* Andy Lutomirski <l...@kernel.org> wrote:
> The kernel is very erratic as to which pagetables have _PAGE_USER
> set. The vsyscall page gets lucky: it seems that all of the
> relevant pagetables are among the apparently arbitrary ones that set
> _PAGE_USER. Rather than relying on chance, just explicitly set
> _PAGE_USER.
>
> This will let us clean up pagetable setup to stop setting
> _PAGE_USER. The added code can also be reused by pagetable
> isolation to manage the _PAGE_USER bit in the usermode tables.
>
> Signed-off-by: Andy Lutomirski <l...@kernel.org>
> ---
> arch/x86/entry/vsyscall/vsyscall_64.c | 33 ++++++++++++++++++++++++++++++++-
> 1 file changed, 32 insertions(+), 1 deletion(-)
Btw., would it make sense to clean up all this confusion?
In particular a 'KERNEL' pre of post fix is ambiguous in this context I think,
and
the PAGE_KERNEL_ prefix is actively harmful I think and is at the root of the
confusion.
So if renamed it and used this nomenclature consistently instead:
PAGE_USER_
PAGE_SYSTEM_
... and got rid of PAGE_KERNEL uses in arch/x86/, then it would be obvious at
first glance what kind of mapping is established in a particular place - and it
would stay so in the future as well.
( There's some interaction with generic MM code which needs the original
defines
like PAGE_KERNEL[_EXEC], but those generic masks could be defined as aliases,
to
keep this cleanup within x86 for now. )
Thanks,
Ingo
