runtime: add crash stack support for wasm

Currently if morestack on g0 happens the wasm runtime prints
"RuntimeError: memory access out of bounds", which is quite misleading.
By switching to a crash stack we can get better stacktraces
for the error.

There is no way to automate tests for this feature on wasm, since
TestG0StackOverflow relies on spawning a subprocess which is not
supported by the wasm port.

The way I got this tested manually is to comment everything in
TestG0StackOverflow, leaving just runtime.G0StackOverflow().

Then it is a matter of invoking the test:

    GOOS=js GOARCH=wasm go test runtime -v -run=TestG0StackOverflow

Change-Id: If450f3ee5209bb32efc1abd0a34b1cc4a29d0c46
GitHub-Last-Rev: 0d7c396e4cfeadc1188cae2b55661af10c8189e7
GitHub-Pull-Request: golang/go#63956
Reviewed-on: https://go-review.googlesource.com/c/go/+/539995
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

diff --git a/src/runtime/asm.s b/src/runtime/asm.s
index 45ba467806b2a49f193d16217b0363512801a66c..24cd0c95db64ad21bdd4298c4fcdc428e60da954 100644 (file)
--- a/src/runtime/asm.s
+++ b/src/runtime/asm.s
@@ -20,6 +20,7 @@ TEXT ·mapinitnoop<ABIInternal>(SB),NOSPLIT,$0-0
 #ifndef GOARCH_ppc64
 #ifndef GOARCH_ppc64le
 #ifndef GOARCH_riscv64
+#ifndef GOARCH_wasm
 // stub to appease shared build mode.
 TEXT ·switchToCrashStack0<ABIInternal>(SB),NOSPLIT,$0-0
        UNDEF
@@ -30,3 +31,4 @@ TEXT ·switchToCrashStack0<ABIInternal>(SB),NOSPLIT,$0-0
 #endif
 #endif
 #endif
+#endif

diff --git a/src/runtime/asm_wasm.s b/src/runtime/asm_wasm.s
index a96115b02cf5beef674dfc6d496b3fdd40249f0f..b44a4f7dd4983d0319d08ceb1b953f594a851187 100644 (file)
--- a/src/runtime/asm_wasm.s
+++ b/src/runtime/asm_wasm.s
@@ -140,6 +140,7 @@ TEXT runtime·systemstack(SB), NOSPLIT, $0-8
        I64Ne
        If
                CALLNORESUME runtime·badsystemstack(SB)
+               CALLNORESUME runtime·abort(SB)
        End
 
        // switch:
@@ -181,6 +182,9 @@ TEXT runtime·systemstack(SB), NOSPLIT, $0-8
 TEXT runtime·systemstack_switch(SB), NOSPLIT, $0-0
        RET
 
+TEXT runtime·abort(SB),NOSPLIT|NOFRAME,$0-0
+       UNDEF
+
 // AES hashing not implemented for wasm
 TEXT runtime·memhash(SB),NOSPLIT|NOFRAME,$0-32
        JMP     runtime·memhashFallback(SB)
@@ -208,6 +212,33 @@ TEXT runtime·procyield(SB), NOSPLIT, $0-0 // FIXME
 TEXT runtime·breakpoint(SB), NOSPLIT, $0-0
        UNDEF
 
+// func switchToCrashStack0(fn func())
+TEXT runtime·switchToCrashStack0(SB), NOSPLIT, $0-8
+       MOVD fn+0(FP), CTXT     // context register
+       MOVD    g_m(g), R2      // curm
+
+       // set g to gcrash
+       MOVD    $runtime·gcrash(SB), g // g = &gcrash
+       MOVD    R2, g_m(g)      // g.m = curm
+       MOVD    g, m_g0(R2)     // curm.g0 = g
+
+       // switch to crashstack
+       I64Load (g_stack+stack_hi)(g)
+       I64Const $(-4*8)
+       I64Add
+       I32WrapI64
+       Set SP
+
+       // call target function
+       Get CTXT
+       I32WrapI64
+       I64Load $0
+       CALL
+
+       // should never return
+       CALL    runtime·abort(SB)
+       UNDEF
+
 // Called during function prolog when more stack is needed.
 //
 // The traceback routines see morestack on a g0 as being
@@ -221,12 +252,19 @@ TEXT runtime·morestack(SB), NOSPLIT, $0-0
        // R2 = g0
        MOVD m_g0(R1), R2
 
+       // Set g->sched to context in f.
+       NOP     SP      // tell vet SP changed - stop checking offsets
+       MOVD 0(SP), g_sched+gobuf_pc(g)
+       MOVD $8(SP), g_sched+gobuf_sp(g) // f's SP
+       MOVD CTXT, g_sched+gobuf_ctxt(g)
+
        // Cannot grow scheduler stack (m->g0).
        Get g
        Get R2
        I64Eq
        If
                CALLNORESUME runtime·badmorestackg0(SB)
+               CALLNORESUME runtime·abort(SB)
        End
 
        // Cannot grow signal stack (m->gsignal).
@@ -235,20 +273,15 @@ TEXT runtime·morestack(SB), NOSPLIT, $0-0
        I64Eq
        If
                CALLNORESUME runtime·badmorestackgsignal(SB)
+               CALLNORESUME runtime·abort(SB)
        End
 
        // Called from f.
        // Set m->morebuf to f's caller.
-       NOP     SP      // tell vet SP changed - stop checking offsets
        MOVD 8(SP), m_morebuf+gobuf_pc(R1)
        MOVD $16(SP), m_morebuf+gobuf_sp(R1) // f's caller's SP
        MOVD g, m_morebuf+gobuf_g(R1)
 
-       // Set g->sched to context in f.
-       MOVD 0(SP), g_sched+gobuf_pc(g)
-       MOVD $8(SP), g_sched+gobuf_sp(g) // f's SP
-       MOVD CTXT, g_sched+gobuf_ctxt(g)
-
        // Call newstack on m->g0's stack.
        MOVD R2, g
        MOVD g_sched+gobuf_sp(R2), SP

diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index ea011e3192d6d1ff0211bee5bb5f79b9f7ac4531..18826abb0628e6446f41377a35febee6a9d1cc7e 100644 (file)
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -576,7 +576,7 @@ func switchToCrashStack(fn func()) {
        abort()
 }
 
-const crashStackImplemented = GOARCH == "amd64" || GOARCH == "arm64" || GOARCH == "mips64" || GOARCH == "mips64le" || GOARCH == "ppc64" || GOARCH == "ppc64le" || GOARCH == "riscv64"
+const crashStackImplemented = GOARCH == "amd64" || GOARCH == "arm64" || GOARCH == "mips64" || GOARCH == "mips64le" || GOARCH == "ppc64" || GOARCH == "ppc64le" || GOARCH == "riscv64" || GOARCH == "wasm"
 
 //go:noescape
 func switchToCrashStack0(fn func()) // in assembly