On Fri, Oct 29, 2021 at 5:17 PM Hengqi Chen <hengqi.chen@xxxxxxxxx> wrote: > > > > On 10/29/21 6:46 AM, Martin KaFai Lau wrote: > > On Thu, Oct 28, 2021 at 06:43:57PM +0200, Florent Revest wrote: > >> Allow the helper to be called from the perf_event_mmap hook. This is > >> convenient to lookup vma->vm_file and implement a similar logic as > >> perf_event_mmap_event in BPF. > > From struct vm_area_struct: > > struct file * vm_file; /* File we map to (can be NULL). */ > > > > Under perf_event_mmap, vm_file won't be NULL or bpf_d_path can handle it? > > > > Hmm, is perf_event_mmap a proper tracing target ? > It does not appear in /sys/kernel/debug/tracing/available_filter_functions. > > I tried using kprobe/fentry to attach to it, both failed. Good observation! :) In the bpf-next tree, perf_event_mmap is still not exposed to tracing because the kernel/events/Makefile specifically removes CC_FLAGS_FTRACE for core.c. However, Song sent a patch to expose the functions of kernel/events/core.c to tracing: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/kernel/events/Makefile?id=79df45731da68772d2285265864a52c900b8c65f That patch is going through Peter Zijlstra's tree so it should percolate down to Linus tree probably at ~the same time as this patch (if it gets in :)). I tested this on bpf-next with Song's patch cherry-picked.
