add pkg/signal

Add pkg/signal to deal with parts of signal processing and translating
signals from string to numeric representations.  The code has been
copied from docker/docker (and attributed with the copyright) but been
reduced to only what libpod needs (on Linux).

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

2 files changed, 155 insertions, 0 deletions

diff --git a/pkg/signal/signal_linux.go b/pkg/signal/signal_linux.go
new file mode 100644
index 000000000..3d549898f
--- /dev/null
+++ b/pkg/signal/signal_linux.go
@@ -0,0 +1,127 @@
+// +build linux
+
+// Signal handling for Linux only.
+package signal
+
+// Copyright 2013-2018 Docker, Inc.
+
+// NOTE: this package has originally been copied from github.com/docker/docker.
+
+import (
+	"fmt"
+	"os"
+	"os/signal"
+	"strconv"
+	"strings"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+const (
+	sigrtmin = 34
+	sigrtmax = 64
+
+	SIGWINCH = syscall.SIGWINCH // For cross-compilation with Windows
+)
+
+// signalMap is a map of Linux signals.
+var signalMap = map[string]syscall.Signal{
+	"ABRT":     unix.SIGABRT,
+	"ALRM":     unix.SIGALRM,
+	"BUS":      unix.SIGBUS,
+	"CHLD":     unix.SIGCHLD,
+	"CLD":      unix.SIGCLD,
+	"CONT":     unix.SIGCONT,
+	"FPE":      unix.SIGFPE,
+	"HUP":      unix.SIGHUP,
+	"ILL":      unix.SIGILL,
+	"INT":      unix.SIGINT,
+	"IO":       unix.SIGIO,
+	"IOT":      unix.SIGIOT,
+	"KILL":     unix.SIGKILL,
+	"PIPE":     unix.SIGPIPE,
+	"POLL":     unix.SIGPOLL,
+	"PROF":     unix.SIGPROF,
+	"PWR":      unix.SIGPWR,
+	"QUIT":     unix.SIGQUIT,
+	"SEGV":     unix.SIGSEGV,
+	"STKFLT":   unix.SIGSTKFLT,
+	"STOP":     unix.SIGSTOP,
+	"SYS":      unix.SIGSYS,
+	"TERM":     unix.SIGTERM,
+	"TRAP":     unix.SIGTRAP,
+	"TSTP":     unix.SIGTSTP,
+	"TTIN":     unix.SIGTTIN,
+	"TTOU":     unix.SIGTTOU,
+	"URG":      unix.SIGURG,
+	"USR1":     unix.SIGUSR1,
+	"USR2":     unix.SIGUSR2,
+	"VTALRM":   unix.SIGVTALRM,
+	"WINCH":    unix.SIGWINCH,
+	"XCPU":     unix.SIGXCPU,
+	"XFSZ":     unix.SIGXFSZ,
+	"RTMIN":    sigrtmin,
+	"RTMIN+1":  sigrtmin + 1,
+	"RTMIN+2":  sigrtmin + 2,
+	"RTMIN+3":  sigrtmin + 3,
+	"RTMIN+4":  sigrtmin + 4,
+	"RTMIN+5":  sigrtmin + 5,
+	"RTMIN+6":  sigrtmin + 6,
+	"RTMIN+7":  sigrtmin + 7,
+	"RTMIN+8":  sigrtmin + 8,
+	"RTMIN+9":  sigrtmin + 9,
+	"RTMIN+10": sigrtmin + 10,
+	"RTMIN+11": sigrtmin + 11,
+	"RTMIN+12": sigrtmin + 12,
+	"RTMIN+13": sigrtmin + 13,
+	"RTMIN+14": sigrtmin + 14,
+	"RTMIN+15": sigrtmin + 15,
+	"RTMAX-14": sigrtmax - 14,
+	"RTMAX-13": sigrtmax - 13,
+	"RTMAX-12": sigrtmax - 12,
+	"RTMAX-11": sigrtmax - 11,
+	"RTMAX-10": sigrtmax - 10,
+	"RTMAX-9":  sigrtmax - 9,
+	"RTMAX-8":  sigrtmax - 8,
+	"RTMAX-7":  sigrtmax - 7,
+	"RTMAX-6":  sigrtmax - 6,
+	"RTMAX-5":  sigrtmax - 5,
+	"RTMAX-4":  sigrtmax - 4,
+	"RTMAX-3":  sigrtmax - 3,
+	"RTMAX-2":  sigrtmax - 2,
+	"RTMAX-1":  sigrtmax - 1,
+	"RTMAX":    sigrtmax,
+}
+
+// ParseSignal translates a string to a valid syscall signal.
+// It returns an error if the signal map doesn't include the given signal.
+func ParseSignal(rawSignal string) (syscall.Signal, error) {
+	s, err := strconv.Atoi(rawSignal)
+	if err == nil {
+		if s == 0 {
+			return -1, fmt.Errorf("invalid signal: %s", rawSignal)
+		}
+		return syscall.Signal(s), nil
+	}
+	signal, ok := signalMap[strings.TrimPrefix(strings.ToUpper(rawSignal), "SIG")]
+	if !ok {
+		return -1, fmt.Errorf("invalid signal: %s", rawSignal)
+	}
+	return signal, nil
+}
+
+// CatchAll catches all signals and relays them to the specified channel.
+func CatchAll(sigc chan os.Signal) {
+	var handledSigs []os.Signal
+	for _, s := range signalMap {
+		handledSigs = append(handledSigs, s)
+	}
+	signal.Notify(sigc, handledSigs...)
+}
+
+// StopCatch stops catching the signals and closes the specified channel.
+func StopCatch(sigc chan os.Signal) {
+	signal.Stop(sigc)
+	close(sigc)
+}
diff --git a/pkg/signal/signal_unsupported.go b/pkg/signal/signal_unsupported.go
new file mode 100644
index 000000000..0a92a5b3a
--- /dev/null
+++ b/pkg/signal/signal_unsupported.go
@@ -0,0 +1,28 @@
+// +build !linux
+
+// Signal handling for Linux only.
+package signal
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+)
+
+const SIGWINCH = syscall.Signal(0xff)
+
+// ParseSignal translates a string to a valid syscall signal.
+// It returns an error if the signal map doesn't include the given signal.
+func ParseSignal(rawSignal string) (syscall.Signal, error) {
+	return 0, fmt.Errorf("unsupported on non-linux platforms")
+}
+
+// CatchAll catches all signals and relays them to the specified channel.
+func CatchAll(sigc chan os.Signal) {
+	panic("Unsupported on non-linux platforms")
+}
+
+// StopCatch stops catching the signals and closes the specified channel.
+func StopCatch(sigc chan os.Signal) {
+	panic("Unsupported on non-linux platforms")
+}