Re: [PATCH v3 01/17] y2038: asm-generic: Extend sysvipc data structures

Arnd Bergmann
2018-04-19T15:20:26Z

On Thu, Apr 19, 2018 at 4:59 PM, Eric W. Biederman
<ebiederm@xmission.com> wrote:
> Arnd Bergmann <arnd@arndb.de> writes:
>>
>> struct msqid64_ds {
>> struct ipc64_perm msg_perm;
>> +#if __BITS_PER_LONG == 64
>> __kernel_time_t msg_stime; /* last msgsnd time */
>> -#if __BITS_PER_LONG != 64
>> - unsigned long __unused1;
>> -#endif
>> __kernel_time_t msg_rtime; /* last msgrcv time */
>> -#if __BITS_PER_LONG != 64
>> - unsigned long __unused2;
>> -#endif
>> __kernel_time_t msg_ctime; /* last change time */
>> -#if __BITS_PER_LONG != 64
>> - unsigned long __unused3;
>> +#else
>> + unsigned long msg_stime; /* last msgsnd time */
>> + unsigned long msg_stime_high;
>> + unsigned long msg_rtime; /* last msgrcv time */
>> + unsigned long msg_rtime_high;
>> + unsigned long msg_ctime; /* last change time */
>> + unsigned long msg_ctime_high;
>> #endif
>
> I suspect you want to use __kernel_ulong_t here instead of a raw
> unsigned long. If nothing else it seems inconsistent to use typedefs
> in one half of the structure and no typedefs in the other half.

Good catch, there is definitely something wrong here, but I think using
__kernel_ulong_t for all members would also be wrong, as that
still changes the layout on x32, which effectively is

struct msqid64_ds {
ipc64_perm msg_perm;
u64 msg_stime;
u32 __unused1;
/* 32 bit implict padding */
u64 msg_rtime;
u32 __unused2;
/* 32 bit implict padding */
u64 msg_ctime;
u32 __unused3;
/* 32 bit implict padding */
__kernel_pid_t shm_cpid; /* pid of creator */
__kernel_pid_t shm_lpid; /* pid of last operator */
....
};

The choices here would be to either use a mix of
__kernel_ulong_t and unsigned long, or taking the x32
version back into arch/x86/include/uapi/asm/ so the
generic version at least makes some sense.

I can't use __kernel_time_t for the lower half on 32-bit
since it really should be unsigned.

Arnd