The -fuzztime flag tells us how much time to spend fuzzing, not
counting time spent running the seed corpus. We shouldn't count time
spent loading the cache either. If the cache is large, the time limit
may be exceeded before the coordinator starts the workers.
Change-Id: If00435faa5d24aabdb9003ebb9337fa2e47f22b6
Reviewed-on: https://go-review.googlesource.com/c/go/+/307310
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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
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Reviewed-by: Cherry Zhang <cherryyz@google.com>
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Assuming this works, will follow up with another CL
that mutates other types.
Change-Id: Id61acaacd56ca41e3be52e400f8f768672313bbb
Reviewed-on: https://go-review.googlesource.com/c/go/+/308169
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This change only includes a stub for the function
which will hook into the runtime to expose
coverage instrumentation while we're fuzzing.
Previously, we discussed an exported API named
FuzzCoverage, but since this is within the
internal/fuzz package, simply naming it coverage
seems appropriate.
Change-Id: Iba3240e53e0c4c434e937aa9bb1711a44fec9975
Reviewed-on: https://go-review.googlesource.com/c/go/+/308191
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This fixes a few issues that were being masked since
log statements weren't being printed to stdout. Now
that they are, fix the bugs, and update the tests.
Also includes a few small refactors which will make
minimizing non-recoverable errors easier.
Change-Id: Ie2fd2e5534b3980317e1e1f3fd8e04750988c17f
Reviewed-on: https://go-review.googlesource.com/c/go/+/307810
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When mutating a byte slice, mutate in place, and only allocate once if
the slice's capacity is less than the maximum size.
mutateBytes already should not allocate; we check a post-condition
that the slice's data pointer does not change.
This speeds up the mutator from 4 ms per value to 200-600 ns. For
example:
goos: darwin
goarch: amd64
pkg: internal/fuzz
cpu: Intel(R) Core(TM) i7-8559U CPU @ 2.70GHz
BenchmarkMutatorBytes/1-8 5908735 275.3 ns/op
BenchmarkMutatorBytes/10-8 5198473 282.0 ns/op
BenchmarkMutatorBytes/100-8 4304750 233.9 ns/op
BenchmarkMutatorBytes/1000-8 4623988 295.2 ns/op
BenchmarkMutatorBytes/10000-8 4252104 458.5 ns/op
BenchmarkMutatorBytes/100000-8 1236751 950.8 ns/op
PASS
ok internal/fuzz 12.993s
Change-Id: I4bf2a04be6c648ef440af2c62bf0ffa3d310172c
Reviewed-on: https://go-review.googlesource.com/c/go/+/306675
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Also improve the error messages for the use of
testing.F functions inside the Fuzz function.
Change-Id: I5fa48f8c7e0460a1da89a49a73e5af83c544e549
Reviewed-on: https://go-review.googlesource.com/c/go/+/298849
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This works by minimizing for a maximum of one minute. We may consider
making this customizable in the future.
This only minimizes []byte inputs which caused a recoverable error. In
the future, it should support minimizing other appopriate types, and
minimizing types which caused non-recoverable errors (though this is
much more expensive).
The code in internal/fuzz/worker.go is copied from, or heavily inspired
by, code originally authored by Dmitry Vyukov and Josh Bleecher Snyder
as part of the go-fuzz project. Thanks to them for their contributions.
See https://github.com/dvyukov/go-fuzz.
Change-Id: I93dbac7ff874d6d0c1b9b9dda23930ae9921480c
Reviewed-on: https://go-review.googlesource.com/c/go/+/298909
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CoordinateFuzzing now continues to run after discovering a crasher. It
waits until all workers have terminated before returning.
This fixes a deadlock that occurred when multiple workers discovered
crashers concurrently. CoordinateFuzzing would receive one crasher,
close doneC (telling workers to stop), then wait for workers to stop
without receiving more crashers. Other workers would block sending
crashers.
Change-Id: I55a64aac0e6e43f5e36b9d03c15051c3d5debb20
Reviewed-on: https://go-review.googlesource.com/c/go/+/293369
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* Appending to the worker environment slice should reallocate it. On
Windows, we pass handles through the environment, and concurrent
workers were writing to the same memory, resulting in
"The handle is invalid" errors.
* Instead of passing a handle to the temporary file, we pass its path
to each worker instead. The worker is responsible for opening and
closing the handle. Previously, all inheritable handles were
inherited by all workers, even though only one was used. This
prevented temporary files from being deleted after a worker stopped,
because other workers would still have open handles to it.
Change-Id: If8b8bcfa5b03fbcadd10ef923b036bb0ee5dc3f5
Reviewed-on: https://go-review.googlesource.com/c/go/+/297034
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If a worker process encounters an error communicating with the
coordinator, or if the setup code reports an error with F.Fail
before calling F.Fuzz, exit with status 70. The coordinator will report
these errors and 'go test' will exit non-zero, but the coordinator
won't record a crasher since the problem is not in the code being
fuzzed.
The coordinator also detects unexpected terminations before the worker
calls F.Fuzz by sending a ping RPC. If the worker terminates before
responding to the ping RPC, the coordinator won't record a crasher.
Exit codes are chosen somewhat arbitrary, but in the Advanced Bash
Scripting Guide, 70 is "internal software error" which is applicable
here. 70 is also ASCII 'F'.
Change-Id: I1e676e39a7b07c5664efaaa3221d055f55240fff
Reviewed-on: https://go-review.googlesource.com/c/go/+/297033
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* Run gofmt with go1.17 build constraint changes.
* Tighten regular expressions used in tests. "ok" got some false
positives with verbose output, so make sure it appears at the start
of a line.
* Return err in deps.RunFuzzWorker instead of nil.
* Call common.Helper from F methods. This prevents F methods from
appearing in stack traces.
Change-Id: I839c70ec8a9f313c1a4ea68e6bb34a4d801dd36f
Reviewed-on: https://go-review.googlesource.com/c/go/+/297032
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Previously, the coordintor used the error string encoded by the worker
to determine whether or not a crash occurred. However, failures caused
by things like t.Fail() which have no output will have an empty error
string, so we can't rely on the error string alone to determine if
something is a crasher or not.
Change-Id: Idcf7f6b1210aa1dc4e8dab222642c87919595693
Reviewed-on: https://go-review.googlesource.com/c/go/+/298351
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This change makes several refactors to start supporting
structured fuzzing. The mutator can still only mutate
byte slices, and future changes will be made to support
mutating other types. However, it does now support
fuzzing more than one []byte.
This change also makes it so that corpus entries are
encoded in the new file format when being written to
testdata or GOCACHE. Any existing GOCACHE data should
be deleted from your local workstation to allow tests
to pass locally.
Change-Id: Iab8fe01a5dc870f0c53010b9d5b0b479bbdb310d
Reviewed-on: https://go-review.googlesource.com/c/go/+/293810
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Based on feedback from rsc@, update the version
encoding to more clearly indicate that this is
about fuzzing with Go.
Change-Id: Id95dec8283608779b157bf662e7147f9a9c8dba8
Reviewed-on: https://go-review.googlesource.com/c/go/+/295110
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We already read the seed corpus from testdata for the
fuzz target, and pass that corpus to the coordinator.
The coordinator doesn't need to read from testdata
again.
Change-Id: Ia7822e3e02b35d56f6918c7082a7b19901b36644
Reviewed-on: https://go-review.googlesource.com/c/go/+/293189
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This change rewrites much of the glue code in testing/fuzz.go to work
more analogously to T.Run. This results in improved behavior:
* If a fuzz target returns without calling F.Skip, F.Fail, or F.Fuzz,
'go test' will report an error and exit non-zero.
* Functions registered with F.Cleanup are called.
* The user can re-run individual inputs using -run=FuzzTarget/name
where name is the base name of the seed corpus file. We now print
the 'go test' command after a crash.
This change doesn't correctly handle T.Parallel calls yet, but it
should be easier to do that in the future.
Highlighted parts of this change:
* Instead of creating one F for all targets, create an F for each
target. F (actually common) holds the status, output, and cleanup
function list for each target, so it's important to keep them
separate.
* Run each target in its own goroutine via fRunner. fRunner is
analogous to tRunner. It runs cleanups and catches inappropriate
Goexits and panics.
* Run each input in its own goroutine via T.Run. This enables subtest
filtering with -test.run and ensures functions registered with
T.Cleanup (not F.Cleanup) are run at the appropriate time.
Change-Id: Iab1da14ead8bcb57746f8a76f4aebc625baa5792
Reviewed-on: https://go-review.googlesource.com/c/go/+/290693
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RunFuzzWorker now accepts a fuzz.CorpusEntry instead of []byte. This
may help us pass structured data in the future.
Change-Id: Idf7754cb890b6a835d887032fd23ade4d0713bcf
Reviewed-on: https://go-review.googlesource.com/c/go/+/290692
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If a worker process exits with status 0, treat it as a communication
error. Previously, we treated this as a crasher, but it seems more
likely to be caused by a bug in the fuzz function rather than a bug in
the code being tested.
Change-Id: I0c4efeaef85537f8a0e9c6def6aac41d75b2b307
Reviewed-on: https://go-review.googlesource.com/c/go/+/290690
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CorpusEntry is now a struct type with Name and Data fields. In the
future, it may have more fields describing multiple values with
different types added with f.Add.
CorpusEntry must be the same type in testing and
internal/fuzz. However, we don't want to export it from testing, and
testing can't import internal/fuzz. We define it to be a type alias of
a struct type instead of a defined type. We need to define it to the
same thing in both places. We'll get a type error when building cmd/go
if there's a difference.
Change-Id: I9df6cd7aed67a6aa48b77ffb3a84bd302d2e5d94
Reviewed-on: https://go-review.googlesource.com/c/go/+/288534
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This change moves the worker's *sharedMem into a buffered chan that
acts as a mutex. The mutex can be locked by receiving from the chan;
it can be unlocked by sending *sharedMem back to the chan. Multiple
objects (like worker, workerClient, workerServer) may have references
to the chan and may hold the lock across several operations.
This is intended to fix a segfault that occurred when
workerClient.fuzz accessed shared memory after it was already closed
and unmapped by the worker's goroutine. workerClient.fuzz is executed
in a separate goroutine so the worker can still receive messages from
the coordinator (like being told to stop and clean up).
Change-Id: I4eb9079ba9e5bfcfacfecd0fc8ad9bed17b33bba
Reviewed-on: https://go-review.googlesource.com/c/go/+/285054
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A worker process may be terminated by SIGINT if it doesn't install the
signal handler before SIGINT is delivered. That's likely when TestMain
or the fuzz target setup take a long time. The coordinator now ignores
these errors.
Also, when testdeps.TestDeps.CoordinateFuzzing and RunFuzzWorker
return, they will send a value on the chan passed to signal.Notify
instead of closing it. This should have been obvious in hindsight, but
the signal handler could still send a value on that channel after
those functions return but before the process exits.
Change-Id: Iea2589115f1f9bb7415bb5e7911defee423e642e
Reviewed-on: https://go-review.googlesource.com/c/go/+/284292
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This method sets the len of the slice returned by valueRef. The worker
now uses this instead of setting the length in the header directly.
Unfortunately, we can't store the whole slice header in the shared
memory header because the pointer won't be valid across processes.
Change-Id: Icef24acfcd85e098cd8c23810568f04b13649a19
Reviewed-on: https://go-review.googlesource.com/c/go/+/284012
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Previously, performing a SIGINT would cause the coordinator
to write a crash to testdata, and would continue to run
despite being interupted.
Also includes a few small cleanups.
Change-Id: Ia3cf7cd231c30ac9ad2a61f4935aa543e241f60d
Reviewed-on: https://go-review.googlesource.com/c/go/+/283634
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This change also allocates a larger capacity (100 MB) for the shared
memory at the start, rather than beginning as small as possible and
immediately needing to grow while mutating. This means that 100 MB is
the maximum size of a corpus entry currently, since growing the shared
memory is not yet supported.
The code in internal/fuzz/mutator.go and internal/fuzz/pcg.go are copied
from, or heavily inspired by, code originally authored by Dmitry Vyukov
and Josh Bleecher Snyder as part of the go-fuzz project. Thanks to them
for their contributions. See https://github.com/dvyukov/go-fuzz.
Change-Id: I0d51d53976e23933072e760ff78e6c4ad9dcd862
Reviewed-on: https://go-review.googlesource.com/c/go/+/281972
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fuzz.CoordinateFuzzing and RunFuzzWorker now accept a context.Context
parameter. They should terminate gracefully when the context is
cancelled. The worker should exit quickly without processing more
inputs. The coordinator should save interesting inputs to the cache.
The testing package can't import context directly, so it provides a
timeout argument to testdeps.CoordinateFuzzing instead. The testdeps
wrapper sets the timeout and installs an interrupt handler (for SIGINT
on POSIX and the equivalent on Windows) that cancels the context when
^C is pressed.
Note that on POSIX platforms, pressing ^C causes the shell to deliver
SIGINT to all processes in the active group: so 'go test', the
coordinator, and the workers should all react to that. On Windows,
pressing ^C only interrupts 'go test'. We may want to look at that
separately.
Change-Id: I924d3be2905f9685dae82ff3c047ca3d6b5e2357
Reviewed-on: https://go-review.googlesource.com/c/go/+/279487
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'go test -fuzz' may now read and write interesting fuzzing values to
directories in $GOCACHE/fuzz. Files in this directory are named
$pkg/$test/$hash where $pkg is the package path containing the fuzz
target, $test is the target name, and $hash is the SHA-256 sum of the
data in the file.
Note that different versions of the same package or packages with the
same path from different modules may share the same directory.
Although files are written into a subdirectory of GOCACHE, they are
not removed automatically, nor are they removed by 'go clean -cache'.
Instead, they may be removed with 'go clean -fuzzcache'. We chose to
nest the fuzzing directory inside GOCACHE to avoid introducing a new
environment variable, since there's no real need for users to specify
a separate directory.
Change-Id: I2032cf8e6c92f715cf36a9fc6a550acf666d2382
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Several small changes, most related to GOFUZZCACHE.
* Use separate channels to send crashers and interesting values to the
coordinator.
* Add a new type, crasherEntry, which is a corpusEntry with an
error message.
* Workers now send fatal errors to the coordinator via errC instead of
returning or closing doneC.
* In CoordinateFuzzing, defer code that closes doneC and waits for
workers to stop. This is the only place where doneC is closed.
* In workerServer and workerClient, always pass input values through
shared memory instead of RPC messages or arguments to avoid
confusion.
* Rename sharedMem.value to valueRef and add valueCopy to make it
clearer whether a reference or copy is needed.
* mutate now operates on shared memory directly.
* mutate will not panic on empty input.
Change-Id: I6e57354875508f0ac4483ed2728f3ba18dc938c4
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This prevents workerClient.Close from closing fuzzIn while
workerClient.fuzz is writing to it concurrently. It also prevents
multiple callers from writing to fuzzIn concurrently, though there's
nothing that does that yet.
This should prevent most "broken pipe" errors, though they may still
be possible if worker.stop is called and it needs to kill the process
due to a timeout. In the future, we should detect and ignore those
errors, but for now, they're useful for debugging.
Also, improve documentation on workerClient and workerServer.
Change-Id: Ie2c870392d5e91674d3b1e32b2fa4f9de9ac3eb0
Reviewed-on: https://go-review.googlesource.com/c/go/+/275173
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The coordinator process creates a temporary file for each worker. Both
coordinator and worker map the file into memory and use it for input
values. Access is synchronized with RPC over pipes.
Change-Id: I43c10d7291a8760a616b472d11c017a3a7bb19cf
Reviewed-on: https://go-review.googlesource.com/c/go/+/263153
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Note that this is an extremely basic mutator, and only
meant to act as a placeholder for future development.
Change-Id: I650691db44f30953345702aac93cbd1cadc21427
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This change also includes a small cleanup of the run()
function and additional tests for error conditions
in fuzz targets.
Change-Id: I2b7722b25a0d071182a84f1dc4b92e82a7ea34d9
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Package fuzz provides common fuzzing functionality for tests built
with "go test" and for programs that use fuzzing functionality in the
testing package.
Change-Id: I3901c6a993a9adb8a93733ae1838b86dd78c7036
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