linux-kernel - Re: [PATCH v3 0/5] tracing/probes: uaccess: Add support user-space access

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Message-Id: <20190228105431.ca1fbf6ae6fca15de2f17c22@kernel.org>
Date:   Thu, 28 Feb 2019 10:54:31 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Changbin Du <changbin.du@...il.com>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...nel.org>,
        Nadav Amit <namit@...are.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 0/5] tracing/probes: uaccess: Add support user-space
 access

On Wed, 27 Feb 2019 14:32:41 -0800
Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:

> On Wed, Feb 27, 2019 at 11:42:15PM +0900, Masami Hiramatsu wrote:
> > 
> > For perf-probe, we can add some attribute for each argument
> > which indicate that the variable in user space. But still
> > we can not decide it automatically by DWARF since __user attribute
> > is not transrated to DWARF attribute.
> 
> clang has partial support for __attribute__((noderef, address_space(1)))
> We'll work on patches to make it complete and pass __user attribute
> all the way to debug info.

Great! That's what I need. Could you point where (or who) I should check the
implementation?
I guess it will add DW_AT_segment to variable instance, if so it is easy
to support it in perf probe.

> 
> If somebody can work with gcc folks to do the same that would be awesome.
> 

Thank you,

-- 
Masami Hiramatsu <mhiramat@...nel.org>