linux-kernel - Re: [PATCH 9/9] perf tools: Unwind properly location after REJECT

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Date:   Fri, 13 Oct 2017 16:50:36 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andi Kleen <andi@...stfloor.org>,
        "Jin, Yao" <yao.jin@...ux.intel.com>,
        "Wangnan (F)" <wangnan0@...wei.com>,
        "Du, Changbin" <changbin.du@...el.com>
Subject: Re: [PATCH 9/9] perf tools: Unwind properly location after REJECT

Em Fri, Oct 13, 2017 at 10:37:36AM +0200, Jiri Olsa escreveu:
> We have defined YY_USER_ACTION to keep trace of the column
> location during events parsing, but we need to clean it up
> when we call REJECT.
> 
> When REJECT is called, the lexer shrinks the text and re-runs
> the matching, so we need to address it in resuming the previous
> location value.

What is this fixing? Please state that, below I show what it is breaking
:-/

Before:

[root@...et ~]# perf trace --no-syscalls -e ~acme/bpf/sys_read.c/max-stack=5/ sleep 1
bpf: builtin compilation failed: -95, try external compiler
     0.000 perf_bpf_probe:func:(ffffffffbb2634e0))
                                       sys_read ([kernel.kallsyms])
                                       entry_SYSCALL_64_fastpath ([kernel.kallsyms])
                                       __read (/usr/lib64/ld-2.25.so)
                                       _dl_map_object (/usr/lib64/ld-2.25.so)

After:

[root@...et ~]# perf trace --no-syscalls -e ~acme/bpf/sys_read.c/max-stack=5/ sleep 1
event syntax error: '/home/acme/bpf/sys_read.c/max-stack=5/'
                     \___ parser error
Run 'perf list' for a list of valid events

 Usage: perf trace [<options>] [<command>]
    or: perf trace [<options>] -- <command> [<options>]
    or: perf trace record [<options>] [<command>]
    or: perf trace record [<options>] -- <command> [<options>]

    -e, --event <event>   event/syscall selector. use 'perf list' to list available events
[root@...et ~]#