Subject: Re: [vserver] A bug about system call on ARM
From: Herbert Poetzl <herbert@13thfloor.at>
Date: Sat, 1 Jun 2013 02:40:23 +0200

On Wed, May 29, 2013 at 01:28:42PM +0800, Wang, Yalin wrote:
> Hi  all,

> I am a new comer to this mailing list ,
> I am happy to join this community .

> I have a bug reported from our android phones which 
> is caused by the system call .
> It seems like kernel bugs from my view .

Hmm, how is that Linux-VServer related?
What kernel and Linux-VServer patch do you use?

Thanks,
Herbert

> Crash in  file  arch\arm\kernel\ entry-common.S

> #if defined(CONFIG_OABI_COMPAT)

>                         /*
>                         * If we have CONFIG_OABI_COMPAT then we need to look at the
swi
>                         * value to determine if it is an EABI or an old ABI call.
>                         */
> #ifdef CONFIG_ARM_THUMB
>                         tst                  r8, #PSR_T_BIT
>                         movne        r10, #0                                     
                                          @ no thumb OABI emulation
>                         ldreq            r10, [lr, #-4]                          
                                           @ get SWI instruction              // crash
at this instruction, when get SWI instruction
> #else
>                         ldr                  r10, [lr, #-4]                      
                                               @ get SWI instruction
>   A710(         and               ip, r10, #0x0f000000                           
                     @ check for SWI                                   )
>   A710(         teq                ip, #0x0f000000                               
                                                                                   
               )
>   A710(         bne               .Larm710bug                                    
                                                                                   
                )
> #endif
> #ifdef CONFIG_CPU_ENDIAN_BE8
>                         rev                 r10, r10                             
                        @ little endian instruction
> #endif



> Then reason why it will crash when get SWI instruction is maybe
> This page is clear to aged by kernel,
> But this MMU fault happpened in kernel,
> So the kernel do_page_fault function will not clear this page to young,
> So that  will crash .

> It should poll this page to make it present or the fault should be handled by fixup
section ,
> Anyway, this place should not crash by kernel .

> The kernel version I used  is  3.4.0
> I have add the kernel log and the call stack recoverd by trace32 tools
> Pls have a look at it .


> Thanks .


> Yalin.Wang
> Software Engineer
> OS Kernel&Graphics

> Sony Mobile Communications
> Tel: +86 10 5966 9819
> Phone: 18610323092
> Address: No.16 Guangshun South Street, Chaoyang, Beijing, P.R.C.

> sonymobile.com<http://sonymobile.com/>

> [cid:image001.jpg@01CE5C5F.6BD2AAE0]





Content-Description: stack.txt
> 	crash_notes_save_this_cpu(type = CRASH_NOTE_CRASHING, cpu = 1)
> 	update_crash_notes(?, ?, ?)
> 	notifier_call_chain(?, val = 0, v = 0xC0ECBE9C, nr_to_call = 5, nr_calls = 0x0)
> 	__atomic_notifier_call_chain(nh = 0xC0ECC29C, val = 0, v = 0xC0ECBE9C, nr_to_call
= -1, nr_calls = 0x0)
> 	atomic_notifier_call_chain(?, ?, ?)
> 	panic(fmt = 0xC098BC02)
> 	die(?, regs = 0xE0601F68, err = 23)
> 	__do_kernel_fault.part.8(mm = 0xC73E7DC0, addr = 1075872796, fsr = 23, regs = 0xE0601F68)
> 	do_page_fault(addr = 3342761408, fsr = 23, regs = 0x4020841C)
> 	do_DataAbort(addr = 1075872796, fsr = 23, regs = 0xE0601F68)
> 	__dabt_svc(asm)
> 	exception
> 	vector_swi(asm)
> 	ret_fast_syscall(asm)
> 	exception
> 	NUR:0xFFFF:0x40208420(asm)
> 	end of frame