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SubjectRe: [RFC 5/8] x86: refcount: prevent gcc distortions
>>> On 16.05.18 at 18:44, <namit@vmware.com> wrote:
> Jan Beulich <JBeulich@suse.com> wrote:
>>>>> On 15.05.18 at 16:11, <namit@vmware.com> wrote:
>>> --- a/arch/x86/include/asm/refcount.h
>>> +++ b/arch/x86/include/asm/refcount.h
>>> @@ -14,34 +14,43 @@
>>> * central refcount exception. The fixup address for the exception points
>>> * back to the regular execution flow in .text.
>>> */
>>> -#define _REFCOUNT_EXCEPTION \
>>> - ".pushsection .text..refcount\n" \
>>> - "111:\tlea %[counter], %%" _ASM_CX "\n" \
>>> - "112:\t" ASM_UD2 "\n" \
>>> - ASM_UNREACHABLE \
>>> - ".popsection\n" \
>>> - "113:\n" \
>>> +
>>> +asm ("\n"
>>> + ".macro __REFCOUNT_EXCEPTION counter:vararg\n\t"
>>> + ".pushsection .text..refcount\n"
>>> + "111:\tlea \\counter, %" _ASM_CX "\n"
>>> + "112:\t" ASM_UD2 "\n\t"
>>> + ASM_UNREACHABLE
>>> + ".popsection\n\t"
>>> + "113:\n"
>>> _ASM_EXTABLE_REFCOUNT(112b, 113b)
>>> + ".endm");
>>
>> A few comments on assembly code formatting - while gas at present is
>> relatively lax in this regard, I wouldn't exclude that there might be a
>> more strict mode in the future, and that such a mode might eventually
>> become the default. Furthermore these formatting aspects affect
>> readability of the assembly produced, should anyone ever find a need
>> to look at it (perhaps because of some breakage) - I certainly do every
>> once in a while.
>>
>> Labels should be placed without any indentation (but of course there
>> may be more than one on a line, in which case subsequent ones may
>> of course be arbitrarily indented). Instructions and directives, otoh,
>> should be placed with at least a single tab or space of indentation
>> (unless preceded by a label, in which case the extra white space still
>> helps readability).
>
> Writing these patches, I looked at the generated assembly, and there did not
> appear to be a standard. IIRC, .pushsection directives were not always
> inlined. I will fix it according to your comments.

Right, I should have made explicit that there's no consistency at all in
pre-existing code. I merely think the issue shouldn't be made worse.

Jan


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