all: fix larger module size in /proc/modules

Module size from /proc/modules is bigger than that from .text size in elf.

3 files changed, 27 insertions, 7 deletions

diff --git a/pkg/cover/backend/elf.go b/pkg/cover/backend/elf.go
index 2126292b4..e81d693ce 100644
--- a/pkg/cover/backend/elf.go
+++ b/pkg/cover/backend/elf.go
@@ -220,7 +220,7 @@ func elfGetCompilerVersion(path string) string {
 	return string(data[:])
 }
 
-func elfReadTextSecRange(module KernelModule) (*SecRange, error) {
+func elfReadTextSecRange(module *KernelModule) (*SecRange, error) {
 	text, err := elfReadTextSec(module)
 	if err != nil {
 		return nil, err
@@ -232,7 +232,7 @@ func elfReadTextSecRange(module KernelModule) (*SecRange, error) {
 	return r, nil
 }
 
-func elfReadTextSec(module KernelModule) (*elf.Section, error) {
+func elfReadTextSec(module *KernelModule) (*elf.Section, error) {
 	file, err := elf.Open(module.Path)
 	if err != nil {
 		return nil, err
diff --git a/pkg/cover/backend/modules.go b/pkg/cover/backend/modules.go
index b91ca8025..249b87d0d 100644
--- a/pkg/cover/backend/modules.go
+++ b/pkg/cover/backend/modules.go
@@ -25,9 +25,19 @@ type KernelModule struct {
 func discoverModules(target *targets.Target, objDir string, moduleObj []string,
 	hostModules []*KernelModule) (
 	[]*KernelModule, error) {
+	module := &KernelModule{
+		Path: filepath.Join(objDir, target.KernelObject),
+	}
+	textRange, err := elfReadTextSecRange(module)
+	if err != nil {
+		return nil, err
+	}
 	modules := []*KernelModule{
 		// A dummy module representing the kernel itself.
-		{Path: filepath.Join(objDir, target.KernelObject)},
+		{
+			Path: module.Path,
+			Size: textRange.End - textRange.Start,
+		},
 	}
 	if target.OS == targets.Linux {
 		modules1, err := discoverModulesLinux(append([]string{objDir}, moduleObj...),
@@ -54,12 +64,18 @@ func discoverModulesLinux(dirs []string, hostModules []*KernelModule) ([]*Kernel
 			log.Logf(0, "failed to discover module %v", mod.Name)
 			continue
 		}
-		log.Logf(0, "module %v -> %v", mod.Name, path)
-		modules = append(modules, &KernelModule{
+		log.Logf(2, "module %v -> %v", mod.Name, path)
+		module := &KernelModule{
 			Name: mod.Name,
 			Addr: mod.Addr,
 			Path: path,
-		})
+		}
+		textRange, err := elfReadTextSecRange(module)
+		if err != nil {
+			return nil, err
+		}
+		module.Size = textRange.End - textRange.Start
+		modules = append(modules, module)
 	}
 	return modules, nil
 }
diff --git a/pkg/vminfo/linux.go b/pkg/vminfo/linux.go
index c8e81dd01..4f180e9ff 100644
--- a/pkg/vminfo/linux.go
+++ b/pkg/vminfo/linux.go
@@ -68,6 +68,10 @@ func (linux) parseModules(files filesystem) ([]*cover.KernelModule, error) {
 		modules = append(modules, &cover.KernelModule{
 			Name: name,
 			Addr: textAddr,
+			// The size is wrong as there is overlap in /proc/modules
+			// ex. module1['Addr'] + module1['Size'] > module2['Addr']
+			// runtime kernel doesn't export .text section size to /sys/module/*/sections/.text
+			// so we need to read it from elf
 			Size: modSize - offset,
 		})
 	}
@@ -75,7 +79,7 @@ func (linux) parseModules(files filesystem) ([]*cover.KernelModule, error) {
 	if err != nil {
 		return nil, err
 	}
-	modules = append(modules, cover.KernelModule{
+	modules = append(modules, &cover.KernelModule{
 		Name: "",
 		Addr: _stext,
 		Size: _etext - _stext,