2 files changed, 93 insertions, 0 deletions
diff --git a/runsc/cmd/BUILD b/runsc/cmd/BUILD
index 2556f6d9e..19520d7ab 100644
--- a/runsc/cmd/BUILD
+++ b/runsc/cmd/BUILD
@@ -32,6 +32,7 @@ go_library(
         "start.go",
         "state.go",
         "statefile.go",
+        "symbolize.go",
         "syscalls.go",
         "wait.go",
     ],
@@ -39,6 +40,7 @@ go_library(
         "//runsc:__subpackages__",
     ],
     deps = [
+        "//pkg/coverage",
         "//pkg/log",
         "//pkg/p9",
         "//pkg/sentry/control",
diff --git a/runsc/cmd/symbolize.go b/runsc/cmd/symbolize.go
new file mode 100644
index 000000000..fc0c69358
--- /dev/null
+++ b/runsc/cmd/symbolize.go
@@ -0,0 +1,91 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"bufio"
+	"context"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/google/subcommands"
+	"gvisor.dev/gvisor/pkg/coverage"
+	"gvisor.dev/gvisor/runsc/flag"
+)
+
+// Symbolize implements subcommands.Command for the "symbolize" command.
+type Symbolize struct {
+	dumpAll bool
+}
+
+// Name implements subcommands.Command.Name.
+func (*Symbolize) Name() string {
+	return "symbolize"
+}
+
+// Synopsis implements subcommands.Command.Synopsis.
+func (*Symbolize) Synopsis() string {
+	return "Convert synthetic instruction pointers from kcov into positions in the runsc source code. Only used when Go coverage is enabled."
+}
+
+// Usage implements subcommands.Command.Usage.
+func (*Symbolize) Usage() string {
+	return `symbolize - converts synthetic instruction pointers into positions in the runsc source code.
+
+This command takes instruction pointers from stdin and converts them into their
+corresponding file names and line/column numbers in the runsc source code. The
+inputs are not interpreted as actual addresses, but as synthetic values that are
+exposed through /sys/kernel/debug/kcov. One can extract coverage information
+from kcov and translate those values into locations in the source code by
+running symbolize on the same runsc binary.
+`
+}
+
+// SetFlags implements subcommands.Command.SetFlags.
+func (c *Symbolize) SetFlags(f *flag.FlagSet) {
+	f.BoolVar(&c.dumpAll, "all", false, "dump information on all coverage blocks along with their synthetic PCs")
+}
+
+// Execute implements subcommands.Command.Execute.
+func (c *Symbolize) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	if f.NArg() != 0 {
+		f.Usage()
+		return subcommands.ExitUsageError
+	}
+	if !coverage.KcovAvailable() {
+		return Errorf("symbolize can only be used when coverage is available.")
+	}
+	coverage.InitCoverageData()
+
+	if c.dumpAll {
+		coverage.WriteAllBlocks(os.Stdout)
+		return subcommands.ExitSuccess
+	}
+
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		// Input is always base 16, but may or may not have a leading "0x".
+		str := strings.TrimPrefix(scanner.Text(), "0x")
+		pc, err := strconv.ParseUint(str, 16 /* base */, 64 /* bitSize */)
+		if err != nil {
+			return Errorf("Failed to symbolize \"%s\": %v", scanner.Text(), err)
+		}
+		if err := coverage.Symbolize(os.Stdout, pc); err != nil {
+			return Errorf("Failed to symbolize \"%s\": %v", scanner.Text(), err)
+		}
+	}
+	return subcommands.ExitSuccess
+}