[CRIU] [PATCH 1/9] parasite: Make parasite arguments variable size

[Pavel Emelyanov]

On 03/01/2013 09:31 PM, Douglas, William wrote:
> On Fri, Mar 1, 2013 at 8:02 AM, Pavel Emelyanov <xemul at parallels.com> wrote:
>> Sometimes we don't know the exact amount of data we would want
>> to send to parasite via args area (e.g. -- while draining fds).
>>
>> Fix this, by moving the args area behind the parasite blob and
>> mmap-ing it with the run-time calculated size.
>>
>> Signed-off-by: Pavel Emelyanov <xemul at parallels.com>
>>
>> ---
>>  arch/arm/parasite-head.S   |  2 --
>>  arch/x86/parasite-head.S   |  3 ---
>>  include/parasite-syscall.h |  1 +
>>  include/parasite.h         |  2 +-
>>  parasite-syscall.c         | 12 +++++++++---
>>  pie/gen-offsets.sh         |  2 +-
>>  pie/pie.lds.S.in           |  2 ++
>>  7 files changed, 14 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/arm/parasite-head.S b/arch/arm/parasite-head.S
>> index b4bffe6..74fd4cb 100644
>> --- a/arch/arm/parasite-head.S
>> +++ b/arch/arm/parasite-head.S
>> @@ -13,8 +13,6 @@ ENTRY(__export_parasite_head_start)
>>  __export_parasite_cmd:
>>         .long 0
>>  __export_parasite_args:
>> -       .long 0
>> -       .space PARASITE_ARG_SIZE,0
>>         .space PARASITE_STACK_SIZE,0
>>
>>          .space 228, 0
>> diff --git a/arch/x86/parasite-head.S b/arch/x86/parasite-head.S
>> index 289672c..0b62750 100644
>> --- a/arch/x86/parasite-head.S
>> +++ b/arch/x86/parasite-head.S
>> @@ -15,9 +15,6 @@ ENTRY(__export_parasite_head_start)
>>         .align 8
>>  __export_parasite_cmd:
>>         .long 0
>> -__export_parasite_args:
>> -       .long 0
>> -       .space PARASITE_ARG_SIZE,0
>>         .space PARASITE_STACK_SIZE,0
>>  __export_parasite_stack:
>>         .long 0
>> diff --git a/include/parasite-syscall.h b/include/parasite-syscall.h
>> index 2f32d03..ee5743e 100644
>> --- a/include/parasite-syscall.h
>> +++ b/include/parasite-syscall.h
>> @@ -19,6 +19,7 @@ struct parasite_ctl {
>>
>>         unsigned int            *addr_cmd;                              /* addr for command */
>>         void                    *addr_args;                             /* address for arguments */
>> +       unsigned long           args_size;
>>         int                     tsock;                                  /* transport socket for transfering fds */
>>  };
>>
>> diff --git a/include/parasite.h b/include/parasite.h
>> index 5d5b8df..66a559e 100644
>> --- a/include/parasite.h
>> +++ b/include/parasite.h
>> @@ -2,7 +2,7 @@
>>  #define __CR_PARASITE_H__
>>
>>  #define PARASITE_STACK_SIZE    (16 << 10)
>> -#define PARASITE_ARG_SIZE      8196
>> +#define PARASITE_ARG_SIZE_MIN  ( 1 << 13)
>>
>>  #define PARASITE_MAX_SIZE      (64 << 10)
>>
>> diff --git a/parasite-syscall.c b/parasite-syscall.c
>> index 6cc6283..03b5546 100644
>> --- a/parasite-syscall.c
>> +++ b/parasite-syscall.c
>> @@ -184,12 +184,12 @@ err:
>>
>>  static void *parasite_args_s(struct parasite_ctl *ctl, int args_size)
>>  {
>> -       BUG_ON(args_size > PARASITE_ARG_SIZE);
>> +       BUG_ON(args_size > ctl->args_size);
>>         return ctl->addr_args;
>>  }
>>
>>  #define parasite_args(ctl, type) ({                            \
>> -               BUILD_BUG_ON(sizeof(type) > PARASITE_ARG_SIZE); \
>> +               BUILD_BUG_ON(sizeof(type) > PARASITE_ARG_SIZE_MIN);\
> 
> This check makes me wonder if MIN is the correct description here.
> Isn't this a MAX check instead?

What I mean here is -- the size of the args area should be _not_ _less_
than the size of an object we're about to put there. And since the area
is _at_ _least_ ARG_SIZE_MIN butes, presumably this BUG_ON is correct.

> .
>