all: determine patched symbols for focused fuzzing

Hash the code section of the individual symbols from vmlinux.o and use
it to determine the functions that changed their bodies between the base
and the patched build.

If the number of affected symbols is reasonable (<5%), fuzz it with the
highest priority.

1 files changed, 28 insertions, 3 deletions

diff --git a/syz-cluster/workflow/build-step/main.go b/syz-cluster/workflow/build-step/main.go
index 1abf5bc4a..3797681ea 100644
--- a/syz-cluster/workflow/build-step/main.go
+++ b/syz-cluster/workflow/build-step/main.go
@@ -10,6 +10,10 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+
 	"github.com/google/syzkaller/pkg/build"
 	"github.com/google/syzkaller/pkg/debugtracer"
 	"github.com/google/syzkaller/pkg/osutil"
@@ -18,9 +22,6 @@ import (
 	"github.com/google/syzkaller/syz-cluster/pkg/api"
 	"github.com/google/syzkaller/syz-cluster/pkg/app"
 	"github.com/google/syzkaller/syz-cluster/pkg/triage"
-	"log"
-	"os"
-	"path/filepath"
 )
 
 var (
@@ -261,8 +262,14 @@ func buildKernel(tracer debugtracer.DebugTracer, req *api.BuildRequest) (*BuildR
 		return nil, err
 	}
 	tracer.Log("build finished successfully")
+
+	err = saveSymbolHashes(tracer)
+	if err != nil {
+		tracer.Log("failed to save symbol hashes: %s", err)
+	}
 	// Note: Output directory has the following structure:
 	//   |-- image
+	//   |-- symbol_hashes.json
 	//   |-- kernel
 	//   |-- kernel.config
 	//   `-- obj
@@ -270,6 +277,24 @@ func buildKernel(tracer debugtracer.DebugTracer, req *api.BuildRequest) (*BuildR
 	return ret, nil
 }
 
+func saveSymbolHashes(tracer debugtracer.DebugTracer) error {
+	hashes, err := build.ElfSymbolHashes(filepath.Join(*flagRepository, "vmlinux.o"))
+	if err != nil {
+		return fmt.Errorf("failed to query symbol hashes: %w", err)
+	}
+	tracer.Log("extracted hashes for %d symbols", len(hashes))
+	file, err := os.Create(filepath.Join(*flagOutput, "symbol_hashes.json"))
+	if err != nil {
+		return fmt.Errorf("failed to open symbol_hashes.json: %w", err)
+	}
+	defer file.Close()
+	err = json.NewEncoder(file).Encode(hashes)
+	if err != nil {
+		return fmt.Errorf("failed to serialize: %w", err)
+	}
+	return nil
+}
+
 func ensureFlags(args ...string) {
 	for i := 0; i+1 < len(args); i += 2 {
 		if args[i] == "" {