Re: [Qemu-devel] [PATCH] linux-user: fix signal() syscall on x86_64

[Wirth, Allan]

On 7/7/16, 3:09 PM, "Laurent Vivier" <address@hidden> wrote:

>
>
>Le 07/07/2016 à 21:04, Wirth, Allan a écrit :
>> 
>> 
>> On 7/7/16, 3:02 PM, "Laurent Vivier" <address@hidden> wrote:
>> 
>>>
>>>
>>> Le 07/07/2016 à 20:49, Riku Voipio a écrit :
>>>> On Sat, Jul 02, 2016 at 09:12:09PM +0100, Peter Maydell wrote:
>>>>> On 2 July 2016 at 17:41, Laurent Vivier <address@hidden> wrote:
>>>>>> Sadly, this can't work:
>>>>>>
>>>>>> sparc/sparc64/cris use sys_select for NR_select AND NR_newselect.
>>>>>
>>>>>> Not sure all is correct, but it's what I've found:
>>>>>>
>>>>>>             | __NR_select    | __NR__newselect
>>>>>> ------------+----------------+-----------------+
>>>>>> arm         | sys_old_select | sys_select      |
>>>>>> ------------+----------------+-----------------+
>>>>>> aarch64     | sys_select     |        -        |
>>>>>> ------------+----------------+-----------------+
>>>>>> alpha       | sys_select     |        -        |
>>>>>> ------------+----------------+-----------------+
>>>>>> cris        | sys_select     | sys_select      |
>>>>>> ------------+----------------+-----------------+
>>>>>> m68k        | sys_old_select | sys_select      |
>>>>>> ------------+----------------+-----------------+
>>>>>> microblaze  | sys_old_select | sys_select      |
>>>>>> ------------+----------------+-----------------+
>>>>>> mips        | sys_old_select | sys_select      |
>>>>>> ------------+----------------+-----------------+
>>>>>> mips64      | sys_select     |        -        |
>>>>>> ------------+----------------+-----------------+
>>>>>> openrisc    | sys_select     |        -        |
>>>>>> ------------+----------------+-----------------+
>>>>>> ppc         | sys_old_select | sys_select      |
>>>>>> ------------+----------------+-----------------+
>>>>>> s390x       | sys_select     |        -        |
>>>>>> ------------+----------------+-----------------+
>>>>>> sh4         | sys_old_select | sys_select      |
>>>>>> ------------+----------------+-----------------+
>>>>>> sparc       | sys_select     | sys_select      |
>>>>>> ------------+----------------+-----------------+
>>>>>> sparc64     | sys_select     | sys_select      |
>>>>>> ------------+----------------+-----------------+
>>>>>> tilegx      | sys_select     |        -        |
>>>>>> ------------+----------------+-----------------+
>>>>>> unicore32   | sys_select     |        -        |
>>>>>> ------------+----------------+-----------------+
>>>>>> x86_64      | sys_select     |        -        |
>>>>>> ------------+----------------+-----------------+
>>>>>> i386        | sys_old_select | sys_select      |
>>>>>> ------------+----------------+-----------------+
>>>>>
>>>>> Hmm. Looking at current Linux git master, I get
>>>>> slightly different results. The only architectures which
>>>>> define __ARCH_WANT_SYS_OLD_SELECT are:
>>>>>  arm, m68k, mn10300, x86
>>>>> and no others use sys_old_select.
>>>>>
>>>>> So I think we have the following behaviours:
>>>>>
>>>>> (1) Define neither NR_select nor NR__newselect
>>>>>  (and use pselect6 syscall for select):
>>>>>  aarch64, openrisc, tilegx, unicore32, presumably any future arch
>>>>>
>>>>> (2) only define NR__newselect, it is new select:
>>>>>  mips, mips64, sh, s390
>>>>>
>>>>> (3) Only define NR_select, want that to be new select:
>>>>>  alpha, x86_64, s390x
>>>>>
>>>>> (4) NR__newselect is new select, NR_select is old_select:
>>>>>  i386, m68k, arm if kernel is not CONFIG_AEABI
>>>>>
>>>>> (5) NR__newselect is new select, NR_select is defined but
>>>>>  if called returns ENOSYS:
>>>>>  microblaze, arm if CONFIG_AEABI, ppc64
>>>>>
>>>>> (6) NR__newselect is new select, NR_select is a bonkers custom
>>>>>  thing that tries to autodetect the calling convention:
>>>>> http://lxr.free-electrons.com/source/arch/powerpc/kernel/syscalls.c#L86
>>>>>  ppc32 (but only native 32-bit; 32-bit compat support
>>>>>  on a ppc64 kernel is category 5, so I vote for ignoring
>>>>>  this weirdness and calling ppc category 5)
>>>>>
>>>>> (7) NR_select and NR__newselect are different numbers
>>>>>  but both are new select:
>>>>>  cris, sparc, sparc64
>>>>>
>>>>> which is a pretty confusing mess, but I think it equates to:
>>>>> (0) if defined, NR__newselect is always new select
>>>>> (1) if NR_select is defined, the choices are:
>>>>>  (a) NR_select is old_select:
>>>>>    i386, m68k, arm
>>>>>  (b) NR_select is defined but should ENOSYS:
>>>>>    microblaze, ppc
>>>>>  (c) NR_select defined and is new select:
>>>>>    everything else (alpha, x86-64, s390x, cris, sparc, sparc64)
>>>>>
>>>>> and I think we should handle that by having the code in syscall.c
>>>>> be something like:
>>>>>
>>>>> #ifdef TARGET_NR_select
>>>>>     case TARGET_NR_select:
>>>>> #if defined(TARGET_WANT_NI_OLD_SELECT)
>>>>>         /* some architectures used to have old_select here
>>>>>          * but now ENOSYS it.
>>>>>          */
>>>>>         ret = -TARGET_ENOSYS;
>>>>>         break;
>>>>> #elif defined(TARGET_WANT_OLD_SYS_SELECT)
>>>>>         /* code for old select here; maybe factored out to
>>>>>          * its own function: ret = do_old_select() ?
>>>>>          */
>>>>> #else
>>>>>         /* select is new style select */
>>>>>         ret = do_select(...);
>>>>> #endif
>>>>> #endif
>>>>
>>>> I agree, this seems to be the best way to fix select properly.
>>>
>>> Ok, if no one is already working on that, I'm going to send a patch
>>> according to Peter's comments.
>>>
>>> Laurent
>> 
>> I was hoping to, but I do not think that I will get around to it anytime 
>> soon.
>
>If I provide a patch, could you test it for your test case?
>
>Thanks,
>Laurent

Definitely I would be happy to. I would be very grateful if you did.

Thanks,
Allan