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kprobes-decode.c

/*
 * 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 kernel go from SVC mode to SVC
 * mode losing the link register.  Instead we use an
 * undefined instruction.  To simplify processing, the
 * undefined instruction used for kprobes must be reserved
 * exclusively for kprobes use.
 *
 * TODO: ifdef out some instruction decoding based on architecture.
 */

#include <linux/kernel.h>
#include <linux/kprobes.h>

#define sign_extend(x, signbit) ((x) | (0 - ((x) & (1 << (signbit)))))

#define branch_displacement(insn) sign_extend(((insn) & 0xffffff) << 2, 25)

#define PSR_fs    (PSR_f|PSR_s)

#define KPROBE_RETURN_INSTRUCTION   0xe1a0f00e  /* mov pc, lr */
#define SET_R0_TRUE_INSTRUCTION           0xe3a00001  /* mov      r0, #1 */

#define     truecc_insn(insn) (((insn) & 0xf0000000) | \
                         (SET_R0_TRUE_INSTRUCTION & 0x0fffffff))

typedef long (insn_0arg_fn_t)(void);
typedef long (insn_1arg_fn_t)(long);
typedef long (insn_2arg_fn_t)(long, long);
typedef long (insn_3arg_fn_t)(long, long, long);
typedef long (insn_4arg_fn_t)(long, long, long, long);
typedef long long (insn_llret_0arg_fn_t)(void);
typedef long long (insn_llret_3arg_fn_t)(long, long, long);
typedef long long (insn_llret_4arg_fn_t)(long, long, long, long);

union reg_pair {
      long long   dr;
#ifdef __LITTLE_ENDIAN
      struct { long     r0, r1; };
#else
      struct { long     r1, r0; };
#endif
};

/*
 * For STR and STM instructions, an ARM core may choose to use either
 * a +8 or a +12 displacement from the current instruction's address.
 * Whichever value is chosen for a given core, it must be the same for
 * both instructions and may not change.  This function measures it.
 */

static int str_pc_offset;

static void __init find_str_pc_offset(void)
{
      int addr, scratch, ret;

      __asm__ (
            "sub  %[ret], pc, #4          \n\t"
            "str  pc, %[addr]       \n\t"
            "ldr  %[scr], %[addr]         \n\t"
            "sub  %[ret], %[scr], %[ret]  \n\t"
            : [ret] "=r" (ret), [scr] "=r" (scratch), [addr] "+m" (addr));

      str_pc_offset = ret;
}

/*
 * The insnslot_?arg_r[w]flags() functions below are to keep the
 * msr -> *fn -> mrs instruction sequences indivisible so that
 * the state of the CPSR flags aren't inadvertently modified
 * just before or just after the call.
 */

static inline long __kprobes
insnslot_0arg_rflags(long cpsr, insn_0arg_fn_t *fn)
{
      register long ret asm("r0");

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[cpsr]  \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            : "=r" (ret)
            : [cpsr] "r" (cpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      return ret;
}

static inline long long __kprobes
insnslot_llret_0arg_rflags(long cpsr, insn_llret_0arg_fn_t *fn)
{
      register long ret0 asm("r0");
      register long ret1 asm("r1");
      union reg_pair fnr;

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[cpsr]  \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            : "=r" (ret0), "=r" (ret1)
            : [cpsr] "r" (cpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      fnr.r0 = ret0;
      fnr.r1 = ret1;
      return fnr.dr;
}

static inline long __kprobes
insnslot_1arg_rflags(long r0, long cpsr, insn_1arg_fn_t *fn)
{
      register long rr0 asm("r0") = r0;
      register long ret asm("r0");

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[cpsr]  \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            : "=r" (ret)
            : "0" (rr0), [cpsr] "r" (cpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      return ret;
}

static inline long __kprobes
insnslot_2arg_rflags(long r0, long r1, long cpsr, insn_2arg_fn_t *fn)
{
      register long rr0 asm("r0") = r0;
      register long rr1 asm("r1") = r1;
      register long ret asm("r0");

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[cpsr]  \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            : "=r" (ret)
            : "0" (rr0), "r" (rr1),
              [cpsr] "r" (cpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      return ret;
}

static inline long __kprobes
insnslot_3arg_rflags(long r0, long r1, long r2, long cpsr, insn_3arg_fn_t *fn)
{
      register long rr0 asm("r0") = r0;
      register long rr1 asm("r1") = r1;
      register long rr2 asm("r2") = r2;
      register long ret asm("r0");

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[cpsr]  \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            : "=r" (ret)
            : "0" (rr0), "r" (rr1), "r" (rr2),
              [cpsr] "r" (cpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      return ret;
}

static inline long long __kprobes
insnslot_llret_3arg_rflags(long r0, long r1, long r2, long cpsr,
                     insn_llret_3arg_fn_t *fn)
{
      register long rr0 asm("r0") = r0;
      register long rr1 asm("r1") = r1;
      register long rr2 asm("r2") = r2;
      register long ret0 asm("r0");
      register long ret1 asm("r1");
      union reg_pair fnr;

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[cpsr]  \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            : "=r" (ret0), "=r" (ret1)
            : "0" (rr0), "r" (rr1), "r" (rr2),
              [cpsr] "r" (cpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      fnr.r0 = ret0;
      fnr.r1 = ret1;
      return fnr.dr;
}

static inline long __kprobes
insnslot_4arg_rflags(long r0, long r1, long r2, long r3, long cpsr,
                 insn_4arg_fn_t *fn)
{
      register long rr0 asm("r0") = r0;
      register long rr1 asm("r1") = r1;
      register long rr2 asm("r2") = r2;
      register long rr3 asm("r3") = r3;
      register long ret asm("r0");

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[cpsr]  \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            : "=r" (ret)
            : "0" (rr0), "r" (rr1), "r" (rr2), "r" (rr3),
              [cpsr] "r" (cpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      return ret;
}

static inline long __kprobes
insnslot_1arg_rwflags(long r0, long *cpsr, insn_1arg_fn_t *fn)
{
      register long rr0 asm("r0") = r0;
      register long ret asm("r0");
      long oldcpsr = *cpsr;
      long newcpsr;

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[oldcpsr]     \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            "mrs  %[newcpsr], cpsr  \n\t"
            : "=r" (ret), [newcpsr] "=r" (newcpsr)
            : "0" (rr0), [oldcpsr] "r" (oldcpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      *cpsr = (oldcpsr & ~PSR_fs) | (newcpsr & PSR_fs);
      return ret;
}

static inline long __kprobes
insnslot_2arg_rwflags(long r0, long r1, long *cpsr, insn_2arg_fn_t *fn)
{
      register long rr0 asm("r0") = r0;
      register long rr1 asm("r1") = r1;
      register long ret asm("r0");
      long oldcpsr = *cpsr;
      long newcpsr;

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[oldcpsr]     \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            "mrs  %[newcpsr], cpsr  \n\t"
            : "=r" (ret), [newcpsr] "=r" (newcpsr)
            : "0" (rr0), "r" (rr1), [oldcpsr] "r" (oldcpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      *cpsr = (oldcpsr & ~PSR_fs) | (newcpsr & PSR_fs);
      return ret;
}

static inline long __kprobes
insnslot_3arg_rwflags(long r0, long r1, long r2, long *cpsr,
                  insn_3arg_fn_t *fn)
{
      register long rr0 asm("r0") = r0;
      register long rr1 asm("r1") = r1;
      register long rr2 asm("r2") = r2;
      register long ret asm("r0");
      long oldcpsr = *cpsr;
      long newcpsr;

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[oldcpsr]     \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            "mrs  %[newcpsr], cpsr  \n\t"
            : "=r" (ret), [newcpsr] "=r" (newcpsr)
            : "0" (rr0), "r" (rr1), "r" (rr2),
              [oldcpsr] "r" (oldcpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      *cpsr = (oldcpsr & ~PSR_fs) | (newcpsr & PSR_fs);
      return ret;
}

static inline long __kprobes
insnslot_4arg_rwflags(long r0, long r1, long r2, long r3, long *cpsr,
                  insn_4arg_fn_t *fn)
{
      register long rr0 asm("r0") = r0;
      register long rr1 asm("r1") = r1;
      register long rr2 asm("r2") = r2;
      register long rr3 asm("r3") = r3;
      register long ret asm("r0");
      long oldcpsr = *cpsr;
      long newcpsr;

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[oldcpsr]     \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            "mrs  %[newcpsr], cpsr  \n\t"
            : "=r" (ret), [newcpsr] "=r" (newcpsr)
            : "0" (rr0), "r" (rr1), "r" (rr2), "r" (rr3),
              [oldcpsr] "r" (oldcpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      *cpsr = (oldcpsr & ~PSR_fs) | (newcpsr & PSR_fs);
      return ret;
}

static inline long long __kprobes
insnslot_llret_4arg_rwflags(long r0, long r1, long r2, long r3, long *cpsr,
                      insn_llret_4arg_fn_t *fn)
{
      register long rr0 asm("r0") = r0;
      register long rr1 asm("r1") = r1;
      register long rr2 asm("r2") = r2;
      register long rr3 asm("r3") = r3;
      register long ret0 asm("r0");
      register long ret1 asm("r1");
      long oldcpsr = *cpsr;
      long newcpsr;
      union reg_pair fnr;

      __asm__ __volatile__ (
            "msr  cpsr_fs, %[oldcpsr]     \n\t"
            "mov  lr, pc                  \n\t"
            "mov  pc, %[fn]         \n\t"
            "mrs  %[newcpsr], cpsr  \n\t"
            : "=r" (ret0), "=r" (ret1), [newcpsr] "=r" (newcpsr)
            : "0" (rr0), "r" (rr1), "r" (rr2), "r" (rr3),
              [oldcpsr] "r" (oldcpsr), [fn] "r" (fn)
            : "lr", "cc"
      );
      *cpsr = (oldcpsr & ~PSR_fs) | (newcpsr & PSR_fs);
      fnr.r0 = ret0;
      fnr.r1 = ret1;
      return fnr.dr;
}

/*
 * To avoid the complications of mimicing single-stepping on a
 * processor without a Next-PC or a single-step mode, and to
 * avoid having to deal with the side-effects of boosting, we
 * simulate or emulate (almost) all ARM instructions.
 *
 * "Simulation" is where the instruction's behavior is duplicated in
 * C code.  "Emulation" is where the original instruction is rewritten
 * and executed, often by altering its registers.
 *
 * By having all behavior of the kprobe'd instruction completed before
 * returning from the kprobe_handler(), all locks (scheduler and
 * interrupt) can safely be released.  There is no need for secondary
 * breakpoints, no race with MP or preemptable kernels, nor having to
 * clean up resources counts at a later time impacting overall system
 * performance.  By rewriting the instruction, only the minimum registers
 * need to be loaded and saved back optimizing performance.
 *
 * Calling the insnslot_*_rwflags version of a function doesn't hurt
 * anything even when the CPSR flags aren't updated by the
 * instruction.  It's just a little slower in return for saving
 * a little space by not having a duplicate function that doesn't
 * update the flags.  (The same optimization can be said for
 * instructions that do or don't perform register writeback)
 * Also, instructions can either read the flags, only write the
 * flags, or read and write the flags.  To save combinations
 * rather than for sheer performance, flag functions just assume
 * read and write of flags.
 */

static void __kprobes simulate_bbl(struct kprobe *p, struct pt_regs *regs)
{
      insn_1arg_fn_t *i_fn = (insn_1arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      long iaddr = (long)p->addr;
      int disp  = branch_displacement(insn);

      if (!insnslot_1arg_rflags(0, regs->ARM_cpsr, i_fn))
            return;

      if (insn & (1 << 24))
            regs->ARM_lr = iaddr + 4;

      regs->ARM_pc = iaddr + 8 + disp;
}

static void __kprobes simulate_blx1(struct kprobe *p, struct pt_regs *regs)
{
      kprobe_opcode_t insn = p->opcode;
      long iaddr = (long)p->addr;
      int disp = branch_displacement(insn);

      regs->ARM_lr = iaddr + 4;
      regs->ARM_pc = iaddr + 8 + disp + ((insn >> 23) & 0x2);
      regs->ARM_cpsr |= PSR_T_BIT;
}

static void __kprobes simulate_blx2bx(struct kprobe *p, struct pt_regs *regs)
{
      insn_1arg_fn_t *i_fn = (insn_1arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rm = insn & 0xf;
      long rmv = regs->uregs[rm];

      if (!insnslot_1arg_rflags(0, regs->ARM_cpsr, i_fn))
            return;

      if (insn & (1 << 5))
            regs->ARM_lr = (long)p->addr + 4;

      regs->ARM_pc = rmv & ~0x1;
      regs->ARM_cpsr &= ~PSR_T_BIT;
      if (rmv & 0x1)
            regs->ARM_cpsr |= PSR_T_BIT;
}

static void __kprobes simulate_ldm1stm1(struct kprobe *p, struct pt_regs *regs)
{
      insn_1arg_fn_t *i_fn = (insn_1arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rn = (insn >> 16) & 0xf;
      int lbit = insn & (1 << 20);
      int wbit = insn & (1 << 21);
      int ubit = insn & (1 << 23);
      int pbit = insn & (1 << 24);
      long *addr = (long *)regs->uregs[rn];
      int reg_bit_vector;
      int reg_count;

      if (!insnslot_1arg_rflags(0, regs->ARM_cpsr, i_fn))
            return;

      reg_count = 0;
      reg_bit_vector = insn & 0xffff;
      while (reg_bit_vector) {
            reg_bit_vector &= (reg_bit_vector - 1);
            ++reg_count;
      }

      if (!ubit)
            addr -= reg_count;
      addr += (!pbit ^ !ubit);

      reg_bit_vector = insn & 0xffff;
      while (reg_bit_vector) {
            int reg = __ffs(reg_bit_vector);
            reg_bit_vector &= (reg_bit_vector - 1);
            if (lbit)
                  regs->uregs[reg] = *addr++;
            else
                  *addr++ = regs->uregs[reg];
      }

      if (wbit) {
            if (!ubit)
                  addr -= reg_count;
            addr -= (!pbit ^ !ubit);
            regs->uregs[rn] = (long)addr;
      }
}

static void __kprobes simulate_stm1_pc(struct kprobe *p, struct pt_regs *regs)
{
      insn_1arg_fn_t *i_fn = (insn_1arg_fn_t *)&p->ainsn.insn[0];

      if (!insnslot_1arg_rflags(0, regs->ARM_cpsr, i_fn))
            return;

      regs->ARM_pc = (long)p->addr + str_pc_offset;
      simulate_ldm1stm1(p, regs);
      regs->ARM_pc = (long)p->addr + 4;
}

static void __kprobes simulate_mov_ipsp(struct kprobe *p, struct pt_regs *regs)
{
      regs->uregs[12] = regs->uregs[13];
}

static void __kprobes emulate_ldcstc(struct kprobe *p, struct pt_regs *regs)
{
      insn_1arg_fn_t *i_fn = (insn_1arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rn = (insn >> 16) & 0xf;
      long rnv = regs->uregs[rn];

      /* Save Rn in case of writeback. */
      regs->uregs[rn] = insnslot_1arg_rflags(rnv, regs->ARM_cpsr, i_fn);
}

static void __kprobes emulate_ldrd(struct kprobe *p, struct pt_regs *regs)
{
      insn_2arg_fn_t *i_fn = (insn_2arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;
      int rm = insn & 0xf;  /* rm may be invalid, don't care. */

      /* Not following the C calling convention here, so need asm(). */
      __asm__ __volatile__ (
            "ldr  r0, %[rn]   \n\t"
            "ldr  r1, %[rm]   \n\t"
            "msr  cpsr_fs, %[cpsr]\n\t"
            "mov  lr, pc            \n\t"
            "mov  pc, %[i_fn] \n\t"
            "str  r0, %[rn]   \n\t" /* in case of writeback */
            "str  r2, %[rd0]  \n\t"
            "str  r3, %[rd1]  \n\t"
            : [rn]  "+m" (regs->uregs[rn]),
              [rd0] "=m" (regs->uregs[rd]),
              [rd1] "=m" (regs->uregs[rd+1])
            : [rm]   "m" (regs->uregs[rm]),
              [cpsr] "r" (regs->ARM_cpsr),
              [i_fn] "r" (i_fn)
            : "r0", "r1", "r2", "r3", "lr", "cc"
      );
}

static void __kprobes emulate_strd(struct kprobe *p, struct pt_regs *regs)
{
      insn_4arg_fn_t *i_fn = (insn_4arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;
      int rm  = insn & 0xf;
      long rnv = regs->uregs[rn];
      long rmv = regs->uregs[rm];  /* rm/rmv may be invalid, don't care. */

      regs->uregs[rn] = insnslot_4arg_rflags(rnv, rmv, regs->uregs[rd],
                                     regs->uregs[rd+1],
                                     regs->ARM_cpsr, i_fn);
}

static void __kprobes emulate_ldr(struct kprobe *p, struct pt_regs *regs)
{
      insn_llret_3arg_fn_t *i_fn = (insn_llret_3arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      union reg_pair fnr;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;
      int rm = insn & 0xf;
      long rdv;
      long rnv  = regs->uregs[rn];
      long rmv  = regs->uregs[rm]; /* rm/rmv may be invalid, don't care. */
      long cpsr = regs->ARM_cpsr;

      fnr.dr = insnslot_llret_3arg_rflags(rnv, 0, rmv, cpsr, i_fn);
      regs->uregs[rn] = fnr.r0;  /* Save Rn in case of writeback. */
      rdv = fnr.r1;

      if (rd == 15) {
#if __LINUX_ARM_ARCH__ >= 5
            cpsr &= ~PSR_T_BIT;
            if (rdv & 0x1)
                  cpsr |= PSR_T_BIT;
            regs->ARM_cpsr = cpsr;
            rdv &= ~0x1;
#else
            rdv &= ~0x2;
#endif
      }
      regs->uregs[rd] = rdv;
}

static void __kprobes emulate_str(struct kprobe *p, struct pt_regs *regs)
{
      insn_3arg_fn_t *i_fn = (insn_3arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      long iaddr = (long)p->addr;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;
      int rm = insn & 0xf;
      long rdv = (rd == 15) ? iaddr + str_pc_offset : regs->uregs[rd];
      long rnv = (rn == 15) ? iaddr +  8 : regs->uregs[rn];
      long rmv = regs->uregs[rm];  /* rm/rmv may be invalid, don't care. */

      /* Save Rn in case of writeback. */
      regs->uregs[rn] =
            insnslot_3arg_rflags(rnv, rdv, rmv, regs->ARM_cpsr, i_fn);
}

static void __kprobes emulate_mrrc(struct kprobe *p, struct pt_regs *regs)
{
      insn_llret_0arg_fn_t *i_fn = (insn_llret_0arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      union reg_pair fnr;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;

      fnr.dr = insnslot_llret_0arg_rflags(regs->ARM_cpsr, i_fn);
      regs->uregs[rn] = fnr.r0;
      regs->uregs[rd] = fnr.r1;
}

static void __kprobes emulate_mcrr(struct kprobe *p, struct pt_regs *regs)
{
      insn_2arg_fn_t *i_fn = (insn_2arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;
      long rnv = regs->uregs[rn];
      long rdv = regs->uregs[rd];

      insnslot_2arg_rflags(rnv, rdv, regs->ARM_cpsr, i_fn);
}

static void __kprobes emulate_sat(struct kprobe *p, struct pt_regs *regs)
{
      insn_1arg_fn_t *i_fn = (insn_1arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 12) & 0xf;
      int rm = insn & 0xf;
      long rmv = regs->uregs[rm];

      /* Writes Q flag */
      regs->uregs[rd] = insnslot_1arg_rwflags(rmv, &regs->ARM_cpsr, i_fn);
}

static void __kprobes emulate_sel(struct kprobe *p, struct pt_regs *regs)
{
      insn_2arg_fn_t *i_fn = (insn_2arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;
      int rm = insn & 0xf;
      long rnv = regs->uregs[rn];
      long rmv = regs->uregs[rm];

      /* Reads GE bits */
      regs->uregs[rd] = insnslot_2arg_rflags(rnv, rmv, regs->ARM_cpsr, i_fn);
}

static void __kprobes emulate_none(struct kprobe *p, struct pt_regs *regs)
{
      insn_0arg_fn_t *i_fn = (insn_0arg_fn_t *)&p->ainsn.insn[0];

      insnslot_0arg_rflags(regs->ARM_cpsr, i_fn);
}

static void __kprobes emulate_rd12(struct kprobe *p, struct pt_regs *regs)
{
      insn_0arg_fn_t *i_fn = (insn_0arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 12) & 0xf;

      regs->uregs[rd] = insnslot_0arg_rflags(regs->ARM_cpsr, i_fn);
}

static void __kprobes emulate_ird12(struct kprobe *p, struct pt_regs *regs)
{
      insn_1arg_fn_t *i_fn = (insn_1arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int ird = (insn >> 12) & 0xf;

      insnslot_1arg_rflags(regs->uregs[ird], regs->ARM_cpsr, i_fn);
}

static void __kprobes emulate_rn16(struct kprobe *p, struct pt_regs *regs)
{
      insn_1arg_fn_t *i_fn = (insn_1arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rn = (insn >> 16) & 0xf;
      long rnv = regs->uregs[rn];

      insnslot_1arg_rflags(rnv, regs->ARM_cpsr, i_fn);
}

static void __kprobes emulate_rd12rm0(struct kprobe *p, struct pt_regs *regs)
{
      insn_1arg_fn_t *i_fn = (insn_1arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 12) & 0xf;
      int rm = insn & 0xf;
      long rmv = regs->uregs[rm];

      regs->uregs[rd] = insnslot_1arg_rflags(rmv, regs->ARM_cpsr, i_fn);
}

static void __kprobes
emulate_rd12rn16rm0_rwflags(struct kprobe *p, struct pt_regs *regs)
{
      insn_2arg_fn_t *i_fn = (insn_2arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;
      int rm = insn & 0xf;
      long rnv = regs->uregs[rn];
      long rmv = regs->uregs[rm];

      regs->uregs[rd] =
            insnslot_2arg_rwflags(rnv, rmv, &regs->ARM_cpsr, i_fn);
}

static void __kprobes
emulate_rd16rn12rs8rm0_rwflags(struct kprobe *p, struct pt_regs *regs)
{
      insn_3arg_fn_t *i_fn = (insn_3arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 16) & 0xf;
      int rn = (insn >> 12) & 0xf;
      int rs = (insn >> 8) & 0xf;
      int rm = insn & 0xf;
      long rnv = regs->uregs[rn];
      long rsv = regs->uregs[rs];
      long rmv = regs->uregs[rm];

      regs->uregs[rd] =
            insnslot_3arg_rwflags(rnv, rsv, rmv, &regs->ARM_cpsr, i_fn);
}

static void __kprobes
emulate_rd16rs8rm0_rwflags(struct kprobe *p, struct pt_regs *regs)
{
      insn_2arg_fn_t *i_fn = (insn_2arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 16) & 0xf;
      int rs = (insn >> 8) & 0xf;
      int rm = insn & 0xf;
      long rsv = regs->uregs[rs];
      long rmv = regs->uregs[rm];

      regs->uregs[rd] =
            insnslot_2arg_rwflags(rsv, rmv, &regs->ARM_cpsr, i_fn);
}

static void __kprobes
emulate_rdhi16rdlo12rs8rm0_rwflags(struct kprobe *p, struct pt_regs *regs)
{
      insn_llret_4arg_fn_t *i_fn = (insn_llret_4arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      union reg_pair fnr;
      int rdhi = (insn >> 16) & 0xf;
      int rdlo = (insn >> 12) & 0xf;
      int rs   = (insn >> 8) & 0xf;
      int rm   = insn & 0xf;
      long rsv = regs->uregs[rs];
      long rmv = regs->uregs[rm];

      fnr.dr = insnslot_llret_4arg_rwflags(regs->uregs[rdhi],
                                   regs->uregs[rdlo], rsv, rmv,
                                   &regs->ARM_cpsr, i_fn);
      regs->uregs[rdhi] = fnr.r0;
      regs->uregs[rdlo] = fnr.r1;
}

static void __kprobes
emulate_alu_imm_rflags(struct kprobe *p, struct pt_regs *regs)
{
      insn_1arg_fn_t *i_fn = (insn_1arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;
      long rnv = (rn == 15) ? (long)p->addr + 8 : regs->uregs[rn];

      regs->uregs[rd] = insnslot_1arg_rflags(rnv, regs->ARM_cpsr, i_fn);
}

static void __kprobes
emulate_alu_imm_rwflags(struct kprobe *p, struct pt_regs *regs)
{
      insn_1arg_fn_t *i_fn = (insn_1arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;
      long rnv = (rn == 15) ? (long)p->addr + 8 : regs->uregs[rn];

      regs->uregs[rd] = insnslot_1arg_rwflags(rnv, &regs->ARM_cpsr, i_fn);
}

static void __kprobes
emulate_alu_rflags(struct kprobe *p, struct pt_regs *regs)
{
      insn_3arg_fn_t *i_fn = (insn_3arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      long ppc = (long)p->addr + 8;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;  /* rn/rnv/rs/rsv may be */
      int rs = (insn >> 8) & 0xf;   /* invalid, don't care. */
      int rm = insn & 0xf;
      long rnv = (rn == 15) ? ppc : regs->uregs[rn];
      long rmv = (rm == 15) ? ppc : regs->uregs[rm];
      long rsv = regs->uregs[rs];

      regs->uregs[rd] =
            insnslot_3arg_rflags(rnv, rmv, rsv, regs->ARM_cpsr, i_fn);
}

static void __kprobes
emulate_alu_rwflags(struct kprobe *p, struct pt_regs *regs)
{
      insn_3arg_fn_t *i_fn = (insn_3arg_fn_t *)&p->ainsn.insn[0];
      kprobe_opcode_t insn = p->opcode;
      long ppc = (long)p->addr + 8;
      int rd = (insn >> 12) & 0xf;
      int rn = (insn >> 16) & 0xf;  /* rn/rnv/rs/rsv may be */
      int rs = (insn >> 8) & 0xf;   /* invalid, don't care. */
      int rm = insn & 0xf;
      long rnv = (rn == 15) ? ppc : regs->uregs[rn];
      long rmv = (rm == 15) ? ppc : regs->uregs[rm];
      long rsv = regs->uregs[rs];

      regs->uregs[rd] =
            insnslot_3arg_rwflags(rnv, rmv, rsv, &regs->ARM_cpsr, i_fn);
}

static enum kprobe_insn __kprobes
prep_emulate_ldr_str(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      int ibit = (insn & (1 << 26)) ? 25 : 22;

      insn &= 0xfff00fff;
      insn |= 0x00001000;     /* Rn = r0, Rd = r1 */
      if (insn & (1 << ibit)) {
            insn &= ~0xf;
            insn |= 2;  /* Rm = r2 */
      }
      asi->insn[0] = insn;
      asi->insn_handler = (insn & (1 << 20)) ? emulate_ldr : emulate_str;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
prep_emulate_rd12rm0(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      insn &= 0xffff0ff0;     /* Rd = r0, Rm = r0 */
      asi->insn[0] = insn;
      asi->insn_handler = emulate_rd12rm0;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
prep_emulate_rd12(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      insn &= 0xffff0fff;     /* Rd = r0 */
      asi->insn[0] = insn;
      asi->insn_handler = emulate_rd12;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
prep_emulate_rd12rn16rm0_wflags(kprobe_opcode_t insn,
                        struct arch_specific_insn *asi)
{
      insn &= 0xfff00ff0;     /* Rd = r0, Rn = r0 */
      insn |= 0x00000001;     /* Rm = r1 */
      asi->insn[0] = insn;
      asi->insn_handler = emulate_rd12rn16rm0_rwflags;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
prep_emulate_rd16rs8rm0_wflags(kprobe_opcode_t insn,
                         struct arch_specific_insn *asi)
{
      insn &= 0xfff0f0f0;     /* Rd = r0, Rs = r0 */
      insn |= 0x00000001;     /* Rm = r1          */
      asi->insn[0] = insn;
      asi->insn_handler = emulate_rd16rs8rm0_rwflags;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
prep_emulate_rd16rn12rs8rm0_wflags(kprobe_opcode_t insn,
                           struct arch_specific_insn *asi)
{
      insn &= 0xfff000f0;     /* Rd = r0, Rn = r0 */
      insn |= 0x00000102;     /* Rs = r1, Rm = r2 */
      asi->insn[0] = insn;
      asi->insn_handler = emulate_rd16rn12rs8rm0_rwflags;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
prep_emulate_rdhi16rdlo12rs8rm0_wflags(kprobe_opcode_t insn,
                               struct arch_specific_insn *asi)
{
      insn &= 0xfff000f0;     /* RdHi = r0, RdLo = r1 */
      insn |= 0x00001203;     /* Rs = r2, Rm = r3 */
      asi->insn[0] = insn;
      asi->insn_handler = emulate_rdhi16rdlo12rs8rm0_rwflags;
      return INSN_GOOD;
}

/*
 * For the instruction masking and comparisons in all the "space_*"
 * functions below, Do _not_ rearrange the order of tests unless
 * you're very, very sure of what you are doing.  For the sake of
 * efficiency, the masks for some tests sometimes assume other test
 * have been done prior to them so the number of patterns to test
 * for an instruction set can be as broad as possible to reduce the
 * number of tests needed.
 */

static enum kprobe_insn __kprobes
space_1111(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      /* CPS mmod == 1 : 1111 0001 0000 xx10 xxxx xxxx xx0x xxxx */
      /* RFE           : 1111 100x x0x1 xxxx xxxx 1010 xxxx xxxx */
      /* SRS           : 1111 100x x1x0 1101 xxxx 0101 xxxx xxxx */
      if ((insn & 0xfff30020) == 0xf1020000 ||
          (insn & 0xfe500f00) == 0xf8100a00 ||
          (insn & 0xfe5f0f00) == 0xf84d0500)
            return INSN_REJECTED;

      /* PLD : 1111 01x1 x101 xxxx xxxx xxxx xxxx xxxx : */
      if ((insn & 0xfd700000) == 0xf4500000) {
            insn &= 0xfff0ffff;     /* Rn = r0 */
            asi->insn[0] = insn;
            asi->insn_handler = emulate_rn16;
            return INSN_GOOD;
      }

      /* BLX(1) : 1111 101x xxxx xxxx xxxx xxxx xxxx xxxx : */
      if ((insn & 0xfe000000) == 0xfa000000) {
            asi->insn_handler = simulate_blx1;
            return INSN_GOOD_NO_SLOT;
      }

      /* SETEND : 1111 0001 0000 0001 xxxx xxxx 0000 xxxx */
      /* CDP2   : 1111 1110 xxxx xxxx xxxx xxxx xxx0 xxxx */
      if ((insn & 0xffff00f0) == 0xf1010000 ||
          (insn & 0xff000010) == 0xfe000000) {
            asi->insn[0] = insn;
            asi->insn_handler = emulate_none;
            return INSN_GOOD;
      }

      /* MCRR2 : 1111 1100 0100 xxxx xxxx xxxx xxxx xxxx : (Rd != Rn) */
      /* MRRC2 : 1111 1100 0101 xxxx xxxx xxxx xxxx xxxx : (Rd != Rn) */
      if ((insn & 0xffe00000) == 0xfc400000) {
            insn &= 0xfff00fff;     /* Rn = r0 */
            insn |= 0x00001000;     /* Rd = r1 */
            asi->insn[0] = insn;
            asi->insn_handler =
                  (insn & (1 << 20)) ? emulate_mrrc : emulate_mcrr;
            return INSN_GOOD;
      }

      /* LDC2 : 1111 110x xxx1 xxxx xxxx xxxx xxxx xxxx */
      /* STC2 : 1111 110x xxx0 xxxx xxxx xxxx xxxx xxxx */
      if ((insn & 0xfe000000) == 0xfc000000) {
            insn &= 0xfff0ffff;      /* Rn = r0 */
            asi->insn[0] = insn;
            asi->insn_handler = emulate_ldcstc;
            return INSN_GOOD;
      }

      /* MCR2 : 1111 1110 xxx0 xxxx xxxx xxxx xxx1 xxxx */
      /* MRC2 : 1111 1110 xxx1 xxxx xxxx xxxx xxx1 xxxx */
      insn &= 0xffff0fff;     /* Rd = r0 */
      asi->insn[0]      = insn;
      asi->insn_handler = (insn & (1 << 20)) ? emulate_rd12 : emulate_ird12;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
space_cccc_000x(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      /* cccc 0001 0xx0 xxxx xxxx xxxx xxxx xxx0 xxxx */
      if ((insn & 0x0f900010) == 0x01000000) {

            /* BXJ  : cccc 0001 0010 xxxx xxxx xxxx 0010 xxxx */
            /* MSR  : cccc 0001 0x10 xxxx xxxx xxxx 0000 xxxx */
            if ((insn & 0x0ff000f0) == 0x01200020 ||
                (insn & 0x0fb000f0) == 0x01200000)
                  return INSN_REJECTED;

            /* MRS : cccc 0001 0x00 xxxx xxxx xxxx 0000 xxxx */
            if ((insn & 0x0fb00010) == 0x01000000)
                  return prep_emulate_rd12(insn, asi);

            /* SMLALxy : cccc 0001 0100 xxxx xxxx xxxx 1xx0 xxxx */
            if ((insn & 0x0ff00090) == 0x01400080)
                  return prep_emulate_rdhi16rdlo12rs8rm0_wflags(insn, asi);

            /* SMULWy : cccc 0001 0010 xxxx xxxx xxxx 1x10 xxxx */
            /* SMULxy : cccc 0001 0110 xxxx xxxx xxxx 1xx0 xxxx */
            if ((insn & 0x0ff000b0) == 0x012000a0 ||
                (insn & 0x0ff00090) == 0x01600080)
                  return prep_emulate_rd16rs8rm0_wflags(insn, asi);

            /* SMLAxy : cccc 0001 0000 xxxx xxxx xxxx 1xx0 xxxx : Q */
            /* SMLAWy : cccc 0001 0010 xxxx xxxx xxxx 0x00 xxxx : Q */
            return prep_emulate_rd16rn12rs8rm0_wflags(insn, asi);

      }

      /* cccc 0001 0xx0 xxxx xxxx xxxx xxxx 0xx1 xxxx */
      else if ((insn & 0x0f900090) == 0x01000010) {

            /* BKPT : 1110 0001 0010 xxxx xxxx xxxx 0111 xxxx */
            if ((insn & 0xfff000f0) == 0xe1200070)
                  return INSN_REJECTED;

            /* BLX(2) : cccc 0001 0010 xxxx xxxx xxxx 0011 xxxx */
            /* BX     : cccc 0001 0010 xxxx xxxx xxxx 0001 xxxx */
            if ((insn & 0x0ff000d0) == 0x01200010) {
                  asi->insn[0] = truecc_insn(insn);
                  asi->insn_handler = simulate_blx2bx;
                  return INSN_GOOD;
            }

            /* CLZ : cccc 0001 0110 xxxx xxxx xxxx 0001 xxxx */
            if ((insn & 0x0ff000f0) == 0x01600010)
                  return prep_emulate_rd12rm0(insn, asi);

            /* QADD    : cccc 0001 0000 xxxx xxxx xxxx 0101 xxxx :Q */
            /* QSUB    : cccc 0001 0010 xxxx xxxx xxxx 0101 xxxx :Q */
            /* QDADD   : cccc 0001 0100 xxxx xxxx xxxx 0101 xxxx :Q */
            /* QDSUB   : cccc 0001 0110 xxxx xxxx xxxx 0101 xxxx :Q */
            return prep_emulate_rd12rn16rm0_wflags(insn, asi);
      }

      /* cccc 0000 xxxx xxxx xxxx xxxx xxxx 1001 xxxx */
      else if ((insn & 0x0f000090) == 0x00000090) {

            /* MUL    : cccc 0000 0000 xxxx xxxx xxxx 1001 xxxx :   */
            /* MULS   : cccc 0000 0001 xxxx xxxx xxxx 1001 xxxx :cc */
            /* MLA    : cccc 0000 0010 xxxx xxxx xxxx 1001 xxxx :   */
            /* MLAS   : cccc 0000 0011 xxxx xxxx xxxx 1001 xxxx :cc */
            /* UMAAL  : cccc 0000 0100 xxxx xxxx xxxx 1001 xxxx :   */
            /* UMULL  : cccc 0000 1000 xxxx xxxx xxxx 1001 xxxx :   */
            /* UMULLS : cccc 0000 1001 xxxx xxxx xxxx 1001 xxxx :cc */
            /* UMLAL  : cccc 0000 1010 xxxx xxxx xxxx 1001 xxxx :   */
            /* UMLALS : cccc 0000 1011 xxxx xxxx xxxx 1001 xxxx :cc */
            /* SMULL  : cccc 0000 1100 xxxx xxxx xxxx 1001 xxxx :   */
            /* SMULLS : cccc 0000 1101 xxxx xxxx xxxx 1001 xxxx :cc */
            /* SMLAL  : cccc 0000 1110 xxxx xxxx xxxx 1001 xxxx :   */
            /* SMLALS : cccc 0000 1111 xxxx xxxx xxxx 1001 xxxx :cc */
            if ((insn & 0x0fe000f0) == 0x00000090) {
                   return prep_emulate_rd16rs8rm0_wflags(insn, asi);
            } else if  ((insn & 0x0fe000f0) == 0x00200090) {
                   return prep_emulate_rd16rn12rs8rm0_wflags(insn, asi);
            } else {
                   return prep_emulate_rdhi16rdlo12rs8rm0_wflags(insn, asi);
            }
      }

      /* cccc 000x xxxx xxxx xxxx xxxx xxxx 1xx1 xxxx */
      else if ((insn & 0x0e000090) == 0x00000090) {

            /* SWP   : cccc 0001 0000 xxxx xxxx xxxx 1001 xxxx */
            /* SWPB  : cccc 0001 0100 xxxx xxxx xxxx 1001 xxxx */
            /* LDRD  : cccc 000x xxx0 xxxx xxxx xxxx 1101 xxxx */
            /* STRD  : cccc 000x xxx0 xxxx xxxx xxxx 1111 xxxx */
            /* STREX : cccc 0001 1000 xxxx xxxx xxxx 1001 xxxx */
            /* LDREX : cccc 0001 1001 xxxx xxxx xxxx 1001 xxxx */
            /* LDRH  : cccc 000x xxx1 xxxx xxxx xxxx 1011 xxxx */
            /* STRH  : cccc 000x xxx0 xxxx xxxx xxxx 1011 xxxx */
            /* LDRSB : cccc 000x xxx1 xxxx xxxx xxxx 1101 xxxx */
            /* LDRSH : cccc 000x xxx1 xxxx xxxx xxxx 1111 xxxx */
            if ((insn & 0x0fb000f0) == 0x01000090) {
                  /* SWP/SWPB */
                  return prep_emulate_rd12rn16rm0_wflags(insn, asi);
            } else if ((insn & 0x0e1000d0) == 0x00000d0) {
                  /* STRD/LDRD */
                  insn &= 0xfff00fff;
                  insn |= 0x00002000;     /* Rn = r0, Rd = r2 */
                  if (insn & (1 << 22)) {
                        /* I bit */
                        insn &= ~0xf;
                        insn |= 1;  /* Rm = r1 */
                  }
                  asi->insn[0] = insn;
                  asi->insn_handler =
                        (insn & (1 << 5)) ? emulate_strd : emulate_ldrd;
                  return INSN_GOOD;
            }

            return prep_emulate_ldr_str(insn, asi);
      }

      /* cccc 000x xxxx xxxx xxxx xxxx xxxx xxxx xxxx */

      /*
       * ALU op with S bit and Rd == 15 :
       *    cccc 000x xxx1 xxxx 1111 xxxx xxxx xxxx
       */
      if ((insn & 0x0e10f000) == 0x0010f000)
            return INSN_REJECTED;

      /*
       * "mov ip, sp" is the most common kprobe'd instruction by far.
       * Check and optimize for it explicitly.
       */
      if (insn == 0xe1a0c00d) {
            asi->insn_handler = simulate_mov_ipsp;
            return INSN_GOOD_NO_SLOT;
      }

      /*
       * Data processing: Immediate-shift / Register-shift
       * ALU op : cccc 000x xxxx xxxx xxxx xxxx xxxx xxxx
       * CPY    : cccc 0001 1010 xxxx xxxx 0000 0000 xxxx
       * MOV    : cccc 0001 101x xxxx xxxx xxxx xxxx xxxx
       * *S (bit 20) updates condition codes
       * ADC/SBC/RSC reads the C flag
       */
      insn &= 0xfff00ff0;     /* Rn = r0, Rd = r0 */
      insn |= 0x00000001;     /* Rm = r1 */
      if (insn & 0x010) {
            insn &= 0xfffff0ff;     /* register shift */
            insn |= 0x00000200;     /* Rs = r2 */
      }
      asi->insn[0] = insn;
      asi->insn_handler = (insn & (1 << 20)) ?  /* S-bit */
                        emulate_alu_rwflags : emulate_alu_rflags;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
space_cccc_001x(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      /*
       * MSR   : cccc 0011 0x10 xxxx xxxx xxxx xxxx xxxx
       * Undef : cccc 0011 0x00 xxxx xxxx xxxx xxxx xxxx
       * ALU op with S bit and Rd == 15 :
       *       cccc 001x xxx1 xxxx 1111 xxxx xxxx xxxx
       */
      if ((insn & 0x0f900000) == 0x03200000 ||  /* MSR & Undef */
          (insn & 0x0e10f000) == 0x0210f000)          /* ALU s-bit, R15  */
            return INSN_REJECTED;

      /*
       * Data processing: 32-bit Immediate
       * ALU op : cccc 001x xxxx xxxx xxxx xxxx xxxx xxxx
       * MOV    : cccc 0011 101x xxxx xxxx xxxx xxxx xxxx
       * *S (bit 20) updates condition codes
       * ADC/SBC/RSC reads the C flag
       */
      insn &= 0xfff00fff;     /* Rn = r0, Rd = r0 */
      asi->insn[0] = insn;
      asi->insn_handler = (insn & (1 << 20)) ?  /* S-bit */
                  emulate_alu_imm_rwflags : emulate_alu_imm_rflags;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
space_cccc_0110__1(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      /* SEL : cccc 0110 1000 xxxx xxxx xxxx 1011 xxxx GE: !!! */
      if ((insn & 0x0ff000f0) == 0x068000b0) {
            insn &= 0xfff00ff0;     /* Rd = r0, Rn = r0 */
            insn |= 0x00000001;     /* Rm = r1 */
            asi->insn[0] = insn;
            asi->insn_handler = emulate_sel;
            return INSN_GOOD;
      }

      /* SSAT   : cccc 0110 101x xxxx xxxx xxxx xx01 xxxx :Q */
      /* USAT   : cccc 0110 111x xxxx xxxx xxxx xx01 xxxx :Q */
      /* SSAT16 : cccc 0110 1010 xxxx xxxx xxxx 0011 xxxx :Q */
      /* USAT16 : cccc 0110 1110 xxxx xxxx xxxx 0011 xxxx :Q */
      if ((insn & 0x0fa00030) == 0x06a00010 ||
          (insn & 0x0fb000f0) == 0x06a00030) {
            insn &= 0xffff0ff0;     /* Rd = r0, Rm = r0 */
            asi->insn[0] = insn;
            asi->insn_handler = emulate_sat;
            return INSN_GOOD;
      }

      /* REV    : cccc 0110 1011 xxxx xxxx xxxx 0011 xxxx */
      /* REV16  : cccc 0110 1011 xxxx xxxx xxxx 1011 xxxx */
      /* REVSH  : cccc 0110 1111 xxxx xxxx xxxx 1011 xxxx */
      if ((insn & 0x0ff00070) == 0x06b00030 ||
          (insn & 0x0ff000f0) == 0x06f000b0)
            return prep_emulate_rd12rm0(insn, asi);

      /* SADD16    : cccc 0110 0001 xxxx xxxx xxxx 0001 xxxx :GE */
      /* SADDSUBX  : cccc 0110 0001 xxxx xxxx xxxx 0011 xxxx :GE */
      /* SSUBADDX  : cccc 0110 0001 xxxx xxxx xxxx 0101 xxxx :GE */
      /* SSUB16    : cccc 0110 0001 xxxx xxxx xxxx 0111 xxxx :GE */
      /* SADD8     : cccc 0110 0001 xxxx xxxx xxxx 1001 xxxx :GE */
      /* SSUB8     : cccc 0110 0001 xxxx xxxx xxxx 1111 xxxx :GE */
      /* QADD16    : cccc 0110 0010 xxxx xxxx xxxx 0001 xxxx :   */
      /* QADDSUBX  : cccc 0110 0010 xxxx xxxx xxxx 0011 xxxx :   */
      /* QSUBADDX  : cccc 0110 0010 xxxx xxxx xxxx 0101 xxxx :   */
      /* QSUB16    : cccc 0110 0010 xxxx xxxx xxxx 0111 xxxx :   */
      /* QADD8     : cccc 0110 0010 xxxx xxxx xxxx 1001 xxxx :   */
      /* QSUB8     : cccc 0110 0010 xxxx xxxx xxxx 1111 xxxx :   */
      /* SHADD16   : cccc 0110 0011 xxxx xxxx xxxx 0001 xxxx :   */
      /* SHADDSUBX : cccc 0110 0011 xxxx xxxx xxxx 0011 xxxx :   */
      /* SHSUBADDX : cccc 0110 0011 xxxx xxxx xxxx 0101 xxxx :   */
      /* SHSUB16   : cccc 0110 0011 xxxx xxxx xxxx 0111 xxxx :   */
      /* SHADD8    : cccc 0110 0011 xxxx xxxx xxxx 1001 xxxx :   */
      /* SHSUB8    : cccc 0110 0011 xxxx xxxx xxxx 1111 xxxx :   */
      /* UADD16    : cccc 0110 0101 xxxx xxxx xxxx 0001 xxxx :GE */
      /* UADDSUBX  : cccc 0110 0101 xxxx xxxx xxxx 0011 xxxx :GE */
      /* USUBADDX  : cccc 0110 0101 xxxx xxxx xxxx 0101 xxxx :GE */
      /* USUB16    : cccc 0110 0101 xxxx xxxx xxxx 0111 xxxx :GE */
      /* UADD8     : cccc 0110 0101 xxxx xxxx xxxx 1001 xxxx :GE */
      /* USUB8     : cccc 0110 0101 xxxx xxxx xxxx 1111 xxxx :GE */
      /* UQADD16   : cccc 0110 0110 xxxx xxxx xxxx 0001 xxxx :   */
      /* UQADDSUBX : cccc 0110 0110 xxxx xxxx xxxx 0011 xxxx :   */
      /* UQSUBADDX : cccc 0110 0110 xxxx xxxx xxxx 0101 xxxx :   */
      /* UQSUB16   : cccc 0110 0110 xxxx xxxx xxxx 0111 xxxx :   */
      /* UQADD8    : cccc 0110 0110 xxxx xxxx xxxx 1001 xxxx :   */
      /* UQSUB8    : cccc 0110 0110 xxxx xxxx xxxx 1111 xxxx :   */
      /* UHADD16   : cccc 0110 0111 xxxx xxxx xxxx 0001 xxxx :   */
      /* UHADDSUBX : cccc 0110 0111 xxxx xxxx xxxx 0011 xxxx :   */
      /* UHSUBADDX : cccc 0110 0111 xxxx xxxx xxxx 0101 xxxx :   */
      /* UHSUB16   : cccc 0110 0111 xxxx xxxx xxxx 0111 xxxx :   */
      /* UHADD8    : cccc 0110 0111 xxxx xxxx xxxx 1001 xxxx :   */
      /* UHSUB8    : cccc 0110 0111 xxxx xxxx xxxx 1111 xxxx :   */
      /* PKHBT     : cccc 0110 1000 xxxx xxxx xxxx x001 xxxx :   */
      /* PKHTB     : cccc 0110 1000 xxxx xxxx xxxx x101 xxxx :   */
      /* SXTAB16   : cccc 0110 1000 xxxx xxxx xxxx 0111 xxxx :   */
      /* SXTB      : cccc 0110 1010 xxxx xxxx xxxx 0111 xxxx :   */
      /* SXTAB     : cccc 0110 1010 xxxx xxxx xxxx 0111 xxxx :   */
      /* SXTAH     : cccc 0110 1011 xxxx xxxx xxxx 0111 xxxx :   */
      /* UXTAB16   : cccc 0110 1100 xxxx xxxx xxxx 0111 xxxx :   */
      /* UXTAB     : cccc 0110 1110 xxxx xxxx xxxx 0111 xxxx :   */
      /* UXTAH     : cccc 0110 1111 xxxx xxxx xxxx 0111 xxxx :   */
      return prep_emulate_rd12rn16rm0_wflags(insn, asi);
}

static enum kprobe_insn __kprobes
space_cccc_0111__1(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      /* Undef : cccc 0111 1111 xxxx xxxx xxxx 1111 xxxx */
      if ((insn & 0x0ff000f0) == 0x03f000f0)
            return INSN_REJECTED;

      /* USADA8 : cccc 0111 1000 xxxx xxxx xxxx 0001 xxxx */
      /* USAD8  : cccc 0111 1000 xxxx 1111 xxxx 0001 xxxx */
      if ((insn & 0x0ff000f0) == 0x07800010)
             return prep_emulate_rd16rn12rs8rm0_wflags(insn, asi);

      /* SMLALD : cccc 0111 0100 xxxx xxxx xxxx 00x1 xxxx */
      /* SMLSLD : cccc 0111 0100 xxxx xxxx xxxx 01x1 xxxx */
      if ((insn & 0x0ff00090) == 0x07400010)
            return prep_emulate_rdhi16rdlo12rs8rm0_wflags(insn, asi);

      /* SMLAD  : cccc 0111 0000 xxxx xxxx xxxx 00x1 xxxx :Q */
      /* SMLSD  : cccc 0111 0000 xxxx xxxx xxxx 01x1 xxxx :Q */
      /* SMMLA  : cccc 0111 0101 xxxx xxxx xxxx 00x1 xxxx :  */
      /* SMMLS  : cccc 0111 0101 xxxx xxxx xxxx 11x1 xxxx :  */
      if ((insn & 0x0ff00090) == 0x07000010 ||
          (insn & 0x0ff000d0) == 0x07500010 ||
          (insn & 0x0ff000d0) == 0x075000d0)
            return prep_emulate_rd16rn12rs8rm0_wflags(insn, asi);

      /* SMUSD  : cccc 0111 0000 xxxx xxxx xxxx 01x1 xxxx :  */
      /* SMUAD  : cccc 0111 0000 xxxx 1111 xxxx 00x1 xxxx :Q */
      /* SMMUL  : cccc 0111 0101 xxxx 1111 xxxx 00x1 xxxx :  */
      return prep_emulate_rd16rs8rm0_wflags(insn, asi);
}

static enum kprobe_insn __kprobes
space_cccc_01xx(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      /* LDR   : cccc 01xx x0x1 xxxx xxxx xxxx xxxx xxxx */
      /* LDRB  : cccc 01xx x1x1 xxxx xxxx xxxx xxxx xxxx */
      /* LDRBT : cccc 01x0 x111 xxxx xxxx xxxx xxxx xxxx */
      /* LDRT  : cccc 01x0 x011 xxxx xxxx xxxx xxxx xxxx */
      /* STR   : cccc 01xx x0x0 xxxx xxxx xxxx xxxx xxxx */
      /* STRB  : cccc 01xx x1x0 xxxx xxxx xxxx xxxx xxxx */
      /* STRBT : cccc 01x0 x110 xxxx xxxx xxxx xxxx xxxx */
      /* STRT  : cccc 01x0 x010 xxxx xxxx xxxx xxxx xxxx */
      return prep_emulate_ldr_str(insn, asi);
}

static enum kprobe_insn __kprobes
space_cccc_100x(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      /* LDM(2) : cccc 100x x101 xxxx 0xxx xxxx xxxx xxxx */
      /* LDM(3) : cccc 100x x1x1 xxxx 1xxx xxxx xxxx xxxx */
      if ((insn & 0x0e708000) == 0x85000000 ||
          (insn & 0x0e508000) == 0x85010000)
            return INSN_REJECTED;

      /* LDM(1) : cccc 100x x0x1 xxxx xxxx xxxx xxxx xxxx */
      /* STM(1) : cccc 100x x0x0 xxxx xxxx xxxx xxxx xxxx */
      asi->insn[0] = truecc_insn(insn);
      asi->insn_handler = ((insn & 0x108000) == 0x008000) ? /* STM & R15 */
                        simulate_stm1_pc : simulate_ldm1stm1;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
space_cccc_101x(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      /* B  : cccc 1010 xxxx xxxx xxxx xxxx xxxx xxxx */
      /* BL : cccc 1011 xxxx xxxx xxxx xxxx xxxx xxxx */
      asi->insn[0] = truecc_insn(insn);
      asi->insn_handler = simulate_bbl;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
space_cccc_1100_010x(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      /* MCRR : cccc 1100 0100 xxxx xxxx xxxx xxxx xxxx : (Rd!=Rn) */
      /* MRRC : cccc 1100 0101 xxxx xxxx xxxx xxxx xxxx : (Rd!=Rn) */
      insn &= 0xfff00fff;
      insn |= 0x00001000;     /* Rn = r0, Rd = r1 */
      asi->insn[0] = insn;
      asi->insn_handler = (insn & (1 << 20)) ? emulate_mrrc : emulate_mcrr;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
space_cccc_110x(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      /* LDC : cccc 110x xxx1 xxxx xxxx xxxx xxxx xxxx */
      /* STC : cccc 110x xxx0 xxxx xxxx xxxx xxxx xxxx */
      insn &= 0xfff0ffff;     /* Rn = r0 */
      asi->insn[0] = insn;
      asi->insn_handler = emulate_ldcstc;
      return INSN_GOOD;
}

static enum kprobe_insn __kprobes
space_cccc_111x(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      /* BKPT : 1110 0001 0010 xxxx xxxx xxxx 0111 xxxx */
      /* SWI  : cccc 1111 xxxx xxxx xxxx xxxx xxxx xxxx */
      if ((insn & 0xfff000f0) == 0xe1200070 ||
          (insn & 0x0f000000) == 0x0f000000)
            return INSN_REJECTED;

      /* CDP : cccc 1110 xxxx xxxx xxxx xxxx xxx0 xxxx */
      if ((insn & 0x0f000010) == 0x0e000000) {
            asi->insn[0] = insn;
            asi->insn_handler = emulate_none;
            return INSN_GOOD;
      }

      /* MCR : cccc 1110 xxx0 xxxx xxxx xxxx xxx1 xxxx */
      /* MRC : cccc 1110 xxx1 xxxx xxxx xxxx xxx1 xxxx */
      insn &= 0xffff0fff;     /* Rd = r0 */
      asi->insn[0] = insn;
      asi->insn_handler = (insn & (1 << 20)) ? emulate_rd12 : emulate_ird12;
      return INSN_GOOD;
}

/* Return:
 *   INSN_REJECTED     If instruction is one not allowed to kprobe,
 *   INSN_GOOD         If instruction is supported and uses instruction slot,
 *   INSN_GOOD_NO_SLOT If instruction is supported but doesn't use its slot.
 *
 * For instructions we don't want to kprobe (INSN_REJECTED return result):
 *   These are generally ones that modify the processor state making
 *   them "hard" to simulate such as switches processor modes or
 *   make accesses in alternate modes.  Any of these could be simulated
 *   if the work was put into it, but low return considering they
 *   should also be very rare.
 */
enum kprobe_insn __kprobes
arm_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
      asi->insn[1] = KPROBE_RETURN_INSTRUCTION;

      if ((insn & 0xf0000000) == 0xf0000000) {

            return space_1111(insn, asi);

      } else if ((insn & 0x0e000000) == 0x00000000) {

            return space_cccc_000x(insn, asi);

      } else if ((insn & 0x0e000000) == 0x02000000) {

            return space_cccc_001x(insn, asi);

      } else if ((insn & 0x0f000010) == 0x06000010) {

            return space_cccc_0110__1(insn, asi);

      } else if ((insn & 0x0f000010) == 0x07000010) {

            return space_cccc_0111__1(insn, asi);

      } else if ((insn & 0x0c000000) == 0x04000000) {

            return space_cccc_01xx(insn, asi);

      } else if ((insn & 0x0e000000) == 0x08000000) {

            return space_cccc_100x(insn, asi);

      } else if ((insn & 0x0e000000) == 0x0a000000) {

            return space_cccc_101x(insn, asi);

      } else if ((insn & 0x0fe00000) == 0x0c400000) {

            return space_cccc_1100_010x(insn, asi);

      } else if ((insn & 0x0e000000) == 0x0c400000) {

            return space_cccc_110x(insn, asi);

      }

      return space_cccc_111x(insn, asi);
}

void __init arm_kprobe_decode_init(void)
{
      find_str_pc_offset();
}


/*
 * All ARM instructions listed below.
 *
 * Instructions and their general purpose registers are given.
 * If a particular register may not use R15, it is prefixed with a "!".
 * If marked with a "*" means the value returned by reading R15
 * is implementation defined.
 *
 * ADC/ADD/AND/BIC/CMN/CMP/EOR/MOV/MVN/ORR/RSB/RSC/SBC/SUB/TEQ
 *     TST: Rd, Rn, Rm, !Rs
 * BX: Rm
 * BLX(2): !Rm
 * BX: Rm (R15 legal, but discouraged)
 * BXJ: !Rm,
 * CLZ: !Rd, !Rm
 * CPY: Rd, Rm
 * LDC/2,STC/2 immediate offset & unindex: Rn
 * LDC/2,STC/2 immediate pre/post-indexed: !Rn
 * LDM(1/3): !Rn, register_list
 * LDM(2): !Rn, !register_list
 * LDR,STR,PLD immediate offset: Rd, Rn
 * LDR,STR,PLD register offset: Rd, Rn, !Rm
 * LDR,STR,PLD scaled register offset: Rd, !Rn, !Rm
 * LDR,STR immediate pre/post-indexed: Rd, !Rn
 * LDR,STR register pre/post-indexed: Rd, !Rn, !Rm
 * LDR,STR scaled register pre/post-indexed: Rd, !Rn, !Rm
 * LDRB,STRB immediate offset: !Rd, Rn
 * LDRB,STRB register offset: !Rd, Rn, !Rm
 * LDRB,STRB scaled register offset: !Rd, !Rn, !Rm
 * LDRB,STRB immediate pre/post-indexed: !Rd, !Rn
 * LDRB,STRB register pre/post-indexed: !Rd, !Rn, !Rm
 * LDRB,STRB scaled register pre/post-indexed: !Rd, !Rn, !Rm
 * LDRT,LDRBT,STRBT immediate pre/post-indexed: !Rd, !Rn
 * LDRT,LDRBT,STRBT register pre/post-indexed: !Rd, !Rn, !Rm
 * LDRT,LDRBT,STRBT scaled register pre/post-indexed: !Rd, !Rn, !Rm
 * LDRH/SH/SB/D,STRH/SH/SB/D immediate offset: !Rd, Rn
 * LDRH/SH/SB/D,STRH/SH/SB/D register offset: !Rd, Rn, !Rm
 * LDRH/SH/SB/D,STRH/SH/SB/D immediate pre/post-indexed: !Rd, !Rn
 * LDRH/SH/SB/D,STRH/SH/SB/D register pre/post-indexed: !Rd, !Rn, !Rm
 * LDREX: !Rd, !Rn
 * MCR/2: !Rd
 * MCRR/2,MRRC/2: !Rd, !Rn
 * MLA: !Rd, !Rn, !Rm, !Rs
 * MOV: Rd
 * MRC/2: !Rd (if Rd==15, only changes cond codes, not the register)
 * MRS,MSR: !Rd
 * MUL: !Rd, !Rm, !Rs
 * PKH{BT,TB}: !Rd, !Rn, !Rm
 * QDADD,[U]QADD/16/8/SUBX: !Rd, !Rm, !Rn
 * QDSUB,[U]QSUB/16/8/ADDX: !Rd, !Rm, !Rn
 * REV/16/SH: !Rd, !Rm
 * RFE: !Rn
 * {S,U}[H]ADD{16,8,SUBX},{S,U}[H]SUB{16,8,ADDX}: !Rd, !Rn, !Rm
 * SEL: !Rd, !Rn, !Rm
 * SMLA<x><y>,SMLA{D,W<y>},SMLSD,SMML{A,S}: !Rd, !Rn, !Rm, !Rs
 * SMLAL<x><y>,SMLA{D,LD},SMLSLD,SMMULL,SMULW<y>: !RdHi, !RdLo, !Rm, !Rs
 * SMMUL,SMUAD,SMUL<x><y>,SMUSD: !Rd, !Rm, !Rs
 * SSAT/16: !Rd, !Rm
 * STM(1/2): !Rn, register_list* (R15 in reg list not recommended)
 * STRT immediate pre/post-indexed: Rd*, !Rn
 * STRT register pre/post-indexed: Rd*, !Rn, !Rm
 * STRT scaled register pre/post-indexed: Rd*, !Rn, !Rm
 * STREX: !Rd, !Rn, !Rm
 * SWP/B: !Rd, !Rn, !Rm
 * {S,U}XTA{B,B16,H}: !Rd, !Rn, !Rm
 * {S,U}XT{B,B16,H}: !Rd, !Rm
 * UM{AA,LA,UL}L: !RdHi, !RdLo, !Rm, !Rs
 * USA{D8,A8,T,T16}: !Rd, !Rm, !Rs
 *
 * May transfer control by writing R15 (possible mode changes or alternate
 * mode accesses marked by "*"):
 * ALU op (* with s-bit), B, BL, BKPT, BLX(1/2), BX, BXJ, CPS*, CPY,
 * LDM(1), LDM(2/3)*, LDR, MOV, RFE*, SWI*
 *
 * Instructions that do not take general registers, nor transfer control:
 * CDP/2, SETEND, SRS*
 */

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