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SubjectRE: [PATCH V7 03/20] compat: consolidate the compat_flock{,64} definition
Date
From: Guo Ren
> Sent: 28 February 2022 11:52
>
> On Mon, Feb 28, 2022 at 2:40 PM David Laight <David.Laight@aculab.com> wrote:
> >
> > From: guoren@kernel.org
> > > Sent: 27 February 2022 16:28
> > >
> > > From: Christoph Hellwig <hch@lst.de>
> > >
> > > Provide a single common definition for the compat_flock and
> > > compat_flock64 structures using the same tricks as for the native
> > > variants. Another extra define is added for the packing required on
> > > x86.
> > ...
> > > diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
> > ...
> > > /*
> > > - * IA32 uses 4 byte alignment for 64 bit quantities,
> > > - * so we need to pack this structure.
> > > + * IA32 uses 4 byte alignment for 64 bit quantities, so we need to pack the
> > > + * compat flock64 structure.
> > > */
> > ...
> > > +#define __ARCH_NEED_COMPAT_FLOCK64_PACKED
> > >
> > > struct compat_statfs {
> > > int f_type;
> > > diff --git a/include/linux/compat.h b/include/linux/compat.h
> > > index 1c758b0e0359..a0481fe6c5d5 100644
> > > --- a/include/linux/compat.h
> > > +++ b/include/linux/compat.h
> > > @@ -258,6 +258,37 @@ struct compat_rlimit {
> > > compat_ulong_t rlim_max;
> > > };
> > >
> > > +#ifdef __ARCH_NEED_COMPAT_FLOCK64_PACKED
> > > +#define __ARCH_COMPAT_FLOCK64_PACK __attribute__((packed))
> > > +#else
> > > +#define __ARCH_COMPAT_FLOCK64_PACK
> > > +#endif
> > ...
> > > +struct compat_flock64 {
> > > + short l_type;
> > > + short l_whence;
> > > + compat_loff_t l_start;
> > > + compat_loff_t l_len;
> > > + compat_pid_t l_pid;
> > > +#ifdef __ARCH_COMPAT_FLOCK64_PAD
> > > + __ARCH_COMPAT_FLOCK64_PAD
> > > +#endif
> > > +} __ARCH_COMPAT_FLOCK64_PACK;
> > > +
> >
> > Provided compat_loff_t are correctly defined with __aligned__(4)
> See include/asm-generic/compat.h
>
> typedef s64 compat_loff_t;
>
> Only:
> #ifdef CONFIG_COMPAT_FOR_U64_ALIGNMENT
> typedef s64 __attribute__((aligned(4))) compat_s64;
>
> So how do you think compat_loff_t could be defined with __aligned__(4)?

compat_loff_t should be compat_s64 not s64.

The same should be done for all 64bit 'compat' types.

David

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