[CRIU] [PATCH 2/2] cr-check: add compat_restore check

[Pavel Emelyanov]

On 01/10/2017 04:08 PM, Dmitry Safonov wrote:
> On 01/10/2017 04:06 PM, Dmitry Safonov wrote:
>> On 01/10/2017 03:34 PM, Pavel Emelyanov wrote:
>>> On 01/09/2017 07:59 PM, Dmitry Safonov wrote:
>>>> Initialy, I thought to name it "compat_restore", but after I've dropped
>>>> the second 32-bit parasite (which surely made compat code lesser and
>>>> easier), our parasite works in 64-bit in 32-bit task and ptrace()
>>>> for setting registers in this long-jumped situation will work correctly
>>>> only after v4.9 kernel. Maybe it can be work-arounded if needed,
>>>> but yet no compatible dump for pre-v4.9 kernels.
>>>>
>>>> Requested-by: Andrei Vagin <avagin at virtuozzo.com>
>>>> Signed-off-by: Dmitry Safonov <dsafonov at virtuozzo.com>
>>>> ---
>>>>  criu/cr-check.c | 10 ++++++++++
>>>>  1 file changed, 10 insertions(+)
>>>>
>>>> diff --git a/criu/cr-check.c b/criu/cr-check.c
>>>> index 60279e135dfa..94c5074557ce 100644
>>>> --- a/criu/cr-check.c
>>>> +++ b/criu/cr-check.c
>>>> @@ -48,6 +48,7 @@
>>>>  #include "libnetlink.h"
>>>>  #include "net.h"
>>>>  #include "linux/userfaultfd.h"
>>>> +#include "restorer.h"
>>>>
>>>>  static char *feature_name(int (*func)());
>>>>
>>>> @@ -1134,6 +1135,14 @@ static int check_loginuid(void)
>>>>      return 0;
>>>>  }
>>>>
>>>> +static int check_compat_cr(void)
>>>
>>> Call for this should also be added to cr_check()
>>
>> Hmm, and what about tun/userns/loginuid features?
>> Should them be also in cr_check()?
>> I don't completely get the policy why some are(not) there.
> 
> Tun is actually checked with other parameter.
> Should userns and loginuid also be in cr_check()?

Well, there are three things with cr-check.

1. Any kernel functionality that may be or may be not in the
   kernel should be checked with 'criu check' action. 

2. Depending on the how bad the functionality is required it 
   can be in one of 3 groups -- must have, optional and
   experimental.

3. Individual features can be added to --feature <name> checking
   if this is needed by zdtm

So as far as userns and loginuid are concerned -- if there's anything
in the kernel that is needed to dump OR restore one and that can be
in or out (e.g. appeared after 3.11) -- it should be in cr-check.

>>
>>>
>>>> +{
>>>> +    if (kdat_compat_sigreturn_test())
>>>> +        return 0;
>>>> +    pr_err("compat_cr is not supported. Requires kernel >= v4.9\n");
>>>> +    return -1;
>>>> +}
>>>> +
>>>>  struct feature_list {
>>>>      char *name;
>>>>      int (*func)();
>>>> @@ -1154,6 +1163,7 @@ static struct feature_list feature_list[] = {
>>>>      { "autofs", check_autofs },
>>>>      { "tcp_half_closed", check_tcp_halt_closed },
>>>>      { "lazy_pages", check_uffd },
>>>> +    { "compat_cr", check_compat_cr },
>>>>      { NULL, NULL },
>>>>  };
>>>>
>>>>
>>>
>>
>>
> 
>