netdev - Re: [PATCHv2 RFC bpf-next 0/7] bpf: Add support for ftrace probe

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Message-ID: <YHi09yyqVEkZsn7p@krava>
Date:   Thu, 15 Apr 2021 23:49:43 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>, Daniel Xu <dxu@...uu.xyz>,
        Jesper Brouer <jbrouer@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Viktor Malik <vmalik@...hat.com>
Subject: Re: [PATCHv2 RFC bpf-next 0/7] bpf: Add support for ftrace probe

On Thu, Apr 15, 2021 at 02:21:20PM -0400, Steven Rostedt wrote:
> On Thu, 15 Apr 2021 14:18:31 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> > My last release of that code is here:
> > 
> >   https://lore.kernel.org/lkml/20190525031633.811342628@goodmis.org/
> > 
> > It allows you to "reserve data" to pass from the caller to the return, and
> > that could hold the arguments. See patch 15 of that series.
> 
> Note that implementation only lets you save up to 4 words on the stack, but
> that can be changed. Or you could have a separate shadow stack for saving
> arguments, and only pass the pointer to the location on the other stack
> where those arguments are.

right, I quickly checked on that and it looks exactly like
the thing we need

I'll try to rebase that on the current code and try to use
it with the bpf ftrace probe to see how it fits

any chance you could plan on reposting it? ;-)

thanks,
jirka