Move ERESTART* error definitions to syserror package.

This is needed to avoid circular dependencies between the vfs and kernel
packages.

PiperOrigin-RevId: 327355524

3 files changed, 8 insertions, 74 deletions

diff --git a/pkg/sentry/kernel/task_run.go b/pkg/sentry/kernel/task_run.go
index abaf29216..aa3a573c0 100644
--- a/pkg/sentry/kernel/task_run.go
+++ b/pkg/sentry/kernel/task_run.go
@@ -26,6 +26,7 @@ import (
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
+	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
@@ -189,8 +190,8 @@ func (app *runApp) execute(t *Task) taskRunState {
 	// a pending signal, causing another interruption, but that signal should
 	// not interact with the interrupted syscall.)
 	if t.haveSyscallReturn {
-		if sre, ok := SyscallRestartErrnoFromReturn(t.Arch().Return()); ok {
-			if sre == ERESTART_RESTARTBLOCK {
+		if sre, ok := syserror.SyscallRestartErrnoFromReturn(t.Arch().Return()); ok {
+			if sre == syserror.ERESTART_RESTARTBLOCK {
 				t.Debugf("Restarting syscall %d with restart block after errno %d: not interrupted by handled signal", t.Arch().SyscallNo(), sre)
 				t.Arch().RestartSyscallWithRestartBlock()
 			} else {
diff --git a/pkg/sentry/kernel/task_signals.go b/pkg/sentry/kernel/task_signals.go
index cff2a8365..d6a2040bc 100644
--- a/pkg/sentry/kernel/task_signals.go
+++ b/pkg/sentry/kernel/task_signals.go
@@ -159,7 +159,7 @@ func (t *Task) deliverSignal(info *arch.SignalInfo, act arch.SignalAct) taskRunS
 	sigact := computeAction(linux.Signal(info.Signo), act)
 
 	if t.haveSyscallReturn {
-		if sre, ok := SyscallRestartErrnoFromReturn(t.Arch().Return()); ok {
+		if sre, ok := syserror.SyscallRestartErrnoFromReturn(t.Arch().Return()); ok {
 			// Signals that are ignored, cause a thread group stop, or
 			// terminate the thread group do not interact with interrupted
 			// syscalls; in Linux terms, they are never returned to the signal
@@ -168,11 +168,11 @@ func (t *Task) deliverSignal(info *arch.SignalInfo, act arch.SignalAct) taskRunS
 			// signal that is actually handled (by userspace).
 			if sigact == SignalActionHandler {
 				switch {
-				case sre == ERESTARTNOHAND:
+				case sre == syserror.ERESTARTNOHAND:
 					fallthrough
-				case sre == ERESTART_RESTARTBLOCK:
+				case sre == syserror.ERESTART_RESTARTBLOCK:
 					fallthrough
-				case (sre == ERESTARTSYS && !act.IsRestart()):
+				case (sre == syserror.ERESTARTSYS && !act.IsRestart()):
 					t.Debugf("Not restarting syscall %d after errno %d: interrupted by signal %d", t.Arch().SyscallNo(), sre, info.Signo)
 					t.Arch().SetReturn(uintptr(-ExtractErrno(syserror.EINTR, -1)))
 				default:
diff --git a/pkg/sentry/kernel/task_syscall.go b/pkg/sentry/kernel/task_syscall.go
index a5903b0b5..2dbf86547 100644
--- a/pkg/sentry/kernel/task_syscall.go
+++ b/pkg/sentry/kernel/task_syscall.go
@@ -29,75 +29,8 @@ import (
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
-// SyscallRestartErrno represents a ERESTART* errno defined in the Linux's kernel
-// include/linux/errno.h. These errnos are never returned to userspace
-// directly, but are used to communicate the expected behavior of an
-// interrupted syscall from the syscall to signal handling.
-type SyscallRestartErrno int
-
-// These numeric values are significant because ptrace syscall exit tracing can
-// observe them.
-//
-// For all of the following errnos, if the syscall is not interrupted by a
-// signal delivered to a user handler, the syscall is restarted.
-const (
-	// ERESTARTSYS is returned by an interrupted syscall to indicate that it
-	// should be converted to EINTR if interrupted by a signal delivered to a
-	// user handler without SA_RESTART set, and restarted otherwise.
-	ERESTARTSYS = SyscallRestartErrno(512)
-
-	// ERESTARTNOINTR is returned by an interrupted syscall to indicate that it
-	// should always be restarted.
-	ERESTARTNOINTR = SyscallRestartErrno(513)
-
-	// ERESTARTNOHAND is returned by an interrupted syscall to indicate that it
-	// should be converted to EINTR if interrupted by a signal delivered to a
-	// user handler, and restarted otherwise.
-	ERESTARTNOHAND = SyscallRestartErrno(514)
-
-	// ERESTART_RESTARTBLOCK is returned by an interrupted syscall to indicate
-	// that it should be restarted using a custom function. The interrupted
-	// syscall must register a custom restart function by calling
-	// Task.SetRestartSyscallFn.
-	ERESTART_RESTARTBLOCK = SyscallRestartErrno(516)
-)
-
 var vsyscallCount = metric.MustCreateNewUint64Metric("/kernel/vsyscall_count", false /* sync */, "Number of times vsyscalls were invoked by the application")
 
-// Error implements error.Error.
-func (e SyscallRestartErrno) Error() string {
-	// Descriptions are borrowed from strace.
-	switch e {
-	case ERESTARTSYS:
-		return "to be restarted if SA_RESTART is set"
-	case ERESTARTNOINTR:
-		return "to be restarted"
-	case ERESTARTNOHAND:
-		return "to be restarted if no handler"
-	case ERESTART_RESTARTBLOCK:
-		return "interrupted by signal"
-	default:
-		return "(unknown interrupt error)"
-	}
-}
-
-// SyscallRestartErrnoFromReturn returns the SyscallRestartErrno represented by
-// rv, the value in a syscall return register.
-func SyscallRestartErrnoFromReturn(rv uintptr) (SyscallRestartErrno, bool) {
-	switch int(rv) {
-	case -int(ERESTARTSYS):
-		return ERESTARTSYS, true
-	case -int(ERESTARTNOINTR):
-		return ERESTARTNOINTR, true
-	case -int(ERESTARTNOHAND):
-		return ERESTARTNOHAND, true
-	case -int(ERESTART_RESTARTBLOCK):
-		return ERESTART_RESTARTBLOCK, true
-	default:
-		return 0, false
-	}
-}
-
 // SyscallRestartBlock represents the restart block for a syscall restartable
 // with a custom function. It encapsulates the state required to restart a
 // syscall across a S/R.
@@ -447,7 +380,7 @@ func ExtractErrno(err error, sysno int) int {
 		return 0
 	case syscall.Errno:
 		return int(err)
-	case SyscallRestartErrno:
+	case syserror.SyscallRestartErrno:
 		return int(err)
 	case *memmap.BusError:
 		// Bus errors may generate SIGBUS, but for syscalls they still