linux-kernel - Re: [PATCH v8 01/28] linkage: new macros for assembler symbols

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Date:   Thu, 29 Aug 2019 12:48:24 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     Borislav Petkov <bp@...en8.de>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Ingo Molnar <mingo@...nel.org>, jpoimboe@...hat.com,
        Juergen Gross <jgross@...e.com>,
        Len Brown <len.brown@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-pm@...r.kernel.org, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v8 01/28] linkage: new macros for assembler symbols

On 12. 08. 19, 19:06, Borislav Petkov wrote:
>> +  Again, every ``SYM_CODE_START*`` **shall** be coupled by ``SYM_CODE_END``.
> 
> Btw, this coupling: I haven't gone through the whole patchset but do we
> have automatic checking which makes sure a starting macro is coupled
> with the correct ending macro?

I do, but it's not part of this series. It's a pinch of link-time magic,
but it works reliably (see e.g. 1cbec37b3f9c). I will post it if/after
this gets merged. There were other approaches proposed in the past too
-- using objtool for that (not implemented).

>> +Overriding Macros
>> +~~~~~~~~~~~~~~~~~
>> +Architecture can also override any of the macros in their own
> 
> "Other architectures... "

Not only "other", x86 can override the types if need be too.

>> +``asm/linkage.h``, including macros specifying the type of a symbol
>> +(``SYM_T_FUNC``, ``SYM_T_OBJECT``, and ``SYM_T_NONE``).  As every macro
>> +described in this file is surrounded by ``#ifdef`` + ``#endif``, it is enough
>> +to define the macros differently in the aforementioned architecture-dependent
>> +header.

thanks,
-- 
js
suse labs