Valgrind-mmt is a Valgrind modification which allows tracing application accesses to mmaped memory (which is how userspace parts of graphics drivers communicate with hardware). It was created by Dave Airlie and then extended/fixed by others.

Installation: [[!format txt """ git clone git://people.freedesktop.org/~mslusarz/valgrind git clone git://people.freedesktop.org/~mslusarz/vex valgrind/VEX cd valgrind ./autogen.sh ./configure --prefix=... make make install """]] Update: [[!format txt """ cd valgrind git pull cd VEX git pull cd .. """]] Use: [[!format txt """ valgrind --tool=mmt --mmt-trace-file=/dev/nvidia0 --mmt-trace-nvidia-ioctls Xorg """]] Options: [[!format txt """ --mmt-trace-file=path trace loads and stores to memory mapped for this file (e.g. /dev/nvidia0) (you can pass this option multiple times) --mmt-trace-all-files trace loads and stores to memory mapped for all files --mmt-trace-nvidia-ioctls trace nvidia ioctls on /dev/nvidiactl --mmt-trace-nouveau-ioctls trace nouveau ioctls on /dev/dri/cardX --mmt-trace-all-opens trace all 'open' syscalls --mmt-trace-marks send mmiotrace marks before and after ioctls """]] Some notes about tracing Xorg:

• valgrind can't trace suid binaries, you have to copy Xorg to e.g. Xorg-nosuid
• running plain Xorg won't load any windowmanager - before starting X, start on another console:[[!format txt """ export DISPLAY=:0; while [ true ]; do xterm; sleep 1; done """]]
• tracing slows down Xorg considerably - ~20x
• nvidia ioctl tracing is fragile - can crash easily
• when valgrind crashes, Xorg leaves only black screen - you need to press Alt-SysRq-R, switch to some free console (ctrl-alt-fxx), blindly login and start normal Xorg (startx)