Messages in this thread | | | Date | Thu, 28 May 2015 18:58:22 +0900 | From | AKASHI Takahiro <> | Subject | Re: [RFC 0/4] arm64: add livepatch support |
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On 05/28/2015 05:58 PM, Will Deacon wrote: > On Thu, May 28, 2015 at 07:08:42AM +0100, Li Bin wrote: >> 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 > > Just for the avoidance of confusion, this looks like a function with > a live parameter in x0, which explains the str to the stack and the > juggling of x30 into x0. I don't think there's necessarily a golden > template for the prologue code.
We just started the discussion about gcc, -mfentry vs. a more generic option that I mentioned in: http://lists.infradead.org/pipermail/linux-arm-kernel/2015-May/346632.html on gcc's devel ML.
-Takahiro AKASHI
> Will >
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