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SubjectRe: [RFC PATCH 3/3] objtool/mcount: Add powerpc specific functions
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Hi Peter, Hi Josh

Le 18/03/2022 à 13:26, Peter Zijlstra a écrit :
> On Fri, Mar 18, 2022 at 04:21:40PM +0530, Sathvika Vasireddy wrote:
>> This patch adds powerpc specific functions required for
>> 'objtool mcount' to work, and enables mcount for ppc.
>
> I would love to see more objtool enablement for Power :-)
>
>

I'm also very happy someone started to look at it.

I thought it would be more difficult to get it work on powerpc.

Iml looking forward to being able to use it and implement INLINE STATIC
CALLs on PPC32 to start with.

I'm wondering what are the plans on your side and what we should wait
for and what we could start with.

I could do the same as done by Sathvika for static calls, in extenso get
it out of check.c into a standalone feature. On the other hand I
understood that Josh is also working at making the different features of
objtool independant, so should I wait for that ? Any idea of when it
comes out ?

Second point is the endianess and 32/64 selection, especially when
crossbuilding. There is already some stuff regarding endianess based on
bswap_if_needed() but that's based on constant selection at build time
and I couldn't find an easy way to set it conditionaly based on the
target being built.

Regarding 32/64 selection, there is almost nothing, it's based on using
type 'long' which means that at the time being the target and the build
platform must both be 32 bits or 64 bits.

For both cases (endianess and 32/64) I think the solution should
probably be to start with the fileformat of the object file being
reworked by objtool.

What are current works in progress on objtool ? Should I wait Josh's
changes before starting looking at all this ? Should I wait for anything
else ?

Christophe
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