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* [Tarantool-patches] [PATCH luajit v4 0/2] debug: generalized extension
@ 2023-12-06 13:57 Maxim Kokryashkin via Tarantool-patches
  2023-12-06 13:57 ` [Tarantool-patches] [PATCH luajit v4 1/2] " Maxim Kokryashkin via Tarantool-patches
  0 siblings, 1 reply; 2+ messages in thread
From: Maxim Kokryashkin via Tarantool-patches @ 2023-12-06 13:57 UTC (permalink / raw)
  To: tarantool-patches, skaplun, sergeyb, imun

Changes in v4:
- Fixed comments as per review by Sergey Bronnikov

Branch: https://github.com/tarantool/luajit/tree/fckxorg/generalized-debugger

Maksim Kokryashkin (1):
  test: add tests for debugging extensions

Maxim Kokryashkin (1):
  debug: generalized extension

 .flake8rc                                     |   4 +
 src/luajit-gdb.py                             | 885 ------------------
 src/{luajit_lldb.py => luajit_dbg.py}         | 616 ++++++++----
 test/CMakeLists.txt                           |   3 +
 .../CMakeLists.txt                            | 102 ++
 .../debug-extension-tests.py                  | 262 ++++++
 .../gh-5688-tool-cli-flag-memprofdata.tmp.bin | Bin 0 -> 142337 bytes
 .../gh-5688-tool-cli-flag-sysprofdata.tmp.bin | Bin 0 -> 11208539 bytes
 ...resolving-of-c-symbols-memprofdata.tmp.bin | Bin 0 -> 281242 bytes
 .../misclib-sysprof-lapi-sysprofdata.tmp.bin  | Bin 0 -> 972279 bytes
 10 files changed, 787 insertions(+), 1085 deletions(-)
 delete mode 100644 src/luajit-gdb.py
 rename src/{luajit_lldb.py => luajit_dbg.py} (63%)
 create mode 100644 test/LuaJIT-debug-extensions-tests/CMakeLists.txt
 create mode 100644 test/LuaJIT-debug-extensions-tests/debug-extension-tests.py
 create mode 100644 test/tarantool-tests/gh-5688-tool-cli-flag-memprofdata.tmp.bin
 create mode 100644 test/tarantool-tests/gh-5688-tool-cli-flag-sysprofdata.tmp.bin
 create mode 100644 test/tarantool-tests/gh-5813-resolving-of-c-symbols-memprofdata.tmp.bin
 create mode 100644 test/tarantool-tests/misclib-sysprof-lapi-sysprofdata.tmp.bin

--
2.43.0


^ permalink raw reply	[flat|nested] 2+ messages in thread

* [Tarantool-patches] [PATCH luajit v4 1/2] debug: generalized extension
  2023-12-06 13:57 [Tarantool-patches] [PATCH luajit v4 0/2] debug: generalized extension Maxim Kokryashkin via Tarantool-patches
@ 2023-12-06 13:57 ` Maxim Kokryashkin via Tarantool-patches
  0 siblings, 0 replies; 2+ messages in thread
From: Maxim Kokryashkin via Tarantool-patches @ 2023-12-06 13:57 UTC (permalink / raw)
  To: tarantool-patches, skaplun, sergeyb, imun

This patch joins the LLDB and GDB LuaJIT debugging extensions
into one, so now the extension logic can be debugger-agnostic.
To do that, an adapter class is introduced, and all of the
debugger-specific behavior is encapsulated there. The extension
auto-detects the debugger it was loaded into and selects the
correct low-level logic implementation.
---
 src/luajit-gdb.py                     | 885 --------------------------
 src/{luajit_lldb.py => luajit_dbg.py} | 617 ++++++++++++------
 2 files changed, 417 insertions(+), 1085 deletions(-)
 delete mode 100644 src/luajit-gdb.py
 rename src/{luajit_lldb.py => luajit_dbg.py} (63%)

diff --git a/src/luajit-gdb.py b/src/luajit-gdb.py
deleted file mode 100644
index d2070e9b..00000000
--- a/src/luajit-gdb.py
+++ /dev/null
@@ -1,885 +0,0 @@
-# GDB extension for LuaJIT post-mortem analysis.
-# To use, just put 'source <path-to-repo>/src/luajit-gdb.py' in gdb.
-
-import re
-import gdb
-import sys
-
-# make script compatible with the ancient Python {{{
-
-
-LEGACY = re.match(r'^2\.', sys.version)
-
-if LEGACY:
-    CONNECTED = False
-    int = long
-    range = xrange
-
-
-# }}}
-
-
-gtype_cache = {}
-
-
-def gtype(typestr):
-    global gtype_cache
-    if typestr in gtype_cache:
-        return gtype_cache[typestr]
-
-    m = re.match(r'((?:(?:struct|union) )?\S*)\s*[*]', typestr)
-
-    gtype = gdb.lookup_type(typestr) if m is None \
-        else gdb.lookup_type(m.group(1)).pointer()
-
-    gtype_cache[typestr] = gtype
-    return gtype
-
-
-def cast(typestr, val):
-    return gdb.Value(val).cast(gtype(typestr))
-
-
-def lookup(symbol):
-    variable, _ = gdb.lookup_symbol(symbol)
-    return variable.value() if variable else None
-
-
-def parse_arg(arg):
-    if not arg:
-        return None
-
-    ret = gdb.parse_and_eval(arg)
-
-    if not ret:
-        raise gdb.GdbError('table argument empty')
-
-    return ret
-
-
-def tou64(val):
-    return cast('uint64_t', val) & 0xFFFFFFFFFFFFFFFF
-
-
-def tou32(val):
-    return cast('uint32_t', val) & 0xFFFFFFFF
-
-
-def i2notu32(val):
-    return ~int(val) & 0xFFFFFFFF
-
-
-def strx64(val):
-    return re.sub('L?$', '',
-                  hex(int(cast('uint64_t', val) & 0xFFFFFFFFFFFFFFFF)))
-
-
-# Types {{{
-
-
-LJ_T = {
-    'NIL':     i2notu32(0),
-    'FALSE':   i2notu32(1),
-    'TRUE':    i2notu32(2),
-    'LIGHTUD': i2notu32(3),
-    'STR':     i2notu32(4),
-    'UPVAL':   i2notu32(5),
-    'THREAD':  i2notu32(6),
-    'PROTO':   i2notu32(7),
-    'FUNC':    i2notu32(8),
-    'TRACE':   i2notu32(9),
-    'CDATA':   i2notu32(10),
-    'TAB':     i2notu32(11),
-    'UDATA':   i2notu32(12),
-    'NUMX':    i2notu32(13),
-}
-
-
-def typenames(value):
-    return {
-        LJ_T[k]: 'LJ_T' + k for k in LJ_T.keys()
-    }.get(int(value), 'LJ_TINVALID')
-
-
-# }}}
-
-# Frames {{{
-
-
-FRAME_TYPE = 0x3
-FRAME_P = 0x4
-FRAME_TYPEP = FRAME_TYPE | FRAME_P
-
-FRAME = {
-    'LUA':    0x0,
-    'C':      0x1,
-    'CONT':   0x2,
-    'VARG':   0x3,
-    'LUAP':   0x4,
-    'CP':     0x5,
-    'PCALL':  0x6,
-    'PCALLH': 0x7,
-}
-
-
-def frametypes(ft):
-    return {
-        FRAME['LUA']:  'L',
-        FRAME['C']:    'C',
-        FRAME['CONT']: 'M',
-        FRAME['VARG']: 'V',
-    }.get(ft, '?')
-
-
-def bc_a(ins):
-    return (ins >> 8) & 0xff
-
-
-def frame_ftsz(framelink):
-    return cast('ptrdiff_t', framelink['ftsz'] if LJ_FR2
-                else framelink['fr']['tp']['ftsz'])
-
-
-def frame_pc(framelink):
-    return cast('BCIns *', frame_ftsz(framelink)) if LJ_FR2 \
-        else mref('BCIns *', framelink['fr']['tp']['pcr'])
-
-
-def frame_prevl(framelink):
-    return framelink - (1 + LJ_FR2 + bc_a(frame_pc(framelink)[-1]))
-
-
-def frame_ispcall(framelink):
-    return (frame_ftsz(framelink) & FRAME['PCALL']) == FRAME['PCALL']
-
-
-def frame_sized(framelink):
-    return (frame_ftsz(framelink) & ~FRAME_TYPEP)
-
-
-def frame_prevd(framelink):
-    return cast('TValue *', cast('char *', framelink) - frame_sized(framelink))
-
-
-def frame_type(framelink):
-    return frame_ftsz(framelink) & FRAME_TYPE
-
-
-def frame_typep(framelink):
-    return frame_ftsz(framelink) & FRAME_TYPEP
-
-
-def frame_islua(framelink):
-    return frametypes(int(frame_type(framelink))) == 'L' \
-        and int(frame_ftsz(framelink)) > 0
-
-
-def frame_prev(framelink):
-    return frame_prevl(framelink) if frame_islua(framelink) \
-        else frame_prevd(framelink)
-
-
-def frame_sentinel(L):
-    return mref('TValue *', L['stack']) + LJ_FR2
-
-
-# }}}
-
-# Const {{{
-
-
-LJ_64 = None
-LJ_GC64 = None
-LJ_FR2 = None
-LJ_DUALNUM = None
-
-LJ_GCVMASK = ((1 << 47) - 1)
-LJ_TISNUM = None
-PADDING = None
-
-# These constants are meaningful only for 'LJ_64' mode.
-LJ_LIGHTUD_BITS_SEG = 8
-LJ_LIGHTUD_BITS_LO = 47 - LJ_LIGHTUD_BITS_SEG
-LIGHTUD_SEG_MASK = (1 << LJ_LIGHTUD_BITS_SEG) - 1
-LIGHTUD_LO_MASK = (1 << LJ_LIGHTUD_BITS_LO) - 1
-
-
-# }}}
-
-
-def itype(o):
-    return cast('uint32_t', o['it64'] >> 47) if LJ_GC64 else o['it']
-
-
-def mref(typename, obj):
-    return cast(typename, obj['ptr64'] if LJ_GC64 else obj['ptr32'])
-
-
-def gcref(obj):
-    return cast('GCobj *', obj['gcptr64'] if LJ_GC64
-                else cast('uintptr_t', obj['gcptr32']))
-
-
-def gcval(obj):
-    return cast('GCobj *', obj['gcptr64'] & LJ_GCVMASK if LJ_GC64
-                else cast('uintptr_t', obj['gcptr32']))
-
-
-def gcnext(obj):
-    return gcref(obj)['gch']['nextgc']
-
-
-def L(L=None):
-    # lookup a symbol for the main coroutine considering the host app
-    # XXX Fragile: though the loop initialization looks like a crap but it
-    # respects both Python 2 and Python 3.
-    for lstate in [L] + list(map(lambda main: lookup(main), (
-        # LuaJIT main coro (see luajit/src/luajit.c)
-        'globalL',
-        # Tarantool main coro (see tarantool/src/lua/init.h)
-        'tarantool_L',
-        # TODO: Add more
-    ))):
-        if lstate:
-            return cast('lua_State *', lstate)
-
-
-def G(L):
-    return mref('global_State *', L['glref'])
-
-
-def J(g):
-    typeGG = gtype('GG_State')
-
-    return cast('jit_State *', int(cast('char *', g))
-                - int(typeGG['g'].bitpos / 8)
-                + int(typeGG['J'].bitpos / 8))
-
-
-def vm_state(g):
-    return {
-        i2notu32(0): 'INTERP',
-        i2notu32(1): 'LFUNC',
-        i2notu32(2): 'FFUNC',
-        i2notu32(3): 'CFUNC',
-        i2notu32(4): 'GC',
-        i2notu32(5): 'EXIT',
-        i2notu32(6): 'RECORD',
-        i2notu32(7): 'OPT',
-        i2notu32(8): 'ASM',
-    }.get(int(tou32(g['vmstate'])), 'TRACE')
-
-
-def gc_state(g):
-    return {
-        0: 'PAUSE',
-        1: 'PROPAGATE',
-        2: 'ATOMIC',
-        3: 'SWEEPSTRING',
-        4: 'SWEEP',
-        5: 'FINALIZE',
-        6: 'LAST',
-    }.get(int(g['gc']['state']), 'INVALID')
-
-
-def jit_state(g):
-    return {
-        0:    'IDLE',
-        0x10: 'ACTIVE',
-        0x11: 'RECORD',
-        0x12: 'START',
-        0x13: 'END',
-        0x14: 'ASM',
-        0x15: 'ERR',
-    }.get(int(J(g)['state']), 'INVALID')
-
-
-def tvisint(o):
-    return LJ_DUALNUM and itype(o) == LJ_TISNUM
-
-
-def tvisnumber(o):
-    return itype(o) <= LJ_TISNUM
-
-
-def tvislightud(o):
-    if LJ_64 and not LJ_GC64:
-        return (cast('int32_t', itype(o)) >> 15) == -2
-    else:
-        return itype(o) == LJ_T['LIGHTUD']
-
-
-def strdata(obj):
-    # String is printed with pointer to it, thanks to gdb. Just strip it.
-    try:
-        return str(cast('char *', cast('GCstr *', obj) + 1))[len(PADDING):]
-    except UnicodeEncodeError:
-        return "<luajit-gdb: error occurred while rendering non-ascii slot>"
-
-
-def itypemap(o):
-    if LJ_64 and not LJ_GC64:
-        return LJ_T['NUMX'] if tvisnumber(o)       \
-            else LJ_T['LIGHTUD'] if tvislightud(o) \
-            else itype(o)
-    else:
-        return LJ_T['NUMX'] if tvisnumber(o) else itype(o)
-
-
-def funcproto(func):
-    assert func['ffid'] == 0
-
-    return cast('GCproto *',
-                mref('char *', func['pc']) - gdb.lookup_type('GCproto').sizeof)
-
-
-def gclistlen(root, end=0x0):
-    count = 0
-    while (gcref(root) != end):
-        count += 1
-        root = gcnext(root)
-    return count
-
-
-def gcringlen(root):
-    if not gcref(root):
-        return 0
-    elif gcref(root) == gcref(gcnext(root)):
-        return 1
-    else:
-        return 1 + gclistlen(gcnext(root), gcref(root))
-
-
-gclen = {
-    'root':      gclistlen,
-    'gray':      gclistlen,
-    'grayagain': gclistlen,
-    'weak':      gclistlen,
-    # XXX: gc.mmudata is a ring-list.
-    'mmudata':   gcringlen,
-}
-
-
-# The generator that implements frame iterator.
-# Every frame is represented as a tuple of framelink and frametop.
-def frames(L):
-    frametop = L['top']
-    framelink = L['base'] - 1
-    framelink_sentinel = frame_sentinel(L)
-    while True:
-        yield framelink, frametop
-        frametop = framelink - (1 + LJ_FR2)
-        if framelink <= framelink_sentinel:
-            break
-        framelink = frame_prev(framelink)
-
-
-def lightudV(tv):
-    if LJ_64:
-        u = int(tv['u64'])
-        # lightudseg macro expanded.
-        seg = (u >> LJ_LIGHTUD_BITS_LO) & LIGHTUD_SEG_MASK
-        segmap = mref('uint32_t *', G(L(None))['gc']['lightudseg'])
-        # lightudlo macro expanded.
-        return (int(segmap[seg]) << 32) | (u & LIGHTUD_LO_MASK)
-    else:
-        return gcval(tv['gcr'])
-
-
-# Dumpers {{{
-
-
-def dump_lj_tnil(tv):
-    return 'nil'
-
-
-def dump_lj_tfalse(tv):
-    return 'false'
-
-
-def dump_lj_ttrue(tv):
-    return 'true'
-
-
-def dump_lj_tlightud(tv):
-    return 'light userdata @ {}'.format(strx64(lightudV(tv)))
-
-
-def dump_lj_tstr(tv):
-    return 'string {body} @ {address}'.format(
-        body=strdata(gcval(tv['gcr'])),
-        address=strx64(gcval(tv['gcr']))
-    )
-
-
-def dump_lj_tupval(tv):
-    return 'upvalue @ {}'.format(strx64(gcval(tv['gcr'])))
-
-
-def dump_lj_tthread(tv):
-    return 'thread @ {}'.format(strx64(gcval(tv['gcr'])))
-
-
-def dump_lj_tproto(tv):
-    return 'proto @ {}'.format(strx64(gcval(tv['gcr'])))
-
-
-def dump_lj_tfunc(tv):
-    func = cast('struct GCfuncC *', gcval(tv['gcr']))
-    ffid = func['ffid']
-
-    if ffid == 0:
-        pt = funcproto(func)
-        return 'Lua function @ {addr}, {nups} upvalues, {chunk}:{line}'.format(
-            addr=strx64(func),
-            nups=int(func['nupvalues']),
-            chunk=strdata(cast('GCstr *', gcval(pt['chunkname']))),
-            line=pt['firstline']
-        )
-    elif ffid == 1:
-        return 'C function @ {}'.format(strx64(func['f']))
-    else:
-        return 'fast function #{}'.format(int(ffid))
-
-
-def dump_lj_ttrace(tv):
-    trace = cast('struct GCtrace *', gcval(tv['gcr']))
-    return 'trace {traceno} @ {addr}'.format(
-        traceno=strx64(trace['traceno']),
-        addr=strx64(trace)
-    )
-
-
-def dump_lj_tcdata(tv):
-    return 'cdata @ {}'.format(strx64(gcval(tv['gcr'])))
-
-
-def dump_lj_ttab(tv):
-    table = cast('GCtab *', gcval(tv['gcr']))
-    return 'table @ {gcr} (asize: {asize}, hmask: {hmask})'.format(
-        gcr=strx64(table),
-        asize=table['asize'],
-        hmask=strx64(table['hmask']),
-    )
-
-
-def dump_lj_tudata(tv):
-    return 'userdata @ {}'.format(strx64(gcval(tv['gcr'])))
-
-
-def dump_lj_tnumx(tv):
-    if tvisint(tv):
-        return 'integer {}'.format(cast('int32_t', tv['i']))
-    else:
-        return 'number {}'.format(cast('double', tv['n']))
-
-
-def dump_lj_invalid(tv):
-    return 'not valid type @ {}'.format(strx64(gcval(tv['gcr'])))
-
-
-# }}}
-
-
-dumpers = {
-    'LJ_TNIL':     dump_lj_tnil,
-    'LJ_TFALSE':   dump_lj_tfalse,
-    'LJ_TTRUE':    dump_lj_ttrue,
-    'LJ_TLIGHTUD': dump_lj_tlightud,
-    'LJ_TSTR':     dump_lj_tstr,
-    'LJ_TUPVAL':   dump_lj_tupval,
-    'LJ_TTHREAD':  dump_lj_tthread,
-    'LJ_TPROTO':   dump_lj_tproto,
-    'LJ_TFUNC':    dump_lj_tfunc,
-    'LJ_TTRACE':   dump_lj_ttrace,
-    'LJ_TCDATA':   dump_lj_tcdata,
-    'LJ_TTAB':     dump_lj_ttab,
-    'LJ_TUDATA':   dump_lj_tudata,
-    'LJ_TNUMX':    dump_lj_tnumx,
-}
-
-
-def dump_tvalue(tvalue):
-    return dumpers.get(typenames(itypemap(tvalue)), dump_lj_invalid)(tvalue)
-
-
-def dump_framelink_slot_address(fr):
-    return '{}:{}'.format(fr - 1, fr) if LJ_FR2 \
-        else '{}'.format(fr) + PADDING
-
-
-def dump_framelink(L, fr):
-    if fr == frame_sentinel(L):
-        return '{addr} [S   ] FRAME: dummy L'.format(
-            addr=dump_framelink_slot_address(fr),
-        )
-    return '{addr} [    ] FRAME: [{pp}] delta={d}, {f}'.format(
-        addr=dump_framelink_slot_address(fr),
-        pp='PP' if frame_ispcall(fr) else '{frname}{p}'.format(
-            frname=frametypes(int(frame_type(fr))),
-            p='P' if frame_typep(fr) & FRAME_P else ''
-        ),
-        d=cast('TValue *', fr) - cast('TValue *', frame_prev(fr)),
-        f=dump_lj_tfunc(fr - LJ_FR2),
-    )
-
-
-def dump_stack_slot(L, slot, base=None, top=None):
-    base = base or L['base']
-    top = top or L['top']
-
-    return '{addr}{padding} [ {B}{T}{M}] VALUE: {value}'.format(
-        addr=strx64(slot),
-        padding=PADDING,
-        B='B' if slot == base else ' ',
-        T='T' if slot == top else ' ',
-        M='M' if slot == mref('TValue *', L['maxstack']) else ' ',
-        value=dump_tvalue(slot),
-    )
-
-
-def dump_stack(L, base=None, top=None):
-    base = base or L['base']
-    top = top or L['top']
-    stack = mref('TValue *', L['stack'])
-    maxstack = mref('TValue *', L['maxstack'])
-    red = 5 + 2 * LJ_FR2
-
-    dump = [
-        '{padding} Red zone: {nredslots: >2} slots {padding}'.format(
-            padding='-' * len(PADDING),
-            nredslots=red,
-        ),
-    ]
-    dump.extend([
-        dump_stack_slot(L, maxstack + offset, base, top)
-            for offset in range(red, 0, -1)  # noqa: E131
-    ])
-    dump.extend([
-        '{padding} Stack: {nstackslots: >5} slots {padding}'.format(
-            padding='-' * len(PADDING),
-            nstackslots=int((tou64(maxstack) - tou64(stack)) >> 3),
-        ),
-        dump_stack_slot(L, maxstack, base, top),
-        '{start}:{end} [    ] {nfreeslots} slots: Free stack slots'.format(
-            start=strx64(top + 1),
-            end=strx64(maxstack - 1),
-            nfreeslots=int((tou64(maxstack) - tou64(top) - 8) >> 3),
-        ),
-    ])
-
-    for framelink, frametop in frames(L):
-        # Dump all data slots in the (framelink, top) interval.
-        dump.extend([
-            dump_stack_slot(L, framelink + offset, base, top)
-                for offset in range(frametop - framelink, 0, -1)  # noqa: E131
-        ])
-        # Dump frame slot (2 slots in case of GC64).
-        dump.append(dump_framelink(L, framelink))
-
-    return '\n'.join(dump)
-
-
-def dump_gc(g):
-    gc = g['gc']
-    stats = ['{key}: {value}'.format(key=f, value=gc[f]) for f in (
-        'total', 'threshold', 'debt', 'estimate', 'stepmul', 'pause'
-    )]
-
-    stats += ['sweepstr: {sweepstr}/{strmask}'.format(
-        sweepstr=gc['sweepstr'],
-        # String hash mask (size of hash table - 1).
-        strmask=g['strmask'] + 1,
-    )]
-
-    stats += ['{key}: {number} objects'.format(
-        key=stat,
-        number=handler(gc[stat])
-    ) for stat, handler in gclen.items()]
-
-    return '\n'.join(map(lambda s: '\t' + s, stats))
-
-
-class LJBase(gdb.Command):
-
-    def __init__(self, name):
-        # XXX Fragile: though the command initialization looks like a crap but
-        # it respects both Python 2 and Python 3.
-        gdb.Command.__init__(self, name, gdb.COMMAND_DATA)
-        gdb.write('{} command initialized\n'.format(name))
-
-
-class LJDumpArch(LJBase):
-    '''
-lj-arch
-
-The command requires no args and dumps values of LJ_64 and LJ_GC64
-compile-time flags. These values define the sizes of host and GC
-pointers respectively.
-    '''
-
-    def invoke(self, arg, from_tty):
-        gdb.write(
-            'LJ_64: {LJ_64}, LJ_GC64: {LJ_GC64}, LJ_DUALNUM: {LJ_DUALNUM}\n'
-            .format(
-                LJ_64=LJ_64,
-                LJ_GC64=LJ_GC64,
-                LJ_DUALNUM=LJ_DUALNUM
-            )
-        )
-
-
-class LJDumpTValue(LJBase):
-    '''
-lj-tv <TValue *>
-
-The command receives a pointer to <tv> (TValue address) and dumps
-the type and some info related to it.
-
-* LJ_TNIL: nil
-* LJ_TFALSE: false
-* LJ_TTRUE: true
-* LJ_TLIGHTUD: light userdata @ <gcr>
-* LJ_TSTR: string <string payload> @ <gcr>
-* LJ_TUPVAL: upvalue @ <gcr>
-* LJ_TTHREAD: thread @ <gcr>
-* LJ_TPROTO: proto @ <gcr>
-* LJ_TFUNC: <LFUNC|CFUNC|FFUNC>
-  <LFUNC>: Lua function @ <gcr>, <nupvals> upvalues, <chunk:line>
-  <CFUNC>: C function <mcode address>
-  <FFUNC>: fast function #<ffid>
-* LJ_TTRACE: trace <traceno> @ <gcr>
-* LJ_TCDATA: cdata @ <gcr>
-* LJ_TTAB: table @ <gcr> (asize: <asize>, hmask: <hmask>)
-* LJ_TUDATA: userdata @ <gcr>
-* LJ_TNUMX: number <numeric payload>
-
-Whether the type of the given address differs from the listed above, then
-error message occurs.
-    '''
-
-    def invoke(self, arg, from_tty):
-        tv = cast('TValue *', parse_arg(arg))
-        gdb.write('{}\n'.format(dump_tvalue(tv)))
-
-
-class LJDumpString(LJBase):
-    '''
-lj-str <GCstr *>
-
-The command receives a <gcr> of the corresponding GCstr object and dumps
-the payload, size in bytes and hash.
-
-*Caveat*: Since Python 2 provides no native Unicode support, the payload
-is replaced with the corresponding error when decoding fails.
-    '''
-
-    def invoke(self, arg, from_tty):
-        string = cast('GCstr *', parse_arg(arg))
-        gdb.write("String: {body} [{len} bytes] with hash {hash}\n".format(
-            body=strdata(string),
-            hash=strx64(string['hash']),
-            len=string['len'],
-        ))
-
-
-class LJDumpTable(LJBase):
-    '''
-lj-tab <GCtab *>
-
-The command receives a GCtab address and dumps the table contents:
-* Metatable address whether the one is set
-* Array part <asize> slots:
-  <aslot ptr>: [<index>]: <tv>
-* Hash part <hsize> nodes:
-  <hnode ptr>: { <tv> } => { <tv> }; next = <next hnode ptr>
-    '''
-
-    def invoke(self, arg, from_tty):
-        t = cast('GCtab *', parse_arg(arg))
-        array = mref('TValue *', t['array'])
-        nodes = mref('struct Node *', t['node'])
-        mt = gcval(t['metatable'])
-        capacity = {
-            'apart': int(t['asize']),
-            'hpart': int(t['hmask'] + 1) if t['hmask'] > 0 else 0
-        }
-
-        if mt != 0:
-            gdb.write('Metatable detected: {}\n'.format(strx64(mt)))
-
-        gdb.write('Array part: {} slots\n'.format(capacity['apart']))
-        for i in range(capacity['apart']):
-            slot = array + i
-            gdb.write('{ptr}: [{index}]: {value}\n'.format(
-                ptr=slot,
-                index=i,
-                value=dump_tvalue(slot)
-            ))
-
-        gdb.write('Hash part: {} nodes\n'.format(capacity['hpart']))
-        # See hmask comment in lj_obj.h
-        for i in range(capacity['hpart']):
-            node = nodes + i
-            gdb.write('{ptr}: {{ {key} }} => {{ {val} }}; next = {n}\n'.format(
-                ptr=node,
-                key=dump_tvalue(node['key']),
-                val=dump_tvalue(node['val']),
-                n=mref('struct Node *', node['next'])
-            ))
-
-
-class LJDumpStack(LJBase):
-    '''
-lj-stack [<lua_State *>]
-
-The command receives a lua_State address and dumps the given Lua
-coroutine guest stack:
-
-<slot ptr> [<slot attributes>] <VALUE|FRAME>
-
-* <slot ptr>: guest stack slot address
-* <slot attributes>:
-  - S: Bottom of the stack (the slot L->stack points to)
-  - B: Base of the current guest frame (the slot L->base points to)
-  - T: Top of the current guest frame (the slot L->top points to)
-  - M: Last slot of the stack (the slot L->maxstack points to)
-* <VALUE>: see help lj-tv for more info
-* <FRAME>: framelink slot differs from the value slot: it contains info
-  related to the function being executed within this guest frame, its
-  type and link to the parent guest frame
-  [<frame type>] delta=<slots in frame>, <lj-tv for LJ_TFUNC slot>
-  - <frame type>:
-    + L:  VM performs a call as a result of bytecode execution
-    + C:  VM performs a call as a result of lj_vm_call
-    + M:  VM performs a call to a metamethod as a result of bytecode
-          execution
-    + V:  Variable-length frame for storing arguments of a variadic
-          function
-    + CP: Protected C frame
-    + PP: VM performs a call as a result of executinig pcall or xpcall
-
-If L is omitted the main coroutine is used.
-    '''
-
-    def invoke(self, arg, from_tty):
-        gdb.write('{}\n'.format(dump_stack(L(parse_arg(arg)))))
-
-
-class LJState(LJBase):
-    '''
-lj-state
-The command requires no args and dumps current VM and GC states
-* VM state: <INTERP|C|GC|EXIT|RECORD|OPT|ASM|TRACE>
-* GC state: <PAUSE|PROPAGATE|ATOMIC|SWEEPSTRING|SWEEP|FINALIZE|LAST>
-* JIT state: <IDLE|ACTIVE|RECORD|START|END|ASM|ERR>
-    '''
-
-    def invoke(self, arg, from_tty):
-        g = G(L(None))
-        gdb.write('{}\n'.format('\n'.join(
-            map(lambda t: '{} state: {}'.format(*t), {
-                'VM':  vm_state(g),
-                'GC':  gc_state(g),
-                'JIT': jit_state(g),
-            }.items())
-        )))
-
-
-class LJGC(LJBase):
-    '''
-lj-gc
-
-The command requires no args and dumps current GC stats:
-* total: <total number of allocated bytes in GC area>
-* threshold: <limit when gc step is triggered>
-* debt: <how much GC is behind schedule>
-* estimate: <estimate of memory actually in use>
-* stepmul: <incremental GC step granularity>
-* pause: <pause between successive GC cycles>
-* sweepstr: <sweep position in string table>
-* root: <number of all collectable objects>
-* gray: <number of gray objects>
-* grayagain: <number of objects for atomic traversal>
-* weak: <number of weak tables (to be cleared)>
-* mmudata: <number of udata|cdata to be finalized>
-    '''
-
-    def invoke(self, arg, from_tty):
-        g = G(L(None))
-        gdb.write('GC stats: {state}\n{stats}\n'.format(
-            state=gc_state(g),
-            stats=dump_gc(g)
-        ))
-
-
-def init(commands):
-    global LJ_64, LJ_GC64, LJ_FR2, LJ_DUALNUM, LJ_TISNUM, PADDING
-
-    # XXX Fragile: though connecting the callback looks like a crap but it
-    # respects both Python 2 and Python 3 (see #4828).
-    def connect(callback):
-        if LEGACY:
-            global CONNECTED
-            CONNECTED = True
-        gdb.events.new_objfile.connect(callback)
-
-    # XXX Fragile: though disconnecting the callback looks like a crap but it
-    # respects both Python 2 and Python 3 (see #4828).
-    def disconnect(callback):
-        if LEGACY:
-            global CONNECTED
-            if not CONNECTED:
-                return
-            CONNECTED = False
-        gdb.events.new_objfile.disconnect(callback)
-
-    try:
-        # Try to remove the callback at first to not append duplicates to
-        # gdb.events.new_objfile internal list.
-        disconnect(load)
-    except Exception:
-        # Callback is not connected.
-        pass
-
-    try:
-        # Detect whether libluajit objfile is loaded.
-        gdb.parse_and_eval('luaJIT_setmode')
-    except Exception:
-        gdb.write('luajit-gdb.py initialization is postponed '
-                  'until libluajit objfile is loaded\n')
-        # Add a callback to be executed when the next objfile is loaded.
-        connect(load)
-        return
-
-    try:
-        LJ_64 = str(gdb.parse_and_eval('IRT_PTR')) == 'IRT_P64'
-        LJ_FR2 = LJ_GC64 = str(gdb.parse_and_eval('IRT_PGC')) == 'IRT_P64'
-        LJ_DUALNUM = gdb.lookup_global_symbol('lj_lib_checknumber') is not None
-    except Exception:
-        gdb.write('luajit-gdb.py failed to load: '
-                  'no debugging symbols found for libluajit\n')
-        return
-
-    for name, command in commands.items():
-        command(name)
-
-    PADDING = ' ' * len(':' + hex((1 << (47 if LJ_GC64 else 32)) - 1))
-    LJ_TISNUM = 0xfffeffff if LJ_64 and not LJ_GC64 else LJ_T['NUMX']
-
-    gdb.write('luajit-gdb.py is successfully loaded\n')
-
-
-def load(event=None):
-    init({
-        'lj-arch':  LJDumpArch,
-        'lj-tv':    LJDumpTValue,
-        'lj-str':   LJDumpString,
-        'lj-tab':   LJDumpTable,
-        'lj-stack': LJDumpStack,
-        'lj-state': LJState,
-        'lj-gc':    LJGC,
-    })
-
-
-load(None)
diff --git a/src/luajit_lldb.py b/src/luajit_dbg.py
similarity index 63%
rename from src/luajit_lldb.py
rename to src/luajit_dbg.py
index 5ac11b65..e79b7c32 100644
--- a/src/luajit_lldb.py
+++ b/src/luajit_dbg.py
@@ -1,10 +1,231 @@
-# LLDB extension for LuaJIT post-mortem analysis.
-# To use, just put 'command script import <path-to-repo>/src/luajit_lldb.py'
-# in lldb.
+# Debug extension for LuaJIT post-mortem analysis.
+# To use in LLDB: 'command script import <path-to-repo>/src/luajit_dbg.py'
+# To use in GDB: 'source <path-to-repo>/src/luajit_dbg.py'
 
 import abc
 import re
-import lldb
+import sys
+import types
+
+from importlib import import_module
+
+# make script compatible with the ancient Python {{{
+
+
+LEGACY = re.match(r'^2\.', sys.version)
+
+if LEGACY:
+    CONNECTED = False
+    int = long
+    range = xrange
+
+
+def is_integer_type(val):
+    return isinstance(val, int) or (LEGACY and isinstance(val, types.IntType))
+
+
+# }}}
+
+
+class Debugger(object):
+    def __init__(self):
+        self.GDB = False
+        self.LLDB = False
+
+        debuggers = {
+            'gdb': lambda lib: True,
+            'lldb': lambda lib: lib.debugger is not None,
+        }
+        for name, healthcheck in debuggers.items():
+            lib = None
+            try:
+                lib = import_module(name)
+            except ImportError:
+                continue
+
+            if healthcheck(lib):
+                setattr(self, name.upper(), True)
+                globals()[name] = lib
+                self.name = name
+
+        assert self.LLDB != self.GDB
+
+    def setup_target(self, debugger):
+        global target
+        if self.LLDB:
+            target = debugger.GetSelectedTarget()
+
+    def write(self, msg):
+        if self.LLDB:
+            print(msg)
+        else:
+            gdb.write(msg + '\n')
+
+    def cmd_init(self, cmd_cls, debugger=None):
+        if self.LLDB:
+            debugger.HandleCommand(
+                'command script add --overwrite --class '
+                'luajit_dbg.{cls} {cmd}'
+                .format(
+                    cls=cmd_cls.__name__,
+                    cmd=cmd_cls.command,
+                )
+            )
+        else:
+            cmd_cls()
+
+    def event_connect(self, callback):
+        if not self.LLDB:
+            # XXX Fragile: though connecting the callback looks like a crap but
+            # it respects both Python 2 and Python 3 (see #4828).
+            if LEGACY:
+                global CONNECTED
+                CONNECTED = True
+            gdb.events.new_objfile.connect(callback)
+
+    def event_disconnect(self, callback):
+        if not self.LLDB:
+            # XXX Fragile: though disconnecting the callback looks like a crap
+            # but it respects both Python 2 and Python 3 (see #4828).
+            if LEGACY:
+                global CONNECTED
+                if not CONNECTED:
+                    return
+                CONNECTED = False
+            gdb.events.new_objfile.disconnect(callback)
+
+    def lookup_variable(self, name):
+        if self.LLDB:
+            return target.FindFirstGlobalVariable(name)
+        else:
+            variable, _ = gdb.lookup_symbol(name)
+            return variable.value() if variable else None
+
+    def lookup_symbol(self, sym):
+        if self.LLDB:
+            return target.modules[0].FindSymbol(sym)
+        else:
+            return gdb.lookup_global_symbol(sym)
+
+    def to_unsigned(self, val):
+        return val.unsigned if self.LLDB else int(val)
+
+    def to_signed(self, val):
+        return val.signed if self.LLDB else int(val)
+
+    def to_str(self, val):
+        return val.value if self.LLDB else str(val)
+
+    def find_type(self, typename):
+        if self.LLDB:
+            return target.FindFirstType(typename)
+        else:
+            return gdb.lookup_type(typename)
+
+    def type_to_pointer_type(self, tp):
+        if self.LLDB:
+            return tp.GetPointerType()
+        else:
+            return tp.pointer()
+
+    def cast_impl(self, value, t, pointer_type):
+        if self.LLDB:
+            if is_integer_type(value):
+                # Integer casts require some black magic
+                # for lldb to behave properly.
+                if pointer_type:
+                    return target.CreateValueFromAddress(
+                        'value',
+                        lldb.SBAddress(value, target),
+                        t.GetPointeeType(),
+                    ).address_of
+                else:
+                    return target.CreateValueFromData(
+                        name='value',
+                        data=lldb.SBData.CreateDataFromInt(value, size=8),
+                        type=t,
+                    )
+            else:
+                return value.Cast(t)
+        else:
+            return gdb.Value(value).cast(t)
+
+    def dereference(self, val):
+        if self.LLDB:
+            return val.Dereference()
+        else:
+            return val.dereference()
+
+    def eval(self, expression):
+        if self.LLDB:
+            process = target.GetProcess()
+            thread = process.GetSelectedThread()
+            frame = thread.GetSelectedFrame()
+
+            if not expression:
+                return None
+
+            return frame.EvaluateExpression(expression)
+        else:
+            return gdb.parse_and_eval(expression)
+
+    def type_sizeof_impl(self, tp):
+        if self.LLDB:
+            return tp.GetByteSize()
+        else:
+            return tp.sizeof
+
+    def summary(self, val):
+        if self.LLDB:
+            return val.summary
+        else:
+            return str(val)[len(PADDING):].strip()
+
+    def type_member(self, type_obj, name):
+        if self.LLDB:
+            return next((x for x in type_obj.members if x.name == name), None)
+        else:
+            return type_obj[name]
+
+    def type_member_offset(self, member):
+        if self.LLDB:
+            return member.GetOffsetInBytes()
+        else:
+            return member.bitpos / 8
+
+    def get_member(self, value, member_name):
+        if self.LLDB:
+            return value.GetChildMemberWithName(member_name)
+        else:
+            return value[member_name]
+
+    def address_of(self, value):
+        if self.LLDB:
+            return value.address_of
+        else:
+            return value.address
+
+    def arch_init(self):
+        global LJ_64, LJ_GC64, LJ_FR2, LJ_DUALNUM, PADDING, LJ_TISNUM, target
+        if self.LLDB:
+            irtype_enum = dbg.find_type('IRType').enum_members
+            for member in irtype_enum:
+                if member.name == 'IRT_PTR':
+                    LJ_64 = dbg.to_unsigned(member) & 0x1f == IRT_P64
+                if member.name == 'IRT_PGC':
+                    LJ_GC64 = dbg.to_unsigned(member) & 0x1f == IRT_P64
+        else:
+            LJ_64 = str(dbg.eval('IRT_PTR')) == 'IRT_P64'
+            LJ_GC64 = str(dbg.eval('IRT_PGC')) == 'IRT_P64'
+
+        LJ_FR2 = LJ_GC64
+        LJ_DUALNUM = dbg.lookup_symbol('lj_lib_checknumber') is not None
+        # Two extra characters are required to fit in the `0x` part.
+        PADDING = ' ' * len(strx64(L()))
+        LJ_TISNUM = 0xfffeffff if LJ_64 and not LJ_GC64 else LJ_T['NUMX']
+
+
+dbg = Debugger()
 
 LJ_64 = None
 LJ_GC64 = None
@@ -17,68 +238,73 @@ IRT_P64 = 9
 LJ_GCVMASK = ((1 << 47) - 1)
 LJ_TISNUM = None
 
-# Debugger specific {{{
-
-
 # Global
 target = None
 
 
-class Ptr:
+class Ptr(object):
     def __init__(self, value, normal_type):
         self.value = value
         self.normal_type = normal_type
 
     @property
     def __deref(self):
-        return self.normal_type(self.value.Dereference())
+        return self.normal_type(dbg.dereference(self.value))
 
     def __add__(self, other):
-        assert isinstance(other, int)
+        assert is_integer_type(other)
         return self.__class__(
             cast(
                 self.normal_type.__name__ + ' *',
                 cast(
                     'uintptr_t',
-                    self.value.unsigned + other * self.value.deref.size,
+                    dbg.to_unsigned(self.value) + other * sizeof(
+                        self.normal_type.__name__
+                    ),
                 ),
             ),
         )
 
     def __sub__(self, other):
-        assert isinstance(other, int) or isinstance(other, Ptr)
-        if isinstance(other, int):
+        assert is_integer_type(other) or isinstance(other, Ptr)
+        if is_integer_type(other):
             return self.__add__(-other)
         else:
-            return int((self.value.unsigned - other.value.unsigned)
-                       / sizeof(self.normal_type.__name__))
+            return int(
+                (
+                    dbg.to_unsigned(self.value) - dbg.to_unsigned(other.value)
+                ) / sizeof(self.normal_type.__name__)
+            )
 
     def __eq__(self, other):
-        assert isinstance(other, Ptr) or isinstance(other, int) and other >= 0
+        assert isinstance(other, Ptr) or is_integer_type(other)
         if isinstance(other, Ptr):
-            return self.value.unsigned == other.value.unsigned
+            return dbg.to_unsigned(self.value) == dbg.to_unsigned(other.value)
         else:
-            return self.value.unsigned == other
+            return dbg.to_unsigned(self.value) == other
 
     def __ne__(self, other):
         return not self == other
 
     def __gt__(self, other):
         assert isinstance(other, Ptr)
-        return self.value.unsigned > other.value.unsigned
+        return dbg.to_unsigned(self.value) > dbg.to_unsigned(other.value)
 
     def __ge__(self, other):
         assert isinstance(other, Ptr)
-        return self.value.unsigned >= other.value.unsigned
+        return dbg.to_unsigned(self.value) >= dbg.to_unsigned(other.value)
 
     def __bool__(self):
-        return self.value.unsigned != 0
+        return dbg.to_unsigned(self.value) != 0
 
     def __int__(self):
-        return self.value.unsigned
+        return dbg.to_unsigned(self.value)
+
+    def __long__(self):
+        return dbg.to_unsigned(self.value)
 
     def __str__(self):
-        return self.value.value
+        return dbg.to_str(self.value)
 
     def __getattr__(self, name):
         if name != '__deref':
@@ -86,53 +312,26 @@ class Ptr:
         return self.__deref
 
 
-class MetaStruct(type):
-    def __init__(cls, name, bases, nmspc):
-        super(MetaStruct, cls).__init__(name, bases, nmspc)
-
-        def make_general(field, tp):
-            builtin = {
-                        'uint':   'unsigned',
-                        'int':    'signed',
-                        'string': 'value',
-                    }
-            if tp in builtin.keys():
-                return lambda self: getattr(self[field], builtin[tp])
-            else:
-                return lambda self: globals()[tp](self[field])
-
-        if hasattr(cls, 'metainfo'):
-            for field in cls.metainfo:
-                if not isinstance(field[0], str):
-                    setattr(cls, field[1], field[0])
-                else:
-                    setattr(
-                        cls,
-                        field[1],
-                        property(make_general(field[1], field[0])),
-                    )
-
-
-class Struct(metaclass=MetaStruct):
+class Struct(object):
     def __init__(self, value):
         self.value = value
 
     def __getitem__(self, name):
-        return self.value.GetChildMemberWithName(name)
+        return dbg.get_member(self.value, name)
 
     @property
     def addr(self):
-        return self.value.address_of
+        return dbg.address_of(self.value)
 
 
 c_structs = {
     'MRef': [
-        (property(lambda self: self['ptr64'].unsigned if LJ_GC64
-                  else self['ptr32'].unsigned), 'ptr')
+        (property(lambda self: dbg.to_unsigned(self['ptr64']) if LJ_GC64
+                  else dbg.to_unsigned(self['ptr32'])), 'ptr')
     ],
     'GCRef': [
-        (property(lambda self: self['gcptr64'].unsigned if LJ_GC64
-                  else self['gcptr32'].unsigned), 'gcptr')
+        (property(lambda self: dbg.to_unsigned(self['gcptr64']) if LJ_GC64
+                  else dbg.to_unsigned(self['gcptr32'])), 'gcptr')
     ],
     'TValue': [
         ('GCRef', 'gcr'),
@@ -141,8 +340,12 @@ c_structs = {
         ('int', 'it64'),
         ('string', 'n'),
         (property(lambda self: FR(self['fr']) if not LJ_GC64 else None), 'fr'),
-        (property(lambda self: self['ftsz'].signed if LJ_GC64 else None),
-         'ftsz')
+        (
+            property(
+                lambda self: dbg.to_signed(self['ftsz']) if LJ_GC64 else None
+            ),
+            'ftsz'
+        )
     ],
     'GCState': [
         ('GCRef', 'root'),
@@ -216,26 +419,51 @@ c_structs = {
         ('TValue', 'val'),
         ('MRef', 'next')
     ],
-    'BCIns': []
+    'BCIns': [],
 }
 
 
-for cls in c_structs.keys():
-    globals()[cls] = type(cls, (Struct, ), {'metainfo': c_structs[cls]})
+def make_property_from_metadata(field, tp):
+    builtin = {
+        'uint':   dbg.to_unsigned,
+        'int':    dbg.to_signed,
+        'string': dbg.to_str,
+    }
+    if tp in builtin.keys():
+        return lambda self: builtin[tp](self[field])
+    else:
+        return lambda self: globals()[tp](self[field])
+
+
+for cls, metainfo in c_structs.items():
+    cls_dict = {}
+    for field in metainfo:
+        if not isinstance(field[0], str):
+            cls_dict[field[1]] = field[0]
+        else:
+            cls_dict[field[1]] = property(
+                make_property_from_metadata(field[1], field[0])
+            )
+    globals()[cls] = type(cls, (Struct, ), cls_dict)
 
 
 for cls in Struct.__subclasses__():
     ptr_name = cls.__name__ + 'Ptr'
 
+    def make_init(cls):
+        return lambda self, value: super(type(self), self).__init__(value, cls)
+
     globals()[ptr_name] = type(ptr_name, (Ptr,), {
-        '__init__':
-            lambda self, value: super(type(self), self).__init__(value, cls)
+        '__init__': make_init(cls)
     })
 
 
-class Command(object):
-    def __init__(self, debugger, unused):
-        pass
+class Command(object if dbg.LLDB else gdb.Command):
+    def __init__(self, debugger=None, unused=None):
+        if dbg.GDB:
+            # XXX Fragile: though initialization looks like a crap but it
+            # respects both Python 2 and Python 3 (see #4828).
+            gdb.Command.__init__(self, self.command, gdb.COMMAND_DATA)
 
     def get_short_help(self):
         return self.__doc__.splitlines()[0]
@@ -245,21 +473,15 @@ class Command(object):
 
     def __call__(self, debugger, command, exe_ctx, result):
         try:
-            self.execute(debugger, command, result)
+            self.execute(command)
         except Exception as e:
             msg = 'Failed to execute command `{}`: {}'.format(self.command, e)
             result.SetError(msg)
 
     def parse(self, command):
-        process = target.GetProcess()
-        thread = process.GetSelectedThread()
-        frame = thread.GetSelectedFrame()
-
         if not command:
             return None
-
-        ret = frame.EvaluateExpression(command)
-        return ret
+        return dbg.to_unsigned(dbg.eval(command))
 
     @abc.abstractproperty
     def command(self):
@@ -270,7 +492,7 @@ class Command(object):
         """
 
     @abc.abstractmethod
-    def execute(self, debugger, args, result):
+    def execute(self, args):
         """Implementation of the command.
         Subclasses override this method to implement the logic of a given
         command, e.g. printing a stacktrace. The command output should be
@@ -278,6 +500,11 @@ class Command(object):
         properly routed to LLDB frontend. Any unhandled exception will be
         automatically transformed into proper errors.
         """
+    def invoke(self, arg, from_tty):
+        try:
+            self.execute(arg)
+        except Exception as e:
+            dbg.write(e)
 
 
 def cast(typename, value):
@@ -299,75 +526,38 @@ def cast(typename, value):
             name = name[:-1].strip()
             pointer_type = True
 
-    # Get the lldb type representation.
-    t = target.FindFirstType(name)
+    # Get the inferior type representation.
+    t = dbg.find_type(name)
     if pointer_type:
-        t = t.GetPointerType()
-
-    if isinstance(value, int):
-        # Integer casts require some black magic for lldb to behave properly.
-        if pointer_type:
-            casted = target.CreateValueFromAddress(
-                'value',
-                lldb.SBAddress(value, target),
-                t.GetPointeeType(),
-            ).address_of
-        else:
-            casted = target.CreateValueFromData(
-                name='value',
-                data=lldb.SBData.CreateDataFromInt(value, size=8),
-                type=t,
-            )
-    else:
-        casted = value.Cast(t)
+        t = dbg.type_to_pointer_type(t)
+
+    casted = dbg.cast_impl(value, t, pointer_type)
 
     if isinstance(typename, type):
-        # Wrap lldb object, if possible
+        # Wrap inferior object, if possible
         return typename(casted)
     else:
         return casted
 
 
-def lookup_global(name):
-    return target.FindFirstGlobalVariable(name)
-
-
-def type_member(type_obj, name):
-    return next((x for x in type_obj.members if x.name == name), None)
-
-
-def find_type(typename):
-    return target.FindFirstType(typename)
-
-
 def offsetof(typename, membername):
-    type_obj = find_type(typename)
-    member = type_member(type_obj, membername)
+    type_obj = dbg.find_type(typename)
+    member = dbg.type_member(type_obj, membername)
     assert member is not None
-    return member.GetOffsetInBytes()
+    return dbg.type_member_offset(member)
 
 
 def sizeof(typename):
-    type_obj = find_type(typename)
-    return type_obj.GetByteSize()
+    type_obj = dbg.find_type(typename)
+    return dbg.type_sizeof_impl(type_obj)
 
 
 def vtou64(value):
-    return value.unsigned & 0xFFFFFFFFFFFFFFFF
+    return dbg.to_unsigned(value) & 0xFFFFFFFFFFFFFFFF
 
 
 def vtoi(value):
-    return value.signed
-
-
-def dbg_eval(expr):
-    process = target.GetProcess()
-    thread = process.GetSelectedThread()
-    frame = thread.GetSelectedFrame()
-    return frame.EvaluateExpression(expr)
-
-
-# }}} Debugger specific
+    return dbg.to_signed(value)
 
 
 def gcval(obj):
@@ -393,7 +583,7 @@ def gclistlen(root, end=0x0):
 
 
 def gcringlen(root):
-    if not gcref(root):
+    if gcref(root) == 0:
         return 0
     elif gcref(root) == gcref(gcnext(root)):
         return 1
@@ -439,7 +629,7 @@ def J(g):
     J_offset = offsetof('GG_State', 'J')
     return cast(
         jit_StatePtr,
-        vtou64(cast('char *', g)) - g_offset + J_offset,
+        int(vtou64(cast('char *', g)) - g_offset + J_offset),
     )
 
 
@@ -451,7 +641,7 @@ def L(L=None):
     # lookup a symbol for the main coroutine considering the host app
     # XXX Fragile: though the loop initialization looks like a crap but it
     # respects both Python 2 and Python 3.
-    for lstate in [L] + list(map(lambda main: lookup_global(main), (
+    for lstate in [L] + list(map(lambda main: dbg.lookup_variable(main), (
         # LuaJIT main coro (see luajit/src/luajit.c)
         'globalL',
         # Tarantool main coro (see tarantool/src/lua/init.h)
@@ -459,7 +649,7 @@ def L(L=None):
         # TODO: Add more
     ))):
         if lstate:
-            return lua_State(lstate)
+            return lua_StatePtr(lstate)
 
 
 def tou32(val):
@@ -523,9 +713,9 @@ def funcproto(func):
 def strdata(obj):
     try:
         ptr = cast('char *', obj + 1)
-        return ptr.summary
+        return dbg.summary(ptr)
     except UnicodeEncodeError:
-        return "<luajit-lldb: error occurred while rendering non-ascii slot>"
+        return "<luajit_dbg: error occured while rendering non-ascii slot>"
 
 
 def itype(o):
@@ -730,12 +920,12 @@ def frame_pc(framelink):
 
 
 def frame_prevl(framelink):
-    # We are evaluating the `frame_pc(framelink)[-1])` with lldb's
+    # We are evaluating the `frame_pc(framelink)[-1])` with
     # REPL, because the lldb API is faulty and it's not possible to cast
     # a struct member of 32-bit type to 64-bit type without getting onto
     # the next property bits, despite the fact that it's an actual value, not
     # a pointer to it.
-    bcins = vtou64(dbg_eval('((BCIns *)' + str(frame_pc(framelink)) + ')[-1]'))
+    bcins = vtou64(dbg.eval('((BCIns *)' + str(frame_pc(framelink)) + ')[-1]'))
     return framelink - (1 + LJ_FR2 + bc_a(bcins))
 
 
@@ -789,12 +979,12 @@ def frames(L):
 
 def dump_framelink_slot_address(fr):
     return '{start:{padding}}:{end:{padding}}'.format(
-        start=hex(int(fr - 1)),
-        end=hex(int(fr)),
+        start=strx64(fr - 1),
+        end=strx64(fr),
         padding=len(PADDING),
     ) if LJ_FR2 else '{addr:{padding}}'.format(
-        addr=hex(int(fr)),
-        padding=len(PADDING),
+        addr=strx64(fr),
+        padding=2 * len(PADDING) + 1,
     )
 
 
@@ -863,7 +1053,6 @@ def dump_stack(L, base=None, top=None):
             nfreeslots=int((maxstack - top - 8) >> 3),
         ),
     ])
-
     for framelink, frametop in frames(L):
         # Dump all data slots in the (framelink, top) interval.
         dump.extend([
@@ -904,9 +1093,11 @@ the type and some info related to it.
 Whether the type of the given address differs from the listed above, then
 error message occurs.
     '''
-    def execute(self, debugger, args, result):
+    command = 'lj-tv'
+
+    def execute(self, args):
         tvptr = TValuePtr(cast('TValue *', self.parse(args)))
-        print('{}'.format(dump_tvalue(tvptr)))
+        dbg.write('{}'.format(dump_tvalue(tvptr)))
 
 
 class LJState(Command):
@@ -917,9 +1108,11 @@ The command requires no args and dumps current VM and GC states
 * GC state: <PAUSE|PROPAGATE|ATOMIC|SWEEPSTRING|SWEEP|FINALIZE|LAST>
 * JIT state: <IDLE|ACTIVE|RECORD|START|END|ASM|ERR>
     '''
-    def execute(self, debugger, args, result):
+    command = 'lj-state'
+
+    def execute(self, args):
         g = G(L(None))
-        print('{}'.format('\n'.join(
+        dbg.write('{}'.format('\n'.join(
             map(lambda t: '{} state: {}'.format(*t), {
                 'VM':  vm_state(g),
                 'GC':  gc_state(g),
@@ -936,8 +1129,10 @@ The command requires no args and dumps values of LJ_64 and LJ_GC64
 compile-time flags. These values define the sizes of host and GC
 pointers respectively.
     '''
-    def execute(self, debugger, args, result):
-        print(
+    command = 'lj-arch'
+
+    def execute(self, args):
+        dbg.write(
             'LJ_64: {LJ_64}, LJ_GC64: {LJ_GC64}, LJ_DUALNUM: {LJ_DUALNUM}'
             .format(
                 LJ_64=LJ_64,
@@ -965,9 +1160,11 @@ The command requires no args and dumps current GC stats:
 * weak: <number of weak tables (to be cleared)>
 * mmudata: <number of udata|cdata to be finalized>
     '''
-    def execute(self, debugger, args, result):
+    command = 'lj-gc'
+
+    def execute(self, args):
         g = G(L(None))
-        print('GC stats: {state}\n{stats}'.format(
+        dbg.write('GC stats: {state}\n{stats}'.format(
             state=gc_state(g),
             stats=dump_gc(g)
         ))
@@ -983,9 +1180,11 @@ the payload, size in bytes and hash.
 *Caveat*: Since Python 2 provides no native Unicode support, the payload
 is replaced with the corresponding error when decoding fails.
     '''
-    def execute(self, debugger, args, result):
+    command = 'lj-str'
+
+    def execute(self, args):
         string_ptr = GCstrPtr(cast('GCstr *', self.parse(args)))
-        print("String: {body} [{len} bytes] with hash {hash}".format(
+        dbg.write("String: {body} [{len} bytes] with hash {hash}".format(
             body=strdata(string_ptr),
             hash=strx64(string_ptr.hash),
             len=string_ptr.len,
@@ -1003,7 +1202,9 @@ The command receives a GCtab address and dumps the table contents:
 * Hash part <hsize> nodes:
   <hnode ptr>: { <tv> } => { <tv> }; next = <next hnode ptr>
     '''
-    def execute(self, debugger, args, result):
+    command = 'lj-tab'
+
+    def execute(self, args):
         t = GCtabPtr(cast('GCtab *', self.parse(args)))
         array = mref(TValuePtr, t.array)
         nodes = mref(NodePtr, t.node)
@@ -1014,22 +1215,22 @@ The command receives a GCtab address and dumps the table contents:
         }
 
         if mt:
-            print('Metatable detected: {}'.format(strx64(mt)))
+            dbg.write('Metatable detected: {}'.format(strx64(mt)))
 
-        print('Array part: {} slots'.format(capacity['apart']))
+        dbg.write('Array part: {} slots'.format(capacity['apart']))
         for i in range(capacity['apart']):
             slot = array + i
-            print('{ptr}: [{index}]: {value}'.format(
+            dbg.write('{ptr}: [{index}]: {value}'.format(
                 ptr=strx64(slot),
                 index=i,
                 value=dump_tvalue(slot)
             ))
 
-        print('Hash part: {} nodes'.format(capacity['hpart']))
+        dbg.write('Hash part: {} nodes'.format(capacity['hpart']))
         # See hmask comment in lj_obj.h
         for i in range(capacity['hpart']):
             node = nodes + i
-            print('{ptr}: {{ {key} }} => {{ {val} }}; next = {n}'.format(
+            dbg.write('{ptr}: {{ {key} }} => {{ {val} }}; next = {n}'.format(
                 ptr=strx64(node),
                 key=dump_tvalue(TValuePtr(node.key.addr)),
                 val=dump_tvalue(TValuePtr(node.val.addr)),
@@ -1069,56 +1270,72 @@ coroutine guest stack:
 
 If L is omitted the main coroutine is used.
     '''
-    def execute(self, debugger, args, result):
+    command = 'lj-stack'
+
+    def execute(self, args):
         lstate = self.parse(args)
-        lstate_ptr = cast('lua_State *', lstate) if coro is not None else None
-        print('{}'.format(dump_stack(L(lstate_ptr))))
+        lstate_ptr = cast('lua_State *', lstate) if lstate else None
+        dbg.write('{}'.format(dump_stack(L(lstate_ptr))))
 
 
-def register_commands(debugger, commands):
-    for command, cls in commands.items():
-        cls.command = command
-        debugger.HandleCommand(
-            'command script add --overwrite --class luajit_lldb.{cls} {cmd}'
-            .format(
-                cls=cls.__name__,
-                cmd=cls.command,
-            )
-        )
-        print('{cmd} command intialized'.format(cmd=cls.command))
+LJ_COMMANDS = [
+    LJDumpTValue,
+    LJState,
+    LJDumpArch,
+    LJGC,
+    LJDumpString,
+    LJDumpTable,
+    LJDumpStack,
+]
+
 
+def register_commands(commands, debugger=None):
+    for cls in commands:
+        dbg.cmd_init(cls, debugger)
+        dbg.write('{cmd} command intialized'.format(cmd=cls.command))
 
-def configure(debugger):
-    global LJ_64, LJ_GC64, LJ_FR2, LJ_DUALNUM, PADDING, LJ_TISNUM, target
-    target = debugger.GetSelectedTarget()
-    module = target.modules[0]
-    LJ_DUALNUM = module.FindSymbol('lj_lib_checknumber') is not None
 
+def configure(debugger=None):
+    global PADDING, LJ_TISNUM, LJ_DUALNUM
+    dbg.setup_target(debugger)
     try:
-        irtype_enum = target.FindFirstType('IRType').enum_members
-        for member in irtype_enum:
-            if member.name == 'IRT_PTR':
-                LJ_64 = member.unsigned & 0x1f == IRT_P64
-            if member.name == 'IRT_PGC':
-                LJ_FR2 = LJ_GC64 = member.unsigned & 0x1f == IRT_P64
+        # Try to remove the callback at first to not append duplicates to
+        # gdb.events.new_objfile internal list.
+        dbg.event_disconnect(load)
     except Exception:
-        print('luajit_lldb.py failed to load: '
-              'no debugging symbols found for libluajit')
-        return
-
-    PADDING = ' ' * len(strx64((TValuePtr(L().addr))))
-    LJ_TISNUM = 0xfffeffff if LJ_64 and not LJ_GC64 else LJ_T['NUMX']
-
-
-def __lldb_init_module(debugger, internal_dict):
-    configure(debugger)
-    register_commands(debugger, {
-        'lj-tv':    LJDumpTValue,
-        'lj-state': LJState,
-        'lj-arch':  LJDumpArch,
-        'lj-gc':    LJGC,
-        'lj-str':   LJDumpString,
-        'lj-tab':   LJDumpTable,
-        'lj-stack': LJDumpStack,
-    })
-    print('luajit_lldb.py is successfully loaded')
+        # Callback is not connected.
+        pass
+
+    try:
+        # Detect whether libluajit objfile is loaded.
+        dbg.eval('luaJIT_setmode')
+    except Exception:
+        dbg.write('luajit_dbg.py initialization is postponed '
+                  'until libluajit objfile is loaded\n')
+        # Add a callback to be executed when the next objfile is loaded.
+        dbg.event_connect(load)
+        return False
+
+    try:
+        dbg.arch_init()
+    except Exception:
+        dbg.write('LuaJIT debug extension failed to load: '
+                  'no debugging symbols found for libluajit')
+        return False
+    return True
+
+
+# XXX: The dummy parameter is needed for this function to
+# work as a gdb callback.
+def load(_=None, debugger=None):
+    if configure(debugger):
+        register_commands(LJ_COMMANDS, debugger)
+        dbg.write('LuaJIT debug extension is successfully loaded')
+
+
+def __lldb_init_module(debugger, _=None):
+    load(None, debugger)
+
+
+if dbg.GDB:
+    load()
-- 
2.43.0


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