Re: [PATCH] cleanup vmalloc_fault for 64bit kernel

[Wu Fei <at.wufei@gmail.com>]

On Wed, Sep 09, 2009 at 08:35:26AM -0700, David Daney wrote:
> Wu Fei wrote:
>> 64bit kernel won't arrive vmalloc_fault, it's not necessary or possible
>> to copy the page table from init_mm.pgd. swapper_pg_dir, module_pg_dir
>> and the process's pgd represent the different virtual address area, and
>> the tlb exception handler accesses the suitable one directly.
>>
>> Signed-off-by: Wu Fei <at.wufei@gmail.com>
>> ---
>>  arch/mips/mm/fault.c |    6 +++---
>>  1 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c
>> index f956ecb..e769789 100644
>> --- a/arch/mips/mm/fault.c
>> +++ b/arch/mips/mm/fault.c
>> @@ -58,11 +58,9 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
>>  	 * only copy the information from the master page table,
>>  	 * nothing more.
>>  	 */
>> +#ifdef CONFIG_32BIT
>>  	if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
>>  		goto vmalloc_fault;
>> -#ifdef MODULE_START
>> -	if (unlikely(address >= MODULE_START && address < MODULE_END))
>> -		goto vmalloc_fault;
>>  #endif
>>  
>
> That is not correct.  You can still arrive at do_page_fault() from  
> faults in the vmalloc range.  We need to go directly to the panic code  

That's not a real problem, if do_page_fault() from faults in the vmalloc
range, find_vma() returns NULL and eventually it will arrive no_context.
But anyway, I think your patch is better and readable.

Thanks,
Wufei.

> as I did in my patch: Message-Id:  
> <1251931654-21268-1-git-send-email-ddaney@caviumnetworks.com>
>
> AKA: [PATCH] MIPS: Don't corrupt page tables on vmalloc fault.
>
>
>
>>  	/*
>> @@ -203,6 +201,7 @@ do_sigbus:
>>  	force_sig_info(SIGBUS, &info, tsk);
>>   	return;
>> +#ifdef CONFIG_32BIT
>>  vmalloc_fault:
>>  	{
>>  		/*
>> @@ -241,4 +240,5 @@ vmalloc_fault:
>>  			goto no_context;
>>  		return;
>>  	}
>> +#endif
>>  }
>