netdev - Re: [PATCH][v4] uprobes/x86: emulate push insns for uprobe on x86

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Message-ID: <03f91999-10b4-251f-aa9e-07de5ca096d2@fb.com>
Date:   Mon, 27 Nov 2017 10:06:16 -0800
From:   Yonghong Song <yhs@...com>
To:     Oleg Nesterov <oleg@...hat.com>, <mingo@...nel.org>,
        <peterz@...radead.org>
CC:     <tglx@...utronix.de>, <linux-kernel@...r.kernel.org>,
        <x86@...nel.org>, <netdev@...r.kernel.org>, <ast@...com>,
        <kernel-team@...com>
Subject: Re: [PATCH][v4] uprobes/x86: emulate push insns for uprobe on x86

Hi, Ingo and Peter,

This patch has been reviewed by Oleg Nesterov. Could you
take a look and help merge it upstream?

Thanks!

Yonghong


On 11/20/17 10:25 AM, Yonghong Song wrote:
> 
> 
> On 11/20/17 8:41 AM, Oleg Nesterov wrote:
>> On 11/17, Yonghong Song wrote:
>>>
>>> On 11/17/17 9:25 AM, Oleg Nesterov wrote:
>>>> On 11/15, Yonghong Song wrote:
>>>>>
>>>>> v3 -> v4:
>>>>>    . Revert most of v3 change as 32bit emulation is not really working
>>>>>      on x86_64 platform as among other issues, function 
>>>>> emulate_push_stack()
>>>>>      needs to account for 32bit app on 64bit platform.
>>>>>      A separate effort is ongoing to address this issue.
>>>>
>>>> Reviewed-by: Oleg Nesterov <oleg@...hat.com>
>>>>
>>>>
>>>>
>>>> Please test your patch with the fix below, in this particular case the
>>>> TIF_IA32 check should be fine. Although this is not what we really 
>>>> want,
>>>> we should probably use user_64bit_mode(regs) which checks ->cs. But 
>>>> this
>>>> needs more changes and doesn't solve other problems (get_unmapped_area)
>>>> so I still can't decide what should we do right now...
>>>
>>> I tested the below change with my patch. On x86_64, both 64bit and 32bit
>>> program can be uprobe emulated properly.
>>
>> Good, so your patch is fine.
> 
> Thanks!
> 
>>
>>> On x86_32, however, there is a
>>> compilation error like below:
>>
>> Yes, yes, when I said "in this particular case" I meant x86_64 system 
>> only.
>>
>> Sorry for confusion, I asked you to test this additional change just to
>> ensure that we didn't miss something and your patch has no problems with
>> 32bit tasks on 64bit system, except those we need to fix anyway.
> 
> Understood. I actually tried a little to see whether I could have a 
> simple way to fix 32bit compilation error without using ugly "#ifdef 
> CONFIG_X86_64". Maybe is_64bit_mm is a good choice. But we could defer 
> this until you have a comprehensive fix for 32bit app uprobe on 64bit 
> systems as there are multiple issues for this.
> 
>>
>> Oleg.
>>