[lkml]   [2017]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] x86/selftests: add clobbers for int80 on x86_64
On 02/10/2017 07:45 PM, Andy Lutomirski wrote:
> On Fri, Feb 10, 2017 at 8:28 AM, Dmitry Safonov <> wrote:
>> On 02/10/2017 07:13 PM, Andy Lutomirski wrote:
>>> On Fri, Feb 10, 2017 at 3:52 AM, Dmitry Safonov <>
>>> wrote:
>>>> Kernel erases R8..R11 registers prior returning to userspace
>>>> from int80:
>>>> GCC can reuse this registers and doesn't expect them to change
>>>> during syscall invocation. I met this kind of bug in CRIU once
>>>> gcc 6.1 and clang stored local variables in those registers
>>>> and the kernel zerofied them during syscall:
>>>> By that reason I suggest to add those registers to clobbers
>>>> in selftests.
>>> Seems reasonable, but presumably INT80_CLOBBERS should be defined the
>>> same way in all the tests. IOW, if the "flags" clobber is actually
>>> needed, it should be "flags", INT80_CLOBBERS (possibly without the
>>> comma if it's problematic).
>> Well, that was my initial attempt: I've defined it as:
>> +# define INT80_CLOBBERS , "r8", "r9", "r10", "r11"
>> But that hanging comma looks awful, so I added "flags" there.
>> And if I do define it without coma and leave it in asm statement,
>> 32-bit version would be unhappy.
>> So, I found that it's easier to define it with flags included.
> Woudl the right answer be to get rid of "flags" in the test where it
> appears? I'm not sure it's needed in the first place.

I think it can live without it.
But I didn't want to change it in the same patch and wasn't sure if I
fail to see the reason for it.
So, I'll resend with flags removing, thanks.


 \ /
  Last update: 2017-02-10 19:55    [W:0.225 / U:0.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site