Improve loader related error messages returned to users.

PiperOrigin-RevId: 228382827
Change-Id: Ica1d30e0df826bdd77f180a5092b2b735ea5c804

6 files changed, 27 insertions, 29 deletions

diff --git a/pkg/sentry/kernel/BUILD b/pkg/sentry/kernel/BUILD
index 490f674c0..7d41626dc 100644
--- a/pkg/sentry/kernel/BUILD
+++ b/pkg/sentry/kernel/BUILD
@@ -184,6 +184,7 @@ go_library(
         "//pkg/state",
         "//pkg/state/statefile",
         "//pkg/sync",
+        "//pkg/syserr",
         "//pkg/syserror",
         "//pkg/tcpip",
         "//pkg/tcpip/stack",
diff --git a/pkg/sentry/kernel/kernel.go b/pkg/sentry/kernel/kernel.go
index cb61e27f1..43e9823cb 100644
--- a/pkg/sentry/kernel/kernel.go
+++ b/pkg/sentry/kernel/kernel.go
@@ -31,6 +31,7 @@
 package kernel
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"path/filepath"
@@ -658,9 +659,9 @@ func (k *Kernel) CreateProcess(args CreateProcessArgs) (*ThreadGroup, ThreadID,
 
 	// Create a fresh task context.
 	remainingTraversals = uint(args.MaxSymlinkTraversals)
-	tc, err := k.LoadTaskImage(ctx, k.mounts, root, wd, &remainingTraversals, args.Filename, args.Argv, args.Envv, k.featureSet)
-	if err != nil {
-		return nil, 0, err
+	tc, se := k.LoadTaskImage(ctx, k.mounts, root, wd, &remainingTraversals, args.Filename, args.Argv, args.Envv, k.featureSet)
+	if se != nil {
+		return nil, 0, errors.New(se.String())
 	}
 
 	// Take a reference on the FDMap, which will be transferred to
diff --git a/pkg/sentry/kernel/task_context.go b/pkg/sentry/kernel/task_context.go
index aaff309f0..ee3e49d17 100644
--- a/pkg/sentry/kernel/task_context.go
+++ b/pkg/sentry/kernel/task_context.go
@@ -15,9 +15,9 @@
 package kernel
 
 import (
-	"errors"
 	"fmt"
 
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/cpuid"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
@@ -26,10 +26,10 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/loader"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserr"
 )
 
-// ErrNoSyscalls is returned if there is no syscall table.
-var ErrNoSyscalls = errors.New("no syscall table found")
+var errNoSyscalls = syserr.New("no syscall table found", linux.ENOEXEC)
 
 // Auxmap contains miscellaneous data for the task.
 type Auxmap map[string]interface{}
@@ -142,7 +142,7 @@ func (t *Task) Stack() *arch.Stack {
 //  * argv: Binary argv
 //  * envv: Binary envv
 //  * fs: Binary FeatureSet
-func (k *Kernel) LoadTaskImage(ctx context.Context, mounts *fs.MountNamespace, root, wd *fs.Dirent, maxTraversals *uint, filename string, argv, envv []string, fs *cpuid.FeatureSet) (*TaskContext, error) {
+func (k *Kernel) LoadTaskImage(ctx context.Context, mounts *fs.MountNamespace, root, wd *fs.Dirent, maxTraversals *uint, filename string, argv, envv []string, fs *cpuid.FeatureSet) (*TaskContext, *syserr.Error) {
 	// Prepare a new user address space to load into.
 	m := mm.NewMemoryManager(k)
 	defer m.DecUsers(ctx)
@@ -155,8 +155,9 @@ func (k *Kernel) LoadTaskImage(ctx context.Context, mounts *fs.MountNamespace, r
 	// Lookup our new syscall table.
 	st, ok := LookupSyscallTable(os, ac.Arch())
 	if !ok {
-		// No syscall table found. Yikes.
-		return nil, ErrNoSyscalls
+		// No syscall table found. This means that the ELF binary does not match
+		// the architecture.
+		return nil, errNoSyscalls
 	}
 
 	if !m.IncUsers() {
diff --git a/pkg/sentry/loader/BUILD b/pkg/sentry/loader/BUILD
index 83cad186a..24e734b49 100644
--- a/pkg/sentry/loader/BUILD
+++ b/pkg/sentry/loader/BUILD
@@ -44,6 +44,7 @@ go_library(
         "//pkg/sentry/uniqueid",
         "//pkg/sentry/usage",
         "//pkg/sentry/usermem",
+        "//pkg/syserr",
         "//pkg/syserror",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/loader/loader.go b/pkg/sentry/loader/loader.go
index e955502e3..deb8892f6 100644
--- a/pkg/sentry/loader/loader.go
+++ b/pkg/sentry/loader/loader.go
@@ -17,6 +17,7 @@ package loader
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"path"
 
@@ -30,6 +31,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserr"
 	"gvisor.googlesource.com/gvisor/pkg/syserror"
 )
 
@@ -196,20 +198,18 @@ func loadPath(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespac
 // Preconditions:
 //  * The Task MemoryManager is empty.
 //  * Load is called on the Task goroutine.
-func Load(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespace, root, wd *fs.Dirent, maxTraversals *uint, fs *cpuid.FeatureSet, filename string, argv, envv []string, extraAuxv []arch.AuxEntry, vdso *VDSO) (abi.OS, arch.Context, string, error) {
+func Load(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespace, root, wd *fs.Dirent, maxTraversals *uint, fs *cpuid.FeatureSet, filename string, argv, envv []string, extraAuxv []arch.AuxEntry, vdso *VDSO) (abi.OS, arch.Context, string, *syserr.Error) {
 	// Load the binary itself.
 	loaded, ac, d, argv, err := loadPath(ctx, m, mounts, root, wd, maxTraversals, fs, filename, argv)
 	if err != nil {
-		ctx.Infof("Failed to load %s: %v", filename, err)
-		return 0, nil, "", err
+		return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to load %s: %v", filename, err), syserr.FromError(err).ToLinux())
 	}
 	defer d.DecRef()
 
 	// Load the VDSO.
 	vdsoAddr, err := loadVDSO(ctx, m, vdso, loaded)
 	if err != nil {
-		ctx.Infof("Error loading VDSO: %v", err)
-		return 0, nil, "", err
+		return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Error loading VDSO: %v", err), syserr.FromError(err).ToLinux())
 	}
 
 	// Setup the heap. brk starts at the next page after the end of the
@@ -217,35 +217,30 @@ func Load(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespace, r
 	// loaded.end is available for its use.
 	e, ok := loaded.end.RoundUp()
 	if !ok {
-		ctx.Warningf("brk overflows: %#x", loaded.end)
-		return 0, nil, "", syserror.ENOEXEC
+		return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("brk overflows: %#x", loaded.end), linux.ENOEXEC)
 	}
 	m.BrkSetup(ctx, e)
 
 	// Allocate our stack.
 	stack, err := allocStack(ctx, m, ac)
 	if err != nil {
-		ctx.Infof("Failed to allocate stack: %v", err)
-		return 0, nil, "", err
+		return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to allocate stack: %v", err), syserr.FromError(err).ToLinux())
 	}
 
 	// Push the original filename to the stack, for AT_EXECFN.
 	execfn, err := stack.Push(filename)
 	if err != nil {
-		ctx.Infof("Failed to push exec filename: %v", err)
-		return 0, nil, "", err
+		return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to push exec filename: %v", err), syserr.FromError(err).ToLinux())
 	}
 
 	// Push 16 random bytes on the stack which AT_RANDOM will point to.
 	var b [16]byte
 	if _, err := rand.Read(b[:]); err != nil {
-		ctx.Infof("Failed to read random bytes: %v", err)
-		return 0, nil, "", err
+		return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to read random bytes: %v", err), syserr.FromError(err).ToLinux())
 	}
 	random, err := stack.Push(b)
 	if err != nil {
-		ctx.Infof("Failed to push random bytes: %v", err)
-		return 0, nil, "", err
+		return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to push random bytes: %v", err), syserr.FromError(err).ToLinux())
 	}
 
 	c := auth.CredentialsFromContext(ctx)
@@ -266,8 +261,7 @@ func Load(ctx context.Context, m *mm.MemoryManager, mounts *fs.MountNamespace, r
 
 	sl, err := stack.Load(argv, envv, auxv)
 	if err != nil {
-		ctx.Infof("Failed to load stack: %v", err)
-		return 0, nil, "", err
+		return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to load stack: %v", err), syserr.FromError(err).ToLinux())
 	}
 
 	m.SetArgvStart(sl.ArgvStart)
diff --git a/pkg/sentry/syscalls/linux/sys_thread.go b/pkg/sentry/syscalls/linux/sys_thread.go
index c12693ee2..61cafefb9 100644
--- a/pkg/sentry/syscalls/linux/sys_thread.go
+++ b/pkg/sentry/syscalls/linux/sys_thread.go
@@ -104,9 +104,9 @@ func Execve(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 	// Load the new TaskContext.
 	maxTraversals := uint(linux.MaxSymlinkTraversals)
-	tc, err := t.Kernel().LoadTaskImage(t, t.MountNamespace(), root, wd, &maxTraversals, filename, argv, envv, t.Arch().FeatureSet())
-	if err != nil {
-		return 0, nil, err
+	tc, se := t.Kernel().LoadTaskImage(t, t.MountNamespace(), root, wd, &maxTraversals, filename, argv, envv, t.Arch().FeatureSet())
+	if se != nil {
+		return 0, nil, se.ToError()
 	}
 
 	ctrl, err := t.Execve(tc)