/*
* arch/arm/kernel/kprobes-decode.c
*
* Copyright (C) 2006, 2007 Motorola Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
/*
* We do not have hardware single-stepping on ARM, This
* effort is further complicated by the ARM not having a
* "next PC" register. Instructions that change the PC
* can't be safely single-stepped in a MP environment, so
* we have a lot of work to do:
*
* In the prepare phase:
* *) If it is an instruction that does anything
* with the CPU mode, we reject it for a kprobe.
* (This is out of laziness rather than need. The
* instructions could be simulated.)
*
* *) Otherwise, decode the instruction rewriting its
* registers to take fixed, ordered registers and
* setting a handler for it to run the instruction.
*
* In the execution phase by an instruction's handler:
*
* *) If the PC is written to by the instruction, the
* instruction must be fully simulated in software.
* If it is a conditional instruction, the handler
* will use insn[0] to copy its condition code to
* set r0 to 1 and insn[1] to "mov pc, lr" to return.
*
* *) Otherwise, a modified form of the instruction is
* directly executed. Its handler calls the
* instruction in insn[0]. In insn[1] is a
* "mov pc, lr" to return.
*
* Before calling, load up the reordered registers
* from the original instruction's registers. If one
* of the original input registers is the PC, compute
* and adjust the appropriate input register.
*
* After call completes, copy the output registers to
* the original instruction's original registers.
*
* We don't use a real breakpoint instruction since that
* would have us in the ke
