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Date: Thu, 28 May 2015 14:08:42 +0800
From: Li Bin <huawei.libin@huawei.com>
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To: Jiri Kosina <jkosina@suse.cz>,
        AKASHI Takahiro <takahiro.akashi@linaro.org>
CC: <linaro-kernel@lists.linaro.org>, <catalin.marinas@arm.com>,
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Subject: Re: [RFC 0/4] arm64: add livepatch support
References: <1429843449-7388-1-git-send-email-takahiro.akashi@linaro.org> <alpine.LNX.2.00.1504241126430.3695@pobox.suse.cz>
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On 2015/4/24 17:27, Jiri Kosina wrote:
> On Fri, 24 Apr 2015, AKASHI Takahiro wrote:
> 
>> This patchset enables livepatch support on arm64.
>>
>> Livepatch was merged in v4.0, and allows replacying a function dynamically
>> based on ftrace framework, but it also requires -mfentry option of gcc.
>> Currently arm64 gcc doesn't support it, but by adding a helper function to
>> ftrace, we will be able to support livepatch on arch's which don't support
>> this option.
>>
>> I submit this patchset as RFC since I'm not quite sure that I'm doing
>> in the right way, or we should definitely support -fentry instead.
> 
> I don't have arm64 cross-compiler handy, could you please copy/paste how 
> does function prologue, generated by gcc -pg on arm64 look like?
> 

The function prologue on arm64 with gcc -pg look like as following:
func:
        stp     x29, x30, [sp, -48]!
        add     x29, sp, 0
        mov     x1, x30
        str     w0, [x29,28]
        mov     x0, x1
        bl      _mcount
	...
Thanks,
	Li Bin

> Thanks,
>