Re: [LTP] clone tests fails

Michal Simek
2010-01-07T14:13:38Z

Jiri Palecek wrote:
> Michal Simek napsal(a):
>> Jiri Palecek wrote:
>>> Serge E. Hallyn napsal(a):
>>>> Quoting Michal Simek (michal.simek@petalogix.com):
>>>>> Serge E. Hallyn wrote:
>>>>>> Quoting Michal Simek (michal.simek@petalogix.com):
>>>>>>> Hi Mike,
>>>>>>>
>>>>>>> I have one question about one your big patch
>>>>>>>
>>>>>>> http://git.kernel.org/?p=linux/kernel/git/galak/ltp.git;a=commitdiff;h=391dc18fe3271fbf2ca1864a5299f091c31e0018
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> My question is why you add -1 in lib/cloner.c:65
>>>>>>>
>>>>>>> + ret = clone(fn, (stack ? stack + stack_size - 1 : NULL),
>>>>>>> + clone_flags, arg);
>>>>>>>
>>>>>>> In previous code in clone testcases was nothing like this.
>>>>>>> What reason have you had to add it?
>>>>>>
>>>>>> Because the same thing was done in lots of places all over the
>>>>>> testsuite (and done wrong). This consolidates them all.
>>>>>
>>>>>
>>>>> I don't have anything against consolidation. I just want to know why
>>>>> there is that -1 which weren't in any clone testcases. Nothing more
>>>>> nothing less.
>>>>
>>>> ooooh. Because if we've done stack = malloc(stack_size), then
>>>> stack+stack_size is 1 above the the top of stack.
>>>
>>> If the value of the parameter is the stack pointer of the created
>>> thread, it shouldn't matter - the address should never be used (read
>>> or written).
>>>
>>> Michal, I suspect the failures you see are somehow related to
>>> alignment (that your architecture doesn't like odd addresses). Is that
>>> right? Under x86, the address gets aligned (so some of the space is
>>> unused).
>>
>> yes, alignment is problem. I need to subtract at least -4.
>>
>> As you can see below I am getting fault in kernel about task_size exceed.
>>
>> # ./clone01
>> kernel task_size exceed, 0xffffffff, 0xc0000000
>> Oops: Exception in kernel mode, sig: 11
>> Registers dump: mode=1
>> r1=CDC3FF50, r2=00000000, r3=000008A1, r4=FFFFFFFF
>> r5=00000000, r6=00000800, r7=CDC3FF68, r8=00000028
>> r9=481804AC, r10=00000000, r11=000045AA, r12=C00011C4
>> r13=00000000, r14=6B6B6B6B, r15=C00083F8, r16=6B6B6B6B
>> r17=6B6B6B6B, r18=00000000, r19=FFFFFFFF, r20=100074C8
>> r21=00000000, r22=100073CC, r23=00000000, r24=00000000
>> r25=1000C050, r26=00000001, r27=10005310, r28=10001060
>> r29=00000000, r30=00000000, r31=CDD4C358, rPC=C00011DC
>> msr=000045AA, ear=FFFFFFFF, esr=000000B2, fsr=10005310
>> clone01 1 TPASS : clone() returned 66
>
> I do not understand this dump fully, but couldn't it be just that your
> arch needs the 4 bytes of memory above what you pass as stack top
> (task_size exceeded should mean you accessed some address outside
> userspace)? Could you please test this by trying to run the tests with
> stack_size%4 != 0 (eg. pass PAGE_SIZE+1 to ltp_clone, subtract 1 in
> ltp_clone and so on).

It is just reaction on unaligned access. if is aligned then system has
no problem.

Thanks,
Michal

>
> Regards
> Jiri Palecek

--
Michal Simek, Ing. (M.Eng)
PetaLogix - Linux Solutions for a Reconfigurable World
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