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Re: [RFC] Kernel livepatching support in GCC


On 05/28/2015 01:39 AM, Maxim Kuvyrkov wrote:
> Hi,
> 
> Akashi-san and I have been discussing required GCC changes to make kernel's livepatching work for AArch64 and other architectures.  At the moment livepatching is supported for x86[_64] using the following options: "-pg -mfentry -mrecord-mcount -mnop-mcount" which is geek-speak for "please add several NOPs at the very beginning of each function, and make a section with addresses of all those NOP pads".

FYI, there is also the darwin/rs6000 -mfix-and-continue support, which
adds 5 nops to the prologue.  This was a part of a gdb feature, to allow
one to load a fixed function into a binary inside the debugger, and then
continue executing with the fixed code.  It sounds like your kernel
feature is doing something very similar.  If you are making this a
generic feature, then maybe the darwin/rs6000 -mfix-and-continue support
can be merged with it somehow.

Jim


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