ARM: kprobes: Disallow instructions with PC and register specified shift

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>

2 files changed, 15 insertions, 13 deletions

diff --git a/arch/arm/kernel/kprobes-test-arm.c b/arch/arm/kernel/kprobes-test-arm.c
index 9db4b659d03e..e73f9cff9225 100644
--- a/arch/arm/kernel/kprobes-test-arm.c
+++ b/arch/arm/kernel/kprobes-test-arm.c
@@ -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")                \
@@ -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")
@@ -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")                      \
@@ -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")
@@ -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")
diff --git a/arch/arm/kernel/probes-arm.c b/arch/arm/kernel/probes-arm.c
index 51a13a027989..8eaef81d8344 100644
--- a/arch/arm/kernel/probes-arm.c
+++ b/arch/arm/kernel/probes-arm.c
@@ -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 */
@@ -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
 };