Allow runsc to generate coverage reports.

Add a coverage-report flag that will cause the sandbox to generate a coverage
report (with suffix .cov) in the debug log directory upon exiting. For the
report to be generated, runsc must have been built with the following Bazel
flags: `--collect_code_coverage --instrumentation_filter=...`.

With coverage reports, we should be able to aggregate results across all tests
to surface code coverage statistics for the project as a whole.

The report is simply a text file with each line representing a covered block
as `file:start_line.start_col,end_line.end_col`. Note that this is similar to
the format of coverage reports generated with `go test -coverprofile`,
although we omit the count and number of statements, which are not useful for
us.

Some simple ways of getting coverage reports:

bazel test <some_test> --collect_code_coverage \
  --instrumentation_filter=//pkg/...

bazel build //runsc --collect_code_coverage \
  --instrumentation_filter=//pkg/...
runsc -coverage-report=dir/ <other_flags> do ...

PiperOrigin-RevId: 368952911

1 files changed, 8 insertions, 0 deletions

diff --git a/runsc/cli/main.go b/runsc/cli/main.go
index 6db6614cc..79eb85cff 100644
--- a/runsc/cli/main.go
+++ b/runsc/cli/main.go
@@ -27,6 +27,7 @@ import (
 
 	"github.com/google/subcommands"
 	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/coverage"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
@@ -50,6 +51,7 @@ var (
 	logFD      = flag.Int("log-fd", -1, "file descriptor to log to.  If set, the 'log' flag is ignored.")
 	debugLogFD = flag.Int("debug-log-fd", -1, "file descriptor to write debug logs to.  If set, the 'debug-log-dir' flag is ignored.")
 	panicLogFD = flag.Int("panic-log-fd", -1, "file descriptor to write Go's runtime messages.")
+	coverageFD = flag.Int("coverage-fd", -1, "file descriptor to write Go coverage output.")
 )
 
 // Main is the main entrypoint.
@@ -205,6 +207,10 @@ func Main(version string) {
 	} else if conf.AlsoLogToStderr {
 		e = &log.MultiEmitter{e, newEmitter(conf.DebugLogFormat, os.Stderr)}
 	}
+	if *coverageFD >= 0 {
+		f := os.NewFile(uintptr(*coverageFD), "coverage file")
+		coverage.EnableReport(f)
+	}
 
 	log.SetTarget(e)
 
@@ -234,6 +240,8 @@ func Main(version string) {
 	// Call the subcommand and pass in the configuration.
 	var ws unix.WaitStatus
 	subcmdCode := subcommands.Execute(context.Background(), conf, &ws)
+	// Write coverage report before os.Exit().
+	coverage.Report()
 	if subcmdCode == subcommands.ExitSuccess {
 		log.Infof("Exiting with status: %v", ws)
 		if ws.Signaled() {