From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [PATCH 1/2] bpf: Remove struct bpf_verifier_env argument from print_bpf_insn Date: Thu, 22 Mar 2018 10:34:18 +0100 Message-ID: References: <20180321150212.5586-1-jolsa@kernel.org> <20180321183749.GF2707@krava> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: Jiri Olsa , Alexei Starovoitov , lkml , netdev@vger.kernel.org To: Jiri Olsa , Quentin Monnet Return-path: In-Reply-To: <20180321183749.GF2707@krava> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 03/21/2018 07:37 PM, Jiri Olsa wrote: > On Wed, Mar 21, 2018 at 05:25:33PM +0000, Quentin Monnet wrote: >> 2018-03-21 16:02 UTC+0100 ~ Jiri Olsa >>> We use print_bpf_insn in user space (bpftool and soon perf), >>> so it'd be nice to keep it generic and strip it off the kernel >>> struct bpf_verifier_env argument. >>> >>> This argument can be safely removed, because its users can >>> use the struct bpf_insn_cbs::private_data to pass it. >>> >>> Signed-off-by: Jiri Olsa >>> --- >>> kernel/bpf/disasm.c | 52 +++++++++++++++++++++++++-------------------------- >>> kernel/bpf/disasm.h | 5 +---- >>> kernel/bpf/verifier.c | 6 +++--- >>> 3 files changed, 30 insertions(+), 33 deletions(-) >> >> [...] >> >>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >>> index c6eff108aa99..9f27d3fa7259 100644 >>> --- a/kernel/bpf/verifier.c >>> +++ b/kernel/bpf/verifier.c >>> @@ -202,8 +202,7 @@ EXPORT_SYMBOL_GPL(bpf_verifier_log_write); >>> * generic for symbol export. The function was renamed, but not the calls in >>> * the verifier to avoid complicating backports. Hence the alias below. >>> */ >>> -static __printf(2, 3) void verbose(struct bpf_verifier_env *env, >>> - const char *fmt, ...) >>> +static __printf(2, 3) void verbose(void *private_data, const char *fmt, ...) >>> __attribute__((alias("bpf_verifier_log_write"))); >> >> Just as a note, verbose() will be aliased to a function whose prototype >> differs (bpf_verifier_log_write() still expects a struct >> bpf_verifier_env as its first argument). I am not so familiar with >> function aliases, could this change be a concern? > > yea, but as it was pointer for pointer switch I did not > see any problem with that.. I'll check more Ok, holding off for now until we have clarification. Other option could also be to make it void *private_data everywhere and for the kernel writer then do struct bpf_verifier_env *env = private_data.