Re: [PATCH v3 3/4] openrisc: Add unit tests for KProbes on branch instructions

[Sahil <sahilcdq0@gmail.com>]

On 11/8/26 1:33 PM, Stafford Horne wrote:
> On Tue, Oct 27, 2026 at 01:42:39AM +0530, Sahil Siddiq wrote:
>> Tests already exist lib/tests to verify the generic functionality of
>> KProbes. Add unit tests to verify that KProbes work on instructions
>> that require simulation in the OpenRISC ISA, and that the corresponding
>> delay slots are handled correctly.
>>
>> Signed-off-by: Sahil Siddiq <sahilcdq0@gmail.com>
>> ---
>> Changes v2 -> v3:
>> - arch/openrisc/kernel/tests/test_kprobes_asm.S:
>>    - (test_kprobes_*): Set value in r11 register to 0 prior to running tests
>>    - (test_kprobes_adrp):
>>      Place function at page-aligned address
>>      Use PAGE_SIZE macro instead of magic number
>>      Move value in r13 to r11 before exiting
>>
>> Changes v1 -> v2: New commit
>>
>>   arch/openrisc/Kconfig.debug                   |  30 +++-
>>   arch/openrisc/kernel/Makefile                 |   1 +
>>   arch/openrisc/kernel/tests/Makefile           |   3 +
>>   arch/openrisc/kernel/tests/test_kprobes.c     |  59 +++++++
>>   arch/openrisc/kernel/tests/test_kprobes.h     |  24 +++
>>   arch/openrisc/kernel/tests/test_kprobes_asm.S | 157 ++++++++++++++++++
>>   6 files changed, 273 insertions(+), 1 deletion(-)
>>   create mode 100644 arch/openrisc/kernel/tests/Makefile
>>   create mode 100644 arch/openrisc/kernel/tests/test_kprobes.c
>>   create mode 100644 arch/openrisc/kernel/tests/test_kprobes.h
>>   create mode 100644 arch/openrisc/kernel/tests/test_kprobes_asm.S
>>
>> [...]
>> diff --git a/arch/openrisc/kernel/tests/test_kprobes_asm.S b/arch/openrisc/kernel/tests/test_kprobes_asm.S
>> new file mode 100644
>> index 000000000000..bc87a5fb00d5
>> --- /dev/null
>> +++ b/arch/openrisc/kernel/tests/test_kprobes_asm.S
>> @@ -0,0 +1,157 @@
>> +/* SPDX-License-Identifier: GPL-2.0-or-later */
>> +/*
>> + * KProbes unit tests for OpenRISC
>> + *
>> + * Unit tests borrowed liberally from similar work of RISC-V. All
>> + * original copyrights apply as per the original source declaration.
>> + */
>> +
>> +#include <linux/linkage.h>
>> +#include <asm/asm.h>
>> +#include <asm/page.h>
>> +
>> +#include "test_kprobes.h"
>> +
>> +SYM_FUNC_START(test_kprobes_j)
>> +test_kprobes_j_addr1:
>> +	l.addi	r11,r0,0
>> +	l.j	2f
>> +	l.nop
> 
> Just a tiny comment here about indenting the delay slots.

Got it, I'll indent this.

> You could also use the delayslots here, for example:
> 
> 	l.j	2f
> 	 l.addi	r11,r0,0

I initially thought of that too. But then I thought by keeping l.addi
before l.j, I would also be able to test this for the case when
there are no delay slots. I can reshuffle the instructions if that
test isn't required. Please let me know what your thoughts are.

>> +1:	l.ori	r13,r13,KPROBE_TEST_MAGIC_LOWER
>> +	l.addi	r11,r13,0
>> +	l.jr	r9
>> +	l.nop
>> +2:	l.movhi	r13,KPROBE_TEST_MAGIC_UPPER
>> +test_kprobes_j_addr2:
>> +	l.j	1b
>> +	l.nop
>> +SYM_FUNC_END(test_kprobes_j)
>> [...]
>> -- 
>> 2.55.0
>>

Regards,
Sahil