Daroc
Security updates for Friday
[$] Hash table memory usage and a BPF interpreter bug
Anton Protopopov led a short discussion at the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit about amount of memory used by hash tables in BPF programs. He thinks that the current memory layout is inefficient, and wants to split the structure that holds table entries into two variants for different kinds of maps. When that proposal proved uncontroversial, he also took the chance to talk about a bug in BPF's call instruction.
[$] Filtering fanotify events with BPF
Linux systems can have large filesystems; trying to keep up with the stream of fanotify filesystem-monitoring notifications for them can be a struggle. Fanotify is one of a few ways to monitor accesses to filesystems provided by the kernel. Song Liu led a discussion on how to improve in-kernel filtering of fanotify events to a joint session of the filesystem and BPF tracks at the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit. He wants to combine the best parts of a few different approaches to efficiently filter filesystem events.
Security updates for Friday
[$] Better debugging information for inlined kernel functions
Modern compilers perform a lot of optimizations, which can complicate debugging. Song Liu and Thierry Treyer spoke about a potential improvement to BPF Type Format (BTF) debugging information that could partially combat that problem at the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit. They want to add information on selectively inlined functions to BTF in order to better support tracing tools. Treyer participated remotely.