Profiling and optimising with Flamegraph
Flamegraph is a software which generates SVG graphics to visualise stack-sampling based profiles. It processes data collected with tools such as Linux perf, SystemTap, DTrace.
View ArticleCopy-on-write snapshots for the SimGrid model checker
The SimGrid model checker explores the graph of possible executions of a simulated distributed application in order to verify safety and liveness properties. The model checker needs to store the state...
View ArticlePer-page shallow snapshots for the SimGrid model checker
I looked at my options to achieve efficient/cheap snapshots of the simulated application for the Simgrid model checker using copy-on-write. Here I look at another solution to achieve this without using...
View ArticleCustom (X11/xkb) keyboard layout without being root
Short tutorial about creating a custom keyboard layout without being root.
View ArticleSDL2 gamepad calibration
Many recent games do not provide an option to map the keys/axes of the gamepad to specific actions. They assume that the gamepad is XBox compatible: if it is not the game is completely unusable. SDL2...
View ArticlePage store for the Simgrid model checker
The first (lower) layer of the per-page snapshot mechanism is a page store: its responsibility is to store immutable shareable reference-counted memory pages independently of the snapshoting logic....
View ArticleSample watchpoints or breakpoints with GDB (and FlameGraph)
GDB can be used to get the stack each time a breakpoint is reached.
View ArticleResults on same-page-merging snapshots
In the previous episode, I talked about the implementation of a same-page-merging page store. On top of this, we can build same-page-merging snapshots for the SimGrid model checker.
View ArticleCompile a mixed 32 bit/64 bit wine for Debian
The Wine🍷 wiki has instructions for building a shared WoW64 Wine : this needs two out of source builds. The issue is that some developement packages are not multiarch co-installable. Another wiki page...
View ArticleJoomla to Wordpress redirections
There are some good plugins to export Joomla content to WordPress. However, the free version does not rewrite the URIs. It is quite simple to read the Joomla database and generates a bunch of Apache...
View ArticleFiltering the clipboard using UNIX filters
I had a few Joomla posts that I wanted to clean up semi-automatically. Here are a few scripts, to pass the content of the clipboard (or the current selection) through a UNIX filter.
View ArticleAdding a basic LLVM pass
The SimGrid model checker uses memory introspection (of the heap, stack and global variables) in order to detect the equality of the state of a distributed application at the different nodes of its...
View ArticleCleaning the stack in a LLVM pass
In the previous episode, we implemented a LLVM pass which does nothing. Now we are trying to modify this to create a (proof-of-concept) LLVM pass which fills the current stack frame with zero before...
View ArticleCleaning the stack by filtering the assembly
In order to help the SimGridMC state comparison code, I wrote a proof-of-concept LLVM pass which cleans each stack frame before using it. However, SimGridMC currently does not work properly when...
View ArticleAvoiding to clean the stack
In two previous posts, I looked into cleaning the stack frame of a function before using it by adding assembly at the beginning of each function. This was done either by modifying LLVM with a custom...
View ArticleBetter isolation for SimGridMC
In an attempt to simplify the development around the SimGrid model-checker, we were thinking about moving the model-checker out in a different process. Another different approach would be to use a...
View Articlenginx, Logstash and vhost-combined log format
The Apache HTTP server ships with a split-logfile utility which parses Combined Log File entries prefixed with the virtual host: some notes about this and its inclusion in nginx and logstash.
View ArticleRecover a (forgotten) password in a process memory
Today, I managed to forget a password but I had a Icedove (Thunderbird) process running containing the password.
View ArticleELF loading and dynamic linking
Some notes on ELF 🧝 loading and dynamic linking mainly for GNU userland (ld.so, libc, libdl) running on top of the Linux kernel. Some prior knowlegde on the topic (virtual memory, shared objects,...
View ArticleRecursive DNS over TLS over TCP 443
You might want to use an open recursive DNS servers if your ISP's DNS server is lying. However, if your network/ISP is intercepting all DNS requests, a standard open recursive DNS server won't help....
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