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Commit 983ebd93 authored by Jon Medhurst's avatar Jon Medhurst Committed by Nicolas Pitre
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ARM: kprobes: Reject probing of instructions which write to PC unpredictably. 



Signed-off-by: default avatarJon Medhurst <tixy@yxit.co.uk>
Signed-off-by: default avatarNicolas Pitre <nicolas.pitre@linaro.org>
parent c412aba2

arch/arm/kernel/kprobes-decode.c

+28 −0
Original line number Diff line number Diff line
@@ -68,6 +68,8 @@ 


#define branch_displacement(insn) sign_extend(((insn) & 0xffffff) << 2, 25)



#define is_r15(insn, bitpos) (((insn) & (0xf << bitpos)) == (0xf << bitpos))



#define PSR_fs	(PSR_f|PSR_s)



#define KPROBE_RETURN_INSTRUCTION	0xe1a0f00e	/* mov pc, lr */
@@ -897,6 +899,9 @@ prep_emulate_ldr_str(kprobe_opcode_t insn, struct arch_specific_insn *asi) 
static enum kprobe_insn __kprobes

prep_emulate_rd12rm0(kprobe_opcode_t insn, struct arch_specific_insn *asi)

{

	if (is_r15(insn, 12))

		return INSN_REJECTED;	/* Rd is PC */



	insn &= 0xffff0ff0;	/* Rd = r0, Rm = r0 */

	asi->insn[0] = insn;

	asi->insn_handler = emulate_rd12rm0;
@@ -907,6 +912,9 @@ static enum kprobe_insn __kprobes 
prep_emulate_rd12rn16rm0_wflags(kprobe_opcode_t insn,

				struct arch_specific_insn *asi)

{

	if (is_r15(insn, 12))

		return INSN_REJECTED;	/* Rd is PC */



	insn &= 0xfff00ff0;	/* Rd = r0, Rn = r0 */

	insn |= 0x00000001;	/* Rm = r1 */

	asi->insn[0] = insn;
@@ -918,6 +926,9 @@ static enum kprobe_insn __kprobes 
prep_emulate_rd16rs8rm0_wflags(kprobe_opcode_t insn,

			       struct arch_specific_insn *asi)

{

	if (is_r15(insn, 16))

		return INSN_REJECTED;	/* Rd is PC */



	insn &= 0xfff0f0f0;	/* Rd = r0, Rs = r0 */

	insn |= 0x00000001;	/* Rm = r1          */

	asi->insn[0] = insn;
@@ -929,6 +940,9 @@ static enum kprobe_insn __kprobes 
prep_emulate_rd16rn12rs8rm0_wflags(kprobe_opcode_t insn,

				   struct arch_specific_insn *asi)

{

	if (is_r15(insn, 16))

		return INSN_REJECTED;	/* Rd is PC */



	insn &= 0xfff000f0;	/* Rd = r0, Rn = r0 */

	insn |= 0x00000102;	/* Rs = r1, Rm = r2 */

	asi->insn[0] = insn;
@@ -940,6 +954,9 @@ static enum kprobe_insn __kprobes 
prep_emulate_rdhi16rdlo12rs8rm0_wflags(kprobe_opcode_t insn,

				       struct arch_specific_insn *asi)

{

	if (is_r15(insn, 16) || is_r15(insn, 12))

		return INSN_REJECTED;	/* RdHi or RdLo is PC */



	insn &= 0xfff000f0;	/* RdHi = r0, RdLo = r1 */

	insn |= 0x00001203;	/* Rs = r2, Rm = r3 */

	asi->insn[0] = insn;
@@ -1035,6 +1052,8 @@ space_cccc_000x(kprobe_opcode_t insn, struct arch_specific_insn *asi) 


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

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

			if (is_r15(insn, 12))

				return INSN_REJECTED;	/* Rd is PC */

			asi->insn_handler = simulate_mrs;

			return INSN_GOOD_NO_SLOT;

		}
@@ -1065,6 +1084,8 @@ space_cccc_000x(kprobe_opcode_t insn, struct arch_specific_insn *asi) 
		/* BLX(2) : cccc 0001 0010 xxxx xxxx xxxx 0011 xxxx */

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

		if ((insn & 0x0ff000d0) == 0x01200010) {

			if ((insn & 0x0ff000ff) == 0x0120003f)

				return INSN_REJECTED; /* BLX pc */

			asi->insn_handler = simulate_blx2bx;

			return INSN_GOOD_NO_SLOT;

		}
@@ -1234,6 +1255,8 @@ space_cccc_0110__1(kprobe_opcode_t insn, struct arch_specific_insn *asi) 
{

	/* SEL : cccc 0110 1000 xxxx xxxx xxxx 1011 xxxx GE: !!! */

	if ((insn & 0x0ff000f0) == 0x068000b0) {

		if (is_r15(insn, 12))

			return INSN_REJECTED;	/* Rd is PC */

		insn &= 0xfff00ff0;	/* Rd = r0, Rn = r0 */

		insn |= 0x00000001;	/* Rm = r1 */

		asi->insn[0] = insn;
@@ -1247,6 +1270,8 @@ space_cccc_0110__1(kprobe_opcode_t insn, struct arch_specific_insn *asi) 
	/* USAT16 : cccc 0110 1110 xxxx xxxx xxxx 0011 xxxx :Q */

	if ((insn & 0x0fa00030) == 0x06a00010 ||

	    (insn & 0x0fb000f0) == 0x06a00030) {

		if (is_r15(insn, 12))

			return INSN_REJECTED;	/* Rd is PC */

		insn &= 0xffff0ff0;	/* Rd = r0, Rm = r0 */

		asi->insn[0] = insn;

		asi->insn_handler = emulate_sat;
@@ -1384,6 +1409,9 @@ space_cccc_1100_010x(kprobe_opcode_t insn, struct arch_specific_insn *asi) 
{

	/* MCRR : cccc 1100 0100 xxxx xxxx xxxx xxxx xxxx : (Rd!=Rn) */

	/* MRRC : cccc 1100 0101 xxxx xxxx xxxx xxxx xxxx : (Rd!=Rn) */

	if (is_r15(insn, 16) || is_r15(insn, 12))

		return INSN_REJECTED;	/* Rn or Rd is PC */



	insn &= 0xfff00fff;

	insn |= 0x00001000;	/* Rn = r0, Rd = r1 */

	asi->insn[0] = insn;