Replace kernel.ExitStatus with linux.WaitStatus.

PiperOrigin-RevId: 383705129

pkg/abi/linux/wait.go

@@ -14,6 +14,10 @@
 
 package linux
 
+import (
+	"fmt"
+)
+
 // Options for waitpid(2), wait4(2), and/or waitid(2), from
 // include/uapi/linux/wait.h.
 const (
@@ -34,3 +38,124 @@ const (
 	P_PID  = 0x1
 	P_PGID = 0x2
 )
+
+// WaitStatus represents a thread status, as returned by the wait* family of
+// syscalls.
+type WaitStatus uint32
+
+// WaitStatusExit returns a WaitStatus representing the given exit status.
+func WaitStatusExit(status int32) WaitStatus {
+	return WaitStatus(uint32(status) << 8)
+}
+
+// WaitStatusTerminationSignal returns a WaitStatus representing termination by
+// the given signal.
+func WaitStatusTerminationSignal(sig Signal) WaitStatus {
+	return WaitStatus(uint32(sig))
+}
+
+// WaitStatusStopped returns a WaitStatus representing stoppage by the given
+// signal or ptrace trap code.
+func WaitStatusStopped(code uint32) WaitStatus {
+	return WaitStatus(code<<8 | 0x7f)
+}
+
+// WaitStatusContinued returns a WaitStatus representing continuation by
+// SIGCONT.
+func WaitStatusContinued() WaitStatus {
+	return WaitStatus(0xffff)
+}
+
+// WithCoreDump returns a copy of ws that indicates that a core dump was
+// generated.
+//
+// Preconditions: ws.Signaled().
+func (ws WaitStatus) WithCoreDump() WaitStatus {
+	return ws | 0x80
+}
+
+// Exited returns true if ws represents an exit status, consistent with
+// WIFEXITED.
+func (ws WaitStatus) Exited() bool {
+	return ws&0x7f == 0
+}
+
+// Signaled returns true if ws represents a termination by signal, consistent
+// with WIFSIGNALED.
+func (ws WaitStatus) Signaled() bool {
+	// ws&0x7f != 0 (exited) and ws&0x7f != 0x7f (stopped or continued)
+	return ((ws&0x7f)+1)>>1 != 0
+}
+
+// CoreDumped returns true if ws indicates that a core dump was produced,
+// consistent with WCOREDUMP.
+//
+// Preconditions: ws.Signaled().
+func (ws WaitStatus) CoreDumped() bool {
+	return ws&0x80 != 0
+}
+
+// Stopped returns true if ws represents a stoppage, consistent with
+// WIFSTOPPED.
+func (ws WaitStatus) Stopped() bool {
+	return ws&0xff == 0x7f
+}
+
+// Continued returns true if ws represents a continuation by SIGCONT,
+// consistent with WIFCONTINUED.
+func (ws WaitStatus) Continued() bool {
+	return ws == 0xffff
+}
+
+// ExitStatus returns the lower 8 bits of the exit status represented by ws,
+// consistent with WEXITSTATUS.
+//
+// Preconditions: ws.Exited().
+func (ws WaitStatus) ExitStatus() uint32 {
+	return uint32((ws & 0xff00) >> 8)
+}
+
+// TerminationSignal returns the termination signal represented by ws,
+// consistent with WTERMSIG.
+//
+// Preconditions: ws.Signaled().
+func (ws WaitStatus) TerminationSignal() Signal {
+	return Signal(ws & 0x7f)
+}
+
+// StopSignal returns the stop signal represented by ws, consistent with
+// WSTOPSIG.
+//
+// Preconditions: ws.Stopped().
+func (ws WaitStatus) StopSignal() Signal {
+	return Signal((ws & 0xff00) >> 8)
+}
+
+// PtraceEvent returns the PTRACE_EVENT_* field in ws.
+//
+// Preconditions: ws.Stopped().
+func (ws WaitStatus) PtraceEvent() uint32 {
+	return uint32(ws >> 16)
+}
+
+// String implements fmt.Stringer.String.
+func (ws WaitStatus) String() string {
+	switch {
+	case ws.Exited():
+		return fmt.Sprintf("exit status %d", ws.ExitStatus())
+	case ws.Signaled():
+		if ws.CoreDumped() {
+			return fmt.Sprintf("killed by signal %d (core dumped)", ws.TerminationSignal())
+		}
+		return fmt.Sprintf("killed by signal %d", ws.TerminationSignal())
+	case ws.Stopped():
+		if ev := ws.PtraceEvent(); ev != 0 {
+			return fmt.Sprintf("stopped by signal %d (PTRACE_EVENT %d)", ws.StopSignal(), ev)
+		}
+		return fmt.Sprintf("stopped by signal %d", ws.StopSignal())
+	case ws.Continued():
+		return "continued"
+	default:
+		return fmt.Sprintf("unknown status %#x", uint32(ws))
+	}
+}