ARM: kprobes: Decode 16-bit Thumb CBZ and bit manipulation instructions

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

1 files changed, 29 insertions, 0 deletions

diff --git a/arch/arm/kernel/kprobes-thumb.c b/arch/arm/kernel/kprobes-thumb.c
index 2b30828d5f0c..a5bdb2dc39e7 100644
--- a/arch/arm/kernel/kprobes-thumb.c
+++ b/arch/arm/kernel/kprobes-thumb.c
@@ -96,6 +96,20 @@ t16_simulate_add_sp_imm(struct kprobe *p, struct pt_regs *regs)
                 regs->ARM_sp += imm * 4;
 }
 
+static void __kprobes
+t16_simulate_cbz(struct kprobe *p, struct pt_regs *regs)
+{
+        kprobe_opcode_t insn = p->opcode;
+        int rn = insn & 0x7;
+        kprobe_opcode_t nonzero = regs->uregs[rn] ? insn : ~insn;
+        if (nonzero & 0x800) {
+                long i = insn & 0x200;
+                long imm5 = insn & 0xf8;
+                unsigned long pc = thumb_probe_pc(p);
+                regs->ARM_pc = pc + (i >> 3) + (imm5 >> 2);
+        }
+}
+
 static unsigned long __kprobes
 t16_emulate_loregs(struct kprobe *p, struct pt_regs *regs)
 {
@@ -180,6 +194,21 @@ static const union decode_item t16_table_1011[] = {
         /* SUB (SP minus immediate)     1011 0000 1xxx xxxx */
         DECODE_SIMULATE (0xff00, 0xb000, t16_simulate_add_sp_imm),
 
+        /* CBZ                          1011 00x1 xxxx xxxx */
+        /* CBNZ                         1011 10x1 xxxx xxxx */
+        DECODE_SIMULATE (0xf500, 0xb100, t16_simulate_cbz),
+
+        /* SXTH                         1011 0010 00xx xxxx */
+        /* SXTB                         1011 0010 01xx xxxx */
+        /* UXTH                         1011 0010 10xx xxxx */
+        /* UXTB                         1011 0010 11xx xxxx */
+        /* REV                          1011 1010 00xx xxxx */
+        /* REV16                        1011 1010 01xx xxxx */
+        /* ???                          1011 1010 10xx xxxx */
+        /* REVSH                        1011 1010 11xx xxxx */
+        DECODE_REJECT   (0xffc0, 0xba80),
+        DECODE_EMULATE  (0xf500, 0xb000, t16_emulate_loregs_rwflags),
+
         /*
          * If-Then, and hints
          *                              1011 1111 xxxx xxxx