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cmd/internal/obj/wasm: correct return PC for frameless wasmexport wrappers

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For a wasmexport wrapper, we generate a call to the actual
exported Go function, and use the wrapper function's PC 1 as the
(fake) return address. This address is not used for returning,
which is handled by the Wasm call stack. It is used for stack
unwinding, and PC 1 makes it past the prologue and therefore has
the right SP delta. But if the function has no arguments and
results, the wrapper is frameless, with no prologue, and PC 1
doesn't exist. This causes the unwinder to fail. In this case, we
put PC 0, which also has the correct SP delta (0).

Fixes #69584.

Change-Id: Ic047a6e62100db540b5099cc5a56a1d0f16d58b9
Reviewed-on: https://go-review.googlesource.com/c/go/+/624000
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Cherry Mui 2024-11-01 12:04:49 -04:00
parent 26e1010372
commit 4ffa2aecc1
3 changed files with 17 additions and 5 deletions
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1
lib/wasm/wasm_exec.js
View File

@ -217,6 +217,7 @@
}
const testCallExport = (a, b) => {
this._inst.exports.testExport0();
return this._inst.exports.testExport(a, b);
}

16
src/cmd/internal/obj/wasm/wasmobj.go
View File

@ -974,6 +974,10 @@ func genWasmExportWrapper(s *obj.LSym, appendp func(p *obj.Prog, as obj.As, args
Sym: s, // PC_F
Offset: 1, // PC_B=1, past the prologue, so we have the right SP delta
}
if framesize == 0 {
// Frameless function, no prologue.
retAddr.Offset = 0
}
p = appendp(p, AI64Const, retAddr)
p = appendp(p, AI64Store, constAddr(0))
// Set PC_B parameter to function entry
@ -1014,11 +1018,13 @@ func genWasmExportWrapper(s *obj.LSym, appendp func(p *obj.Prog, as obj.As, args
}
// Epilogue. Cannot use ARET as we don't follow Go calling convention.
// SP += framesize
p = appendp(p, AGet, regAddr(REG_SP))
p = appendp(p, AI32Const, constAddr(framesize))
p = appendp(p, AI32Add)
p = appendp(p, ASet, regAddr(REG_SP))
if framesize > 0 {
// SP += framesize
p = appendp(p, AGet, regAddr(REG_SP))
p = appendp(p, AI32Const, constAddr(framesize))
p = appendp(p, AI32Add)
p = appendp(p, ASet, regAddr(REG_SP))
}
p = appendp(p, AReturn)
}

5
src/syscall/js/js_test.go
View File

@ -75,6 +75,11 @@ func testExport(a int32, b int64) int64 {
return <-ch + <-ch
}
//go:wasmexport testExport0
func testExport0() { // no arg or result (see issue 69584)
runtime.GC()
}
var testExportCalled bool
func growStack(n int64) {