ARM: entry: provide uaccess assembly macro hooks

Provide hooks into the kernel entry and exit paths to permit control
of userspace visibility to the kernel.  The intended use is:

- on entry to kernel from user, uaccess_disable will be called to
  disable userspace visibility
- on exit from kernel to user, uaccess_enable will be called to
  enable userspace visibility
- on entry from a kernel exception, uaccess_save_and_disable will be
  called to save the current userspace visibility setting, and disable
  access
- on exit from a kernel exception, uaccess_restore will be called to
  restore the userspace visibility as it was before the exception
  occurred.

These hooks allows us to keep userspace visibility disabled for the
vast majority of the kernel, except for localised regions where we
want to explicitly access userspace.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/arm/mm/abort-ev7.S b/arch/arm/mm/abort-ev7.S
index 4812ad054214..e8d0e08c227f 100644
--- a/arch/arm/mm/abort-ev7.S
+++ b/arch/arm/mm/abort-ev7.S
@@ -15,6 +15,7 @@
 ENTRY(v7_early_abort)
 	mrc	p15, 0, r1, c5, c0, 0		@ get FSR
 	mrc	p15, 0, r0, c6, c0, 0		@ get FAR
+	uaccess_disable ip			@ disable userspace access
 
 	/*
 	 * V6 code adjusts the returned DFSR.