[Tarantool-patches] [PATCH 2/2] gdb: refactor iteration over frames while dumping stack
Mikhail Elhimov
elhimov at gmail.com
Sat Jul 23 03:11:20 MSK 2022
Changes:
- Introduce generator to iterate over frames in a Python way
- Dump framelink of the bottom frame in a common way and identify it as
a dummy framelink only inside of common dump function
- Framelink always refers to the slot right before frame's base
- Introduce constant LJ_FRAMELINK_NUM_SLOTS to make slot arithmetic
more obvious. Previous using of boolean LJ_RT2 in arithmetic looked
like a tricky way, both to read and maintain (however places where
LJ_RT2 approach had been originally replicated from the source code
are left intact, because it is expected that maintenance efforts for
them will be minimal)
---
src/luajit-gdb.py | 101 ++++++++++++++++++++++------------------------
1 file changed, 49 insertions(+), 52 deletions(-)
diff --git a/src/luajit-gdb.py b/src/luajit-gdb.py
index 1e9a96fb..d7d34c70 100644
--- a/src/luajit-gdb.py
+++ b/src/luajit-gdb.py
@@ -158,6 +158,7 @@ LJ_64 = None
LJ_GC64 = None
LJ_FR2 = None
LJ_DUALNUM = None
+LJ_FRAMELINK_NUM_SLOTS = None
LJ_GCVMASK = ((1 << 47) - 1)
LJ_TISNUM = None
@@ -299,6 +300,21 @@ gclen = {
'mmudata': gcringlen,
}
+def get_framelink_sentinel(L):
+ stack = mref('TValue *', L['stack'])
+ return stack + LJ_FRAMELINK_NUM_SLOTS - 1
+
+# 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 = get_framelink_sentinel(L)
+ while framelink is not None:
+ yield framelink, frametop
+ frametop = framelink - LJ_FRAMELINK_NUM_SLOTS
+ framelink = frame_prev(framelink) if framelink > framelink_sentinel else None
+
# Dumpers {{{
def dump_lj_tnil(tv):
@@ -397,32 +413,38 @@ dumpers = {
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_func(fr):
+ return dump_lj_tfunc(fr - 1 if LJ_FR2 else fr)
+
def dump_framelink(L, fr):
- fr2 = fr + LJ_FR2
-
- return '{fr}{padding} [ ] FRAME: [{pp}] delta={d}, {f}\n'.format(
- fr = fr,
- padding = ':{fr2}'.format(fr2 = fr2) if LJ_FR2 else PADDING,
- pp = 'PP' if frame_ispcall(fr2) else '{frname}{p}'.format(
- frname = frametypes(int(frame_type(fr2))),
- p = 'P' if frame_typep(fr2) & FRAME_P else ''
+ if fr == get_framelink_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 *', fr2) - cast('TValue *', frame_prev(fr2)),
- f = dump_lj_tfunc(fr),
+ d = cast('TValue *', fr) - cast('TValue *', frame_prev(fr)),
+ f = dump_framelink_func(fr),
)
-def dump_stack_slot(L, slot, base=None, top=None, eol='\n'):
+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}{eol}'.format(
+ 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),
- eol = eol,
)
def dump_stack(L, base=None, top=None):
@@ -438,7 +460,7 @@ def dump_stack(L, base=None, top=None):
nredslots = red,
))
dump.extend([
- dump_stack_slot(L, maxstack + offset, base, top, '')
+ dump_stack_slot(L, maxstack + offset, base, top)
for offset in range(red, 0, -1)
])
dump.extend([
@@ -446,50 +468,24 @@ def dump_stack(L, base=None, top=None):
padding = '-' * len(PADDING),
nstackslots = int((tou64(maxstack) - tou64(stack)) >> 3),
),
- dump_stack_slot(L, maxstack, base, top, ''),
+ 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),
),
])
- dump = '\n'.join(dump) + '\n'
-
- slot = top
- framelink = base - (1 + LJ_FR2)
-
- # XXX: Lua stack unwinding algorithm consists of the following steps:
- # 1. dump all data slots in the (framelink, top) interval
- # 2. check whether there are remaining frames
- # 3. if there are no slots further, stop the unwinding loop
- # 4. otherwise, resolve the next framelink and top and go to (1)
- #
- # Postcondition (i.e. do-while) loops is the most fitting idiom for such
- # case, but Python doesn't provide such lexical construction. Hence step (1)
- # is unrolled for the topmost stack frame.
- while slot > framelink + LJ_FR2:
- dump += dump_stack_slot(L, slot, base, top)
- slot -= 1
-
- while framelink > stack:
- assert slot == framelink + LJ_FR2, "Invalid slot during frame unwind"
- dump += dump_framelink(L, framelink)
- framelink = frame_prev(framelink + LJ_FR2) - LJ_FR2
- slot -= 1 + LJ_FR2
- while slot > framelink + LJ_FR2:
- dump += dump_stack_slot(L, slot, base, top)
- slot -= 1
-
- assert slot == framelink + LJ_FR2, "Invalid slot after frame unwind"
- # Skip a nil slot for the last frame for 2-slot frames.
- slot -= LJ_FR2
-
- dump += '{fr}{padding} [S ] FRAME: dummy L'.format(
- fr = slot,
- padding = ':{nilslot}'.format(nilslot = slot + 1) if LJ_FR2 else PADDING
- )
- return dump
+ 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)
+ ])
+ # 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']
@@ -717,7 +713,7 @@ The command requires no args and dumps current GC stats:
))
def init(commands):
- global LJ_64, LJ_GC64, LJ_FR2, LJ_DUALNUM, LJ_TISNUM, PADDING
+ global LJ_64, LJ_GC64, LJ_FR2, LJ_DUALNUM, LJ_FRAMELINK_NUM_SLOTS, LJ_TISNUM, PADDING
# XXX Fragile: though connecting the callback looks like a crap but it
# respects both Python 2 and Python 3 (see #4828).
@@ -759,6 +755,7 @@ def init(commands):
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
+ LJ_FRAMELINK_NUM_SLOTS = 2 if LJ_FR2 else 1
except:
gdb.write('luajit-gdb.py failed to load: '
'no debugging symbols found for libluajit\n')
--
2.34.1
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