linux/arch/arm/mm/abort-ev5t.S
Russell King 2190fed67b 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>
2015-08-26 20:27:02 +01:00

31 lines
944 B
ArmAsm

#include <linux/linkage.h>
#include <asm/assembler.h>
#include "abort-macro.S"
/*
* Function: v5t_early_abort
*
* Params : r2 = pt_regs
* : r4 = aborted context pc
* : r5 = aborted context psr
*
* Returns : r4 - r11, r13 preserved
*
* Purpose : obtain information about current aborted instruction.
* Note: we read user space. This means we might cause a data
* abort here if the I-TLB and D-TLB aren't seeing the same
* picture. Unfortunately, this does happen. We live with it.
*/
.align 5
ENTRY(v5t_early_abort)
mrc p15, 0, r1, c5, c0, 0 @ get FSR
mrc p15, 0, r0, c6, c0, 0 @ get FAR
do_thumb_abort fsr=r1, pc=r4, psr=r5, tmp=r3
ldreq r3, [r4] @ read aborted ARM instruction
uaccess_disable ip @ disable user access
bic r1, r1, #1 << 11 @ clear bits 11 of FSR
teq_ldrd tmp=ip, insn=r3 @ insn was LDRD?
beq do_DataAbort @ yes
tst r3, #1 << 20 @ check write
orreq r1, r1, #1 << 11
b do_DataAbort