ARM: kprobes: introduces checker

This patch introdces 'checker' to decoding phase, and calls checkers
when instruction decoding. This allows further decoding for specific
instructions.  This patch introduces a stub call of checkers in kprobe
arch_prepare_kprobe() as an example and for further expansion.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Reviewed-by: Jon Medhurst <tixy@linaro.org>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Jon Medhurst <tixy@linaro.org>

arch/arm/probes/kprobes/actions-arm.c

@@ -339,3 +339,5 @@ const union decode_action kprobes_arm_actions[NUM_PROBES_ARM_ACTIONS] = {
 	[PROBES_BRANCH] = {.handler = simulate_bbl},
 	[PROBES_LDMSTM] = {.decoder = kprobe_decode_ldmstm}
 };
+
+const struct decode_checker *kprobes_arm_checkers[] = {NULL};

arch/arm/probes/kprobes/actions-thumb.c

@@ -664,3 +664,6 @@ const union decode_action kprobes_t32_actions[NUM_PROBES_T32_ACTIONS] = {
 	[PROBES_T32_MUL_ADD_LONG] = {
 		.handler = t32_emulate_rdlo12rdhi8rn16rm0_noflags},
 };
+
+const struct decode_checker *kprobes_t32_checkers[] = {NULL};
+const struct decode_checker *kprobes_t16_checkers[] = {NULL};

arch/arm/probes/kprobes/core.c

@@ -61,6 +61,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 	kprobe_decode_insn_t *decode_insn;
 	const union decode_action *actions;
 	int is;
+	const struct decode_checker **checkers;
 
 	if (in_exception_text(addr))
 		return -EINVAL;
@@ -74,9 +75,11 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 		insn = __opcode_thumb32_compose(insn, inst2);
 		decode_insn = thumb32_probes_decode_insn;
 		actions = kprobes_t32_actions;
+		checkers = kprobes_t32_checkers;
 	} else {
 		decode_insn = thumb16_probes_decode_insn;
 		actions = kprobes_t16_actions;
+		checkers = kprobes_t16_checkers;
 	}
 #else /* !CONFIG_THUMB2_KERNEL */
 	thumb = false;
@@ -85,12 +88,13 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 	insn = __mem_to_opcode_arm(*p->addr);
 	decode_insn = arm_probes_decode_insn;
 	actions = kprobes_arm_actions;
+	checkers = kprobes_arm_checkers;
 #endif
 
 	p->opcode = insn;
 	p->ainsn.insn = tmp_insn;
 
-	switch ((*decode_insn)(insn, &p->ainsn, true, actions)) {
+	switch ((*decode_insn)(insn, &p->ainsn, true, actions, checkers)) {
 	case INSN_REJECTED:	/* not supported */
 		return -EINVAL;
 

arch/arm/probes/kprobes/core.h

@@ -37,16 +37,19 @@ kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_probes_insn *asi,
 typedef enum probes_insn (kprobe_decode_insn_t)(probes_opcode_t,
 						struct arch_probes_insn *,
 						bool,
-						const union decode_action *);
+						const union decode_action *,
+						const struct decode_checker *[*]);
 
 #ifdef CONFIG_THUMB2_KERNEL
 
 extern const union decode_action kprobes_t32_actions[];
 extern const union decode_action kprobes_t16_actions[];
-
+extern const struct decode_checker *kprobes_t32_checkers[];
+extern const struct decode_checker *kprobes_t16_checkers[];
 #else /* !CONFIG_THUMB2_KERNEL */
 
 extern const union decode_action kprobes_arm_actions[];
+extern const struct decode_checker *kprobes_arm_checkers[];
 
 #endif