Re: [BUG] binfmt_elf: get_user() called in vma_dump_size() afterset_fs(KERNEL_DS)

[David Miller]

From: Roland McGrath <roland@xxxxxxxxxx>
Date: Fri,  6 Feb 2009 14:07:17 -0800 (PST)

> set_fs is quite cheap at least on most machines.  So a pair of set_fs calls
> around that get_user call doesn't seem so bad.  OTOH, on the machines where
> this actually matters at all (maybe just sparc, arm, s390?) it is
> presumably (much?) more costly.  But it seems like the best solution, and
> certainly is straightforward.

On sparc set_fs() is just a privileged register write, so pretty cheap
and definitely less expensive than get_user_pages() :-)
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