ARM: kprobes: Add condition code checking to Thumb emulation

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

arch/arm/kernel/kprobes-thumb.c

@@ -13,14 +13,36 @@
 
 #include "kprobes.h"
 
+
+/*
+ * True if current instruction is in an IT block.
+ */
+#define in_it_block(cpsr)	((cpsr & 0x06000c00) != 0x00000000)
+
+/*
+ * Return the condition code to check for the currently executing instruction.
+ * This is in ITSTATE<7:4> which is in CPSR<15:12> but is only valid if
+ * in_it_block returns true.
+ */
+#define current_cond(cpsr)	((cpsr >> 12) & 0xf)
+
+static unsigned long __kprobes thumb_check_cc(unsigned long cpsr)
+{
+	if (unlikely(in_it_block(cpsr)))
+		return kprobe_condition_checks[current_cond(cpsr)](cpsr);
+	return true;
+}
+
 enum kprobe_insn __kprobes
 thumb16_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
 {
+	asi->insn_check_cc = thumb_check_cc;
 	return INSN_REJECTED;
 }
 
 enum kprobe_insn __kprobes
 thumb32_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
 {
+	asi->insn_check_cc = thumb_check_cc;
 	return INSN_REJECTED;
 }