7613f5a66b
In commit 8150a153c013 ("powerpc/64s: Use early_mmu_has_feature() in
set_kuap()") we switched the KUAP code to use early_mmu_has_feature(),
to avoid a bug where we called set_kuap() before feature patching had
been done, leading to recursion and crashes.
That path, which called probe_kernel_read() from printk(), has since
been removed, see commit 2ac5a3bf7042 ("vsprintf: Do not break early
boot with probing addresses").
Additionally probe_kernel_read() no longer invokes any KUAP routines,
since commit fe557319aa06 ("maccess: rename probe_kernel_{read,write}
to copy_{from,to}_kernel_nofault") and c33165253492 ("powerpc: use
non-set_fs based maccess routines").
So it should now be safe to use mmu_has_feature() in the KUAP
routines, because we shouldn't invoke them prior to feature patching.
This is essentially a revert of commit 8150a153c013 ("powerpc/64s: Use
early_mmu_has_feature() in set_kuap()"), but we've since added a
second usage of early_mmu_has_feature() in get_kuap(), so we convert
that to use mmu_has_feature() as well.
Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Depends-on: c33165253492 ("powerpc: use non-set_fs based maccess routines").
Link: https://lore.kernel.org/r/20201217005306.895685-1-mpe@ellerman.id.au
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.