runsc: Add more precise error messages in {container,sandbox}.go.

PiperOrigin-RevId: 452158030

runsc/container/container.go

@@ -219,7 +219,7 @@ func New(conf *config.Config, args Args) (*Container, error) {
 	// Lock the container metadata file to prevent concurrent creations of
 	// containers with the same id.
 	if err := c.Saver.lockForNew(); err != nil {
-		return nil, err
+		return nil, fmt.Errorf("cannot lock container metadata file: %w", err)
 	}
 	defer c.Saver.unlockOrDie()
 
@@ -252,14 +252,14 @@ func New(conf *config.Config, args Args) (*Container, error) {
 			// part of the cgroup from the start (and all their children processes).
 			parentCgroup, subCgroup, err = c.setupCgroupForRoot(conf, args.Spec)
 			if err != nil {
-				return nil, err
+				return nil, fmt.Errorf("cannot set up cgroup for root: %w", err)
 			}
 		}
 		c.CompatCgroup = cgroup.CgroupJSON{Cgroup: subCgroup}
 		if err := runInCgroup(parentCgroup, func() error {
 			ioFiles, specFile, err := c.createGoferProcess(args.Spec, conf, args.BundleDir, args.Attached)
 			if err != nil {
-				return err
+				return fmt.Errorf("cannot create gofer process: %w", err)
 			}
 
 			// Start a new sandbox for this container. Any errors after this point
@@ -277,7 +277,7 @@ func New(conf *config.Config, args Args) (*Container, error) {
 			}
 			sand, err := sandbox.New(conf, sandArgs)
 			if err != nil {
-				return err
+				return fmt.Errorf("cannot create sandbox: %w", err)
 			}
 			c.Sandbox = sand
 			return nil
@@ -295,7 +295,7 @@ func New(conf *config.Config, args Args) (*Container, error) {
 		}
 		sb, err := Load(conf.RootDir, fullID, LoadOpts{Exact: true})
 		if err != nil {
-			return nil, err
+			return nil, fmt.Errorf("cannot load sandbox: %w", err)
 		}
 		c.Sandbox = sb.Sandbox
 
@@ -320,7 +320,7 @@ func New(conf *config.Config, args Args) (*Container, error) {
 		}
 
 		if err := c.Sandbox.CreateSubcontainer(conf, c.ID, tty); err != nil {
-			return nil, err
+			return nil, fmt.Errorf("cannot create subcontainer: %w", err)
 		}
 	}
 	c.changeStatus(Created)

runsc/sandbox/sandbox.go

@@ -202,7 +202,7 @@ func New(conf *config.Config, args *Args) (*Sandbox, error) {
 		}
 		args.SinkFiles, err = initConf.Setup()
 		if err != nil {
-			return nil, err
+			return nil, fmt.Errorf("cannot init config: %w", err)
 		}
 	}
 
@@ -219,7 +219,7 @@ func New(conf *config.Config, args *Args) (*Sandbox, error) {
 	// process exits unexpectedly.
 	sandboxSyncFile.Close()
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("cannot create sandbox process: %w", err)
 	}
 
 	// Wait until the sandbox has booted.
@@ -237,7 +237,7 @@ func New(conf *config.Config, args *Args) (*Sandbox, error) {
 				return nil, fmt.Errorf("%v: %v", err, permsErr)
 			}
 		}
-		return nil, err
+		return nil, fmt.Errorf("cannot read client sync file: %w", err)
 	}
 
 	c.Release()
@@ -623,7 +623,7 @@ func (s *Sandbox) createSandboxProcess(conf *config.Config, args *Args, startSyn
 
 	specFile, err := specutils.OpenSpec(args.BundleDir)
 	if err != nil {
-		return err
+		return fmt.Errorf("cannot open spec file in bundle dir %v: %w", args.BundleDir, err)
 	}
 	donations.DonateAndClose("spec-fd", specFile)
 
@@ -634,7 +634,7 @@ func (s *Sandbox) createSandboxProcess(conf *config.Config, args *Args, startSyn
 
 	gPlatform, err := platform.Lookup(conf.Platform)
 	if err != nil {
-		return err
+		return fmt.Errorf("cannot look up platform: %w", err)
 	}
 	if deviceFile, err := gPlatform.OpenDevice(conf.PlatformDevicePath); err != nil {
 		return fmt.Errorf("opening device file for platform %q: %v", conf.Platform, err)