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//      may_leave: [VMGlobalDefinition; component.num_runtime_component_instances],
8//      task_may_block: u32,
9//      trampoline_func_refs: [VMFuncRef; component.num_trampolines],
10//      unsafe_intrinsics: [VMFuncRef; component.num_unsafe_intrinsics],
11//      lowerings: [VMLowering; component.num_lowerings],
12//      memories: [*mut VMMemoryDefinition; component.num_runtime_memories],
13//      tables: [VMTable; component.num_runtime_tables],
14//      reallocs: [*mut VMFuncRef; component.num_runtime_reallocs],
15//      post_returns: [*mut VMFuncRef; component.num_runtime_post_returns],
16//      resource_destructors: [*mut VMFuncRef; component.num_resources],
17// }
18
19use crate::GetPtrSize;
20use crate::PtrSize;
21use crate::component::*;
22
23/// Equivalent of `VMCONTEXT_MAGIC` except for components.
24///
25/// This is stored at the start of all `VMComponentContext` structures and
26/// double-checked on `VMComponentContext::from_opaque`.
27pub const VMCOMPONENT_MAGIC: u32 = u32::from_le_bytes(*b"comp");
28
29/// Runtime offsets within a `VMComponentContext` for a specific component.
30#[derive(Debug, Clone, Copy)]
31pub struct VMComponentOffsets<P> {
32    /// The host pointer size
33    pub ptr: P,
34
35    /// The number of lowered functions this component will be creating.
36    pub num_lowerings: u32,
37    /// The number of memories which are recorded in this component for options.
38    pub num_runtime_memories: u32,
39    /// The number of tables which are recorded in this component for options.
40    pub num_runtime_tables: u32,
41    /// The number of reallocs which are recorded in this component for options.
42    pub num_runtime_reallocs: u32,
43    /// The number of callbacks which are recorded in this component for options.
44    pub num_runtime_callbacks: u32,
45    /// The number of post-returns which are recorded in this component for options.
46    pub num_runtime_post_returns: u32,
47    /// Number of component instances internally in the component (always at
48    /// least 1).
49    pub num_runtime_component_instances: u32,
50    /// Number of cranelift-compiled trampolines required for this component.
51    pub num_trampolines: u32,
52    /// Number of `VMFuncRef`s for unsafe intrinsics within this component's
53    /// context.
54    pub num_unsafe_intrinsics: u32,
55    /// Number of resources within a component which need destructors stored.
56    pub num_resources: u32,
57
58    // precalculated offsets of various member fields
59    magic: u32,
60    builtins: u32,
61    vm_store_context: u32,
62    may_leave: u32,
63    task_may_block: u32,
64    trampoline_func_refs: u32,
65    intrinsic_func_refs: u32,
66    lowerings: u32,
67    memories: u32,
68    tables: u32,
69    reallocs: u32,
70    callbacks: u32,
71    post_returns: u32,
72    resource_destructors: u32,
73    size: u32,
74}
75
76impl<P: PtrSize> GetPtrSize for VMComponentOffsets<P> {
77    type Ptr = P;
78
79    #[inline]
80    fn get_ptr_size(&self) -> &Self::Ptr {
81        &self.ptr
82    }
83}
84
85#[inline]
86fn align(offset: u32, align: u32) -> u32 {
87    assert!(align.is_power_of_two());
88    (offset + (align - 1)) & !(align - 1)
89}
90
91impl<P: PtrSize> VMComponentOffsets<P> {
92    /// Creates a new set of offsets for the `component` specified configured
93    /// additionally for the `ptr` size specified.
94    pub fn new(ptr: P, component: &Component) -> Self {
95        let mut ret = Self {
96            ptr,
97            num_lowerings: component.num_lowerings,
98            num_runtime_memories: component.num_runtime_memories,
99            num_runtime_tables: component.num_runtime_tables,
100            num_runtime_reallocs: component.num_runtime_reallocs,
101            num_runtime_callbacks: component.num_runtime_callbacks,
102            num_runtime_post_returns: component.num_runtime_post_returns,
103            num_runtime_component_instances: component.num_runtime_component_instances,
104            num_trampolines: component.trampolines.len().try_into().unwrap(),
105            num_unsafe_intrinsics: if let Some(i) = component
106                .unsafe_intrinsics
107                .iter()
108                .rposition(|x| x.is_some())
109            {
110                // Note: We do not currently have an indirection between "the
111                // `i`th unsafe intrinsic in the vmctx" and
112                // `UnsafeIntrinsic::from_u32(i)`, so therefore if we are
113                // compiling in *any* intrinsics, we need to include space for
114                // all of them up to the max `i` that is used.
115                //
116                // We _could_ introduce such an indirection via a map in
117                // `Component` like `PrimaryMap<UnsafeIntrinsicIndex,
118                // UnsafeIntrinsic>`, and that would allow us to densely pack
119                // intrinsics in the vmctx. However we do not do that today
120                // because there are very few unsafe intrinsics, and we do not
121                // see that changing anytime soon, so we aren't wasting much
122                // space.
123                u32::try_from(i + 1).unwrap()
124            } else {
125                0
126            },
127            num_resources: component.num_resources,
128            magic: 0,
129            builtins: 0,
130            vm_store_context: 0,
131            may_leave: 0,
132            task_may_block: 0,
133            trampoline_func_refs: 0,
134            intrinsic_func_refs: 0,
135            lowerings: 0,
136            memories: 0,
137            tables: 0,
138            reallocs: 0,
139            callbacks: 0,
140            post_returns: 0,
141            resource_destructors: 0,
142            size: 0,
143        };
144
145        // Convenience functions for checked addition and multiplication.
146        // As side effect this reduces binary size by using only a single
147        // `#[track_caller]` location for each function instead of one for
148        // each individual invocation.
149        #[inline]
150        fn cmul(count: u32, size: u8) -> u32 {
151            count.checked_mul(u32::from(size)).unwrap()
152        }
153
154        let mut next_field_offset = 0;
155
156        macro_rules! fields {
157            (size($field:ident) = $size:expr, $($rest:tt)*) => {
158                ret.$field = next_field_offset;
159                next_field_offset = next_field_offset.checked_add(u32::from($size)).unwrap();
160                fields!($($rest)*);
161            };
162            (align($align:expr), $($rest:tt)*) => {
163                next_field_offset = align(next_field_offset, $align);
164                fields!($($rest)*);
165            };
166            () => {};
167        }
168
169        fields! {
170            size(magic) = 4u32,
171            align(u32::from(ret.ptr.size())),
172            size(builtins) = ret.ptr.size(),
173            size(vm_store_context) = ret.ptr.size(),
174            align(16),
175            size(may_leave) = cmul(ret.num_runtime_component_instances, ret.ptr.size_of_vmglobal_definition()),
176            size(task_may_block) = ret.ptr.size_of_vmglobal_definition(),
177            align(u32::from(ret.ptr.size())),
178            size(trampoline_func_refs) = cmul(ret.num_trampolines, ret.ptr.size_of_vm_func_ref()),
179            size(intrinsic_func_refs) = cmul(ret.num_unsafe_intrinsics, ret.ptr.size_of_vm_func_ref()),
180            size(lowerings) = cmul(ret.num_lowerings, ret.ptr.size() * 2),
181            size(memories) = cmul(ret.num_runtime_memories, ret.ptr.size()),
182            size(tables) = cmul(ret.num_runtime_tables, ret.size_of_vmtable_import()),
183            size(reallocs) = cmul(ret.num_runtime_reallocs, ret.ptr.size()),
184            size(callbacks) = cmul(ret.num_runtime_callbacks, ret.ptr.size()),
185            size(post_returns) = cmul(ret.num_runtime_post_returns, ret.ptr.size()),
186            size(resource_destructors) = cmul(ret.num_resources, ret.ptr.size()),
187        }
188
189        ret.size = next_field_offset;
190
191        // This is required by the implementation of
192        // `VMComponentContext::from_opaque`. If this value changes then this
193        // location needs to be updated.
194        assert_eq!(ret.magic, 0);
195
196        return ret;
197    }
198
199    /// The size, in bytes, of the host pointer.
200    #[inline]
201    pub fn pointer_size(&self) -> u8 {
202        self.ptr.size()
203    }
204
205    /// The offset of the `magic` field.
206    #[inline]
207    pub fn magic(&self) -> u32 {
208        self.magic
209    }
210
211    /// The offset of the `builtins` field.
212    #[inline]
213    pub fn builtins(&self) -> u32 {
214        self.builtins
215    }
216
217    /// The offset of the `may_leave` flag for the given component instance.
218    #[inline]
219    pub fn may_leave(&self, index: RuntimeComponentInstanceIndex) -> u32 {
220        assert!(index.as_u32() < self.num_runtime_component_instances);
221        self.may_leave + index.as_u32() * u32::from(self.ptr.size_of_vmglobal_definition())
222    }
223
224    /// The offset of the `task_may_block` field.
225    pub fn task_may_block(&self) -> u32 {
226        self.task_may_block
227    }
228
229    /// The offset of the `vm_store_context` field.
230    #[inline]
231    pub fn vm_store_context(&self) -> u32 {
232        self.vm_store_context
233    }
234
235    /// The offset of the `trampoline_func_refs` field.
236    #[inline]
237    pub fn trampoline_func_refs(&self) -> u32 {
238        self.trampoline_func_refs
239    }
240
241    /// The offset of `VMFuncRef` for the `index` specified.
242    #[inline]
243    pub fn trampoline_func_ref(&self, index: TrampolineIndex) -> u32 {
244        assert!(index.as_u32() < self.num_trampolines);
245        self.trampoline_func_refs() + index.as_u32() * u32::from(self.ptr.size_of_vm_func_ref())
246    }
247
248    /// The offset of the `unsafe_intrinsic_func_refs` field.
249    #[inline]
250    pub fn unsafe_intrinsic_func_refs(&self) -> u32 {
251        self.intrinsic_func_refs
252    }
253
254    /// The offset of the `VMFuncRef` for the `intrinsic` specified.
255    #[inline]
256    pub fn unsafe_intrinsic_func_ref(&self, intrinsic: UnsafeIntrinsic) -> u32 {
257        assert!(intrinsic.index() < self.num_unsafe_intrinsics);
258        self.unsafe_intrinsic_func_refs()
259            + intrinsic.index() * u32::from(self.ptr.size_of_vm_func_ref())
260    }
261
262    /// The offset of the `lowerings` field.
263    #[inline]
264    pub fn lowerings(&self) -> u32 {
265        self.lowerings
266    }
267
268    /// The offset of the `VMLowering` for the `index` specified.
269    #[inline]
270    pub fn lowering(&self, index: LoweredIndex) -> u32 {
271        assert!(index.as_u32() < self.num_lowerings);
272        self.lowerings() + index.as_u32() * u32::from(2 * self.ptr.size())
273    }
274
275    /// The offset of the `callee` for the `index` specified.
276    #[inline]
277    pub fn lowering_callee(&self, index: LoweredIndex) -> u32 {
278        self.lowering(index) + self.lowering_callee_offset()
279    }
280
281    /// The offset of the `data` for the `index` specified.
282    #[inline]
283    pub fn lowering_data(&self, index: LoweredIndex) -> u32 {
284        self.lowering(index) + self.lowering_data_offset()
285    }
286
287    /// The size of the `VMLowering` type
288    #[inline]
289    pub fn lowering_size(&self) -> u8 {
290        2 * self.ptr.size()
291    }
292
293    /// The offset of the `callee` field within the `VMLowering` type.
294    #[inline]
295    pub fn lowering_callee_offset(&self) -> u32 {
296        0
297    }
298
299    /// The offset of the `data` field within the `VMLowering` type.
300    #[inline]
301    pub fn lowering_data_offset(&self) -> u32 {
302        u32::from(self.ptr.size())
303    }
304
305    /// The offset of the base of the `runtime_memories` field
306    #[inline]
307    pub fn runtime_memories(&self) -> u32 {
308        self.memories
309    }
310
311    /// The offset of the `*mut VMMemoryDefinition` for the runtime index
312    /// provided.
313    #[inline]
314    pub fn runtime_memory(&self, index: RuntimeMemoryIndex) -> u32 {
315        assert!(index.as_u32() < self.num_runtime_memories);
316        self.runtime_memories() + index.as_u32() * u32::from(self.ptr.size())
317    }
318
319    /// The offset of the base of the `runtime_tables` field
320    #[inline]
321    pub fn runtime_tables(&self) -> u32 {
322        self.tables
323    }
324
325    /// The offset of the table for the runtime index provided.
326    #[inline]
327    pub fn runtime_table(&self, index: RuntimeTableIndex) -> u32 {
328        assert!(index.as_u32() < self.num_runtime_tables);
329        self.runtime_tables() + index.as_u32() * u32::from(self.size_of_vmtable_import())
330    }
331
332    /// Return the size of `VMTableImport`, used here to hold the pointers to
333    /// the `VMTableDefinition` and `VMContext`.
334    #[inline]
335    pub fn size_of_vmtable_import(&self) -> u8 {
336        3 * self.pointer_size()
337    }
338
339    /// The offset of the base of the `runtime_reallocs` field
340    #[inline]
341    pub fn runtime_reallocs(&self) -> u32 {
342        self.reallocs
343    }
344
345    /// The offset of the `*mut VMFuncRef` for the runtime index
346    /// provided.
347    #[inline]
348    pub fn runtime_realloc(&self, index: RuntimeReallocIndex) -> u32 {
349        assert!(index.as_u32() < self.num_runtime_reallocs);
350        self.runtime_reallocs() + index.as_u32() * u32::from(self.ptr.size())
351    }
352
353    /// The offset of the base of the `runtime_callbacks` field
354    #[inline]
355    pub fn runtime_callbacks(&self) -> u32 {
356        self.callbacks
357    }
358
359    /// The offset of the `*mut VMFuncRef` for the runtime index
360    /// provided.
361    #[inline]
362    pub fn runtime_callback(&self, index: RuntimeCallbackIndex) -> u32 {
363        assert!(index.as_u32() < self.num_runtime_callbacks);
364        self.runtime_callbacks() + index.as_u32() * u32::from(self.ptr.size())
365    }
366
367    /// The offset of the base of the `runtime_post_returns` field
368    #[inline]
369    pub fn runtime_post_returns(&self) -> u32 {
370        self.post_returns
371    }
372
373    /// The offset of the `*mut VMFuncRef` for the runtime index
374    /// provided.
375    #[inline]
376    pub fn runtime_post_return(&self, index: RuntimePostReturnIndex) -> u32 {
377        assert!(index.as_u32() < self.num_runtime_post_returns);
378        self.runtime_post_returns() + index.as_u32() * u32::from(self.ptr.size())
379    }
380
381    /// The offset of the base of the `resource_destructors` field
382    #[inline]
383    pub fn resource_destructors(&self) -> u32 {
384        self.resource_destructors
385    }
386
387    /// The offset of the `*mut VMFuncRef` for the runtime index
388    /// provided.
389    #[inline]
390    pub fn resource_destructor(&self, index: ResourceIndex) -> u32 {
391        assert!(index.as_u32() < self.num_resources);
392        self.resource_destructors() + index.as_u32() * u32::from(self.ptr.size())
393    }
394
395    /// Return the size of the `VMComponentContext` allocation.
396    #[inline]
397    pub fn size_of_vmctx(&self) -> u32 {
398        self.size
399    }
400}
wasmtime_environ/component/vmcomponent_offsets.rs

wasmtime_environ/component/
vmcomponent_offsets.rs
