Archive for September, 2019

Crash Dump Analysis Patterns (Part 260)

Friday, September 27th, 2019

Manual analysis of Execution Residue in stack regions can be quite daunting so some basic statistics on the distribution of address, value, and symbolic information can be useful. To automate this process we use Pandas python library and interpret preprocessed WinDbg output of dps and dpp commands as DataFrame object:

import pandas as pd
import pandas_profiling

df = pd.read_csv("stack.csv")
html_file = open("stack.html", "w")
html_file.write (pandas_profiling.ProfileReport(df).to_html())

We get a rudimentary profile report: stack.html for stack.csv file. The same was also done for Address, Address/Value, Value, Symbol output of dpp command: stack4columns.html for stack4columns.csv file.

We call this analysis pattern Region Profile since any Memory Region can be used. This analysis pattern is not limited to Python/Pandas and different libraries/scripts/script languages can also be used for statistical and correlational profiling. We plan to provide more examples here in the future.

- Dmitry Vostokov @ + -

Trace Analysis Patterns (Part 178)

Sunday, September 15th, 2019

When we analyze a trace or log we may produce CoTrace of analyzed messages and visited regions. But the ultimate goal of any trace and log analysis is to construct the explanation of the observed behavoir to justify the root cause analysis and the proposed mechanism. There may be several proposed explanations each having a different set of messages from the analyzed trace that illustrate them. We call them Explanation Traces. This is illustrated in the picture where we use the same trace from CoTrace analysis pattern.

- Dmitry Vostokov @ + -

Crash Dump Analysis Patterns (Part 259)

Sunday, September 1st, 2019

Sometimes we have complex plugins or subsystems consisting from several modules that are loaded in the same process address space (and this is also possible in kernel space as well). Usually subsystem components reside in the same persistent folder (including its possible subfolders):

0:000> lmf
start             end                 module name
00007fff`46ee0000 00007fff`4cde8000 libcef C:\Program Files\Adobe\Adobe Photoshop CC 2019\Required\Plug-ins\Spaces\libcef.dll

00007fff`7fa40000 00007fff`7fbc2000 Spaces C:\Program Files\Adobe\Adobe Photoshop CC 2019\Required\Plug-ins\Spaces\Spaces.8li

00007fff`8ba50000 00007fff`8bae3000 chrome_elf C:\Program Files\Adobe\Adobe Photoshop CC 2019\Required\Plug-ins\Spaces\chrome_elf.dll

When we know product architecture we can group modules according to the known design not only by their physical locations.

This analysis pattern, that we call Subsystem Modules, is useful for the analysis of possibles relationships of Stack Traces from Stack Trace Collections and other Historical Information during the root cause analysis of various crash and hang issues. This can also be applicable to .NET managed space analysis that includes various multi-file assemblies.

- Dmitry Vostokov @ + -