tools/syz-db: add more usage info for syz-db

Add some short notes on how syz-db can also be used manually.

Signed-off-by: Simone Weiß <[email protected]>

docs/db.md

@@ -0,0 +1,59 @@
+# syz-db
+
+`syz-db` program can be used to manipulate corpus.db databases that are used
+by syz-managers.
+
+## Build
+
+Build `syz-db` with `make db` or by changing to `tools/syz-db` and run `go build`.
+
+## Options
+
+`syz-db` currently overs the following generic arguments:
+
+```shell
+  -arch string
+    	target arch
+  -os string
+    	target OS
+  -version uint
+    	database version
+  -vv int
+    	verbosity
+```
+
+That can be used with
+
+```
+  syz-db pack dir corpus.db
+```
+
+to pack a database
+
+```
+  syz-db unpack corpus.db dir
+```
+
+to unpack a database. A file containing performed syscalls will be returned.
+
+```
+  syz-db merge dst-corpus.db add-corpus.db* add-prog*
+```
+
+to merge databases. No additional file will be created: The first file will be replaced by the merged result.
+
+```
+  syz-db bench corpus.db
+```
+
+to run a deserialization benchmark. For example:
+
+```
+syz-db -os=linux -arch=amd64 bench corpus.db
+```
+
+could give an output like
+
+```
+allocs 123 MB (123 M), next GC 123 MB, sys heap 123 MB, live allocs 123 MB (123 M), time 324s.
+```

tools/syz-db/syz-db.go

@@ -73,11 +73,24 @@ func main() {
 }
 
 func usage() {
-	fmt.Fprintf(os.Stderr, "usage:\n")
-	fmt.Fprintf(os.Stderr, "  syz-db pack dir corpus.db\n")
-	fmt.Fprintf(os.Stderr, "  syz-db unpack corpus.db dir\n")
-	fmt.Fprintf(os.Stderr, "  syz-db merge dst-corpus.db add-corpus.db* add-prog*\n")
-	fmt.Fprintf(os.Stderr, "  syz-db bench corpus.db\n")
+	fmt.Fprintf(os.Stderr, `usage: syz-db can be used to manipulate corpus
+databases that are used by syz-managers. The following generic arguments are
+offered:
+  -arch string
+  -os string
+  -version uint
+  -vv int
+
+  they can be used for:
+  packing a database:
+    syz-db pack dir corpus.db
+  unpacking a database. A file containing performed syscalls will be returned:
+    syz-db unpack corpus.db dir
+  merging databases. No additional file will be created: The first file will be replaced by the merged result:
+    syz-db merge dst-corpus.db add-corpus.db* add-prog*
+  running a deserialization benchmark:
+    syz-db bench corpus.db
+`)
 	os.Exit(1)
 }