ARM: use a function table for determining instruction interpreter action

Make the instruction interpreter call back to semantic action functions
through a function pointer array provided by the invoker.  The interpreter
decodes the instructions into groups and uses the group number to index
into the supplied array.  kprobes and uprobes code will each supply their
own array of functions.

Signed-off-by: David A. Long <dave.long@linaro.org>
Acked-by: Jon Medhurst <tixy@linaro.org>

1 files changed, 36 insertions, 19 deletions

diff --git a/arch/arm/kernel/probes.h b/arch/arm/kernel/probes.h
index 17f656011aa3..5554f161bdac 100644
--- a/arch/arm/kernel/probes.h
+++ b/arch/arm/kernel/probes.h
@@ -133,7 +133,8 @@ void __kprobes kprobe_simulate_nop(struct kprobe *p, struct pt_regs *regs);
 void __kprobes kprobe_emulate_none(struct kprobe *p, struct pt_regs *regs);
 
 enum kprobe_insn __kprobes
-kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_specific_insn *asi);
+kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_specific_insn *asi,
+		const struct decode_header *h);
 
 /*
  * Test if load/store instructions writeback the address register.
@@ -160,7 +161,7 @@ kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_specific_insn *asi);
  *	{.bits = _type},
  *	{.bits = _mask},
  *	{.bits = _value},
- *	{.handler = _handler},
+ *	{.action = _handler},
  *
  * Initialising a specified member of the union means that the compiler
  * will produce a warning if the argument is of an incorrect type.
@@ -173,19 +174,23 @@ kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_specific_insn *asi);
  *	Instruction decoding jumps to parsing the new sub-table 'table'.
  *
  * DECODE_CUSTOM(mask, value, decoder)
- *	The custom function 'decoder' is called to the complete decoding
- *	of an instruction.
+ *	The value of 'decoder' is used as an index into the array of
+ *	action functions, and the retrieved decoder function is invoked
+ *	to complete decoding of the instruction.
  *
  * DECODE_SIMULATE(mask, value, handler)
- *	Set the probes instruction handler to 'handler', this will be used
- *	to simulate the instruction when the probe is hit. Decoding returns
- *	with INSN_GOOD_NO_SLOT.
+ *	The probes instruction handler is set to the value found by
+ *	indexing into the action array using the value of 'handler'. This
+ *	will be used to simulate the instruction when the probe is hit.
+ *	Decoding returns with INSN_GOOD_NO_SLOT.
  *
  * DECODE_EMULATE(mask, value, handler)
- *	Set the probes instruction handler to 'handler', this will be used
- *	to emulate the instruction when the probe is hit. The modified
- *	instruction (see below) is placed in the probes instruction slot so it
- *	may be called by the emulation code. Decoding returns with INSN_GOOD.
+ *	The probes instruction handler is set to the value found by
+ *	indexing into the action array using the value of 'handler'. This
+ *	will be used to emulate the instruction when the probe is hit. The
+ *	modified instruction (see below) is placed in the probes instruction
+ *	slot so it may be called by the emulation code. Decoding returns
+ *	with INSN_GOOD.
  *
  * DECODE_REJECT(mask, value)
  *	Instruction decoding fails with INSN_REJECTED
@@ -238,7 +243,7 @@ kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_specific_insn *asi);
  * Here is a real example which matches ARM instructions of the form
  * "AND <Rd>,<Rn>,<Rm>,<shift> <Rs>"
  *
- *	DECODE_EMULATEX	(0x0e000090, 0x00000010, emulate_rd12rn16rm0rs8_rwflags,
+ *	DECODE_EMULATEX	(0x0e000090, 0x00000010, PROBES_DATA_PROCESSING_REG,
  *						 REGS(ANY, ANY, NOPC, 0, ANY)),
  *						      ^    ^    ^        ^
  *						      Rn   Rd   Rs       Rm
@@ -249,7 +254,8 @@ kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_specific_insn *asi);
  * Decoding the instruction "AND R4, R5, R6, ASL R7" will be accepted and the
  * instruction will be modified to "AND R0, R2, R3, ASL R1" and then placed into
  * the kprobes instruction slot. This can then be called later by the handler
- * function emulate_rd12rn16rm0rs8_rwflags in order to simulate the instruction.
+ * function emulate_rd12rn16rm0rs8_rwflags (a pointer to which is retrieved from
+ * the indicated slot in the action array), in order to simulate the instruction.
  */
 
 enum decode_type {
@@ -298,10 +304,17 @@ enum decode_reg_type {
 union decode_item {
 	u32			bits;
 	const union decode_item	*table;
-	kprobe_insn_handler_t	*handler;
-	kprobe_decode_insn_t	*decoder;
+	int			action;
 };
 
+typedef enum kprobe_insn (probes_custom_decode_t)(kprobe_opcode_t,
+						  struct arch_specific_insn *,
+						  const struct decode_header *);
+
+union decode_action {
+	kprobe_insn_handler_t	*handler;
+	probes_custom_decode_t	*decoder;
+};
 
 #define DECODE_END			\
 	{.bits = DECODE_TYPE_END}
@@ -336,7 +349,7 @@ struct decode_custom {
 
 #define DECODE_CUSTOM(_mask, _value, _decoder)			\
 	DECODE_HEADER(DECODE_TYPE_CUSTOM, _mask, _value, 0),	\
-	{.decoder = (_decoder)}
+	{.action = (_decoder)}
 
 
 struct decode_simulate {
@@ -346,7 +359,7 @@ struct decode_simulate {
 
 #define DECODE_SIMULATEX(_mask, _value, _handler, _regs)		\
 	DECODE_HEADER(DECODE_TYPE_SIMULATE, _mask, _value, _regs),	\
-	{.handler = (_handler)}
+	{.action = (_handler)}
 
 #define DECODE_SIMULATE(_mask, _value, _handler)	\
 	DECODE_SIMULATEX(_mask, _value, _handler, 0)
@@ -359,7 +372,7 @@ struct decode_emulate {
 
 #define DECODE_EMULATEX(_mask, _value, _handler, _regs)			\
 	DECODE_HEADER(DECODE_TYPE_EMULATE, _mask, _value, _regs),	\
-	{.handler = (_handler)}
+	{.action = (_handler)}
 
 #define DECODE_EMULATE(_mask, _value, _handler)		\
 	DECODE_EMULATEX(_mask, _value, _handler, 0)
@@ -384,14 +397,18 @@ struct decode_reject {
 #ifdef CONFIG_THUMB2_KERNEL
 extern const union decode_item kprobe_decode_thumb16_table[];
 extern const union decode_item kprobe_decode_thumb32_table[];
+extern const union decode_action kprobes_t32_actions[];
+extern const union decode_action kprobes_t16_actions[];
 #else
 extern const union decode_item kprobe_decode_arm_table[];
+extern const union decode_action kprobes_arm_actions[];
 #endif
 
 extern kprobe_check_cc * const kprobe_condition_checks[16];
 
 
 int kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi,
-		       const union decode_item *table, bool thumb16);
+		       const union decode_item *table, bool thumb16,
+		       const union decode_action *actions);
 
 #endif