ARM: kprobes: Fix emulation of MRS instruction

The MRS instruction should set mode and interrupt bits in the read value
so it is simpler to use a new simulation routine (simulate_mrs) rather
than some modified emulation.

prep_emulate_rd12 is now unused and removed.

Signed-off-by: Jon Medhurst <tixy@yxit.co.uk>
Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>

diff --git a/arch/arm/kernel/kprobes-decode.c b/arch/arm/kernel/kprobes-decode.c
index e5bc576..4ab83f4 100644 (file)
--- a/arch/arm/kernel/kprobes-decode.c
+++ b/arch/arm/kernel/kprobes-decode.c
@@ -451,6 +451,14 @@ static void __kprobes simulate_blx2bx(struct kprobe *p, struct pt_regs *regs)
                regs->ARM_cpsr |= PSR_T_BIT;
 }
 
+static void __kprobes simulate_mrs(struct kprobe *p, struct pt_regs *regs)
+{
+       kprobe_opcode_t insn = p->opcode;
+       int rd = (insn >> 12) & 0xf;
+       unsigned long mask = 0xf8ff03df; /* Mask out execution state */
+       regs->uregs[rd] = regs->ARM_cpsr & mask;
+}
+
 static void __kprobes simulate_ldm1stm1(struct kprobe *p, struct pt_regs *regs)
 {
        kprobe_opcode_t insn = p->opcode;
@@ -895,15 +903,6 @@ prep_emulate_rd12rm0(kprobe_opcode_t insn, struct arch_specific_insn *asi)
        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)
@@ -1035,8 +1034,10 @@ space_cccc_000x(kprobe_opcode_t insn, struct arch_specific_insn *asi)
                        return INSN_REJECTED;
 
                /* MRS cpsr : cccc 0001 0000 xxxx xxxx xxxx 0000 xxxx */
-               if ((insn & 0x0ff000f0) == 0x01000000)
-                       return prep_emulate_rd12(insn, asi);
+               if ((insn & 0x0ff000f0) == 0x01000000) {
+                       asi->insn_handler = simulate_mrs;
+                       return INSN_GOOD_NO_SLOT;
+               }
 
                /* SMLALxy : cccc 0001 0100 xxxx xxxx xxxx 1xx0 xxxx */
                if ((insn & 0x0ff00090) == 0x01400080)