diff options
| -rw-r--r-- | pkg/coverage/coverage.go | 39 | ||||
| -rw-r--r-- | pkg/sentry/kernel/kcov.go | 4 | ||||
| -rw-r--r-- | test/syscalls/linux/kcov.cc | 5 |
3 files changed, 26 insertions, 22 deletions
diff --git a/pkg/coverage/coverage.go b/pkg/coverage/coverage.go index 6831adcce..a4f4b2c5e 100644 --- a/pkg/coverage/coverage.go +++ b/pkg/coverage/coverage.go @@ -100,12 +100,9 @@ var coveragePool = sync.Pool{ // instrumentation_filter. // // Note that we "consume", i.e. clear, coverdata when this function is run, to -// ensure that each event is only reported once. -// -// TODO(b/160639712): evaluate whether it is ok to reset the global coverage -// data every time this function is run. We could technically have each thread -// store a local snapshot against which we compare the most recent coverdata so -// that separate threads do not affect each other's view of the data. +// ensure that each event is only reported once. Due to the limitations of Go +// coverage tools, we reset the global coverage data every time this function is +// run. func ConsumeCoverageData(w io.Writer) int { once.Do(initCoverageData) @@ -117,23 +114,23 @@ func ConsumeCoverageData(w io.Writer) int { for fileIndex, file := range globalData.files { counters := coverdata.Cover.Counters[file] for index := 0; index < len(counters); index++ { - val := atomic.SwapUint32(&counters[index], 0) - if val != 0 { - // Calculate the synthetic PC. - pc := globalData.syntheticPCs[fileIndex][index] - - usermem.ByteOrder.PutUint64(pcBuffer[:], pc) - n, err := w.Write(pcBuffer[:]) - if err != nil { - if err == io.EOF { - // Simply stop writing if we encounter EOF; it's ok if we attempted to - // write more than we can hold. - return total + n - } - panic(fmt.Sprintf("Internal error writing PCs to kcov area: %v", err)) + if atomic.LoadUint32(&counters[index]) == 0 { + continue + } + // Non-zero coverage data found; consume it and report as a PC. + atomic.StoreUint32(&counters[index], 0) + pc := globalData.syntheticPCs[fileIndex][index] + usermem.ByteOrder.PutUint64(pcBuffer[:], pc) + n, err := w.Write(pcBuffer[:]) + if err != nil { + if err == io.EOF { + // Simply stop writing if we encounter EOF; it's ok if we attempted to + // write more than we can hold. + return total + n } - total += n + panic(fmt.Sprintf("Internal error writing PCs to kcov area: %v", err)) } + total += n } } diff --git a/pkg/sentry/kernel/kcov.go b/pkg/sentry/kernel/kcov.go index aad63aa99..d3e76ca7b 100644 --- a/pkg/sentry/kernel/kcov.go +++ b/pkg/sentry/kernel/kcov.go @@ -89,6 +89,10 @@ func (kcov *Kcov) TaskWork(t *Task) { kcov.mu.Lock() defer kcov.mu.Unlock() + if kcov.mode != linux.KCOV_TRACE_PC { + return + } + rw := &kcovReadWriter{ mf: kcov.mfp.MemoryFile(), fr: kcov.mappable.FileRange(), diff --git a/test/syscalls/linux/kcov.cc b/test/syscalls/linux/kcov.cc index f3c30444e..6afcb4e75 100644 --- a/test/syscalls/linux/kcov.cc +++ b/test/syscalls/linux/kcov.cc @@ -36,12 +36,13 @@ TEST(KcovTest, Kcov) { constexpr int kSize = 4096; constexpr int KCOV_INIT_TRACE = 0x80086301; constexpr int KCOV_ENABLE = 0x6364; + constexpr int KCOV_DISABLE = 0x6365; int fd; ASSERT_THAT(fd = open("/sys/kernel/debug/kcov", O_RDWR), AnyOf(SyscallSucceeds(), SyscallFailsWithErrno(ENOENT))); - // Kcov not enabled. + // Kcov not available. SKIP_IF(errno == ENOENT); ASSERT_THAT(ioctl(fd, KCOV_INIT_TRACE, kSize), SyscallSucceeds()); @@ -62,6 +63,8 @@ TEST(KcovTest, Kcov) { // Verify that PCs are in the standard kernel range. EXPECT_GT(area[i], 0xffffffff7fffffffL); } + + ASSERT_THAT(ioctl(fd, KCOV_DISABLE, 0), SyscallSucceeds()); } } // namespace |