From 74e397e39accbeb9fcb5382ce963df55014ae7ce Mon Sep 17 00:00:00 2001
From: Ian Lewis <ianlewis@google.com>
Date: Mon, 10 Jun 2019 23:37:32 -0700
Subject: Add introspection for Linux/AMD64 syscalls

Adds simple introspection for syscall compatibility information to Linux/AMD64.
Syscalls registered in the syscall table now have associated metadata like
name, support level, notes, and URLs to relevant issues.

Syscall information can be exported as a table, JSON, or CSV using the new
'runsc help syscalls' command. Users can use this info to debug and get info
on the compatibility of the version of runsc they are running or to generate
documentation.

PiperOrigin-RevId: 252558304
---
 runsc/cmd/help.go | 126 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 runsc/cmd/help.go

(limited to 'runsc/cmd/help.go')

diff --git a/runsc/cmd/help.go b/runsc/cmd/help.go
new file mode 100644
index 000000000..ff4f901cb
--- /dev/null
+++ b/runsc/cmd/help.go
@@ -0,0 +1,126 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"context"
+	"fmt"
+
+	"flag"
+	"github.com/google/subcommands"
+)
+
+// NewHelp returns a help command for the given commander.
+func NewHelp(cdr *subcommands.Commander) *Help {
+	return &Help{
+		cdr: cdr,
+	}
+}
+
+// Help implements subcommands.Command for the "help" command. The 'help'
+// command prints help for commands registered to a Commander but also allows for
+// registering additional help commands that print other documentation.
+type Help struct {
+	cdr      *subcommands.Commander
+	commands []subcommands.Command
+	help     bool
+}
+
+// Name implements subcommands.Command.Name.
+func (*Help) Name() string {
+	return "help"
+}
+
+// Synopsis implements subcommands.Command.Synopsis.
+func (*Help) Synopsis() string {
+	return "Print help documentation."
+}
+
+// Usage implements subcommands.Command.Usage.
+func (*Help) Usage() string {
+	return `help [<subcommand>]:
+	With an argument, prints detailed information on the use of
+	the specified topic or subcommand. With no argument, print a list of
+	all commands and a brief description of each.
+`
+}
+
+// SetFlags implements subcommands.Command.SetFlags.
+func (h *Help) SetFlags(f *flag.FlagSet) {}
+
+// Execute implements subcommands.Command.Execute.
+func (h *Help) Execute(ctx context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	switch f.NArg() {
+	case 0:
+		fmt.Fprintf(h.cdr.Output, "Usage: %s <flags> <subcommand> <subcommand args>\n\n", h.cdr.Name())
+		fmt.Fprintf(h.cdr.Output, `runsc is a command line client for running applications packaged in the Open
+Container Initiative (OCI) format. Applications run by runsc are run in an
+isolated gVisor sandbox that emulates a Linux environment.
+
+gVisor is a user-space kernel, written in Go, that implements a substantial
+portion of the Linux system call interface. It provides an additional layer
+of isolation between running applications and the host operating system.
+
+Functionality is provided by subcommands. For additonal help on individual
+subcommands use "%s %s <subcommand>".
+
+`, h.cdr.Name(), h.Name())
+		h.cdr.VisitGroups(func(g *subcommands.CommandGroup) {
+			h.cdr.ExplainGroup(h.cdr.Output, g)
+		})
+
+		fmt.Fprintf(h.cdr.Output, "Additional help topics (Use \"%s %s <topic>\" to see help on the topic):\n", h.cdr.Name(), h.Name())
+		for _, cmd := range h.commands {
+			fmt.Fprintf(h.cdr.Output, "\t%-15s  %s\n", cmd.Name(), cmd.Synopsis())
+		}
+		fmt.Fprintf(h.cdr.Output, "\nUse \"%s flags\" for a list of top-level flags\n", h.cdr.Name())
+		return subcommands.ExitSuccess
+	default:
+		// Look for commands registered to the commander and print help explanation if found.
+		found := false
+		h.cdr.VisitCommands(func(g *subcommands.CommandGroup, cmd subcommands.Command) {
+			if f.Arg(0) == cmd.Name() {
+				h.cdr.ExplainCommand(h.cdr.Output, cmd)
+				found = true
+			}
+		})
+		if found {
+			return subcommands.ExitSuccess
+		}
+
+		// Next check commands registered to the help command.
+		for _, cmd := range h.commands {
+			if f.Arg(0) == cmd.Name() {
+				fs := flag.NewFlagSet(f.Arg(0), flag.ContinueOnError)
+				fs.Usage = func() { h.cdr.ExplainCommand(h.cdr.Error, cmd) }
+				cmd.SetFlags(fs)
+				if fs.Parse(f.Args()[1:]) != nil {
+					return subcommands.ExitUsageError
+				}
+				return cmd.Execute(ctx, f, args...)
+			}
+		}
+
+		fmt.Fprintf(h.cdr.Error, "Subcommand %s not understood\n", f.Arg(0))
+	}
+
+	f.Usage()
+	return subcommands.ExitUsageError
+}
+
+// Register registers a new help command.
+func (h *Help) Register(cmd subcommands.Command) {
+	h.commands = append(h.commands, cmd)
+}
-- 
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