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Commit f704a6e2 authored by Jon Medhurst's avatar Jon Medhurst Committed by Nicolas Pitre
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ARM: kprobes: Reject probing of undefined data processing instructions 



The instruction decoding in space_cccc_000x needs to reject probing of
instructions with undefined patterns as they may in future become
defined and then emulated faultily - as has already happened with the
SMC instruction.

This fix is achieved by testing for the instruction patterns we want to
probe and making the the default fall-through paths reject probes. This
also allows us to remove some explicit tests for instructions that we
wish to reject, as that is now the default action.

Signed-off-by: default avatarJon Medhurst <tixy@yxit.co.uk>
Signed-off-by: default avatarNicolas Pitre <nicolas.pitre@linaro.org>
parent 72c2bab2

arch/arm/kernel/kprobes-decode.c

+17 −14
Original line number Diff line number Diff line
@@ -966,14 +966,6 @@ space_cccc_000x(kprobe_opcode_t insn, struct arch_specific_insn *asi) 
	/* cccc 0001 0xx0 xxxx xxxx xxxx xxxx xxx0 xxxx */

	if ((insn & 0x0f900010) == 0x01000000) {



		/* BXJ      : cccc 0001 0010 xxxx xxxx xxxx 0010 xxxx */

		/* MSR      : cccc 0001 0x10 xxxx xxxx xxxx 0000 xxxx */

		/* MRS spsr : cccc 0001 0100 xxxx xxxx xxxx 0000 xxxx */

		if ((insn & 0x0ff000f0) == 0x01200020 ||

		    (insn & 0x0fb000f0) == 0x01200000 ||

		    (insn & 0x0ff000f0) == 0x01400000)

			return INSN_REJECTED;



		/* MRS cpsr : cccc 0001 0000 xxxx xxxx xxxx 0000 xxxx */

		if ((insn & 0x0ff000f0) == 0x01000000) {

			if (is_r15(insn, 12))
@@ -994,17 +986,21 @@ space_cccc_000x(kprobe_opcode_t insn, struct arch_specific_insn *asi) 


		/* SMLAxy : cccc 0001 0000 xxxx xxxx xxxx 1xx0 xxxx : Q */

		/* SMLAWy : cccc 0001 0010 xxxx xxxx xxxx 1x00 xxxx : Q */

		if ((insn & 0x0ff00090) == 0x01000080 ||

		    (insn & 0x0ff000b0) == 0x01200080)

			return prep_emulate_rd16rn12rs8rm0_wflags(insn, asi);



		/* BXJ      : cccc 0001 0010 xxxx xxxx xxxx 0010 xxxx */

		/* MSR      : cccc 0001 0x10 xxxx xxxx xxxx 0000 xxxx */

		/* MRS spsr : cccc 0001 0100 xxxx xxxx xxxx 0000 xxxx */



		/* Other instruction encodings aren't yet defined */

		return INSN_REJECTED;

	}



	/* cccc 0001 0xx0 xxxx xxxx xxxx xxxx 0xx1 xxxx */

	else if ((insn & 0x0f900090) == 0x01000010) {



		/* BKPT : 1110 0001 0010 xxxx xxxx xxxx 0111 xxxx */

		if ((insn & 0xfff000f0) == 0xe1200070)

			return INSN_REJECTED;



		/* BLX(2) : cccc 0001 0010 xxxx xxxx xxxx 0011 xxxx */

		/* BX     : cccc 0001 0010 xxxx xxxx xxxx 0001 xxxx */

		if ((insn & 0x0ff000d0) == 0x01200010) {
@@ -1022,7 +1018,14 @@ space_cccc_000x(kprobe_opcode_t insn, struct arch_specific_insn *asi) 
		/* QSUB    : cccc 0001 0010 xxxx xxxx xxxx 0101 xxxx :Q */

		/* QDADD   : cccc 0001 0100 xxxx xxxx xxxx 0101 xxxx :Q */

		/* QDSUB   : cccc 0001 0110 xxxx xxxx xxxx 0101 xxxx :Q */

		if ((insn & 0x0f9000f0) == 0x01000050)

			return prep_emulate_rd12rn16rm0_wflags(insn, asi);



		/* BKPT : 1110 0001 0010 xxxx xxxx xxxx 0111 xxxx */

		/* SMC  : cccc 0001 0110 xxxx xxxx xxxx 0111 xxxx */



		/* Other instruction encodings aren't yet defined */

		return INSN_REJECTED;

	}



	/* cccc 0000 xxxx xxxx xxxx xxxx xxxx 1001 xxxx */