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Commit b5bed7fe authored by Jon Medhurst (Tixy)'s avatar Jon Medhurst (Tixy) Committed by Russell King
Browse files

ARM: 7181/1: Restrict kprobes probing SWP instructions to ARMv5 and below 



The SWP instruction is deprecated on ARMv6 and with ARMv7 it will be
UNDEFINED when CONFIG_SWP_EMULATE is selected. In this case, probing a
SWP instruction will cause an oops when the kprobes emulation code
executes an undefined instruction.

As the SWP instruction should be rare or non-existent in kernels for
ARMv6 and later, we can simply avoid these problems by not allowing
probing of these.

Reported-by: default avatarLeif Lindholm <leif.lindholm@arm.com>
Tested-by: default avatarLeif Lindholm <leif.lindholm@arm.com>
Acked-by: default avatarNicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: default avatarJon Medhurst <tixy@yxit.co.uk>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 14383c29

arch/arm/kernel/kprobes-arm.c

+3 −1
Original line number Original line Diff line number Diff line
@@ -519,10 +519,12 @@ static const union decode_item arm_cccc_0000_____1001_table[] = { 
static const union decode_item arm_cccc_0001_____1001_table[] = {

static const union decode_item arm_cccc_0001_____1001_table[] = {

	/* Synchronization primitives					*/

	/* Synchronization primitives					*/





#if __LINUX_ARM_ARCH__ < 6

	/* Deprecated on ARMv6 and may be UNDEFINED on v7		*/

	/* SMP/SWPB		cccc 0001 0x00 xxxx xxxx xxxx 1001 xxxx */

	/* SMP/SWPB		cccc 0001 0x00 xxxx xxxx xxxx 1001 xxxx */

	DECODE_EMULATEX	(0x0fb000f0, 0x01000090, emulate_rd12rn16rm0_rwflags_nopc,

	DECODE_EMULATEX	(0x0fb000f0, 0x01000090, emulate_rd12rn16rm0_rwflags_nopc,

						 REGS(NOPC, NOPC, 0, 0, NOPC)),

						 REGS(NOPC, NOPC, 0, 0, NOPC)),



#endif

	/* LDREX/STREX{,D,B,H}	cccc 0001 1xxx xxxx xxxx xxxx 1001 xxxx */

	/* LDREX/STREX{,D,B,H}	cccc 0001 1xxx xxxx xxxx xxxx 1001 xxxx */

	/* And unallocated instructions...				*/

	/* And unallocated instructions...				*/

	DECODE_END

	DECODE_END

arch/arm/kernel/kprobes-test-arm.c

+16 −9
Original line number Original line Diff line number Diff line
@@ -427,18 +427,25 @@ void kprobe_arm_test_cases(void) 




	TEST_GROUP("Synchronization primitives")

	TEST_GROUP("Synchronization primitives")





	/*

#if __LINUX_ARM_ARCH__ < 6

	 * Use hard coded constants for SWP instructions to avoid warnings

	TEST_RP("swp	lr, r",7,VAL2,", [r",8,0,"]")

	 * about deprecated instructions.

	TEST_R( "swpvs	r0, r",1,VAL1,", [sp]")

	 */

	TEST_RP("swp	sp, r",14,VAL2,", [r",12,13*4,"]")

	TEST_RP( ".word 0xe108e097 @ swp	lr, r",7,VAL2,", [r",8,0,"]")

#else

	TEST_R(  ".word 0x610d0091 @ swpvs	r0, r",1,VAL1,", [sp]")

	TEST_UNSUPPORTED(".word 0xe108e097 @ swp	lr, r7, [r8]")

	TEST_RP( ".word 0xe10cd09e @ swp	sp, r",14,VAL2,", [r",12,13*4,"]")

	TEST_UNSUPPORTED(".word 0x610d0091 @ swpvs	r0, r1, [sp]")

	TEST_UNSUPPORTED(".word 0xe10cd09e @ swp	sp, r14 [r12]")

#endif

	TEST_UNSUPPORTED(".word 0xe102f091 @ swp pc, r1, [r2]")

	TEST_UNSUPPORTED(".word 0xe102f091 @ swp pc, r1, [r2]")

	TEST_UNSUPPORTED(".word 0xe102009f @ swp r0, pc, [r2]")

	TEST_UNSUPPORTED(".word 0xe102009f @ swp r0, pc, [r2]")

	TEST_UNSUPPORTED(".word 0xe10f0091 @ swp r0, r1, [pc]")

	TEST_UNSUPPORTED(".word 0xe10f0091 @ swp r0, r1, [pc]")

	TEST_RP( ".word 0xe148e097 @ swpb	lr, r",7,VAL2,", [r",8,0,"]")

#if __LINUX_ARM_ARCH__ < 6

	TEST_R(  ".word 0x614d0091 @ swpvsb	r0, r",1,VAL1,", [sp]")

	TEST_RP("swpb	lr, r",7,VAL2,", [r",8,0,"]")

	TEST_R( "swpvsb	r0, r",1,VAL1,", [sp]")

#else

	TEST_UNSUPPORTED(".word 0xe148e097 @ swpb	lr, r7, [r8]")

	TEST_UNSUPPORTED(".word 0x614d0091 @ swpvsb	r0, r1, [sp]")

#endif

	TEST_UNSUPPORTED(".word 0xe142f091 @ swpb pc, r1, [r2]")

	TEST_UNSUPPORTED(".word 0xe142f091 @ swpb pc, r1, [r2]")





	TEST_UNSUPPORTED(".word	0xe1100090") /* Unallocated space */

	TEST_UNSUPPORTED(".word	0xe1100090") /* Unallocated space */