scripts/qmp-shell: move to python/qemu/qmp/qmp_shell.py

The script will be unavailable for a commit or two, which will help
preserve development history attached to the new file. A forwarder will
be added shortly afterwards.

With qmp_shell in the python qemu.qmp package, now it is fully type
checked, linted, etc. via the Python CI. It will be quite a bit harder
to accidentally break it again in the future.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 20210607200649.1840382-41-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

1 files changed, 535 insertions, 0 deletions

diff --git a/python/qemu/qmp/qmp_shell.py b/python/qemu/qmp/qmp_shell.py
new file mode 100644
index 0000000000..337acfce2d
--- /dev/null
+++ b/python/qemu/qmp/qmp_shell.py
@@ -0,0 +1,535 @@
+#
+# Copyright (C) 2009, 2010 Red Hat Inc.
+#
+# Authors:
+#  Luiz Capitulino <lcapitulino@redhat.com>
+#
+# This work is licensed under the terms of the GNU GPL, version 2.  See
+# the COPYING file in the top-level directory.
+#
+
+"""
+Low-level QEMU shell on top of QMP.
+
+usage: qmp-shell [-h] [-H] [-N] [-v] [-p] qmp_server
+
+positional arguments:
+  qmp_server            < UNIX socket path | TCP address:port >
+
+optional arguments:
+  -h, --help            show this help message and exit
+  -H, --hmp             Use HMP interface
+  -N, --skip-negotiation
+                        Skip negotiate (for qemu-ga)
+  -v, --verbose         Verbose (echo commands sent and received)
+  -p, --pretty          Pretty-print JSON
+
+
+Start QEMU with:
+
+# qemu [...] -qmp unix:./qmp-sock,server
+
+Run the shell:
+
+$ qmp-shell ./qmp-sock
+
+Commands have the following format:
+
+   < command-name > [ arg-name1=arg1 ] ... [ arg-nameN=argN ]
+
+For example:
+
+(QEMU) device_add driver=e1000 id=net1
+{'return': {}}
+(QEMU)
+
+key=value pairs also support Python or JSON object literal subset notations,
+without spaces. Dictionaries/objects {} are supported as are arrays [].
+
+   example-command arg-name1={'key':'value','obj'={'prop':"value"}}
+
+Both JSON and Python formatting should work, including both styles of
+string literal quotes. Both paradigms of literal values should work,
+including null/true/false for JSON and None/True/False for Python.
+
+
+Transactions have the following multi-line format:
+
+   transaction(
+   action-name1 [ arg-name1=arg1 ] ... [arg-nameN=argN ]
+   ...
+   action-nameN [ arg-name1=arg1 ] ... [arg-nameN=argN ]
+   )
+
+One line transactions are also supported:
+
+   transaction( action-name1 ... )
+
+For example:
+
+    (QEMU) transaction(
+    TRANS> block-dirty-bitmap-add node=drive0 name=bitmap1
+    TRANS> block-dirty-bitmap-clear node=drive0 name=bitmap0
+    TRANS> )
+    {"return": {}}
+    (QEMU)
+
+Use the -v and -p options to activate the verbose and pretty-print options,
+which will echo back the properly formatted JSON-compliant QMP that is being
+sent to QEMU, which is useful for debugging and documentation generation.
+"""
+
+import argparse
+import ast
+import json
+import logging
+import os
+import re
+import readline
+import sys
+from typing import (
+    Iterator,
+    List,
+    NoReturn,
+    Optional,
+    Sequence,
+)
+
+from qemu import qmp
+from qemu.qmp import QMPMessage
+
+
+LOG = logging.getLogger(__name__)
+
+
+class QMPCompleter:
+    """
+    QMPCompleter provides a readline library tab-complete behavior.
+    """
+    # NB: Python 3.9+ will probably allow us to subclass list[str] directly,
+    # but pylint as of today does not know that List[str] is simply 'list'.
+    def __init__(self) -> None:
+        self._matches: List[str] = []
+
+    def append(self, value: str) -> None:
+        """Append a new valid completion to the list of possibilities."""
+        return self._matches.append(value)
+
+    def complete(self, text: str, state: int) -> Optional[str]:
+        """readline.set_completer() callback implementation."""
+        for cmd in self._matches:
+            if cmd.startswith(text):
+                if state == 0:
+                    return cmd
+                state -= 1
+        return None
+
+
+class QMPShellError(qmp.QMPError):
+    """
+    QMP Shell Base error class.
+    """
+
+
+class FuzzyJSON(ast.NodeTransformer):
+    """
+    This extension of ast.NodeTransformer filters literal "true/false/null"
+    values in a Python AST and replaces them by proper "True/False/None" values
+    that Python can properly evaluate.
+    """
+
+    @classmethod
+    def visit_Name(cls,  # pylint: disable=invalid-name
+                   node: ast.Name) -> ast.AST:
+        """
+        Transform Name nodes with certain values into Constant (keyword) nodes.
+        """
+        if node.id == 'true':
+            return ast.Constant(value=True)
+        if node.id == 'false':
+            return ast.Constant(value=False)
+        if node.id == 'null':
+            return ast.Constant(value=None)
+        return node
+
+
+class QMPShell(qmp.QEMUMonitorProtocol):
+    """
+    QMPShell provides a basic readline-based QMP shell.
+
+    :param address: Address of the QMP server.
+    :param pretty: Pretty-print QMP messages.
+    :param verbose: Echo outgoing QMP messages to console.
+    """
+    def __init__(self, address: qmp.SocketAddrT,
+                 pretty: bool = False, verbose: bool = False):
+        super().__init__(address)
+        self._greeting: Optional[QMPMessage] = None
+        self._completer = QMPCompleter()
+        self._transmode = False
+        self._actions: List[QMPMessage] = []
+        self._histfile = os.path.join(os.path.expanduser('~'),
+                                      '.qmp-shell_history')
+        self.pretty = pretty
+        self.verbose = verbose
+
+    def close(self) -> None:
+        # Hook into context manager of parent to save shell history.
+        self._save_history()
+        super().close()
+
+    def _fill_completion(self) -> None:
+        cmds = self.cmd('query-commands')
+        if 'error' in cmds:
+            return
+        for cmd in cmds['return']:
+            self._completer.append(cmd['name'])
+
+    def _completer_setup(self) -> None:
+        self._completer = QMPCompleter()
+        self._fill_completion()
+        readline.set_history_length(1024)
+        readline.set_completer(self._completer.complete)
+        readline.parse_and_bind("tab: complete")
+        # NB: default delimiters conflict with some command names
+        # (eg. query-), clearing everything as it doesn't seem to matter
+        readline.set_completer_delims('')
+        try:
+            readline.read_history_file(self._histfile)
+        except FileNotFoundError:
+            pass
+        except IOError as err:
+            msg = f"Failed to read history '{self._histfile}': {err!s}"
+            LOG.warning(msg)
+
+    def _save_history(self) -> None:
+        try:
+            readline.write_history_file(self._histfile)
+        except IOError as err:
+            msg = f"Failed to save history file '{self._histfile}': {err!s}"
+            LOG.warning(msg)
+
+    @classmethod
+    def _parse_value(cls, val: str) -> object:
+        try:
+            return int(val)
+        except ValueError:
+            pass
+
+        if val.lower() == 'true':
+            return True
+        if val.lower() == 'false':
+            return False
+        if val.startswith(('{', '[')):
+            # Try first as pure JSON:
+            try:
+                return json.loads(val)
+            except ValueError:
+                pass
+            # Try once again as FuzzyJSON:
+            try:
+                tree = ast.parse(val, mode='eval')
+                transformed = FuzzyJSON().visit(tree)
+                return ast.literal_eval(transformed)
+            except (SyntaxError, ValueError):
+                pass
+        return val
+
+    def _cli_expr(self,
+                  tokens: Sequence[str],
+                  parent: qmp.QMPObject) -> None:
+        for arg in tokens:
+            (key, sep, val) = arg.partition('=')
+            if sep != '=':
+                raise QMPShellError(
+                    f"Expected a key=value pair, got '{arg!s}'"
+                )
+
+            value = self._parse_value(val)
+            optpath = key.split('.')
+            curpath = []
+            for path in optpath[:-1]:
+                curpath.append(path)
+                obj = parent.get(path, {})
+                if not isinstance(obj, dict):
+                    msg = 'Cannot use "{:s}" as both leaf and non-leaf key'
+                    raise QMPShellError(msg.format('.'.join(curpath)))
+                parent[path] = obj
+                parent = obj
+            if optpath[-1] in parent:
+                if isinstance(parent[optpath[-1]], dict):
+                    msg = 'Cannot use "{:s}" as both leaf and non-leaf key'
+                    raise QMPShellError(msg.format('.'.join(curpath)))
+                raise QMPShellError(f'Cannot set "{key}" multiple times')
+            parent[optpath[-1]] = value
+
+    def _build_cmd(self, cmdline: str) -> Optional[QMPMessage]:
+        """
+        Build a QMP input object from a user provided command-line in the
+        following format:
+
+            < command-name > [ arg-name1=arg1 ] ... [ arg-nameN=argN ]
+        """
+        argument_regex = r'''(?:[^\s"']|"(?:\\.|[^"])*"|'(?:\\.|[^'])*')+'''
+        cmdargs = re.findall(argument_regex, cmdline)
+        qmpcmd: QMPMessage
+
+        # Transactional CLI entry:
+        if cmdargs and cmdargs[0] == 'transaction(':
+            self._transmode = True
+            self._actions = []
+            cmdargs.pop(0)
+
+        # Transactional CLI exit:
+        if cmdargs and cmdargs[0] == ')' and self._transmode:
+            self._transmode = False
+            if len(cmdargs) > 1:
+                msg = 'Unexpected input after close of Transaction sub-shell'
+                raise QMPShellError(msg)
+            qmpcmd = {
+                'execute': 'transaction',
+                'arguments': {'actions': self._actions}
+            }
+            return qmpcmd
+
+        # No args, or no args remaining
+        if not cmdargs:
+            return None
+
+        if self._transmode:
+            # Parse and cache this Transactional Action
+            finalize = False
+            action = {'type': cmdargs[0], 'data': {}}
+            if cmdargs[-1] == ')':
+                cmdargs.pop(-1)
+                finalize = True
+            self._cli_expr(cmdargs[1:], action['data'])
+            self._actions.append(action)
+            return self._build_cmd(')') if finalize else None
+
+        # Standard command: parse and return it to be executed.
+        qmpcmd = {'execute': cmdargs[0], 'arguments': {}}
+        self._cli_expr(cmdargs[1:], qmpcmd['arguments'])
+        return qmpcmd
+
+    def _print(self, qmp_message: object) -> None:
+        jsobj = json.dumps(qmp_message,
+                           indent=4 if self.pretty else None,
+                           sort_keys=self.pretty)
+        print(str(jsobj))
+
+    def _execute_cmd(self, cmdline: str) -> bool:
+        try:
+            qmpcmd = self._build_cmd(cmdline)
+        except QMPShellError as err:
+            print(
+                f"Error while parsing command line: {err!s}\n"
+                "command format: <command-name> "
+                "[arg-name1=arg1] ... [arg-nameN=argN",
+                file=sys.stderr
+            )
+            return True
+        # For transaction mode, we may have just cached the action:
+        if qmpcmd is None:
+            return True
+        if self.verbose:
+            self._print(qmpcmd)
+        resp = self.cmd_obj(qmpcmd)
+        if resp is None:
+            print('Disconnected')
+            return False
+        self._print(resp)
+        return True
+
+    def connect(self, negotiate: bool = True) -> None:
+        self._greeting = super().connect(negotiate)
+        self._completer_setup()
+
+    def show_banner(self,
+                    msg: str = 'Welcome to the QMP low-level shell!') -> None:
+        """
+        Print to stdio a greeting, and the QEMU version if available.
+        """
+        print(msg)
+        if not self._greeting:
+            print('Connected')
+            return
+        version = self._greeting['QMP']['version']['qemu']
+        print("Connected to QEMU {major}.{minor}.{micro}\n".format(**version))
+
+    @property
+    def prompt(self) -> str:
+        """
+        Return the current shell prompt, including a trailing space.
+        """
+        if self._transmode:
+            return 'TRANS> '
+        return '(QEMU) '
+
+    def read_exec_command(self) -> bool:
+        """
+        Read and execute a command.
+
+        @return True if execution was ok, return False if disconnected.
+        """
+        try:
+            cmdline = input(self.prompt)
+        except EOFError:
+            print()
+            return False
+
+        if cmdline == '':
+            for event in self.get_events():
+                print(event)
+            self.clear_events()
+            return True
+
+        return self._execute_cmd(cmdline)
+
+    def repl(self) -> Iterator[None]:
+        """
+        Return an iterator that implements the REPL.
+        """
+        self.show_banner()
+        while self.read_exec_command():
+            yield
+        self.close()
+
+
+class HMPShell(QMPShell):
+    """
+    HMPShell provides a basic readline-based HMP shell, tunnelled via QMP.
+
+    :param address: Address of the QMP server.
+    :param pretty: Pretty-print QMP messages.
+    :param verbose: Echo outgoing QMP messages to console.
+    """
+    def __init__(self, address: qmp.SocketAddrT,
+                 pretty: bool = False, verbose: bool = False):
+        super().__init__(address, pretty, verbose)
+        self._cpu_index = 0
+
+    def _cmd_completion(self) -> None:
+        for cmd in self._cmd_passthrough('help')['return'].split('\r\n'):
+            if cmd and cmd[0] != '[' and cmd[0] != '\t':
+                name = cmd.split()[0]  # drop help text
+                if name == 'info':
+                    continue
+                if name.find('|') != -1:
+                    # Command in the form 'foobar|f' or 'f|foobar', take the
+                    # full name
+                    opt = name.split('|')
+                    if len(opt[0]) == 1:
+                        name = opt[1]
+                    else:
+                        name = opt[0]
+                self._completer.append(name)
+                self._completer.append('help ' + name)  # help completion
+
+    def _info_completion(self) -> None:
+        for cmd in self._cmd_passthrough('info')['return'].split('\r\n'):
+            if cmd:
+                self._completer.append('info ' + cmd.split()[1])
+
+    def _other_completion(self) -> None:
+        # special cases
+        self._completer.append('help info')
+
+    def _fill_completion(self) -> None:
+        self._cmd_completion()
+        self._info_completion()
+        self._other_completion()
+
+    def _cmd_passthrough(self, cmdline: str,
+                         cpu_index: int = 0) -> QMPMessage:
+        return self.cmd_obj({
+            'execute': 'human-monitor-command',
+            'arguments': {
+                'command-line': cmdline,
+                'cpu-index': cpu_index
+            }
+        })
+
+    def _execute_cmd(self, cmdline: str) -> bool:
+        if cmdline.split()[0] == "cpu":
+            # trap the cpu command, it requires special setting
+            try:
+                idx = int(cmdline.split()[1])
+                if 'return' not in self._cmd_passthrough('info version', idx):
+                    print('bad CPU index')
+                    return True
+                self._cpu_index = idx
+            except ValueError:
+                print('cpu command takes an integer argument')
+                return True
+        resp = self._cmd_passthrough(cmdline, self._cpu_index)
+        if resp is None:
+            print('Disconnected')
+            return False
+        assert 'return' in resp or 'error' in resp
+        if 'return' in resp:
+            # Success
+            if len(resp['return']) > 0:
+                print(resp['return'], end=' ')
+        else:
+            # Error
+            print('%s: %s' % (resp['error']['class'], resp['error']['desc']))
+        return True
+
+    def show_banner(self, msg: str = 'Welcome to the HMP shell!') -> None:
+        QMPShell.show_banner(self, msg)
+
+
+def die(msg: str) -> NoReturn:
+    """Write an error to stderr, then exit with a return code of 1."""
+    sys.stderr.write('ERROR: %s\n' % msg)
+    sys.exit(1)
+
+
+def main() -> None:
+    """
+    qmp-shell entry point: parse command line arguments and start the REPL.
+    """
+    parser = argparse.ArgumentParser()
+    parser.add_argument('-H', '--hmp', action='store_true',
+                        help='Use HMP interface')
+    parser.add_argument('-N', '--skip-negotiation', action='store_true',
+                        help='Skip negotiate (for qemu-ga)')
+    parser.add_argument('-v', '--verbose', action='store_true',
+                        help='Verbose (echo commands sent and received)')
+    parser.add_argument('-p', '--pretty', action='store_true',
+                        help='Pretty-print JSON')
+
+    default_server = os.environ.get('QMP_SOCKET')
+    parser.add_argument('qmp_server', action='store',
+                        default=default_server,
+                        help='< UNIX socket path | TCP address:port >')
+
+    args = parser.parse_args()
+    if args.qmp_server is None:
+        parser.error("QMP socket or TCP address must be specified")
+
+    shell_class = HMPShell if args.hmp else QMPShell
+
+    try:
+        address = shell_class.parse_address(args.qmp_server)
+    except qmp.QMPBadPortError:
+        parser.error(f"Bad port number: {args.qmp_server}")
+        return  # pycharm doesn't know error() is noreturn
+
+    with shell_class(address, args.pretty, args.verbose) as qemu:
+        try:
+            qemu.connect(negotiate=not args.skip_negotiation)
+        except qmp.QMPConnectError:
+            die("Didn't get QMP greeting message")
+        except qmp.QMPCapabilitiesError:
+            die("Couldn't negotiate capabilities")
+        except OSError as err:
+            die(f"Couldn't connect to {args.qmp_server}: {err!s}")
+
+        for _ in qemu.repl():
+            pass
+
+
+if __name__ == '__main__':
+    main()