libcuda.so logger

As illustration of ideas from my previous blogpost I made PoC for logging all libcuda.so calls - as the cuda-gdb debugger sees them

It just installs own debug handler and receives all messages. Note:

1. only x86_64 linux supported, but logic can be easily extended for x86 32bit and highly likely for arm64 too
2. events generating before each call, so you can’t get result of those calls

Current handler is very simple - it just writes to file, but nothing prevents to add storing to DB, ElasticSearch or gRPC/Apache thrift to send them to some remote storage (or even to WireShark in real time)

Format of messages

Currently almost unknown - for public API events have type 6 and function name at offset 0x30 - and this is all for now. Sure subject for further RE

Dependencies

• udis86 for x86 disassembler
• ELFIO for ELF files parsing

How to build

Patch ELFIO_PATH & UDIS_PATH in Makefile and just run make

Both gcc (12+) and clang 21 are supported

How connect logger to your own application

You just call single function set_logger. Arguments:

• full path to libcuda.so. Note that most structures from it gathered with static code analysis and so require some disasm
• FILE *fp - where to write log
• mask - pointer to array with masks for each event type. Non-zero value means intercept events with this type, 2 - do hexdump of packets
• mask_size - size of mask array. libcuda.so from CUDA 13.1 has 31 event types

+ add libdis.so to linker

Also it’s not difficult to make classical injection with ancient LD_PRELOAD trick or even inject this logger into already running processes