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Refactor some internal accessors of Instance (#3021)

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This commit removes some one-use methods to inline them at their use
site, and otherwise adds bounds checks to other functions like
`imported_function` where previously the `FuncIndex` may have been
accidentally out of bounds, which would cause memory unsafety. There's
no actual bug this was fixing, just trying to improve the safety of the
code internally a little.
This commit is contained in:
Alex Crichton
2021-06-23 12:12:38 -05:00
committed by GitHub
parent 83007b79e3
commit 324d80729a
2 changed files with 41 additions and 110 deletions
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131
crates/runtime/src/instance.rs
View File

@@ -8,9 +8,8 @@ use crate::memory::{Memory, RuntimeMemoryCreator};
use crate::table::{Table, TableElement};
use crate::traphandlers::Trap;
use crate::vmcontext::{
VMBuiltinFunctionsArray, VMCallerCheckedAnyfunc, VMContext, VMFunctionImport,
VMGlobalDefinition, VMGlobalImport, VMInterrupts, VMMemoryDefinition, VMMemoryImport,
VMSharedSignatureIndex, VMTableDefinition, VMTableImport,
VMCallerCheckedAnyfunc, VMContext, VMFunctionImport, VMGlobalDefinition, VMGlobalImport,
VMInterrupts, VMMemoryDefinition, VMMemoryImport, VMTableDefinition, VMTableImport,
};
use crate::{ExportFunction, ExportGlobal, ExportMemory, ExportTable, Store};
use memoffset::offset_of;
@@ -147,53 +146,24 @@ impl Instance {
&self.module
}
/// Return a pointer to the `VMSharedSignatureIndex`s.
fn signature_ids_ptr(&self) -> *mut VMSharedSignatureIndex {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_signature_ids_begin()) }
}
/// Return the indexed `VMFunctionImport`.
fn imported_function(&self, index: FuncIndex) -> &VMFunctionImport {
let index = usize::try_from(index.as_u32()).unwrap();
unsafe { &*self.imported_functions_ptr().add(index) }
}
/// Return a pointer to the `VMFunctionImport`s.
fn imported_functions_ptr(&self) -> *mut VMFunctionImport {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_imported_functions_begin()) }
unsafe { &*self.vmctx_plus_offset(self.offsets.vmctx_vmfunction_import(index)) }
}
/// Return the index `VMTableImport`.
fn imported_table(&self, index: TableIndex) -> &VMTableImport {
let index = usize::try_from(index.as_u32()).unwrap();
unsafe { &*self.imported_tables_ptr().add(index) }
}
/// Return a pointer to the `VMTableImports`s.
fn imported_tables_ptr(&self) -> *mut VMTableImport {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_imported_tables_begin()) }
unsafe { &*self.vmctx_plus_offset(self.offsets.vmctx_vmtable_import(index)) }
}
/// Return the indexed `VMMemoryImport`.
fn imported_memory(&self, index: MemoryIndex) -> &VMMemoryImport {
let index = usize::try_from(index.as_u32()).unwrap();
unsafe { &*self.imported_memories_ptr().add(index) }
}
/// Return a pointer to the `VMMemoryImport`s.
fn imported_memories_ptr(&self) -> *mut VMMemoryImport {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_imported_memories_begin()) }
unsafe { &*self.vmctx_plus_offset(self.offsets.vmctx_vmmemory_import(index)) }
}
/// Return the indexed `VMGlobalImport`.
fn imported_global(&self, index: GlobalIndex) -> &VMGlobalImport {
let index = usize::try_from(index.as_u32()).unwrap();
unsafe { &*self.imported_globals_ptr().add(index) }
}
/// Return a pointer to the `VMGlobalImport`s.
fn imported_globals_ptr(&self) -> *mut VMGlobalImport {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_imported_globals_begin()) }
unsafe { &*self.vmctx_plus_offset(self.offsets.vmctx_vmglobal_import(index)) }
}
/// Return the indexed `VMTableDefinition`.
@@ -211,13 +181,7 @@ impl Instance {
/// Return the indexed `VMTableDefinition`.
fn table_ptr(&self, index: DefinedTableIndex) -> *mut VMTableDefinition {
let index = usize::try_from(index.as_u32()).unwrap();
unsafe { self.tables_ptr().add(index) }
}
/// Return a pointer to the `VMTableDefinition`s.
fn tables_ptr(&self) -> *mut VMTableDefinition {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_tables_begin()) }
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_vmtable_definition(index)) }
}
/// Get a locally defined or imported memory.
@@ -244,13 +208,7 @@ impl Instance {
/// Return the indexed `VMMemoryDefinition`.
fn memory_ptr(&self, index: DefinedMemoryIndex) -> *mut VMMemoryDefinition {
let index = usize::try_from(index.as_u32()).unwrap();
unsafe { self.memories_ptr().add(index) }
}
/// Return a pointer to the `VMMemoryDefinition`s.
fn memories_ptr(&self) -> *mut VMMemoryDefinition {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_memories_begin()) }
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_vmmemory_definition(index)) }
}
/// Return the indexed `VMGlobalDefinition`.
@@ -260,8 +218,7 @@ impl Instance {
/// Return the indexed `VMGlobalDefinition`.
fn global_ptr(&self, index: DefinedGlobalIndex) -> *mut VMGlobalDefinition {
let index = usize::try_from(index.as_u32()).unwrap();
unsafe { self.globals_ptr().add(index) }
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_vmglobal_definition(index)) }
}
/// Get a raw pointer to the global at the given index regardless whether it
@@ -279,16 +236,6 @@ impl Instance {
}
}
/// Return a pointer to the `VMGlobalDefinition`s.
fn globals_ptr(&self) -> *mut VMGlobalDefinition {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_globals_begin()) }
}
/// Return a pointer to the `VMBuiltinFunctionsArray`.
fn builtin_functions_ptr(&self) -> *mut VMBuiltinFunctionsArray {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_builtin_functions_begin()) }
}
/// Return a pointer to the interrupts structure
pub fn interrupts(&self) -> *mut *const VMInterrupts {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_interrupts()) }
@@ -410,32 +357,26 @@ impl Instance {
}
/// Return the table index for the given `VMTableDefinition`.
pub(crate) fn table_index(&self, table: &VMTableDefinition) -> DefinedTableIndex {
let offsets = &self.offsets;
let begin = unsafe {
(&self.vmctx as *const VMContext as *const u8)
.add(usize::try_from(offsets.vmctx_tables_begin()).unwrap())
} as *const VMTableDefinition;
let end: *const VMTableDefinition = table;
// TODO: Use `offset_from` once it stablizes.
unsafe fn table_index(&self, table: &VMTableDefinition) -> DefinedTableIndex {
let index = DefinedTableIndex::new(
(end as usize - begin as usize) / mem::size_of::<VMTableDefinition>(),
usize::try_from(
(table as *const VMTableDefinition)
.offset_from(self.table_ptr(DefinedTableIndex::new(0))),
)
.unwrap(),
);
assert_lt!(index.index(), self.tables.len());
index
}
/// Return the memory index for the given `VMMemoryDefinition`.
pub(crate) fn memory_index(&self, memory: &VMMemoryDefinition) -> DefinedMemoryIndex {
let offsets = &self.offsets;
let begin = unsafe {
(&self.vmctx as *const VMContext as *const u8)
.add(usize::try_from(offsets.vmctx_memories_begin()).unwrap())
} as *const VMMemoryDefinition;
let end: *const VMMemoryDefinition = memory;
// TODO: Use `offset_from` once it stablizes.
unsafe fn memory_index(&self, memory: &VMMemoryDefinition) -> DefinedMemoryIndex {
let index = DefinedMemoryIndex::new(
(end as usize - begin as usize) / mem::size_of::<VMMemoryDefinition>(),
usize::try_from(
(memory as *const VMMemoryDefinition)
.offset_from(self.memory_ptr(DefinedMemoryIndex::new(0))),
)
.unwrap(),
);
assert_lt!(index.index(), self.memories.len());
index
@@ -854,11 +795,8 @@ impl Instance {
/// Get a table by index regardless of whether it is locally-defined or an
/// imported, foreign table.
pub(crate) fn get_table(&mut self, table_index: TableIndex) -> *mut Table {
if let Some(defined_table_index) = self.module.defined_table_index(table_index) {
self.get_defined_table(defined_table_index)
} else {
self.get_foreign_table(table_index)
}
let (idx, instance) = self.get_defined_table_index_and_instance(table_index);
ptr::addr_of_mut!(instance.tables[idx])
}
/// Get a locally-defined table.
@@ -866,15 +804,6 @@ impl Instance {
ptr::addr_of_mut!(self.tables[index])
}
/// Get an imported, foreign table.
pub(crate) fn get_foreign_table(&mut self, index: TableIndex) -> *mut Table {
let import = self.imported_table(index);
let foreign_instance = unsafe { (*import.vmctx).instance_mut() };
let foreign_table = unsafe { &*import.from };
let foreign_index = foreign_instance.table_index(foreign_table);
ptr::addr_of_mut!(foreign_instance.tables[foreign_index])
}
pub(crate) fn get_defined_table_index_and_instance(
&mut self,
index: TableIndex,
@@ -883,10 +812,12 @@ impl Instance {
(defined_table_index, self)
} else {
let import = self.imported_table(index);
let foreign_instance = unsafe { (*import.vmctx).instance_mut() };
let foreign_table_def = unsafe { &*import.from };
let foreign_table_index = foreign_instance.table_index(foreign_table_def);
(foreign_table_index, foreign_instance)
unsafe {
let foreign_instance = (*import.vmctx).instance_mut();
let foreign_table_def = &*import.from;
let foreign_table_index = foreign_instance.table_index(foreign_table_def);
(foreign_table_index, foreign_instance)
}
}
}
@@ -981,7 +912,7 @@ impl InstanceHandle {
}
/// Return the memory index for the given `VMMemoryDefinition` in this instance.
pub fn memory_index(&self, memory: &VMMemoryDefinition) -> DefinedMemoryIndex {
pub unsafe fn memory_index(&self, memory: &VMMemoryDefinition) -> DefinedMemoryIndex {
self.instance().memory_index(memory)
}
@@ -991,7 +922,7 @@ impl InstanceHandle {
}
/// Return the table index for the given `VMTableDefinition` in this instance.
pub fn table_index(&self, table: &VMTableDefinition) -> DefinedTableIndex {
pub unsafe fn table_index(&self, table: &VMTableDefinition) -> DefinedTableIndex {
self.instance().table_index(table)
}