# \[RFC 0/4\] arm64: add livepatch support

- From: Li Bin \<hidden\>
- Date: 2015-05-28 06:06:48 
- List: linux-arm-kernel
- Page: https://ratatoskr.run/linux-arm-kernel/2015/05/8714016
- Thread: https://ratatoskr.run/linux-arm-kernel/2015/04/4478030/t.md

```text
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,
> 
```