linux-kernel - Re: [Xen-devel] [PATCH 4/4] xen: use generated hypercall symbols in arch/x86/xen/xen-head.S

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Date:	Tue, 16 Dec 2014 12:20:04 +0100
From:	Juergen Gross <jgross@...e.com>
To:	David Vrabel <david.vrabel@...rix.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	xen-devel@...ts.xensource.com, konrad.wilk@...cle.com,
	boris.ostrovsky@...cle.com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, mmarek@...e.cz, linux-kbuild@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH 4/4] xen: use generated hypercall symbols
 in arch/x86/xen/xen-head.S

On 12/16/2014 11:24 AM, David Vrabel wrote:
> On 16/12/14 05:55, Juergen Gross wrote:
>> On 12/15/2014 01:05 PM, David Vrabel wrote:
>>> On 11/12/14 18:04, Juergen Gross wrote:
>>>> Instead of manually list each hypercall in arch/x86/xen/xen-head.S
>>>> use the auto generated symbol list.
>>>>
>>>> This also corrects the wrong address of xen_hypercall_mca which was
>>>> located 32 bytes higher than it should.
>>>>
>>>> Symbol addresses have been verified to match the correct ones via
>>>> objdump output.
>>> [...]
>>>> +
>>>> +#define HYPERCALL(n) \
>>>> +    .equ xen_hypercall_##n, hypercall_page + __HYPERVISOR_##n * 32; \
>>>> +    .type xen_hypercall_##n, function; .size xen_hypercall_##n, 32
>>>> +#include <asm/xen-hypercalls.h>
>>>> +#undef HYPERCALL
>>>
>>> The gas manual[1] suggests the syntax you've used for .type is invalid
>>> and suggest using .type <name>, STT_FUNC
>>
>> Really? In the link below I see:
>>
>> The types supported are:
>>
>> STT_FUNC
>> function
>>      Mark the symbol as being a function name.
>> ...
>>
>> So "function" seems to be okay.
>
>>>From the manual
>
>      The syntaxes supported are:
>
>         .type <name> STT_<TYPE_IN_UPPER_CASE>
>         .type <name>,#<type>
>         .type <name>,@<type>
>         .type <name>,%<type>
>         .type <name>,"<type>"
>
> And
>
>      The first variant will be accepted by the GNU assembler on all
>      architectures...

grepping through the x86 assembler sources

.type <name>,@function

seems to be the preferred syntax (100%). I think I'll switch to that.


Juergen

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