Hi Christoph,
On Tue, Jul 11, 2017 at 06:39:48AM -0700, Christoph Hellwig wrote:
> > +#ifdef CONFIG_64BIT
> > +SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
> > + unsigned long, prot, unsigned long, flags,
> > + unsigned long, fd, off_t, offset)
> > +{
> > + if (unlikely(offset & (~PAGE_MASK)))
> > + return -EINVAL;
> > + return sys_mmap_pgoff(addr, len, prot, flags, fd, offset >> PAGE_SHIFT);
> > +}
> > +#else
> > +SYSCALL_DEFINE6(mmap2, unsigned long, addr, unsigned long, len,
> > + unsigned long, prot, unsigned long, flags,
> > + unsigned long, fd, off_t, offset)
> > +{
> > + /*
> > + * Note that the shift for mmap2 is constant (12),
> > + * regardless of PAGE_SIZE
> > + */
> > + if (unlikely(offset & (~PAGE_MASK >> 12)))
> > + return -EINVAL;
> > + return sys_mmap_pgoff(addr, len, prot, flags, fd,
> > + offset >> (PAGE_SHIFT - 12));
> > +}
> > +#endif /* !CONFIG_64BIT */
>
> Most modern ports seem to expose sys_mmap_pgoff as the
> syscall directly. Any reason you're doing this differently?I think Palmer's patch is probably correct here. Exposing sys_mmap_pgoff is only really correct on 32-bit arches where the only page size is 4k. If other page sizes are supported then this is the correct way to handle it as the page offset from 32-bit userland is supposed to be in 4k units. 64-bit doesn't need to worry about squeezing big file offsets into the off_t offset so don't need to do the shift at all. See the mmap2 man page. It says "the final argument specifies the offset into the file in 4096-byte units", and it points out ia64 as an exception where it depends on the page size of the system. > > But even the code for the older ones should probably be consolidated.. Quite probably, yes. Cheers James
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