On Fri, Oct 29, 2021 at 12:47 AM Martin KaFai Lau <kafai@xxxxxx> 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? Thanks Martin, this is a very good point. :) Yes, vm_file can be NULL in perf_event_mmap. I wonder what would happen (and what we could do about it? :|). bpf_d_path is called on &vma->vm_file->f_path So without NULL checks (of vm_file) in BPF, the helper wouldn't be called with a NULL pointer but rather with an address that is offsetof(struct file, f_path).
