syz-cover: accept canonical module info (#3964)

* syz-manager: endpoint to display canonical modules

Add a "/modules" endpoint that displays canonical module
information.

* tools/syz-cover: accept module info

Add support to syz-cover to generate coverage reports for drivers that
are built as kernel modules.

At the moment, ReportGenerator instances are created with no
[]host.KernelModule information. As a result, discoverModulesLinux()
does not process kernel modules, only the vmlinux.

Add a "-modules" flag that accepts module info. This info
can be fetched from the web UI at "/modules".

Usage:
$ ./bin/syz-cover -arch arm64 -kernel_obj ${KOBJ} -kernel_src ${KSRC} \
	-json ~/report.json -modules ~/modules \
	~/rawcover

3 files changed, 43 insertions, 4 deletions

diff --git a/pkg/host/machine_info.go b/pkg/host/machine_info.go
index 6dd2f0686..3c04becab 100644
--- a/pkg/host/machine_info.go
+++ b/pkg/host/machine_info.go
@@ -55,7 +55,7 @@ type machineInfoFunc struct {
 }
 
 type KernelModule struct {
-	Name string
-	Addr uint64
-	Size uint64
+	Name string `json:"Name"`
+	Addr uint64 `json:"Addr"`
+	Size uint64 `json:"Size"`
 }
diff --git a/syz-manager/html.go b/syz-manager/html.go
index d0d20542d..52086ca77 100644
--- a/syz-manager/html.go
+++ b/syz-manager/html.go
@@ -55,6 +55,7 @@ func (mgr *Manager) initHTTP() {
 	handle("/filecover", mgr.httpFileCover)
 	handle("/input", mgr.httpInput)
 	handle("/debuginput", mgr.httpDebugInput)
+	handle("/modules", mgr.modulesInfo)
 	// Browsers like to request this, without special handler this goes to / handler.
 	handle("/favicon.ico", func(w http.ResponseWriter, r *http.Request) {})
 
@@ -507,6 +508,21 @@ func (mgr *Manager) httpDebugInput(w http.ResponseWriter, r *http.Request) {
 	executeTemplate(w, rawCoverTemplate, data)
 }
 
+func (mgr *Manager) modulesInfo(w http.ResponseWriter, r *http.Request) {
+	if mgr.serv.canonicalModules == nil {
+		fmt.Fprintf(w, "module information not retrieved yet, please retry after fuzzing starts\n")
+		return
+	}
+	// NewCanonicalizer() is initialized with serv.modules.
+	modules, err := json.MarshalIndent(mgr.serv.modules, "", "\t")
+	if err != nil {
+		fmt.Fprintf(w, "unable to create JSON modules info: %v", err)
+		return
+	}
+	w.Header().Set("Content-Type", "application/json")
+	w.Write(modules)
+}
+
 func (mgr *Manager) httpReport(w http.ResponseWriter, r *http.Request) {
 	mgr.mu.Lock()
 	defer mgr.mu.Unlock()
diff --git a/tools/syz-cover/syz-cover.go b/tools/syz-cover/syz-cover.go
index 80c58ffc5..a28d8db5d 100644
--- a/tools/syz-cover/syz-cover.go
+++ b/tools/syz-cover/syz-cover.go
@@ -19,6 +19,7 @@ package main
 import (
 	"bufio"
 	"bytes"
+	"encoding/json"
 	"flag"
 	"fmt"
 	"os"
@@ -28,6 +29,7 @@ import (
 	"strings"
 
 	"github.com/google/syzkaller/pkg/cover"
+	"github.com/google/syzkaller/pkg/host"
 	"github.com/google/syzkaller/pkg/osutil"
 	"github.com/google/syzkaller/pkg/tool"
 	"github.com/google/syzkaller/sys/targets"
@@ -41,6 +43,7 @@ func main() {
 		flagKernelSrc      = flag.String("kernel_src", "", "path to kernel sources")
 		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")
+		flagModules        = flag.String("modules", "", "modules info obtained from /modules (optional)")
 		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)")
@@ -72,8 +75,16 @@ func main() {
 	if err != nil {
 		tool.Fail(err)
 	}
+	var modules []host.KernelModule
+	if *flagModules != "" {
+		m, err := loadModules(*flagModules)
+		if err != nil {
+			tool.Fail(err)
+		}
+		modules = m
+	}
 	rg, err := cover.MakeReportGenerator(target, *flagVM, *flagKernelObj,
-		*flagKernelSrc, *flagKernelBuildSrc, nil, nil, nil, false)
+		*flagKernelSrc, *flagKernelBuildSrc, nil, nil, modules, false)
 	if err != nil {
 		tool.Fail(err)
 	}
@@ -140,3 +151,15 @@ func readPCs(files []string) ([]uint64, error) {
 	}
 	return pcs, nil
 }
+
+func loadModules(fname string) ([]host.KernelModule, error) {
+	data, err := os.ReadFile(fname)
+	if err != nil {
+		return nil, err
+	}
+	var modules []host.KernelModule
+	if err := json.Unmarshal(data, &modules); err != nil {
+		return nil, err
+	}
+	return modules, nil
+}