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tests/fixedbugs: make test for issue11656 run known instruction

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As detailed in #11910, the current implementation attempts to execute an area
of memory with unknown content. If the memory is executable, the result is
unpredictable - instead, make the test deterministic by attempting to execute
an instruction that is known to trigger a trap on the given architecture.

The new implementation is written by iant@ and provided via #11910.

Update issue #11910

Change-Id: Ia698c36e0dd98a9d9d16a701f60f6748c6faf896
Reviewed-on: https://go-review.googlesource.com/15058
Run-TryBot: Joel Sing <jsing@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Joel Sing 2015-09-28 04:39:01 +10:00 committed by Ian Lance Taylor
parent b7fa4f27ba
commit 82a9d90eda
1 changed files with 22 additions and 13 deletions
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35
test/fixedbugs/issue11656.go
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@ -4,26 +4,15 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// darwin/386 seems to mangle the PC and SP before
// it manages to invoke the signal handler, so this test fails there.
// +build !darwin !386
//
// openbsd/386 and netbsd/386 don't work, not sure why.
// +build !openbsd !386
// +build !netbsd !386
//
// windows doesn't work, because Windows exception handling
// delivers signals based on the current PC, and that current PC
// doesn't go into the Go runtime.
// +build !windows
//
// arm64 gets "illegal instruction" (why is the data executable?)
// and is unable to do the traceback correctly (why?).
// +build !arm64
package main
import (
"encoding/binary"
"runtime"
"runtime/debug"
"unsafe"
@ -56,7 +45,27 @@ func f(n int) {
var f struct {
x uintptr
}
f.x = uintptr(unsafe.Pointer(&f))
// We want to force an illegal instruction, to get a crash
// at a PC value != 0.
// Not all systems make the data section non-executable.
ill := make([]byte, 64)
switch runtime.GOARCH {
case "386", "amd64":
binary.LittleEndian.PutUint16(ill, 0x0b0f) // ud2
case "arm":
binary.LittleEndian.PutUint32(ill, 0xe7f000f0) // no name, but permanently undefined
case "arm64":
binary.LittleEndian.PutUint32(ill, 0xd4207d00) // brk #1000
case "ppc64":
binary.BigEndian.PutUint32(ill, 0x7fe00008) // trap
case "ppc64le":
binary.LittleEndian.PutUint32(ill, 0x7fe00008) // trap
default:
// Just leave it as 0 and hope for the best.
}
f.x = uintptr(unsafe.Pointer(&ill[0]))
fn := *(*func())(unsafe.Pointer(&f))
fn()
}