Format sigaction in strace

Sample:

I1206 14:24:56.768520    3700 x:0] [   1] ioctl_test E rt_sigaction(SIGSEGV, 0x7ee6edb0c590 {Handler: 0x559c6d915cf0, Flags: SA_SIGINFO|SA_RESTORER|SA_ONSTACK|SA_NODEFER, Restorer: 0x2a9901a259a0, Mask: []}, 0x7ee6edb0c630)
I1206 14:24:56.768530    3700 x:0] [   1] ioctl_test X rt_sigaction(SIGSEGV, 0x7ee6edb0c590 {Handler: 0x559c6d915cf0, Flags: SA_SIGINFO|SA_RESTORER|SA_ONSTACK|SA_NODEFER, Restorer: 0x2a9901a259a0, Mask: []}, 0x7ee6edb0c630 {Handler: SIG_DFL, Flags: 0x0, Restorer: 0x0, Mask: []}) = 0x0 (2.701?s)

PiperOrigin-RevId: 224596606
Change-Id: I3512493aed99d3d75600249263da46686b1dc0e7

pkg/abi/flag.go

@@ -43,6 +43,11 @@ func (s FlagSet) Parse(val uint64) string {
 		flags = append(flags, "0x"+strconv.FormatUint(val, 16))
 	}
 
+	if len(flags) == 0 {
+		// Prefer 0 to an empty string.
+		return "0x0"
+	}
+
 	return strings.Join(flags, "|")
 }
 

pkg/abi/linux/signal.go

@@ -165,15 +165,16 @@ const (
 
 // Signal action flags for rt_sigaction(2), from uapi/asm-generic/signal.h
 const (
-	SA_NOCLDSTOP   = 0x00000001
-	SA_NOCLDWAIT   = 0x00000002
-	SA_SIGINFO     = 0x00000004
-	SA_ONSTACK     = 0x08000000
-	SA_RESTART     = 0x10000000
-	SA_NODEFER     = 0x40000000
-	SA_RESTARTHAND = 0x80000000
-	SA_NOMASK      = SA_NODEFER
-	SA_ONESHOT     = SA_RESTARTHAND
+	SA_NOCLDSTOP = 0x00000001
+	SA_NOCLDWAIT = 0x00000002
+	SA_SIGINFO   = 0x00000004
+	SA_RESTORER  = 0x04000000
+	SA_ONSTACK   = 0x08000000
+	SA_RESTART   = 0x10000000
+	SA_NODEFER   = 0x40000000
+	SA_RESETHAND = 0x80000000
+	SA_NOMASK    = SA_NODEFER
+	SA_ONESHOT   = SA_RESETHAND
 )
 
 // Signal info types.

pkg/sentry/strace/linux64.go

@@ -30,7 +30,7 @@ var linuxAMD64 = SyscallMap{
 	10:  makeSyscallInfo("mprotect", Hex, Hex, Hex),
 	11:  makeSyscallInfo("munmap", Hex, Hex),
 	12:  makeSyscallInfo("brk", Hex),
-	13:  makeSyscallInfo("rt_sigaction", Signal, Hex, Hex),
+	13:  makeSyscallInfo("rt_sigaction", Signal, SigAction, PostSigAction),
 	14:  makeSyscallInfo("rt_sigprocmask", SignalMaskAction, SigSet, PostSigSet, Hex),
 	15:  makeSyscallInfo("rt_sigreturn"),
 	16:  makeSyscallInfo("ioctl", Hex, Hex, Hex),

pkg/sentry/strace/signal.go

@@ -65,6 +65,41 @@ var signalMaskActions = abi.ValueSet{
 	linux.SIG_SETMASK: "SIG_SETMASK",
 }
 
+var sigActionFlags = abi.FlagSet{
+	{
+		Flag: linux.SA_NOCLDSTOP,
+		Name: "SA_NOCLDSTOP",
+	},
+	{
+		Flag: linux.SA_NOCLDWAIT,
+		Name: "SA_NOCLDWAIT",
+	},
+	{
+		Flag: linux.SA_SIGINFO,
+		Name: "SA_SIGINFO",
+	},
+	{
+		Flag: linux.SA_RESTORER,
+		Name: "SA_RESTORER",
+	},
+	{
+		Flag: linux.SA_ONSTACK,
+		Name: "SA_ONSTACK",
+	},
+	{
+		Flag: linux.SA_RESTART,
+		Name: "SA_RESTART",
+	},
+	{
+		Flag: linux.SA_NODEFER,
+		Name: "SA_NODEFER",
+	},
+	{
+		Flag: linux.SA_RESETHAND,
+		Name: "SA_RESETHAND",
+	},
+}
+
 func sigSet(t *kernel.Task, addr usermem.Addr) string {
 	if addr == 0 {
 		return "null"
@@ -77,10 +112,37 @@ func sigSet(t *kernel.Task, addr usermem.Addr) string {
 
 	set := linux.SignalSet(usermem.ByteOrder.Uint64(b[:]))
 
+	return fmt.Sprintf("%#x %s", addr, formatSigSet(set))
+}
+
+func formatSigSet(set linux.SignalSet) string {
 	var signals []string
 	linux.ForEachSignal(set, func(sig linux.Signal) {
 		signals = append(signals, signalNames.ParseDecimal(uint64(sig)))
 	})
 
-	return fmt.Sprintf("%#x [%v]", addr, strings.Join(signals, " "))
+	return fmt.Sprintf("[%v]", strings.Join(signals, " "))
+}
+
+func sigAction(t *kernel.Task, addr usermem.Addr) string {
+	if addr == 0 {
+		return "null"
+	}
+
+	sa, err := t.CopyInSignalAct(addr)
+	if err != nil {
+		return fmt.Sprintf("%#x (error copying sigaction: %v)", addr, err)
+	}
+
+	var handler string
+	switch sa.Handler {
+	case linux.SIG_IGN:
+		handler = "SIG_IGN"
+	case linux.SIG_DFL:
+		handler = "SIG_DFL"
+	default:
+		handler = fmt.Sprintf("%#x", sa.Handler)
+	}
+
+	return fmt.Sprintf("%#x {Handler: %s, Flags: %s, Restorer: %#x, Mask: %s}", addr, handler, sigActionFlags.Parse(sa.Flags), sa.Restorer, formatSigSet(sa.Mask))
 }

pkg/sentry/strace/strace.go

@@ -339,6 +339,8 @@ func (i *SyscallInfo) pre(t *kernel.Task, args arch.SyscallArguments, maximumBlo
 			output = append(output, signalMaskActions.Parse(uint64(args[arg].Int())))
 		case SigSet:
 			output = append(output, sigSet(t, args[arg].Pointer()))
+		case SigAction:
+			output = append(output, sigAction(t, args[arg].Pointer()))
 		case Oct:
 			output = append(output, "0o"+strconv.FormatUint(args[arg].Uint64(), 8))
 		case Hex:
@@ -399,6 +401,8 @@ func (i *SyscallInfo) post(t *kernel.Task, args arch.SyscallArguments, rval uint
 			output[arg] = rusage(t, args[arg].Pointer())
 		case PostSigSet:
 			output[arg] = sigSet(t, args[arg].Pointer())
+		case PostSigAction:
+			output[arg] = sigAction(t, args[arg].Pointer())
 		}
 	}
 }

pkg/sentry/strace/syscalls.go

@@ -182,6 +182,12 @@ const (
 
 	// PostSigSet is a signal set, formatted after syscall execution.
 	PostSigSet
+
+	// SigAction is a struct sigaction.
+	SigAction
+
+	// PostSigAction is a struct sigaction, formatted after syscall execution.
+	PostSigAction
 )
 
 // defaultFormat is the syscall argument format to use if the actual format is