Re: [PATCH v2 dwarves] btf: Remove ftrace filter

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Fri, May 07, 2021 at 12:39:52PM +0200, Jiri Olsa escreveu:
> On Thu, May 06, 2021 at 01:56:22PM -0700, Martin KaFai Lau 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
> > 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.
> > 
> > Those kernel functions are specified under an ELF section .BTF_ids.
> > There was an earlier attempt [0] to add another filter for the functions in
> > the .BTF_ids section.  That discussion concluded that the ftrace filter
> > should be removed instead.
> > 
> > This patch is to remove the ftrace filter and its related functions.
> > 
> > Number of BTF FUNC with and without is_ftrace_func():
> > My kconfig in x86: 40643 vs 46225
> > Jiri reported on arm: 25022 vs 55812
> > 
> > [0]: https://lore.kernel.org/dwarves/20210423213728.3538141-1-kafai@fb.com/
> > 
> > Cc: Andrii Nakryiko <andrii@kernel.org>
> > Cc: Jiri Olsa <jolsa@kernel.org>
> > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > ---
> > v2: Remove sym_sec_idx, last_idx, and sh. (Jiri Olsa)
> 
> Acked-by: Jiri Olsa <jolsa@kernel.org>

Thanks, applied.

- Arnaldo