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author | Ian Lance Taylor <iant@golang.org> | 2022-02-11 14:53:56 -0800 |
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committer | Ian Lance Taylor <iant@golang.org> | 2022-02-11 15:01:19 -0800 |
commit | 8dc2499aa62f768c6395c9754b8cabc1ce25c494 (patch) | |
tree | 43d7fd2bbfd7ad8c9625a718a5e8718889351994 /libgo/go/internal/fuzz/mem.go | |
parent | 9a56779dbc4e2d9c15be8d31e36f2f59be7331a8 (diff) | |
download | gcc-8dc2499aa62f768c6395c9754b8cabc1ce25c494.zip gcc-8dc2499aa62f768c6395c9754b8cabc1ce25c494.tar.gz gcc-8dc2499aa62f768c6395c9754b8cabc1ce25c494.tar.bz2 |
libgo: update to Go1.18beta2
gotools/
* Makefile.am (go_cmd_cgo_files): Add ast_go118.go
(check-go-tool): Copy golang.org/x/tools directories.
* Makefile.in: Regenerate.
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/384695
Diffstat (limited to 'libgo/go/internal/fuzz/mem.go')
-rw-r--r-- | libgo/go/internal/fuzz/mem.go | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/libgo/go/internal/fuzz/mem.go b/libgo/go/internal/fuzz/mem.go new file mode 100644 index 0000000..d6d45be --- /dev/null +++ b/libgo/go/internal/fuzz/mem.go @@ -0,0 +1,140 @@ +// Copyright 2020 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package fuzz + +import ( + "fmt" + "io/ioutil" + "os" + "unsafe" +) + +// sharedMem manages access to a region of virtual memory mapped from a file, +// shared between multiple processes. The region includes space for a header and +// a value of variable length. +// +// When fuzzing, the coordinator creates a sharedMem from a temporary file for +// each worker. This buffer is used to pass values to fuzz between processes. +// Care must be taken to manage access to shared memory across processes; +// sharedMem provides no synchronization on its own. See workerComm for an +// explanation. +type sharedMem struct { + // f is the file mapped into memory. + f *os.File + + // region is the mapped region of virtual memory for f. The content of f may + // be read or written through this slice. + region []byte + + // removeOnClose is true if the file should be deleted by Close. + removeOnClose bool + + // sys contains OS-specific information. + sys sharedMemSys +} + +// sharedMemHeader stores metadata in shared memory. +type sharedMemHeader struct { + // count is the number of times the worker has called the fuzz function. + // May be reset by coordinator. + count int64 + + // valueLen is the number of bytes in region which should be read. + valueLen int + + // randState and randInc hold the state of a pseudo-random number generator. + randState, randInc uint64 + + // rawInMem is true if the region holds raw bytes, which occurs during + // minimization. If true after the worker fails during minimization, this + // indicates that an unrecoverable error occurred, and the region can be + // used to retrive the raw bytes that caused the error. + rawInMem bool +} + +// sharedMemSize returns the size needed for a shared memory buffer that can +// contain values of the given size. +func sharedMemSize(valueSize int) int { + // TODO(jayconrod): set a reasonable maximum size per platform. + return int(unsafe.Sizeof(sharedMemHeader{})) + valueSize +} + +// sharedMemTempFile creates a new temporary file of the given size, then maps +// it into memory. The file will be removed when the Close method is called. +func sharedMemTempFile(size int) (m *sharedMem, err error) { + // Create a temporary file. + f, err := ioutil.TempFile("", "fuzz-*") + if err != nil { + return nil, err + } + defer func() { + if err != nil { + f.Close() + os.Remove(f.Name()) + } + }() + + // Resize it to the correct size. + totalSize := sharedMemSize(size) + if err := f.Truncate(int64(totalSize)); err != nil { + return nil, err + } + + // Map the file into memory. + removeOnClose := true + return sharedMemMapFile(f, totalSize, removeOnClose) +} + +// header returns a pointer to metadata within the shared memory region. +func (m *sharedMem) header() *sharedMemHeader { + return (*sharedMemHeader)(unsafe.Pointer(&m.region[0])) +} + +// valueRef returns the value currently stored in shared memory. The returned +// slice points to shared memory; it is not a copy. +func (m *sharedMem) valueRef() []byte { + length := m.header().valueLen + valueOffset := int(unsafe.Sizeof(sharedMemHeader{})) + return m.region[valueOffset : valueOffset+length] +} + +// valueCopy returns a copy of the value stored in shared memory. +func (m *sharedMem) valueCopy() []byte { + ref := m.valueRef() + b := make([]byte, len(ref)) + copy(b, ref) + return b +} + +// setValue copies the data in b into the shared memory buffer and sets +// the length. len(b) must be less than or equal to the capacity of the buffer +// (as returned by cap(m.value())). +func (m *sharedMem) setValue(b []byte) { + v := m.valueRef() + if len(b) > cap(v) { + panic(fmt.Sprintf("value length %d larger than shared memory capacity %d", len(b), cap(v))) + } + m.header().valueLen = len(b) + copy(v[:cap(v)], b) +} + +// setValueLen sets the length of the shared memory buffer returned by valueRef +// to n, which may be at most the cap of that slice. +// +// Note that we can only store the length in the shared memory header. The full +// slice header contains a pointer, which is likely only valid for one process, +// since each process can map shared memory at a different virtual address. +func (m *sharedMem) setValueLen(n int) { + v := m.valueRef() + if n > cap(v) { + panic(fmt.Sprintf("length %d larger than shared memory capacity %d", n, cap(v))) + } + m.header().valueLen = n +} + +// TODO(jayconrod): add method to resize the buffer. We'll need that when the +// mutator can increase input length. Only the coordinator will be able to +// do it, since we'll need to send a message to the worker telling it to +// remap the file. |