[lldb/crashlog] Skip null image dsym fetching on interactive mode

[mib]

Summary

Sometimes, it can happen that a crash report has null images in its list
of used binaries. This manifests like such:

0x0 - 0xffffffffffffffff ??? (*) <00000000-0000-0000-0000-000000000000> ???

When fetching debug symbols to symbolicate the crashlog stackframe,
having null images causes dsymForUUID to hang for few seconds.

This patch addresses that by skipping null images from being load by the
scripted process.

rdar://97419487

Signed-off-by: Med Ismail Bennani <[e-mail]>

[jasonmolenda]

lldb/examples/python/scripted_process/crashlog_scripted_process.py

28

One of the things I noticed working on https://reviews.llvm.org/D130813 was that our UUID class's IsValid() method detects if the object has any bytes or not, and I wonder if it should check for a null uuid value (all zeroes) and return IsValid()==false in that case. In my patch, I was reading a UUID out of a corefile and I needed to check if it was a null uuid before I copied the bytes into a UUID object to work around it.

[JDevlieghere]

lldb/examples/python/scripted_process/crashlog_scripted_process.py

28

According to the spec [1], the all-zero UUID is indeed a special case called the "Nil UUID". I think it makes sense to have IsValid return false for that.

[1] https://datatracker.ietf.org/doc/html/rfc4122#section-4.1.7

[mib]

lldb/examples/python/scripted_process/crashlog_scripted_process.py

28

Sounds good to me but I think that change is unrelated to this patch: The problem here that we call dsymForUUID from crashlog.py -> DarwinImage:locate_module_and_debug_symbols with a nil UUID, so the issue is external to lldb. I'll make the UUID::IsValid change on a follow-up patch

[JDevlieghere]

LGTM module the inline comment.

lldb/examples/python/scripted_process/crashlog_scripted_process.py

27–30

Sounds good. I would remove the print and just ignore the null images. There's nothing actionable there for the user.

lldb/examples/python/scripted_process/crashlog_scripted_process.py

-import os,json,struct,signal
+import os,json,struct,signal,uuid
 
 from typing import Any, Dict
 
 import lldb
 from lldb.plugins.scripted_process import ScriptedProcess
 from lldb.plugins.scripted_process import ScriptedThread
 
 from lldb.macosx.crashlog import CrashLog,CrashLogParser
def parse_crashlog(self):
         self.addr_mask = crash_log.addr_mask
         self.crashed_thread_idx = crash_log.crashed_thread_idx
         self.loaded_images = []
 
         def load_images(self, images):
             #TODO: Add to self.loaded_images and load images in lldb
             if images:
                 for image in images:
                     if image not in self.loaded_images:
+                        if image.uuid == uuid.UUID(int=0):
+                            continue
                         err = image.add_module(self.target)
                         if err:
+                            # Append to SBCommandReturnObject
                             print(err)
                         else:
                             self.loaded_images.append(image)
 
         for thread in crash_log.threads:
             if self.load_all_images:
                 load_images(self, crash_log.images)
             elif thread.did_crash():

lldb/test/Shell/ScriptInterpreter/Python/Crashlog/Inputs/interactive_crashlog/multithread-test.ips

"usedImages": [
     {
       "arch": "arm64e",
       "base": 6924001280,
       "name": "libsystem_c.dylib",
       "path": "/usr/lib/system/libsystem_c.dylib",
       "size": 528384,
       "source": "P",
       "uuid": "b8f1c3ed-9048-34a6-8070-6c18d4ade541"
+    },
+    {
+      "size" : 0,
+      "source" : "A",
+      "base" : 0,
+      "uuid" : "00000000-0000-0000-0000-000000000000"
     }
   ],
   "userID": 501,
   "version": 2,
   "vmRegionInfo": "0 is not in any region.  Bytes before following region: 4310450176\n      REGION TYPE                    START - END         [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL\n      UNUSED SPACE AT START\n--->  \n      __TEXT                      100ec4000-100ec8000    [   16K] r-x/r-x SM=COW  ...tithread-test",
   "vmSummary": "ReadOnly portion of Libraries: Total=762.9M resident=0K(0%) swapped_out_or_unallocated=762.9M(100%)\nWritable regions: Total=538.2M written=0K(0%) resident=0K(0%) swapped_out=0K(0%) unallocated=538.2M(100%)\n\n                                VIRTUAL   REGION \nREGION TYPE                        SIZE    COUNT (non-coalesced) \n===========                     =======  ======= \nKernel Alloc Once                   32K        1 \nMALLOC                           145.2M       12 \nMALLOC guard page                   96K        5 \nMALLOC_NANO (reserved)           384.0M        1         reserved VM address space (unallocated)\nSTACK GUARD                       56.0M        3 \nStack                             9264K        3 \n__AUTH                              46K       11 \n__AUTH_CONST                        70K       38 \n__DATA                             169K       36 \n__DATA_CONST                       187K       40 \n__DATA_DIRTY                        78K       22 \n__LINKEDIT                       758.0M        2 \n__OBJC_CONST                        11K        5 \n__OBJC_RO                         64.7M        1 \n__OBJC_RW                         1971K        1 \n__TEXT                            5076K       42 \ndyld private memory                256K        1 \nshared memory                       64K        3 \n===========                     =======  ======= \nTOTAL                              1.4G      227 \nTOTAL, minus reserved VM space     1.0G      227 \n",
   "vmregioninfo": "0 is not in any region.  Bytes before following region: 4310450176\n      REGION TYPE                    START - END         [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL\n      UNUSED SPACE AT START\n--->  \n      __TEXT                      100ec4000-100ec8000    [   16K] r-x/r-x SM=COW  ...tithread-test",
   "wakeTime": 214
-}
+}