Re: [PATCH-v3] [SPARC] Add a workaround for the LEON3FT store-store errata

[Sebastian Huber <sebastian.huber@embedded-brains.de>]

On 29/06/17 18:05, David Miller wrote:

> From: Daniel Cederman <cederman@gaisler.com>
> Date: Thu, 29 Jun 2017 17:15:43 +0200
>
>>> I'm not thrilled with this, it's undocumented, the other workaround
>>> don't have
>>> it and I don't think that we really need it.
>> The B2BST errata workaround requires more changes to assembler
>> routines commonly used by operating systems, such as for example
>> register window handling, than what the UT699 workaround needed. It
>> would be nice to have a way to only enable these modification when the
>> -mfix- flag is used. The alternative would be to provide a define
>> directly on the compiler command line in conjunction with -mfix
>> flag. But if more changes are required later on it would be good to
>> have the define more closely tied to the flag to minimize the number
>> of changes to Makefiles and etc.
> Personally, I have never seen compiler based CPP defines as ever being
> useful for tailoring OS assembler code.  Ever.
>
> In most cases you will want to support several families of CPUs and
> therefore sort out the individual cpu support assembler routines
> internally in the kernel sources.

This depends on the operating system you use. For some  embedded systems 
where the application and the operating system are one executable it is 
quite common to use compiler provided defines in assembly code.

For example:

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=blob;f=newlib/libc/machine/arm/memcpy-armv7a.S;h=cd7962e075a30cb90ec073d77b177c3536429b9b;hb=HEAD

For a software development kit, the run-time libraries are built for a 
set of multilibs. Each assembler file may use multilib specific compiler 
defines, e.g. floating point unit present or not, errata XYZ present or 
not, etc.

-- 
Sebastian Huber, embedded brains GmbH

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