patch_instruction() can be called very early on ppc32, when the kernel
isn't yet running at it's linked address. That can cause the !
is_kernel_addr() test in __put_user() to trip and call might_sleep()
which is very bad at that point during boot.

Use a lower level function instead for now, at least until we get to
rework ppc32 boot process to do the code patching later, like ppc64
does.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

For ftrace to use the patch_instruction code, it needs to check for
faults on write. Ftrace updates code all over the kernel, and we need to
know if code is updated or not due to protections that are placed on
some portions of the kernel. If ftrace does not detect a fault, it will
error later on, and it will be much more difficult to find the problem.

By changing patch_instruction() to detect faults, then ftrace will be
able to make use of it too.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

On 32-bit architectures PAGE_ALIGN() truncates 64-bit values to the 32-bit
boundary. For example:

	u64 val = PAGE_ALIGN(size);

always returns a value < 4GB even if size is greater than 4GB.

The problem resides in PAGE_MASK definition (from include/asm-x86/page.h for
example):

#define PAGE_SHIFT      12
#define PAGE_SIZE       (_AC(1,UL) << PAGE_SHIFT)
#define PAGE_MASK       (~(PAGE_SIZE-1))
...
#define PAGE_ALIGN(addr)       (((addr)+PAGE_SIZE-1)&PAGE_MASK)

The "~" is performed on a 32-bit value, so everything in "and" with
PAGE_MASK greater than 4GB will be truncated to the 32-bit boundary.
Using the ALIGN() macro seems to be the right way, because it uses
typeof(addr) for the mask.

Also move the PAGE_ALIGN() definitions out of include/asm-*/page.h in
include/linux/mm.h.

See also lkml discussion: http://lkml.org/lkml/2008/6/11/237

[akpm@linux-foundation.org: fix drivers/media/video/uvc/uvc_queue.c]
[akpm@linux-foundation.org: fix v850]
[akpm@linux-foundation.org: fix powerpc]
[akpm@linux-foundation.org: fix arm]
[akpm@linux-foundation.org: fix mips]
[akpm@linux-foundation.org: fix drivers/media/video/pvrusb2/pvrusb2-dvb.c]
[akpm@linux-foundation.org: fix drivers/mtd/maps/uclinux.c]
[akpm@linux-foundation.org: fix powerpc]
Signed-off-by: NAndrea Righi <righi.andrea@gmail.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add tests of the existing code patching routines, as well as the new
routines added in the last commit.  The self-tests are run late in boot
when CONFIG_CODE_PATCHING_SELFTEST=y, which depends on DEBUG_KERNEL=y.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Acked-by: NKumar Gala <galak@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

This commit adds some new routines for patching code, which will be used
in a following commit.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

If you pass a target value to create_branch() which is more than 32MB - 4,
or - 32MB away from the branch site, then it's impossible to create an
immediate branch.  The current code doesn't check, which will lead to us
creating a branch to somewhere else - which is bad.

For code that cares to check we return 0, which is easy to check for, and
for code that doesn't at least we'll be creating an illegal instruction,
rather than a branch to some random address.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Acked-by: NKumar Gala <galak@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Currently create_branch() creates a branch instruction for you, and
patches it into the call site.  In some circumstances it would be nice
to be able to create the instruction and patch it later, and also some
code might want to check for errors in the branch creation before
doing the patching.  A future commit will change create_branch() to
check for errors.

For callers that don't care, replace create_branch() with
patch_branch(), which just creates the branch and patches it directly.

While we're touching all the callers, change to using unsigned int *,
as this seems to match usage better.  That allows (and requires) us to
remove the volatile in the definition of vector in powermac/smp.c and
mpc86xx_smp.c, that's correct because now that we're passing vector as
an unsigned int * the compiler knows that it's value might change
across the patch_branch() call.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Acked-by: NKumar Gala <galak@kernel.crashing.org>
Acked-by: NJon Loeliger <jdl@freescale.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

We currently have a few routines for patching code in asm/system.h, because
they didn't fit anywhere else. I'd like to clean them up a little and add
some more, so first move them into a dedicated C file - they don't need to
be inlined.

While we're moving the code, drop create_function_call(), it's intended
caller never got merged and will be replaced in future with something
different.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Acked-by: NKumar Gala <galak@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>