On 05/28/2015 05:58 PM, Will Deacon wrote:
On Thu, May 28, 2015 at 07:08:42AM +0100, Li Bin wrote:
quoted
On 2015/4/24 17:27, Jiri Kosina wrote:
quoted
On Fri, 24 Apr 2015, AKASHI Takahiro wrote:
quoted
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