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Commit 28a1899d authored by Wang Nan's avatar Wang Nan Committed by Jon Medhurst
Browse files

ARM: kprobes: check register usage for probed instruction. 



This patch utilizes the previously introduced checker to check
register usage for probed ARM instruction and saves it in a mask.
A further patch will use such information to avoid simulation or
emulation.

Signed-off-by: default avatarWang Nan <wangnan0@huawei.com>
Reviewed-by: default avatarJon Medhurst <tixy@linaro.org>
Signed-off-by: default avatarJon Medhurst <tixy@linaro.org>
parent 4cd872d9

arch/arm/include/asm/probes.h

+1 −0
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ struct arch_probes_insn { 
	probes_insn_singlestep_t	*insn_singlestep;

	probes_insn_fn_t		*insn_fn;

	int				stack_space;

	unsigned long			register_usage_flags;

};



#endif /* __ASSEMBLY__ */

arch/arm/probes/decode.c

+7 −0
Original line number Diff line number Diff line
@@ -435,6 +435,13 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi, 
	 */

	asi->stack_space = 0;



	/*

	 * Similarly to stack_space, register_usage_flags is filled by

	 * checkers. Its default value is set to ~0, which is 'all

	 * registers are used', to prevent any potential optimization.

	 */

	asi->register_usage_flags = ~0UL;



	if (emulate)

		insn = prepare_emulated_insn(insn, asi, thumb);

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

+1 −1
Original line number Diff line number Diff line
@@ -341,4 +341,4 @@ const union decode_action kprobes_arm_actions[NUM_PROBES_ARM_ACTIONS] = { 
	[PROBES_LDMSTM] = {.decoder = kprobe_decode_ldmstm}

};



const struct decode_checker *kprobes_arm_checkers[] = {arm_stack_checker, NULL};
 
const struct decode_checker *kprobes_arm_checkers[] = {arm_stack_checker, arm_regs_checker, NULL};

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

+93 −0
Original line number Diff line number Diff line
@@ -97,3 +97,96 @@ const struct decode_checker arm_stack_checker[NUM_PROBES_ARM_ACTIONS] = { 
	[PROBES_STORE] = {.checker = arm_check_stack},

	[PROBES_LDMSTM] = {.checker = arm_check_stack},

};



static enum probes_insn __kprobes arm_check_regs_nouse(probes_opcode_t insn,

		struct arch_probes_insn *asi,

		const struct decode_header *h)

{

	asi->register_usage_flags = 0;

	return INSN_GOOD;

}



static enum probes_insn arm_check_regs_normal(probes_opcode_t insn,

		struct arch_probes_insn *asi,

		const struct decode_header *h)

{

	u32 regs = h->type_regs.bits >> DECODE_TYPE_BITS;

	int i;



	asi->register_usage_flags = 0;

	for (i = 0; i < 5; regs >>= 4, insn >>= 4, i++)

		if (regs & 0xf)

			asi->register_usage_flags |= 1 << (insn & 0xf);



	return INSN_GOOD;

}





static enum probes_insn arm_check_regs_ldmstm(probes_opcode_t insn,

		struct arch_probes_insn *asi,

		const struct decode_header *h)

{

	unsigned int reglist = insn & 0xffff;

	unsigned int rn = (insn >> 16) & 0xf;

	asi->register_usage_flags = reglist | (1 << rn);

	return INSN_GOOD;

}



static enum probes_insn arm_check_regs_mov_ip_sp(probes_opcode_t insn,

		struct arch_probes_insn *asi,

		const struct decode_header *h)

{

	/* Instruction is 'mov ip, sp' i.e. 'mov r12, r13' */

	asi->register_usage_flags = (1 << 12) | (1<< 13);

	return INSN_GOOD;

}



/*

 *                                    | Rn |Rt/d|         | Rm |

 * LDRD (register)      cccc 000x x0x0 xxxx xxxx xxxx 1101 xxxx

 * STRD (register)      cccc 000x x0x0 xxxx xxxx xxxx 1111 xxxx

 *                                    | Rn |Rt/d|         |imm4L|

 * LDRD (immediate)     cccc 000x x1x0 xxxx xxxx xxxx 1101 xxxx

 * STRD (immediate)     cccc 000x x1x0 xxxx xxxx xxxx 1111 xxxx

 *

 * Such instructions access Rt/d and its next register, so different

 * from others, a specific checker is required to handle this extra

 * implicit register usage.

 */

static enum probes_insn arm_check_regs_ldrdstrd(probes_opcode_t insn,

		struct arch_probes_insn *asi,

		const struct decode_header *h)

{

	int rdt = (insn >> 12) & 0xf;

	arm_check_regs_normal(insn, asi, h);

	asi->register_usage_flags |= 1 << (rdt + 1);

	return INSN_GOOD;

}





const struct decode_checker arm_regs_checker[NUM_PROBES_ARM_ACTIONS] = {

	[PROBES_MRS] = {.checker = arm_check_regs_normal},

	[PROBES_SATURATING_ARITHMETIC] = {.checker = arm_check_regs_normal},

	[PROBES_MUL1] = {.checker = arm_check_regs_normal},

	[PROBES_MUL2] = {.checker = arm_check_regs_normal},

	[PROBES_MUL_ADD_LONG] = {.checker = arm_check_regs_normal},

	[PROBES_MUL_ADD] = {.checker = arm_check_regs_normal},

	[PROBES_LOAD] = {.checker = arm_check_regs_normal},

	[PROBES_LOAD_EXTRA] = {.checker = arm_check_regs_normal},

	[PROBES_STORE] = {.checker = arm_check_regs_normal},

	[PROBES_STORE_EXTRA] = {.checker = arm_check_regs_normal},

	[PROBES_DATA_PROCESSING_REG] = {.checker = arm_check_regs_normal},

	[PROBES_DATA_PROCESSING_IMM] = {.checker = arm_check_regs_normal},

	[PROBES_SEV] = {.checker = arm_check_regs_nouse},

	[PROBES_WFE] = {.checker = arm_check_regs_nouse},

	[PROBES_SATURATE] = {.checker = arm_check_regs_normal},

	[PROBES_REV] = {.checker = arm_check_regs_normal},

	[PROBES_MMI] = {.checker = arm_check_regs_normal},

	[PROBES_PACK] = {.checker = arm_check_regs_normal},

	[PROBES_EXTEND] = {.checker = arm_check_regs_normal},

	[PROBES_EXTEND_ADD] = {.checker = arm_check_regs_normal},

	[PROBES_BITFIELD] = {.checker = arm_check_regs_normal},

	[PROBES_LDMSTM] = {.checker = arm_check_regs_ldmstm},

	[PROBES_MOV_IP_SP] = {.checker = arm_check_regs_mov_ip_sp},

	[PROBES_LDRSTRD] = {.checker = arm_check_regs_ldrdstrd},

};

arch/arm/probes/kprobes/checkers.h

+1 −0
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ extern const union decode_action stack_check_actions[]; 


#ifndef CONFIG_THUMB2_KERNEL

extern const struct decode_checker arm_stack_checker[];

extern const struct decode_checker arm_regs_checker[];

#else

#endif

extern const struct decode_checker t32_stack_checker[];