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ARM: kprobes: Disallow instructions with PC and register specified shift
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ARM data processing instructions which have a register specified shift
are defined as UNPREDICTABLE if PC is used for any register, not just
the shift value as the code was previous assuming. This issue manifests
on A15 devices as either test case failures or undefined instructions
aborts.

Reported-by: David Long <dave.long@linaro.org>
Signed-off-by: Jon Medhurst <tixy@linaro.org>
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Jon Medhurst committed Jul 2, 2014
1 parent 48f7bc8 commit 2722260
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Showing 2 changed files with 15 additions and 13 deletions.
22 changes: 12 additions & 10 deletions arch/arm/kernel/kprobes-test-arm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -74,8 +74,6 @@ void kprobe_arm_test_cases(void)
TEST_RRR( op "lt" s " r11, r",11,VAL1,", r",14,N(val),", asr r",7, 6,"")\
TEST_RR( op "gt" s " r12, r13" ", r",14,val, ", ror r",14,7,"")\
TEST_RR( op "le" s " r14, r",0, val, ", r13" ", lsl r",14,8,"")\
TEST_RR( op s " r12, pc" ", r",14,val, ", ror r",14,7,"")\
TEST_RR( op s " r14, r",0, val, ", pc" ", lsl r",14,8,"")\
TEST_R( op "eq" s " r0, r",11,VAL1,", #0xf5") \
TEST_R( op "ne" s " r11, r",0, VAL1,", #0xf5000000") \
TEST_R( op s " r7, r",8, VAL2,", #0x000af000") \
Expand Down Expand Up @@ -103,8 +101,6 @@ void kprobe_arm_test_cases(void)
TEST_RRR( op "ge r",11,VAL1,", r",14,N(val),", asr r",7, 6,"") \
TEST_RR( op "le r13" ", r",14,val, ", ror r",14,7,"") \
TEST_RR( op "gt r",0, val, ", r13" ", lsl r",14,8,"") \
TEST_RR( op " pc" ", r",14,val, ", ror r",14,7,"") \
TEST_RR( op " r",0, val, ", pc" ", lsl r",14,8,"") \
TEST_R( op "eq r",11,VAL1,", #0xf5") \
TEST_R( op "ne r",0, VAL1,", #0xf5000000") \
TEST_R( op " r",8, VAL2,", #0x000af000")
Expand All @@ -125,7 +121,6 @@ void kprobe_arm_test_cases(void)
TEST_RR( op "ge" s " r11, r",11,N(val),", asr r",7, 6,"") \
TEST_RR( op "lt" s " r12, r",11,val, ", ror r",14,7,"") \
TEST_R( op "gt" s " r14, r13" ", lsl r",14,8,"") \
TEST_R( op "le" s " r14, pc" ", lsl r",14,8,"") \
TEST( op "eq" s " r0, #0xf5") \
TEST( op "ne" s " r11, #0xf5000000") \
TEST( op s " r7, #0x000af000") \
Expand Down Expand Up @@ -159,12 +154,19 @@ void kprobe_arm_test_cases(void)
TEST_SUPPORTED("cmp pc, #0x1000");
TEST_SUPPORTED("cmp sp, #0x1000");

/* Data-processing with PC as shift*/
/* Data-processing with PC and a shift count in a register */
TEST_UNSUPPORTED(__inst_arm(0xe15c0f1e) " @ cmp r12, r14, asl pc")
TEST_UNSUPPORTED(__inst_arm(0xe1a0cf1e) " @ mov r12, r14, asl pc")
TEST_UNSUPPORTED(__inst_arm(0xe08caf1e) " @ add r10, r12, r14, asl pc")

/* Data-processing with PC as shift*/
TEST_UNSUPPORTED(__inst_arm(0xe151021f) " @ cmp r1, pc, lsl r2")
TEST_UNSUPPORTED(__inst_arm(0xe17f0211) " @ cmn pc, r1, lsl r2")
TEST_UNSUPPORTED(__inst_arm(0xe1a0121f) " @ mov r1, pc, lsl r2")
TEST_UNSUPPORTED(__inst_arm(0xe1a0f211) " @ mov pc, r1, lsl r2")
TEST_UNSUPPORTED(__inst_arm(0xe042131f) " @ sub r1, r2, pc, lsl r3")
TEST_UNSUPPORTED(__inst_arm(0xe1cf1312) " @ bic r1, pc, r2, lsl r3")
TEST_UNSUPPORTED(__inst_arm(0xe081f312) " @ add pc, r1, r2, lsl r3")

/* Data-processing with PC as a target and status registers updated */
TEST_UNSUPPORTED("movs pc, r1")
TEST_UNSUPPORTED("movs pc, r1, lsl r2")
TEST_UNSUPPORTED("movs pc, #0x10000")
Expand All @@ -187,14 +189,14 @@ void kprobe_arm_test_cases(void)
TEST_BF_R ("add pc, pc, r",14,2f-1f-8,"")
TEST_BF_R ("add pc, r",14,2f-1f-8,", pc")
TEST_BF_R ("mov pc, r",0,2f,"")
TEST_BF_RR("mov pc, r",0,2f,", asl r",1,0,"")
TEST_BF_R ("add pc, pc, r",14,(2f-1f-8)*2,", asr #1")
TEST_BB( "sub pc, pc, #1b-2b+8")
#if __LINUX_ARM_ARCH__ == 6 && !defined(CONFIG_CPU_V7)
TEST_BB( "sub pc, pc, #1b-2b+8-2") /* UNPREDICTABLE before and after ARMv6 */
#endif
TEST_BB_R( "sub pc, pc, r",14, 1f-2f+8,"")
TEST_BB_R( "rsb pc, r",14,1f-2f+8,", pc")
TEST_RR( "add pc, pc, r",10,-2,", asl r",11,1,"")
TEST_R( "add pc, pc, r",10,-2,", asl #1")
#ifdef CONFIG_THUMB2_KERNEL
TEST_ARM_TO_THUMB_INTERWORK_R("add pc, pc, r",0,3f-1f-8+1,"")
TEST_ARM_TO_THUMB_INTERWORK_R("sub pc, r",0,3f+8+1,", #8")
Expand Down
6 changes: 3 additions & 3 deletions arch/arm/kernel/probes-arm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -341,12 +341,12 @@ static const union decode_item arm_cccc_000x_table[] = {
/* CMP (reg-shift reg) cccc 0001 0101 xxxx xxxx xxxx 0xx1 xxxx */
/* CMN (reg-shift reg) cccc 0001 0111 xxxx xxxx xxxx 0xx1 xxxx */
DECODE_EMULATEX (0x0f900090, 0x01100010, PROBES_DATA_PROCESSING_REG,
REGS(ANY, 0, NOPC, 0, ANY)),
REGS(NOPC, 0, NOPC, 0, NOPC)),

/* MOV (reg-shift reg) cccc 0001 101x xxxx xxxx xxxx 0xx1 xxxx */
/* MVN (reg-shift reg) cccc 0001 111x xxxx xxxx xxxx 0xx1 xxxx */
DECODE_EMULATEX (0x0fa00090, 0x01a00010, PROBES_DATA_PROCESSING_REG,
REGS(0, ANY, NOPC, 0, ANY)),
REGS(0, NOPC, NOPC, 0, NOPC)),

/* AND (reg-shift reg) cccc 0000 000x xxxx xxxx xxxx 0xx1 xxxx */
/* EOR (reg-shift reg) cccc 0000 001x xxxx xxxx xxxx 0xx1 xxxx */
Expand All @@ -359,7 +359,7 @@ static const union decode_item arm_cccc_000x_table[] = {
/* ORR (reg-shift reg) cccc 0001 100x xxxx xxxx xxxx 0xx1 xxxx */
/* BIC (reg-shift reg) cccc 0001 110x xxxx xxxx xxxx 0xx1 xxxx */
DECODE_EMULATEX (0x0e000090, 0x00000010, PROBES_DATA_PROCESSING_REG,
REGS(ANY, ANY, NOPC, 0, ANY)),
REGS(NOPC, NOPC, NOPC, 0, NOPC)),

DECODE_END
};
Expand Down

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