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Re: [PATCH] aarch64: Fix ipc_perm definition for ILP32

• From: Yury Norov <ynorov at caviumnetworks dot com>
• To: Szabolcs Nagy <szabolcs dot nagy at arm dot com>
• Cc: sellcey at cavium dot com, libc-alpha <libc-alpha at sourceware dot org>, nd at arm dot com
• Date: Wed, 23 Aug 2017 13:10:23 +0300
• Subject: Re: [PATCH] aarch64: Fix ipc_perm definition for ILP32
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On Wed, Aug 23, 2017 at 10:55:02AM +0100, Szabolcs Nagy wrote:> On 22/08/17 18:46, Steve Ellcey wrote:> > Here is another aarch64 ILP32 patch.  The mode field in ipc_perm in ILP32> > should be a 16 bit field, not a 32 bit one.  This was out-of-sync with what the> > kernel had.  This was causing sysvipc/test-sysvsem to fail in ILP32 mode.> > This change is only needed for ILP32 so it doesn't need to go in until we add> > that ABI but I am sending out for review and comments.> > > > 2017-08-22  Yury Norov  <ynorov@caviumnetworks.com>> >     Steve Ellcey  <sellcey@cavium.com>> > > > * sysdeps/unix/sysv/linux/aarch64/bits/ipc.h (ipc_perm):> > Ifdef and pad the mode field for ILP32.> > > > > > diff --git a/sysdeps/unix/sysv/linux/aarch64/bits/ipc.h b/sysdeps/unix/sysv/linu> > x/aarch64/bits/ipc.h> > index cd1f06e..cd05b74 100644> > --- a/sysdeps/unix/sysv/linux/aarch64/bits/ipc.h> > +++ b/sysdeps/unix/sysv/linux/aarch64/bits/ipc.h> > @@ -46,7 +46,12 @@ struct ipc_perm> >      __gid_t gid;/* Owner's group ID.  */> >      __uid_t cuid;/* Creator's user ID.  */> >      __gid_t cgid;/* Creator's group ID.  */> > +#ifdef __LP64> >      unsigned int mode;/* Read/write permission.  */> > +#else> > +    unsigned short int mode;/* Read/write permission.  */> > +    unsigned short int __pad0;> > +#endif> > when did this happen?> > as far as i can tell staging/ilp32-4.12 branch in> git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git> still has unsigned int __kernel_mode_t in uapi, so this is> an abi change compared to that branch.> > i guess it's for 32bit compat, but i'd like to see the> kernel patch for this.It is there from the very beginning of ILP32 patches. The patch changesthe ABI only for arm64/ilp32. LP64 remains untouched, and it works correctwith and without ilp32 patches and this fix.To reproduce:struct semid_ds seminfo;static char name[] = "Hello";key_t key = ftok (name, 'G');semid = semget(key, 1, IPC_CREAT | IPC_EXCL | 0644);semctl (semid, 0, IPC_STAT, &seminfo);printf("%o\n", seminfo.sem_perm.mode); // bits 16-31 contain garbageOn kernel side no fixes needed because arm64/ilp32 ipc requests arewired to compat layer, and the layout for structure is like this:arch/arm64/include/asm/compat.h:246 struct compat_ipc64_perm {247         compat_key_t key;248         __compat_uid32_t uid;249         __compat_gid32_t gid;250         __compat_uid32_t cuid;251         __compat_gid32_t cgid;252         unsigned short mode;253         unsigned short __pad1;254         unsigned short seq;255         unsigned short __pad2;256         compat_ulong_t unused1;257         compat_ulong_t unused2;258 };So I would prefer to treat it not as the change of ABI, bit thefix of ABI incompatibility on GLIBC side.Yury

• Follow-Ups:
  • Re: [PATCH] aarch64: Fix ipc_perm definition for ILP32
    • From: Szabolcs Nagy

• References:
  • [PATCH] aarch64: Fix ipc_perm definition for ILP32
    • From: Steve Ellcey
  • Re: [PATCH] aarch64: Fix ipc_perm definition for ILP32
    • From: Szabolcs Nagy