tools/syz-cover: allow for exporting source line coverage info

Add a `json` CLI flag that allows for writing out a JSON file with the
following coverage information.
* Module
* Filename
* Covered source lines
* Uncovered source lines
* Both source lines

This can be used to view syzkaller coverage information on other source
browsing/viewing tools.

Usage:
$ ./syz-cover -kernel_obj <path/to/vmlinux> -json <output_json> rawcover

1 files changed, 10 insertions, 0 deletions

diff --git a/tools/syz-cover/syz-cover.go b/tools/syz-cover/syz-cover.go
index e161eac07..80c58ffc5 100644
--- a/tools/syz-cover/syz-cover.go
+++ b/tools/syz-cover/syz-cover.go
@@ -42,6 +42,7 @@ func main() {
 		flagKernelBuildSrc = flag.String("kernel_build_src", "", "path to kernel image's build dir (optional)")
 		flagKernelObj      = flag.String("kernel_obj", "", "path to kernel build/obj dir")
 		flagExportCSV      = flag.String("csv", "", "export coverage data in csv format (optional)")
+		flagExportLineJSON = flag.String("json", "", "export coverage data with source line info in json format (optional)")
 		flagExportHTML     = flag.String("html", "", "save coverage HTML report to file (optional)")
 	)
 	defer tool.Init()()
@@ -87,6 +88,15 @@ func main() {
 		}
 		return
 	}
+	if *flagExportLineJSON != "" {
+		if err := rg.DoLineJSON(buf, progs, nil); err != nil {
+			tool.Fail(err)
+		}
+		if err := osutil.WriteFile(*flagExportLineJSON, buf.Bytes()); err != nil {
+			tool.Fail(err)
+		}
+		return
+	}
 	if err := rg.DoHTML(buf, progs, nil); err != nil {
 		tool.Fail(err)
 	}