Re: [microblaze-uclinux] Re: microblaze syscall list

[Michal Simek <monstr@xxxxxxxxx>]

Hi John,

I think Steve and John L read git@xxxxxxxxxxx I will cc you.
I don't know who remove it from cc list.

M



> Michal,
> 
> Can you please cc: me, steve N and John L on this stuff as requested?
> 
> Thanks,
> 
> John
> 
> Michal Simek wrote:
>> Hi Arnd,
>>
>>>> I would like to fix syscalls in Microblaze repo. Can you give me a
>>>> hint how to
>>>> do it?
>>> I think we need to do it on a case-by-case basis, best here on the
>>> linux-arch mailing list. I'm sure there are some controversial ones,
>>> but most should be pretty clear.
>>>  
>>>> I look at Blackfin arch and I compared files with microblaze. There
>>>> are some
>>>> differences but not so much.
>>>> Can you tell me how to test it which syscall is necessary for platform.
>>>> I have never found any documentation about.
>>> Hopefully we can get to this kind of documentation by the end of this
>>> discussion. scripts/checksyscalls.sh is some part of the documentation,
>>> and we can refine that.
>> :-)
>>
>>> Maybe we can even have an asm-generic/unistd.h that defines all the
>>> still relevant syscalls, plus a per-architecture range that you can
>>> use for microblaze-specific calls in your own unistd.h.
>>
>> That will be really useful. Good idea.
>>
>>>> In my syscall_table.S (on some arch in entry.S) is one big jump
>>>> table with
>>>> reference to syscalls. In unistd.h is definition.
>>>>
>>>> Is there any convention which syscalls are use for all archs and
>>>> which are
>>>> architecture specific?
>>> Not really. There are very few syscalls that are needed only on certain
>>> architectures. The more common case is that a syscall has been replaced
>>> by a more complex interface, and a new architecture only needs one of
>>> the
>>> two, while older architectures still need both.
>>>
>>> Let me just comment on your syscall table as it is today:
>>>
>>>> ENTRY(sys_call_table)
>>>>     .long sys_restart_syscall    /* 0 - old "setup()" system call,
>>>>                      * used for restarting */
>>> The comment is irrelevant and misleading -- microblaze never had
>>> sys_setup.
>>
>> I removed this comment.
>>
>>>>     .long sys_exit
>>>>     .long sys_ni_syscall        /* was fork */
>>> it might be useful to renumber your calls once all the irrelevant ones
>>> have been removed, so you can get rid of all the sys_ni_syscalls here.
>>
>> I'll delete all sys_ni_syscall from syscall_table.S and I'll remove it
>> from
>> unistd.h too. I hope I'll keep the same call numbers.
>>
>>>>     .long sys_read
>>>>     .long sys_write
>>>>     .long sys_open            /* 5 */
>>> Since we have all the new sys_*at calls like openat, we don't really
>>> need the old versions any more. The kernel implementation of sys_open
>>> basically calls openat. You could do the same in libc instead.
>>> Don't know if that's worth it though, opinions?
>>
>> I looked at it and there are the different arguments for open and openat
>> syscalls. Implementation is almost the same. I keep it now.
>>
>>>>     .long sys_close
>>>>     .long sys_waitpid
>>> waitpid and wait4 can be replaced with waitid
>>
>> Can I keep number of syscall(unistd.h) and only add reference to
>> waitid in
>> syscall_table? or just remove?
>>
>>>>     .long sys_creat
>>>>     .long sys_link
>>>>     .long sys_unlink        /* 10 */
>>>>     .long sys_execve_wrapper
>>> having an execve_wrapper instead of execve looks like a strange
>>> convention,
>>> though I guess you had a good reason for it, could you explain?
>>>
>>> This one looks architecture specific, so you may want to rename it
>>> microblaze_execve_wrapper instead of sys_execve_wrapper.
>>
>> I looked at it and the same of style is used in arm
>> (arch/arm/kernel/entry-common.S) and some others arch. This wrapper
>> only set one
>> parameter to correct pointer to stack.
>>
>> I'll comment the rest later. I need time to look at it.
>>
>> Thanks for your big help. I really appreciate this.
>>
>> Michal
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> 
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