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Message-ID: <20131105192401.GA772@redhat.com>
Date: Tue, 5 Nov 2013 20:24:01 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
Namhyung Kim <namhyung.kim@....com>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Hyeoncheol Lee <cheol.lee@....com>,
Hemant Kumar <hkshaw@...ux.vnet.ibm.com>,
LKML <linux-kernel@...r.kernel.org>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: [PATCHSET 00/13] tracing/uprobes: Add support for more fetch
methods (v6)
On 11/05, Oleg Nesterov wrote:
>
> As for "-= tu->offset"... Can't we avoid it? User-space needs to calculate
> the "@" argument anyway, why it can't also substruct this offset?
>
> Or perhaps we can change parse_probe_arg("@") to update "param" ? Yes,
> in this case it needs another argument, not sure...
Or,
> + if (is_ret_probe(tu)) {
> + saved_ip = instruction_pointer(regs);
> + instruction_pointer_set(func);
> + }
> store_trace_args(...);
> + if (is_ret_probe(tu))
> + instruction_pointer_set(saved_ip);
we can put "-= tu->offset" here.
> although not pretty.
Yes.
Or. Perhaps we can leave "case '@'" in parse_probe_arg() and
FETCH_MTD_memory alone. You seem to agree that "absolute address"
can be useful anyway.
Instead, perhaps we can add FETCH_MTD_memory_do_fancy_addr_translation,
and, say, the new "case '*'" in parse_probe_arg() should add all the
neccessary info as f->data (like, say, FETCH_MTD_symbol).
But, just in case, I do not have a strong opinion. Just I think it
is better to discuss every choice we have.
Oleg.
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