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wasm: fix scanning of the stack #3291

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Merged
merged 1 commit into from
Nov 17, 2022
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wasm: fix scanning of the stack #3291

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8 changes: 8 additions & 0 deletions src/runtime/gc_stack_portable.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ package runtime

import (
"internal/task"
"runtime/volatile"
"unsafe"
)

Expand Down Expand Up @@ -39,6 +40,13 @@ type stackChainObject struct {
// stackChainStart. Luckily we don't need to scan these, as these globals are
// stored on the goroutine stack and are therefore already getting scanned.
func markStack() {
// Hack to force LLVM to consider stackChainStart to be live.
// Without this hack, loads and stores may be considered dead and objects on
// the stack might not be correctly tracked. With this volatile load, LLVM
// is forced to consider stackChainStart (and everything it points to) as
// live.
volatile.LoadUint32((*uint32)(unsafe.Pointer(&stackChainStart)))

if task.OnSystemStack() {
markRoots(getCurrentStackPointer(), stackTop)
}
Expand Down