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::component::*;
18use crate::PtrSize;
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.try_into().unwrap(),
94            num_runtime_tables: component.num_runtime_tables.try_into().unwrap(),
95            num_runtime_reallocs: component.num_runtime_reallocs.try_into().unwrap(),
96            num_runtime_callbacks: component.num_runtime_callbacks.try_into().unwrap(),
97            num_runtime_post_returns: component.num_runtime_post_returns.try_into().unwrap(),
98            num_runtime_component_instances: component
99                .num_runtime_component_instances
100                .try_into()
101                .unwrap(),
102            num_trampolines: component.trampolines.len().try_into().unwrap(),
103            num_resources: component.num_resources,
104            magic: 0,
105            builtins: 0,
106            vm_store_context: 0,
107            flags: 0,
108            trampoline_func_refs: 0,
109            lowerings: 0,
110            memories: 0,
111            tables: 0,
112            reallocs: 0,
113            callbacks: 0,
114            post_returns: 0,
115            resource_destructors: 0,
116            size: 0,
117        };
118
119        // Convenience functions for checked addition and multiplication.
120        // As side effect this reduces binary size by using only a single
121        // `#[track_caller]` location for each function instead of one for
122        // each individual invocation.
123        #[inline]
124        fn cmul(count: u32, size: u8) -> u32 {
125            count.checked_mul(u32::from(size)).unwrap()
126        }
127
128        let mut next_field_offset = 0;
129
130        macro_rules! fields {
131            (size($field:ident) = $size:expr, $($rest:tt)*) => {
132                ret.$field = next_field_offset;
133                next_field_offset = next_field_offset.checked_add(u32::from($size)).unwrap();
134                fields!($($rest)*);
135            };
136            (align($align:expr), $($rest:tt)*) => {
137                next_field_offset = align(next_field_offset, $align);
138                fields!($($rest)*);
139            };
140            () => {};
141        }
142
143        fields! {
144            size(magic) = 4u32,
145            align(u32::from(ret.ptr.size())),
146            size(builtins) = ret.ptr.size(),
147            size(vm_store_context) = ret.ptr.size(),
148            align(16),
149            size(flags) = cmul(ret.num_runtime_component_instances, ret.ptr.size_of_vmglobal_definition()),
150            align(u32::from(ret.ptr.size())),
151            size(trampoline_func_refs) = cmul(ret.num_trampolines, ret.ptr.size_of_vm_func_ref()),
152            size(lowerings) = cmul(ret.num_lowerings, ret.ptr.size() * 2),
153            size(memories) = cmul(ret.num_runtime_memories, ret.ptr.size()),
154            size(tables) = cmul(ret.num_runtime_tables, ret.size_of_vmtable()),
155            size(reallocs) = cmul(ret.num_runtime_reallocs, ret.ptr.size()),
156            size(callbacks) = cmul(ret.num_runtime_callbacks, ret.ptr.size()),
157            size(post_returns) = cmul(ret.num_runtime_post_returns, ret.ptr.size()),
158            size(resource_destructors) = cmul(ret.num_resources, ret.ptr.size()),
159        }
160
161        ret.size = next_field_offset;
162
163        // This is required by the implementation of
164        // `VMComponentContext::from_opaque`. If this value changes then this
165        // location needs to be updated.
166        assert_eq!(ret.magic, 0);
167
168        return ret;
169    }
170
171    /// The size, in bytes, of the host pointer.
172    #[inline]
173    pub fn pointer_size(&self) -> u8 {
174        self.ptr.size()
175    }
176
177    /// The offset of the `magic` field.
178    #[inline]
179    pub fn magic(&self) -> u32 {
180        self.magic
181    }
182
183    /// The offset of the `builtins` field.
184    #[inline]
185    pub fn builtins(&self) -> u32 {
186        self.builtins
187    }
188
189    /// The offset of the `flags` field.
190    #[inline]
191    pub fn instance_flags(&self, index: RuntimeComponentInstanceIndex) -> u32 {
192        assert!(index.as_u32() < self.num_runtime_component_instances);
193        self.flags + index.as_u32() * u32::from(self.ptr.size_of_vmglobal_definition())
194    }
195
196    /// The offset of the `vm_store_context` field.
197    #[inline]
198    pub fn vm_store_context(&self) -> u32 {
199        self.vm_store_context
200    }
201
202    /// The offset of the `trampoline_func_refs` field.
203    #[inline]
204    pub fn trampoline_func_refs(&self) -> u32 {
205        self.trampoline_func_refs
206    }
207
208    /// The offset of `VMFuncRef` for the `index` specified.
209    #[inline]
210    pub fn trampoline_func_ref(&self, index: TrampolineIndex) -> u32 {
211        assert!(index.as_u32() < self.num_trampolines);
212        self.trampoline_func_refs() + index.as_u32() * u32::from(self.ptr.size_of_vm_func_ref())
213    }
214
215    /// The offset of the `lowerings` field.
216    #[inline]
217    pub fn lowerings(&self) -> u32 {
218        self.lowerings
219    }
220
221    /// The offset of the `VMLowering` for the `index` specified.
222    #[inline]
223    pub fn lowering(&self, index: LoweredIndex) -> u32 {
224        assert!(index.as_u32() < self.num_lowerings);
225        self.lowerings() + index.as_u32() * u32::from(2 * self.ptr.size())
226    }
227
228    /// The offset of the `callee` for the `index` specified.
229    #[inline]
230    pub fn lowering_callee(&self, index: LoweredIndex) -> u32 {
231        self.lowering(index) + self.lowering_callee_offset()
232    }
233
234    /// The offset of the `data` for the `index` specified.
235    #[inline]
236    pub fn lowering_data(&self, index: LoweredIndex) -> u32 {
237        self.lowering(index) + self.lowering_data_offset()
238    }
239
240    /// The size of the `VMLowering` type
241    #[inline]
242    pub fn lowering_size(&self) -> u8 {
243        2 * self.ptr.size()
244    }
245
246    /// The offset of the `callee` field within the `VMLowering` type.
247    #[inline]
248    pub fn lowering_callee_offset(&self) -> u32 {
249        0
250    }
251
252    /// The offset of the `data` field within the `VMLowering` type.
253    #[inline]
254    pub fn lowering_data_offset(&self) -> u32 {
255        u32::from(self.ptr.size())
256    }
257
258    /// The offset of the base of the `runtime_memories` field
259    #[inline]
260    pub fn runtime_memories(&self) -> u32 {
261        self.memories
262    }
263
264    /// The offset of the `*mut VMMemoryDefinition` for the runtime index
265    /// provided.
266    #[inline]
267    pub fn runtime_memory(&self, index: RuntimeMemoryIndex) -> u32 {
268        assert!(index.as_u32() < self.num_runtime_memories);
269        self.runtime_memories() + index.as_u32() * u32::from(self.ptr.size())
270    }
271
272    /// The offset of the base of the `runtime_tables` field
273    #[inline]
274    pub fn runtime_tables(&self) -> u32 {
275        self.tables
276    }
277
278    /// The offset of the table for the runtime index provided.
279    #[inline]
280    pub fn runtime_table(&self, index: RuntimeTableIndex) -> u32 {
281        assert!(index.as_u32() < self.num_runtime_tables);
282        self.runtime_tables() + index.as_u32() * u32::from(self.size_of_vmtable())
283    }
284
285    /// Return the size of `VMTable`, used here to hold the pointers to
286    /// the `VMTableDefinition` and `VMContext`.
287    #[inline]
288    pub fn size_of_vmtable(&self) -> u8 {
289        2 * self.pointer_size()
290    }
291
292    /// The offset of the base of the `runtime_reallocs` field
293    #[inline]
294    pub fn runtime_reallocs(&self) -> u32 {
295        self.reallocs
296    }
297
298    /// The offset of the `*mut VMFuncRef` for the runtime index
299    /// provided.
300    #[inline]
301    pub fn runtime_realloc(&self, index: RuntimeReallocIndex) -> u32 {
302        assert!(index.as_u32() < self.num_runtime_reallocs);
303        self.runtime_reallocs() + index.as_u32() * u32::from(self.ptr.size())
304    }
305
306    /// The offset of the base of the `runtime_callbacks` field
307    #[inline]
308    pub fn runtime_callbacks(&self) -> u32 {
309        self.callbacks
310    }
311
312    /// The offset of the `*mut VMFuncRef` for the runtime index
313    /// provided.
314    #[inline]
315    pub fn runtime_callback(&self, index: RuntimeCallbackIndex) -> u32 {
316        assert!(index.as_u32() < self.num_runtime_callbacks);
317        self.runtime_callbacks() + index.as_u32() * u32::from(self.ptr.size())
318    }
319
320    /// The offset of the base of the `runtime_post_returns` field
321    #[inline]
322    pub fn runtime_post_returns(&self) -> u32 {
323        self.post_returns
324    }
325
326    /// The offset of the `*mut VMFuncRef` for the runtime index
327    /// provided.
328    #[inline]
329    pub fn runtime_post_return(&self, index: RuntimePostReturnIndex) -> u32 {
330        assert!(index.as_u32() < self.num_runtime_post_returns);
331        self.runtime_post_returns() + index.as_u32() * u32::from(self.ptr.size())
332    }
333
334    /// The offset of the base of the `resource_destructors` field
335    #[inline]
336    pub fn resource_destructors(&self) -> u32 {
337        self.resource_destructors
338    }
339
340    /// The offset of the `*mut VMFuncRef` for the runtime index
341    /// provided.
342    #[inline]
343    pub fn resource_destructor(&self, index: ResourceIndex) -> u32 {
344        assert!(index.as_u32() < self.num_resources);
345        self.resource_destructors() + index.as_u32() * u32::from(self.ptr.size())
346    }
347
348    /// Return the size of the `VMComponentContext` allocation.
349    #[inline]
350    pub fn size_of_vmctx(&self) -> u32 {
351        self.size
352    }
353}
wasmtime_environ/component/vmcomponent_offsets.rs

wasmtime_environ/component/
vmcomponent_offsets.rs
