Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH v4 00/24] ILP32 for ARM64 | Date | Mon, 20 Apr 2015 19:40:37 +0200 |
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On Monday 20 April 2015 16:56:00 Catalin Marinas wrote: > On Fri, Apr 17, 2015 at 05:49:44PM +0200, Arnd Bergmann wrote: > > On Friday 17 April 2015 15:46:57 Catalin Marinas wrote: > > > On Fri, Apr 17, 2015 at 02:17:32PM +0100, Arnd Bergmann wrote: > > | typedef unsigned short __kernel_mode_t; > > | typedef unsigned short __kernel_ipc_pid_t; > > > > Both of these affect all sysvipc, but very little else > > > > | typedef unsigned short __kernel_uid_t; > > | typedef unsigned short __kernel_gid_t; > > > > sysvipc, ncpfs, and core dumps (probably fine since they are separate > > anyway), > > Not all ipc functions are affected AFAICT. msgsnd, msgrcv, msgctl look > to me like we can just use the compat variants with the generic > definitions for the types above (unless I missed something). Similarly > for shmat, compat_sys_shmat just does some compat_ptr casting.
Right.
> > | typedef unsigned short __kernel_old_dev_t; /* compat gets this wrong */ > > > > old-style loopdev ioctl > > > > | struct stat { ... } /* possibly not needed */ > > > > - lustre ioctls (needs to be fixed anyway) > > - old stat syscalls (won't be used with asm-generic/unistd.h) > > > > | struct stat64 { ... } > > > > - lustre ioctls > > - new style stat syscalls > > For stat64 the wrappers don't look complicated, so we could add arm64 > ILP32-specific ones.
stat is never easy ;-)
Note that for new architectures, we use 'struct stat64' on 32-bit systems but 'struct stat' on 64-bit systems. Old architectures like arch/arm has both, and neither of them matches the on from arch/arm64.
Also, the asm-generic definition of 'struct stat64' is wrong and really needs to be fixed to have the same layout that 'struct stat' has on a 64-bit architecture. The only difference between the two is the size of the time related 'st_atime' etc members, and having them defined this way was my biggest mistake when I created the uapi/asm-generic headers.
> > So, in essence the difference comes down to the syscalls for stat > > and ipc. If we use the aarch32 data types, we can share the > > fstatat64, fstat64, semctl, msgsnd, msgrcv, msgctl, shmat, > > and shmctl compat system calls between aarch32-compat and > > aarch64-ilp32-compat. Otherwise we have to duplicate or extend > > them to cover both cases at runtime. That would be rather ugly > > but entirely doable. The ioctls are hardly affected, the few > > ones that differ once __kernel_long_t matches could easily be > > fixed up as you say. > > I'd prefer a cleaner ABI even if we are to write some specific wrappers.
Ok, makes sense. As I replied to Philipp later, even with the cleaner definition of 'stat64' and the sysipc syscalls, we should be able to trivially reuse the native 64-bit version in the way that the current patch set does for a lot of other syscalls, but keep all the other syscalls using the normal 32-bit __kernel_long_t variants that we already have.
Arnd
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