.size())),
143            size(builtins) = ret.ptr.size(),
144            size(vm_store_context) = ret.ptr.size(),
145            align(16),
146            size(flags) = cmul(ret.num_runtime_component_instances, ret.ptr.size_of_vmglobal_definition()),
147            align(u32::from(ret.ptr.size())),
148            size(trampoline_func_refs) = cmul(ret.num_trampolines, ret.ptr.size_of_vm_func_ref()),
149            size(lowerings) = cmul(ret.num_lowerings, ret.ptr.size() * 2),
150            size(memories) = cmul(ret.num_runtime_memories, ret.ptr.size()),
151            size(tables) = cmul(ret.num_runtime_tables, ret.size_of_vmtable_import()),
152            size(reallocs) = cmul(ret.num_runtime_reallocs, ret.ptr.size()),
153            size(callbacks) = cmul(ret.num_runtime_callbacks, ret.ptr.size()),
154            size(post_returns) = cmul(ret.num_runtime_post_returns, ret.ptr.size()),
155            size(resource_destructors) = cmul(ret.num_resources, ret.ptr.size()),
156        }
157
158        ret.size = next_field_offset;
159
160        // This is required by the implementation of
161        // `VMComponentContext::from_opaque`. If this value changes then this
162        // location needs to be updated.
163        assert_eq!(ret.magic, 0);
164
165        return ret;
166    }
167
168    /// The size, in bytes, of the host pointer.
169    #[inline]
170    pub fn pointer_size(&self) -> u8 {
171        self.ptr.size()
172    }
173
174    /// The offset of the `magic` field.
175    #[inline]
176    pub fn magic(&self) -> u32 {
177        self.magic
178    }
179
180    /// The offset of the `builtins` field.
181    #[inline]
182    pub fn builtins(&self) -> u32 {
183        self.builtins
184    }
185
186    /// The offset of the `flags` field.
187    #[inline]
188    pub fn instance_flags(&self, index: RuntimeComponentInstanceIndex) -> u32 {
189        assert!(index.as_u32() < self.num_runtime_component_instances);
190        self.flags + index.as_u32() * u32::from(self.ptr.size_of_vmglobal_definition())
191    }
192
193    /// The offset of the `vm_store_context` field.
194    #[inline]
195    pub fn vm_store_context(&self) -> u32 {
196        self.vm_store_context
197    }
198
199    /// The offset of the `trampoline_func_refs` field.
200    #[inline]
201    pub fn trampoline_func_refs(&self) -> u32 {
202        self.trampoline_func_refs
203    }
204
205    /// The offset of `VMFuncRef` for the `index` specified.
206    #[inline]
207    pub fn trampoline_func_ref(&self, index: TrampolineIndex) -> u32 {
208        assert!(index.as_u32() < self.num_trampolines);
209        self.trampoline_func_refs() + index.as_u32() * u32::from(self.ptr.size_of_vm_func_ref())
210    }
211
212    /// The offset of the `lowerings` field.
213    #[inline]
214    pub fn lowerings(&self) -> u32 {
215        self.lowerings
216    }
217
218    /// The offset of the `VMLowering` for the `index` specified.
219    #[inline]
220    pub fn lowering(&self, index: LoweredIndex) -> u32 {
221        assert!(index.as_u32() < self.num_lowerings);
222        self.lowerings() + index.as_u32() * u32::from(2 * self.ptr.size())
223    }
224
225    /// The offset of the `callee` for the `index` specified.
226    #[inline]
227    pub fn lowering_callee(&self, index: LoweredIndex) -> u32 {
228        self.lowering(index) + self.lowering_callee_offset()
229    }
230
231    /// The offset of the `data` for the `index` specified.
232    #[inline]
233    pub fn lowering_data(&self, index: LoweredIndex) -> u32 {
234        self.lowering(index) + self.lowering_data_offset()
235    }
236
237    /// The size of the `VMLowering` type
238    #[inline]
239    pub fn lowering_size(&self) -> u8 {
240        2 * self.ptr.size()
241    }
242
243    /// The offset of the `callee` field within the `VMLowering` type.
244    #[inline]
245    pub fn lowering_callee_offset(&self) -> u32 {
246        0
247    }
248
249    /// The offset of the `data` field within the `VMLowering` type.
250    #[inline]
251    pub fn lowering_data_offset(&self) -> u32 {
252        u32::from(self.ptr.size())
253    }
254
255    /// The offset of the base of the `runtime_memories` field
256    #[inline]
257    pub fn runtime_memories(&self) -> u32 {
258        self.memories
259    }
260
261    /// The offset of the `*mut VMMemoryDefinition` for the runtime index
262    /// provided.
263    #[inline]
264    pub fn runtime_memory(&self, index: RuntimeMemoryIndex) -> u32 {
265        assert!(index.as_u32() < self.num_runtime_memories);
266        self.runtime_memories() + index.as_u32() * u32::from(self.ptr.size())
267    }
268
269    /// The offset of the base of the `runtime_tables` field
270    #[inline]
271    pub fn runtime_tables(&self) -> u32 {
272        self.tables
273    }
274
275    /// The offset of the table for the runtime index provided.
276    #[inline]
277    pub fn runtime_table(&self, index: RuntimeTableIndex) -> u32 {
278        assert!(index.as_u32() < self.num_runtime_tables);
279        self.runtime_tables() + index.as_u32() * u32::from(self.size_of_vmtable_import())
280    }
281
282    /// Return the size of `VMTableImport`, used here to hold the pointers to
283    /// the `VMTableDefinition` and `VMContext`.
284    #[inline]
285    pub fn size_of_vmtable_import(&self) -> u8 {
286        3 * self.pointer_size()
287    }
288
289    /// The offset of the base of the `runtime_reallocs` field
290    #[inline]
291    pub fn runtime_reallocs(&self) -> u32 {
292        self.reallocs
293    }
294
295    /// The offset of the `*mut VMFuncRef` for the runtime index
296    /// provided.
297    #[inline]
298    pub fn runtime_realloc(&self, index: RuntimeReallocIndex) -> u32 {
299        assert!(index.as_u32() < self.num_runtime_reallocs);
300        self.runtime_reallocs() + index.as_u32() * u32::from(self.ptr.size())
301    }
302
303    /// The offset of the base of the `runtime_callbacks` field
304    #[inline]
305    pub fn runtime_callbacks(&self) -> u32 {
306        self.callbacks
307    }
308
309    /// The offset of the `*mut VMFuncRef` for the runtime index
310    /// provided.
311    #[inline]
312    pub fn runtime_callback(&self, index: RuntimeCallbackIndex) -> u32 {
313        assert!(index.as_u32() < self.num_runtime_callbacks);
314        self.runtime_callbacks() + index.as_u32() * u32::from(self.ptr.size())
315    }
316
317    /// The offset of the base of the `runtime_post_returns` field
318    #[inline]
319    pub fn runtime_post_returns(&self) -> u32 {
320        self.post_returns
321    }
322
323    /// The offset of the `*mut VMFuncRef` for the runtime index
324    /// provided.
325    #[inline]
326    pub fn runtime_post_return(&self, index: RuntimePostReturnIndex) -> u32 {
327        assert!(index.as_u32() < self.num_runtime_post_returns);
328        self.runtime_post_returns() + index.as_u32() * u32::from(self.ptr.size())
329    }
330
331    /// The offset of the base of the `resource_destructors` field
332    #[inline]
333    pub fn resource_destructors(&self) -> u32 {
334        self.resource_destructors
335    }
336
337    /// The offset of the `*mut VMFuncRef` for the runtime index
338    /// provided.
339    #[inline]
340    pub fn resource_destructor(&self, index: ResourceIndex) -> u32 {
341        assert!(index.as_u32() < self.num_resources);
342        self.resource_destructors() + index.as_u32() * u32::from(self.ptr.size())
343    }
344
345    /// Return the size of the `VMComponentContext` allocation.
346    #[inline]
347    pub fn size_of_vmctx(&self) -> u32 {
348        self.size
349    }
350}
wasmtime_environ/component/vmcomponent_offsets.rs

wasmtime_environ/component/
vmcomponent_offsets.rs
