On Mon, Feb 14, 2022 at 3:14 PM Alan Maguire <alan.maguire@xxxxxxxxxx> wrote: > > On Mon, 14 Feb 2022, Alexei Starovoitov wrote: > > > Alan, > > can you demo your "okprobe" feature based on this api? > > Any rough patches would do. > > sure; see below. Requires Andrii's v3 patches to be applied first, > and demonstrates okprobe handling for a kprobe function that exists > and one that doesn't - the important thing is skeleton attach > can succeed even when a function is missing (as it would be if > the associated module wasn't loaded). > > > The "o" handling will be done in which callback? > > > > We set program type at init and do custom attach using the function > name (specified in the program section after the "okprobe" prefix). > However we make sure to catch -ENOENT attach failures and return 0 > with a NULL link so skeleton attach can proceed. > > From 9bbd615b71f8f59ff743608bc86d7a2a346da2a8 Mon Sep 17 00:00:00 2001 > From: Alan Maguire <alan.maguire@xxxxxxxxxx> > Date: Mon, 14 Feb 2022 22:57:56 +0000 > Subject: [PATCH bpf-next] selftests/bpf: demonstrate further use of custom > SEC() handling > > Register and use SEC() handling for "okprobe/" kprobe programs > (Optional kprobe) which should be attached as kprobes but > critically should not stop skeleton loading if attach fails > due to non-existence of the to-be-probed function. This mode > of SEC() handling is useful for tracing module functions > where the module might not be loaded. > > Note - this patch is based on the v3 of Andrii's section > handling patches [1] and these need to be applied for it to > apply cleanly. > > [1] https://lore.kernel.org/bpf/20220211211450.2224877-1-andrii@xxxxxxxxxx/ > > Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx> Thanks. The patch certainly helps to understand the api usage. > static int custom_init_prog(struct bpf_program *prog, long cookie) > { > if (cookie == COOKIE_ABC1) > bpf_program__set_autoload(prog, false); > + else if (cookie == COOKIE_OKPROBE) > + bpf_program__set_type(prog, BPF_PROG_TYPE_KPROBE); I think bpf_program__set_type() would have worked from the prepare_load_fn callback as well. What would be a recommended way of setting it?
