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 10:24:45 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Juergen Gross <jgross@...e.com>,
	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 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...

David
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