[syserror] Add conversions to linuxerr with temporary Equals method.

Add Equals method to compare syserror and unix.Errno errors to linuxerr errors.
This will facilitate removal of syserror definitions in a followup, and
finding needed conversions from unix.Errno to linuxerr.

PiperOrigin-RevId: 380909667

pkg/errors/linuxerr/BUILD

@@ -9,6 +9,7 @@ go_library(
     deps = [
         "//pkg/abi/linux/errno",
         "//pkg/errors",
+        "@org_golang_x_sys//unix:go_default_library",
     ],
 )
 

pkg/errors/linuxerr/linuxerr.go

@@ -20,6 +20,7 @@ package linuxerr
 import (
 	"fmt"
 
+	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux/errno"
 	"gvisor.dev/gvisor/pkg/errors"
 )
@@ -325,3 +326,22 @@ func ErrorFromErrno(e errno.Errno) *errors.Error {
 	}
 	panic(fmt.Sprintf("invalid error requested with errno: %d", e))
 }
+
+// Equals compars a linuxerr to a given error
+// TODO(b/34162363): Remove when syserror is removed.
+func Equals(e *errors.Error, err error) bool {
+	if err == nil {
+		return e == NOERROR || e == nil
+	}
+	if e == nil {
+		return err == NOERROR || err == unix.Errno(0)
+	}
+
+	switch err.(type) {
+	case *errors.Error:
+		return e == err
+	case unix.Errno, error:
+		return unix.Errno(e.Errno()) == err
+	}
+	return false
+}

pkg/errors/linuxerr/linuxerr_test.go

@@ -16,6 +16,8 @@ package syserror_test
 
 import (
 	"errors"
+	"io"
+	"io/fs"
 	"syscall"
 	"testing"
 
@@ -243,3 +245,62 @@ func TestSyscallErrnoToErrors(t *testing.T) {
 		})
 	}
 }
+
+// TestEqualsMethod tests that the Equals method correctly compares syerror,
+// unix.Errno and linuxerr.
+// TODO (b/34162363): Remove this.
+func TestEqualsMethod(t *testing.T) {
+	for _, tc := range []struct {
+		name     string
+		linuxErr []*gErrors.Error
+		err      []error
+		equal    bool
+	}{
+		{
+			name:     "compare nil",
+			linuxErr: []*gErrors.Error{nil, linuxerr.NOERROR},
+			err:      []error{nil, linuxerr.NOERROR, unix.Errno(0)},
+			equal:    true,
+		},
+		{
+			name:     "linuxerr nil error not",
+			linuxErr: []*gErrors.Error{nil, linuxerr.NOERROR},
+			err:      []error{unix.Errno(1), linuxerr.EPERM, syserror.EACCES},
+			equal:    false,
+		},
+		{
+			name:     "linuxerr not nil error nil",
+			linuxErr: []*gErrors.Error{linuxerr.ENOENT},
+			err:      []error{nil, unix.Errno(0), linuxerr.NOERROR},
+			equal:    false,
+		},
+		{
+			name:     "equal errors",
+			linuxErr: []*gErrors.Error{linuxerr.ESRCH},
+			err:      []error{linuxerr.ESRCH, syserror.ESRCH, unix.Errno(linuxerr.ESRCH.Errno())},
+			equal:    true,
+		},
+		{
+			name:     "unequal errors",
+			linuxErr: []*gErrors.Error{linuxerr.ENOENT},
+			err:      []error{linuxerr.ESRCH, syserror.ESRCH, unix.Errno(linuxerr.ESRCH.Errno())},
+			equal:    false,
+		},
+		{
+			name:     "other error",
+			linuxErr: []*gErrors.Error{nil, linuxerr.NOERROR, linuxerr.E2BIG, linuxerr.EINVAL},
+			err:      []error{fs.ErrInvalid, io.EOF},
+			equal:    false,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			for _, le := range tc.linuxErr {
+				for _, e := range tc.err {
+					if linuxerr.Equals(le, e) != tc.equal {
+						t.Fatalf("Expected %t from Equals method for linuxerr: %s %T and error: %s %T", tc.equal, le, le, e, e)
+					}
+				}
+			}
+		})
+	}
+}

pkg/sentry/fs/BUILD

@@ -48,6 +48,7 @@ go_library(
         "//pkg/abi/linux",
         "//pkg/amutex",
         "//pkg/context",
+        "//pkg/errors/linuxerr",
         "//pkg/hostarch",
         "//pkg/log",
         "//pkg/p9",
@@ -110,6 +111,7 @@ go_test(
     deps = [
         ":fs",
         "//pkg/context",
+        "//pkg/errors/linuxerr",
         "//pkg/sentry/fs/fsutil",
         "//pkg/sentry/fs/ramfs",
         "//pkg/sentry/fs/tmpfs",

pkg/sentry/fs/copy_up.go

@@ -20,6 +20,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/hostarch"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
@@ -410,7 +411,7 @@ func copyAttributesLocked(ctx context.Context, upper *Inode, lower *Inode) error
 		return err
 	}
 	lowerXattr, err := lower.ListXattr(ctx, linux.XATTR_SIZE_MAX)
-	if err != nil && err != syserror.EOPNOTSUPP {
+	if err != nil && !linuxerr.Equals(linuxerr.EOPNOTSUPP, err) {
 		return err
 	}
 

pkg/sentry/fs/dirent.go

@@ -22,6 +22,7 @@ import (
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
@@ -1439,7 +1440,7 @@ func Rename(ctx context.Context, root *Dirent, oldParent *Dirent, oldName string
 	// replaced is the dirent that is being overwritten by rename.
 	replaced, err := newParent.walk(ctx, root, newName, false /* may unlock */)
 	if err != nil {
-		if err != syserror.ENOENT {
+		if !linuxerr.Equals(linuxerr.ENOENT, err) {
 			return err
 		}
 

pkg/sentry/fs/fdpipe/BUILD

@@ -13,6 +13,7 @@ go_library(
     visibility = ["//pkg/sentry:internal"],
     deps = [
         "//pkg/context",
+        "//pkg/errors/linuxerr",
         "//pkg/fd",
         "//pkg/fdnotifier",
         "//pkg/log",

pkg/sentry/fs/fdpipe/pipe.go

@@ -20,6 +20,7 @@ import (
 
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/fd"
 	"gvisor.dev/gvisor/pkg/fdnotifier"
 	"gvisor.dev/gvisor/pkg/log"
@@ -158,7 +159,7 @@ func (p *pipeOperations) Write(ctx context.Context, file *fs.File, src usermem.I
 // isBlockError unwraps os errors and checks if they are caused by EAGAIN or
 // EWOULDBLOCK. This is so they can be transformed into syserror.ErrWouldBlock.
 func isBlockError(err error) bool {
-	if err == syserror.EAGAIN || err == syserror.EWOULDBLOCK {
+	if linuxerr.Equals(linuxerr.EAGAIN, err) || linuxerr.Equals(linuxerr.EWOULDBLOCK, err) {
 		return true
 	}
 	if pe, ok := err.(*os.PathError); ok {

pkg/sentry/fs/gofer/BUILD

@@ -26,6 +26,7 @@ go_library(
     deps = [
         "//pkg/abi/linux",
         "//pkg/context",
+        "//pkg/errors/linuxerr",
         "//pkg/fd",
         "//pkg/hostarch",
         "//pkg/log",

pkg/sentry/fs/gofer/path.go

@@ -18,6 +18,7 @@ import (
 	"fmt"
 
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/p9"
 	"gvisor.dev/gvisor/pkg/sentry/device"
@@ -66,7 +67,7 @@ func (i *inodeOperations) Lookup(ctx context.Context, dir *fs.Inode, name string
 	// Get a p9.File for name.
 	qids, newFile, mask, p9attr, err := i.fileState.file.walkGetAttr(ctx, []string{name})
 	if err != nil {
-		if err == syserror.ENOENT {
+		if linuxerr.Equals(linuxerr.ENOENT, err) {
 			if cp.cacheNegativeDirents() {
 				// Return a negative Dirent. It will stay cached until something
 				// is created over it.
@@ -298,7 +299,7 @@ func (i *inodeOperations) CreateFifo(ctx context.Context, dir *fs.Inode, name st
 
 	// N.B. FIFOs use major/minor numbers 0.
 	if _, err := i.fileState.file.mknod(ctx, name, mode, 0, 0, p9.UID(owner.UID), p9.GID(owner.GID)); err != nil {
-		if i.session().overrides == nil || err != syserror.EPERM {
+		if i.session().overrides == nil || !linuxerr.Equals(linuxerr.EPERM, err) {
 			return err
 		}
 		// If gofer doesn't support mknod, check if we can create an internal fifo.

pkg/sentry/fs/host/BUILD

@@ -28,6 +28,7 @@ go_library(
     deps = [
         "//pkg/abi/linux",
         "//pkg/context",
+        "//pkg/errors/linuxerr",
         "//pkg/fd",
         "//pkg/fdnotifier",
         "//pkg/iovec",

pkg/sentry/fs/host/socket.go

@@ -21,6 +21,7 @@ import (
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/fd"
 	"gvisor.dev/gvisor/pkg/fdnotifier"
 	"gvisor.dev/gvisor/pkg/refs"
@@ -213,7 +214,7 @@ func (c *ConnectedEndpoint) Send(ctx context.Context, data [][]byte, controlMess
 		// block (and only for stream sockets).
 		err = syserror.EAGAIN
 	}
-	if n > 0 && err != syserror.EAGAIN {
+	if n > 0 && !linuxerr.Equals(linuxerr.EAGAIN, err) {
 		// The caller may need to block to send more data, but
 		// otherwise there isn't anything that can be done about an
 		// error with a partial write.

pkg/sentry/fs/host/tty.go

@@ -17,6 +17,7 @@ package host
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/marshal/primitive"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
@@ -191,7 +192,7 @@ func (t *TTYFileOperations) Ioctl(ctx context.Context, _ *fs.File, io usermem.IO
 		if err := t.checkChange(ctx, linux.SIGTTOU); err != nil {
 			// drivers/tty/tty_io.c:tiocspgrp() converts -EIO from
 			// tty_check_change() to -ENOTTY.
-			if err == syserror.EIO {
+			if linuxerr.Equals(linuxerr.EIO, err) {
 				return 0, syserror.ENOTTY
 			}
 			return 0, err

pkg/sentry/fs/host/util.go

@@ -19,12 +19,12 @@ import (
 
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/device"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
-	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 func nodeType(s *unix.Stat_t) fs.InodeType {
@@ -98,7 +98,7 @@ type dirInfo struct {
 // isBlockError unwraps os errors and checks if they are caused by EAGAIN or
 // EWOULDBLOCK. This is so they can be transformed into syserror.ErrWouldBlock.
 func isBlockError(err error) bool {
-	if err == syserror.EAGAIN || err == syserror.EWOULDBLOCK {
+	if linuxerr.Equals(linuxerr.EAGAIN, err) || linuxerr.Equals(linuxerr.EWOULDBLOCK, err) {
 		return true
 	}
 	if pe, ok := err.(*os.PathError); ok {

pkg/sentry/fs/inode_overlay.go

@@ -19,6 +19,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -71,7 +72,7 @@ func overlayLookup(ctx context.Context, parent *overlayEntry, inode *Inode, name
 		// A file could have been created over a whiteout, so we need to
 		// check if something exists in the upper file system first.
 		child, err := parent.upper.Lookup(ctx, name)
-		if err != nil && err != syserror.ENOENT {
+		if err != nil && !linuxerr.Equals(linuxerr.ENOENT, err) {
 			// We encountered an error that an overlay cannot handle,
 			// we must propagate it to the caller.
 			parent.copyMu.RUnlock()
@@ -125,7 +126,7 @@ func overlayLookup(ctx context.Context, parent *overlayEntry, inode *Inode, name
 		// Check the lower file system.
 		child, err := parent.lower.Lookup(ctx, name)
 		// Same song and dance as above.
-		if err != nil && err != syserror.ENOENT {
+		if err != nil && !linuxerr.Equals(linuxerr.ENOENT, err) {
 			// Don't leak resources.
 			if upperInode != nil {
 				upperInode.DecRef(ctx)
@@ -396,7 +397,7 @@ func overlayRename(ctx context.Context, o *overlayEntry, oldParent *Dirent, rena
 		// newName has been removed out from under us. That's fine;
 		// filesystems where that can happen must handle stale
 		// 'replaced'.
-		if err != nil && err != syserror.ENOENT {
+		if err != nil && !linuxerr.Equals(linuxerr.ENOENT, err) {
 			return err
 		}
 		if err == nil {

pkg/sentry/fs/inode_overlay_test.go

@@ -18,6 +18,7 @@ import (
 	"testing"
 
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/fs/ramfs"
@@ -191,11 +192,11 @@ func TestLookup(t *testing.T) {
 	} {
 		t.Run(test.desc, func(t *testing.T) {
 			dirent, err := test.dir.Lookup(ctx, test.name)
-			if test.found && (err == syserror.ENOENT || dirent.IsNegative()) {
+			if test.found && (linuxerr.Equals(linuxerr.ENOENT, err) || dirent.IsNegative()) {
 				t.Fatalf("lookup %q expected to find positive dirent, got dirent %v err %v", test.name, dirent, err)
 			}
 			if !test.found {
-				if err != syserror.ENOENT && !dirent.IsNegative() {
+				if !linuxerr.Equals(linuxerr.ENOENT, err) && !dirent.IsNegative() {
 					t.Errorf("lookup %q expected to return ENOENT or negative dirent, got dirent %v err %v", test.name, dirent, err)
 				}
 				// Nothing more to check.

pkg/sentry/fs/proc/BUILD

@@ -30,6 +30,7 @@ go_library(
     deps = [
         "//pkg/abi/linux",
         "//pkg/context",
+        "//pkg/errors/linuxerr",
         "//pkg/hostarch",
         "//pkg/log",
         "//pkg/sentry/fs",

pkg/sentry/fs/proc/net.go

@@ -23,6 +23,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/hostarch"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
@@ -34,7 +35,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/socket"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
-	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 )
 
@@ -291,7 +291,7 @@ func (n *netSnmp) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle) ([]s
 			continue
 		}
 		if err := n.s.Statistics(stat, line.prefix); err != nil {
-			if err == syserror.EOPNOTSUPP {
+			if linuxerr.Equals(linuxerr.EOPNOTSUPP, err) {
 				log.Infof("Failed to retrieve %s of /proc/net/snmp: %v", line.prefix, err)
 			} else {
 				log.Warningf("Failed to retrieve %s of /proc/net/snmp: %v", line.prefix, err)

pkg/sentry/fs/splice.go

@@ -19,6 +19,7 @@ import (
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
@@ -139,7 +140,7 @@ func Splice(ctx context.Context, dst *File, src *File, opts SpliceOpts) (int64,
 
 	// Attempt to do a WriteTo; this is likely the most efficient.
 	n, err := src.FileOperations.WriteTo(ctx, src, w, opts.Length, opts.Dup)
-	if n == 0 && err == syserror.ENOSYS && !opts.Dup {
+	if n == 0 && linuxerr.Equals(linuxerr.ENOSYS, err) && !opts.Dup {
 		// Attempt as a ReadFrom. If a WriteTo, a ReadFrom may also be
 		// more efficient than a copy if buffers are cached or readily
 		// available. (It's unlikely that they can actually be donated).
@@ -151,7 +152,7 @@ func Splice(ctx context.Context, dst *File, src *File, opts SpliceOpts) (int64,
 	// if we block at some point, we could lose data. If the source is
 	// not a pipe then reading is not destructive; if the destination
 	// is a regular file, then it is guaranteed not to block writing.
-	if n == 0 && err == syserror.ENOSYS && !opts.Dup && (!dstPipe || !srcPipe) {
+	if n == 0 && linuxerr.Equals(linuxerr.ENOSYS, err) && !opts.Dup && (!dstPipe || !srcPipe) {
 		// Fallback to an in-kernel copy.
 		n, err = io.Copy(w, &io.LimitedReader{
 			R: r,

pkg/sentry/fs/user/BUILD

@@ -12,6 +12,7 @@ go_library(
     deps = [
         "//pkg/abi/linux",
         "//pkg/context",
+        "//pkg/errors/linuxerr",
         "//pkg/fspath",
         "//pkg/log",
         "//pkg/sentry/fs",