Re: [PATCH bpf-next v4 09/27] bpf: Add support to load multi func tracing program

On Tue, Aug 31, 2021 at 04:17:33PM -0700, Andrii Nakryiko wrote:

On Thu, Aug 26, 2021 at 12:40 PM Jiri Olsa [off-list ref] wrote:

quoted

Adding support to load tracing program with new BPF_F_MULTI_FUNC flag,
that allows the program to be loaded without specific function to be
attached to.

Are there any benefits to using a new load flag vs having separate
expected attach types like FENTRY_MULTI/FEXIT_MULTI? I find load flags
a bigger pain to work with compared to expected attach type (and
expected attach type should be more apparent in BPF link info, bpftool
output, etc).

it means more of the additional code, with the flag we just reuse
BPF_TRACE_FENTRY/BPF_TRACE_FEXIT related code because we use
current trampoline paths

I recall trying that approach while back, but ended up with bigger
changes that seemed unnecessary, I can dig it up to get more
details

jirka

quoted

Such program will be allowed to be attached to multiple functions
in following patches.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/linux/bpf.h            |  1 +
 include/uapi/linux/bpf.h       |  7 +++++++
 kernel/bpf/syscall.c           | 35 +++++++++++++++++++++++++++++-----
 kernel/bpf/verifier.c          |  3 ++-
 tools/include/uapi/linux/bpf.h |  7 +++++++
 5 files changed, 47 insertions(+), 6 deletions(-)

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