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74f49f3366
This CL makes two main changes to allow internal/fuzz to support -d=libfuzzer instrumentation: 1. It extends cmd/link to define _counters and _ecounters symbols so internal/fuzz can find the coverage counters. 2. It adds "trace" stub functions that implement the ABI expected by cmd/compile for comparison instrumentation. N.B., that -tags=libfuzzer should *not* be set, so that internal/fuzz's trace routines will be used instead of runtime's libfuzzer trampolines. Also, the current implementation doesn't support multi-module builds (i.e., compiling a Go program that spans multiple .so/.dll files). Presumably this isn't an issue, since "go test -fuzz" will need to recompile the binary with instrumentation anyway so it can make sure to always use a single-module build. But we can revisit this if necessary. Change-Id: I9b1619119ab7477bebcfd5988b4b60499a7ab0d7 Reviewed-on: https://go-review.googlesource.com/c/go/+/308289 Trust: Matthew Dempsky <mdempsky@google.com> Trust: Katie Hockman <katie@golang.org> Reviewed-by: Katie Hockman <katie@golang.org> Reviewed-by: Jay Conrod <jayconrod@google.com> Reviewed-by: Cherry Zhang <cherryyz@google.com> Run-TryBot: Katie Hockman <katie@golang.org> TryBot-Result: Go Bot <gobot@golang.org>
32 lines
1,015 B
Go
32 lines
1,015 B
Go
// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package fuzz
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import (
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"internal/unsafeheader"
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"unsafe"
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)
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// coverage returns a []byte containing unique 8-bit counters for each edge of
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// the instrumented source code. This coverage data will only be generated if
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// `-d=libfuzzer` is set at build time. This can be used to understand the code
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// coverage of a test execution.
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func coverage() []byte {
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addr := unsafe.Pointer(&_counters)
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size := uintptr(unsafe.Pointer(&_ecounters)) - uintptr(addr)
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var res []byte
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*(*unsafeheader.Slice)(unsafe.Pointer(&res)) = unsafeheader.Slice{
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Data: addr,
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Len: int(size),
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Cap: int(size),
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}
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return res
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}
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// _counters and _ecounters mark the start and end, respectively, of where
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// the 8-bit coverage counters reside in memory. They're known to cmd/link,
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// which specially assigns their addresses for this purpose.
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var _counters, _ecounters [0]byte
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