linux-kernel - Re: [RFC PATCH v2 09/15] perf probe: Support $params without debuginfo

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Message-ID: <556759F9.9020908@plumgrid.com>
Date:	Thu, 28 May 2015 11:10:01 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	He Kuang <hekuang@...wei.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	wangnan0@...wei.com, paulus@...ba.org, a.p.zijlstra@...llo.nl,
	mingo@...hat.com, acme@...nel.org, namhyung@...nel.org,
	jolsa@...nel.org, dsahern@...il.com, brendan.d.gregg@...il.com,
	daniel@...earbox.net
CC:	lizefan@...wei.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 09/15] perf probe: Support $params without debuginfo

On 5/28/15 6:01 AM, He Kuang wrote:
>> I don't think you can break it down in two steps like this.
>> >There is no such thing as 'calling regs'. x86_32 with ax,dx,cx
>> >are not 'calling regs'. 64-bit values will be passed in a pair.
>> >Only 'pt_regs + arch + func_proto + asmlinkage' makes sense
>> >from the user point of view.
>> >Adding 'asmlinkage' attr is also trivial.
>> >'func(long, char) asmlinkage' is easy to parse and the user
> I think at this early stage, we could make our bpf variable
> prologue work with debuginfo while keeping bpf 'SEC' syntax
> consistent with original perf probe. After all, we can use
> pt_regs directly or relay to perf-probe cache by Masami to deal
> with non-debug cases.

so you're saying you don't want to support non-debug case for now?
Sure, as long as section name parser will be able to support
'func(long, char) asmlinkage' syntax in the future without breaking
compatibility. I'm mostly interested in cases when debug info
is not available at all. So perf-probe cache is of no use to me.

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