[CRIU] Re: [PATCH v2] parasite-syscall: some cleanup

[Kinsbursky Stanislav]

21.02.2012 20:47, Cyrill Gorcunov пишет:
> On Tue, Feb 21, 2012 at 07:19:06PM +0300, Kinsbursky Stanislav wrote:
>> v2: command is set prior to parasite_execute() call now
>>
>> Removed redundant on-stack variables typeof parasite_status_t and memcpy
>> between them and parasite_ctl->addr_args object. Ando a lot of cleanup done
>> around.
>>
>> Signed-off-by: Stanislav Kinsbursky<skinsbursky at openvz.org>
>> ---
> I thought it'll be a good idea, but after looking into final code
> I fear it's not.
>
> Lets clean it up step-by-step (I'm enumerating what we have now
> and some ideas so we would choose ones which are suitable for us)
>
> 1) Every parasite argument passed must have a header with
>
> 	parasite_status_t       status;
>
>     on top, where the parasite will write the result of operations
>     on return (if there some code where we do not write the result
>     I think we should add it).

There are few parasite commands, which doesn't use this arguments at all. What 
about them?
But all others, which use - have status on top (if I'm not mistaken).

> 2) If parasite finished without error we should use some macro such
>     as say
>
> #define SET_PARASITE_STATUS_SUCCESS(st)			\
> 	do {						\
> 		(st)->ret	= 0,			\
> 		(st)->sys_ret	= 0,			\
> 		(st)->line	= __LINE__;		\
> 	} while (0)
>

I had this idea. But it's useless without implementing of passing arguments in 
every command.

> 3) Parasite alway should pick up arguments. Explicitly. If there
>     a command which requires no arguments -- we must zap arguments space with
>     some predefined poisoned values, so we will be able to catch cases
>     when parasite is called with some command but for some reason caller
>     forgot to pass new arguments.
>

1) What "pick up" means in this context?
2) No objections about poisoning before call. But I don't like on-stack variable 
copying. Let's use final destination instead.

-- 
Best regards,
Stanislav Kinsbursky