Re: [PATCH v3] ARM: kprobes: Add test cases for stack consuming instructions

From: Wang Nan
Date: Thu Dec 11 2014 - 04:57:45 EST

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In reply to: Jon Medhurst (Tixy): "Re: [PATCH v3] ARM: kprobes: Add test cases for stack consuming instructions"
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On 2014/12/10 21:18, Wang Nan wrote:
> On 2014/12/10 20:34, Jon Medhurst (Tixy) wrote:
>> On Wed, 2014-12-10 at 16:23 +0800, Wang Nan wrote:
>>> Hi Tixy,
>>>
>>> I experienced another FAIL during test:
>>>
>>> [11567.220477] Miscellaneous instructions
>>> [11567.265397] ---------------------------------------------------------
>>> [11567.342626] mrs r0, cpsr @ e10f0000
>>> [11568.612656] FAIL: registers differ
>>> [11568.653414] FAIL: Test mrs r0, cpsr
>>> [11568.695210] FAIL: Scenario 5
>>> [11568.729709] initial_regs:
>>> [11568.761083] r0 21522152 | r1 21522052 | r2 21522352 | r3 21522252
>>> [11568.838301] r4 21522552 | r5 21522452 | r6 21522752 | r7 21522652
>>> [11568.915526] r8 21522952 | r9 21522852 | r10 21522b52 | r11 21522a52
>>> [11568.992748] r12 21522d52 | sp ed343cf0 | lr 21522f52 | pc bf11f590
>>> [11569.069969] cpsr 58050013
>>> [11569.101336] expected_regs:
>>> [11569.133750] r0 58050013 | r1 21522052 | r2 21522352 | r3 21522252
>>> [11569.210975] r4 21522552 | r5 21522452 | r6 21522752 | r7 21522652
>>> [11569.288197] r8 21522952 | r9 21522852 | r10 21522b52 | r11 21522a52
>>> [11569.365417] r12 21522d52 | sp ed343cf0 | lr 21522f52 | pc bf11f594
>>> [11569.442634] cpsr 58050013
>>> [11569.474010] result_regs:
>>> [11569.504337] r0 58050113 | r1 21522052 | r2 21522352 | r3 21522252 <--- see R0 in this line
>>> [11569.581556] r4 21522552 | r5 21522452 | r6 21522752 | r7 21522652
>>> [11569.658776] r8 21522952 | r9 21522852 | r10 21522b52 | r11 21522a52
>>> [11569.736000] r12 21522d52 | sp ed343cf0 | lr 21522f52 | pc bf11f594
>>> [11569.813222] cpsr 58050013
>>> [11569.844593] mrspl r7, cpsr @ 510f7000
>>> [11571.842652] mrs r14, cpsr @ e10fe000
>>>
>>> The failure is raise when testing in "mrs r0, cpsr". The added bit is PSR_A_BIT, which
>>> should be ignored.
>>>
>>> So looks like this is also a problem in your test framework. If you don't have
>>> enough time, you can give me some hints to deal with it.
>>
>> The problem is that the A bit can change randomly when interrupts or
>> reschedules happen (I'm not sure it should, and it may be a bug). For
>> the purposes of this test code, we can't disable interrupts and
>> scheduling around all the iterations of a test case, because inserting
>> and removing probes requires them to be enabled. So we need a method of
>> ignoring bits in cpsr, how about the following patch...
>>
>> ----------------------------------------------------------------------------
>>
>> From: Jon Medhurst <tixy@xxxxxxxxxx>
>> Subject: [PATCH] ARM: kprobes: Fix unreliable MRS instruction tests
>>
>> For the instruction 'mrs Rn, cpsr' the resulting value of Rn can vary due to
>> external factors we can't control. So get the test code to mask out these
>> indeterminate bits.
>>
>> Signed-off-by: Jon Medhurst <tixy@xxxxxxxxxx>
>> ---
>> arch/arm/probes/kprobes/test-arm.c | 6 +++---
>> arch/arm/probes/kprobes/test-core.c | 19 ++++++++++---------
>> arch/arm/probes/kprobes/test-core.h | 33 ++++++++++++++++++++++++++++-----
>> arch/arm/probes/kprobes/test-thumb.c | 4 ++--
>> 4 files changed, 43 insertions(+), 19 deletions(-)
>>
>> diff --git a/arch/arm/probes/kprobes/test-arm.c b/arch/arm/probes/kprobes/test-arm.c
>> index 9b3b1b4..e72b07e 100644
>> --- a/arch/arm/probes/kprobes/test-arm.c
>> +++ b/arch/arm/probes/kprobes/test-arm.c
>> @@ -204,9 +204,9 @@ void kprobe_arm_test_cases(void)
>> #endif
>> TEST_GROUP("Miscellaneous instructions")
>>
>> - TEST("mrs r0, cpsr")
>> - TEST("mrspl r7, cpsr")
>> - TEST("mrs r14, cpsr")
>> + TEST_RMASKED("mrs r",0,~PSR_IGNORE_BITS,", cpsr")
>> + TEST_RMASKED("mrspl r",7,~PSR_IGNORE_BITS,", cpsr")
>> + TEST_RMASKED("mrs r",14,~PSR_IGNORE_BITS,", cpsr")
>> TEST_UNSUPPORTED(__inst_arm(0xe10ff000) " @ mrs r15, cpsr")
>> TEST_UNSUPPORTED("mrs r0, spsr")
>> TEST_UNSUPPORTED("mrs lr, spsr")
>> diff --git a/arch/arm/probes/kprobes/test-core.c b/arch/arm/probes/kprobes/test-core.c
>> index 7c5ddd5..e495127 100644
>> --- a/arch/arm/probes/kprobes/test-core.c
>> +++ b/arch/arm/probes/kprobes/test-core.c
>> @@ -1056,15 +1056,6 @@ static int test_case_run_count;
>> static bool test_case_is_thumb;
>> static int test_instance;
>>
>> -/*
>> - * We ignore the state of the imprecise abort disable flag (CPSR.A) because this
>> - * can change randomly as the kernel doesn't take care to preserve or initialise
>> - * this across context switches. Also, with Security Extentions, the flag may
>> - * not be under control of the kernel; for this reason we ignore the state of
>> - * the FIQ disable flag CPSR.F as well.
>> - */
>> -#define PSR_IGNORE_BITS (PSR_A_BIT | PSR_F_BIT)
>> -
>> static unsigned long test_check_cc(int cc, unsigned long cpsr)
>> {
>> int ret = arm_check_condition(cc << 28, cpsr);
>> @@ -1271,11 +1262,21 @@ test_case_pre_handler(struct kprobe *p, struct pt_regs *regs)
>> static int __kprobes
>> test_after_pre_handler(struct kprobe *p, struct pt_regs *regs)
>> {
>> + struct test_arg *args;
>> +
>> if (container_of(p, struct test_probe, kprobe)->hit == test_instance)
>> return 0; /* Already run for this test instance */
>>
>> result_regs = *regs;
>> +
>> + /* Mask out results which are indeterminate */
>> result_regs.ARM_cpsr &= ~PSR_IGNORE_BITS;
>> + for (args = current_args; args[0].type != ARG_TYPE_END; ++args)
>> + if (args[0].type == ARG_TYPE_REG_MASKED) {
>> + struct test_arg_regptr *arg =
>> + (struct test_arg_regptr *)args;
>> + result_regs.uregs[arg->reg] &= arg->val;
>> + }
>>
>> /* Undo any changes done to SP by the test case */
>> regs->ARM_sp = (unsigned long)current_stack;
>> diff --git a/arch/arm/probes/kprobes/test-core.h b/arch/arm/probes/kprobes/test-core.h
>> index 9991754..32f7aa7 100644
>> --- a/arch/arm/probes/kprobes/test-core.h
>> +++ b/arch/arm/probes/kprobes/test-core.h
>> @@ -45,10 +45,11 @@ extern int kprobe_test_cc_position;
>> *
>> */
>>
>> -#define ARG_TYPE_END 0
>> -#define ARG_TYPE_REG 1
>> -#define ARG_TYPE_PTR 2
>> -#define ARG_TYPE_MEM 3
>> +#define ARG_TYPE_END 0
>> +#define ARG_TYPE_REG 1
>> +#define ARG_TYPE_PTR 2
>> +#define ARG_TYPE_MEM 3
>> +#define ARG_TYPE_REG_MASKED 4
>>
>> #define ARG_FLAG_UNSUPPORTED 0x01
>> #define ARG_FLAG_SUPPORTED 0x02
>> @@ -61,7 +62,7 @@ struct test_arg {
>> };
>>
>> struct test_arg_regptr {
>> - u8 type; /* ARG_TYPE_REG or ARG_TYPE_PTR */
>> + u8 type; /* ARG_TYPE_REG or ARG_TYPE_PTR or ARG_TYPE_REG_MASKED */
>> u8 reg;
>> u8 _padding[2];
>> u32 val;
>> @@ -138,6 +139,12 @@ struct test_arg_end {
>> ".short 0 \n\t" \
>> ".word "#val" \n\t"
>>
>> +#define TEST_ARG_REG_MASKED(reg, val) \
>> + ".byte "__stringify(ARG_TYPE_REG_MASKED)" \n\t" \
>> + ".byte "#reg" \n\t" \
>> + ".short 0 \n\t" \
>> + ".word "#val" \n\t"
>> +
>> #define TEST_ARG_END(flags) \
>> ".byte "__stringify(ARG_TYPE_END)" \n\t" \
>> ".byte "TEST_ISA flags" \n\t" \
>> @@ -395,6 +402,22 @@ struct test_arg_end {
>> " "codex" \n\t" \
>> TESTCASE_END
>>
>> +#define TEST_RMASKED(code1, reg, mask, code2) \
>> + TESTCASE_START(code1 #reg code2) \
>> + TEST_ARG_REG_MASKED(reg, mask) \
>> + TEST_ARG_END("") \
>> + TEST_INSTRUCTION(code1 #reg code2) \
>> + TESTCASE_END
>> +
>> +/*
>> + * We ignore the state of the imprecise abort disable flag (CPSR.A) because this
>> + * can change randomly as the kernel doesn't take care to preserve or initialise
>> + * this across context switches. Also, with Security Extensions, the flag may
>> + * not be under control of the kernel; for this reason we ignore the state of
>> + * the FIQ disable flag CPSR.F as well.
>> + */
>> +#define PSR_IGNORE_BITS (PSR_A_BIT | PSR_F_BIT)
>> +
>>
>> /*
>> * Macros for defining space directives spread over multiple lines.
>> diff --git a/arch/arm/probes/kprobes/test-thumb.c b/arch/arm/probes/kprobes/test-thumb.c
>> index e8cf193..b683b45 100644
>> --- a/arch/arm/probes/kprobes/test-thumb.c
>> +++ b/arch/arm/probes/kprobes/test-thumb.c
>> @@ -778,8 +778,8 @@ CONDITION_INSTRUCTIONS(22,
>>
>> TEST_UNSUPPORTED("subs pc, lr, #4")
>>
>> - TEST("mrs r0, cpsr")
>> - TEST("mrs r14, cpsr")
>> + TEST_RMASKED("mrs r",0,~PSR_IGNORE_BITS,", cpsr")
>> + TEST_RMASKED("mrs r",14,~PSR_IGNORE_BITS,", cpsr")
>> TEST_UNSUPPORTED(__inst_thumb32(0xf3ef8d00) " @ mrs sp, spsr")
>> TEST_UNSUPPORTED(__inst_thumb32(0xf3ef8f00) " @ mrs pc, spsr")
>> TEST_UNSUPPORTED("mrs r0, spsr")
>>
>
> Well, I'm just working on a patch which introducing a TEST_INTOFF and disable interrupts
> for "MRS" testcase. Do you think it is inappropriate? I'll use your patch test for a night
> in my hardware, and will let you know the result tomorrow.
>
> Thank you!
>

Hi Tixy,

I'd like to let you know that I have tested your v3 patch in an ARM cortex A15 board
for 8 hours and nothing bad happened. I'll post a v16 patch series to merge your patch.

Thank you!

>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>

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Next message: David Hildenbrand: "Re: [PATCH v4] CPU hotplug: active_writer not woken up in some cases - deadlock"
Previous message: Yunzhi Li: "[PATCH v6 1/5] phy: add a driver for the Rockchip SoC internal USB2.0 PHY"
In reply to: Jon Medhurst (Tixy): "Re: [PATCH v3] ARM: kprobes: Add test cases for stack consuming instructions"
Next in thread: Wang Nan: "[RESEND][PATCH v15 6/7] kprobes: Pass the original kprobe for preparing optimized kprobe"
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