On Tue, Apr 27, 2021 at 01:38:20PM +0200, Jiri Olsa wrote:
> On Mon, Apr 26, 2021 at 04:26:11PM -0700, Andrii Nakryiko wrote:
> > On Fri, Apr 23, 2021 at 2:37 PM Martin KaFai Lau <kafai@xxxxxx> wrote:
> > >
> > > BTF is currently generated for functions that are in ftrace list
> > > or extern.
> > >
> > > A recent use case also needs BTF generated for functions included in
> > > allowlist. In particular, the kernel
> > > commit e78aea8b2170 ("bpf: tcp: Put some tcp cong functions in allowlist for bpf-tcp-cc")
> > > allows bpf program to directly call a few tcp cc kernel functions. Those
> > > functions are specified under an ELF section .BTF_ids. The symbols
> > > in this ELF section is like __BTF_ID__func__<kernel_func>__[digit]+.
> > > For example, __BTF_ID__func__cubictcp_init__1. Those kernel
> > > functions are currently allowed only if CONFIG_DYNAMIC_FTRACE is
> > > set to ensure they are in the ftrace list but this kconfig dependency
> > > is unnecessary.
> > >
> > > pahole can generate BTF for those kernel functions if it knows they
> > > are in the allowlist. This patch is to capture those symbols
> > > in the .BTF_ids section and generate BTF for them.
> > >
> > > Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
> > > Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
> > > ---
> >
> > I wonder if we just record all functions how bad that would be. Jiri,
> > do you remember from the time you were experimenting with static
> > functions how much more functions we'd be recording if we didn't do
> > ftrace filtering?
>
> hum, I can't find that.. but should be just matter of removing
> that is_ftrace_func check
In my kconfig, by ignoring is_ftrace_func(),
number of FUNC: 40643 vs 46225
I would say skip the ftrace filtering instead of my current patch. Thoughts?
