e77175fafa
Commit dea5e2a4c5bcf196f879a66cebdcca07793e8ba4 upstream.
We've so far relied on a patching infrastructure that only gave us
a single alternative, without any way to provide a range of potential
replacement instructions. For a single feature, this is an all or
nothing thing.
It would be interesting to have a more flexible grained way of patching
the kernel though, where we could dynamically tune the code that gets
injected.
In order to achive this, let's introduce a new form of dynamic patching,
assiciating a callback to a patching site. This callback gets source and
target locations of the patching request, as well as the number of
instructions to be patched.
Dynamic patching is declared with the new ALTERNATIVE_CB and alternative_cb
directives:
asm volatile(ALTERNATIVE_CB("mov %0, #0\n", callback)
: "r" (v));
or
alternative_cb callback
mov x0, #0
alternative_cb_end
where callback is the C function computing the alternative.
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.