linux-kernel - Re: [PATCH 08/16] mm/unicore32: use vm_flags

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Message-ID: <4F71570D.4060507@openvz.org>
Date:	Tue, 27 Mar 2012 09:58:37 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Guan Xuetao <gxt@...c.pku.edu.cn>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 08/16] mm/unicore32: use vm_flags_t for vma flags

Guan Xuetao wrote:
> On 03/21/2012 02:56 PM, Konstantin Khlebnikov wrote:
>> The same magic like in arm: assembler code wants to test VM_EXEC,
>> but for big-endian we should get upper word for this.
>>
>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@...nvz.org>
>> Cc: Guan Xuetao<gxt@...c.pku.edu.cn>
>> ---
>>    arch/unicore32/kernel/asm-offsets.c |    6 +++++-
>>    arch/unicore32/mm/fault.c           |    2 +-
>>    2 files changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/unicore32/kernel/asm-offsets.c b/arch/unicore32/kernel/asm-offsets.c
>> index ffcbe75..e3199b5 100644
>> --- a/arch/unicore32/kernel/asm-offsets.c
>> +++ b/arch/unicore32/kernel/asm-offsets.c
>> @@ -87,9 +87,13 @@ int main(void)
>>    	DEFINE(S_FRAME_SIZE,	sizeof(struct pt_regs));
>>    	BLANK();
>>    	DEFINE(VMA_VM_MM,	offsetof(struct vm_area_struct, vm_mm));
>> +#if defined(CONFIG_CPU_BIG_ENDIAN)&&   (NR_VMA_FLAGS>   32)
>> +	DEFINE(VMA_VM_FLAGS,	offsetof(struct vm_area_struct, vm_flags) + 4);
>> +#else
> CONFIG_CPU_BIG/LITTLE_ENDIAN is defined only in some archs, and not
> supported by unicore32.

Ok, I'll drop this in v2

>
>>    	DEFINE(VMA_VM_FLAGS,	offsetof(struct vm_area_struct, vm_flags));
>> +#endif
>>    	BLANK();
>> -	DEFINE(VM_EXEC,		VM_EXEC);
>> +	DEFINE(VM_EXEC,		(__force unsigned int)VM_EXEC);

> Is this check useful for asm-offsets.h?

this forced-typecast to make sparse happy, because  we use here only (int) part of vma->vm_flags.

>
>>    	BLANK();
>>    	DEFINE(PAGE_SZ,		PAGE_SIZE);
>>    	BLANK();
>> diff --git a/arch/unicore32/mm/fault.c b/arch/unicore32/mm/fault.c
>> index 283aa4b..9137996 100644
>> --- a/arch/unicore32/mm/fault.c
>> +++ b/arch/unicore32/mm/fault.c
>> @@ -158,7 +158,7 @@ void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
>>     */
>>    static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
>>    {
>> -	unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
>> +	vm_flags_t mask = VM_READ | VM_WRITE | VM_EXEC;
>
> I am confused  for the type of vm_flags in vm_area_struct being
> 'unsigned long',  not vm_flags_t.

Second patch in this patchset changes it.
vm_flags_t will be unsigned long or or unsigned long long depending on vma flags count.
But more likely it will be unsigned int, because I have another patchset in work,
which currently drop four bits in vm_flags, so we can postpone its expansion.

>
> Regards,
>
> Guan Xuetao
>
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