Re: [PATCH 1/2] riscv: ftrace: Fix the comments about the number of ftrace instruction

[Li Huafei <lihuafei1@huawei.com>]

On 2022/4/26 14:22, Guo Ren wrote:
> On Tue, Apr 26, 2022 at 9:59 AM Li Huafei <lihuafei1@huawei.com> wrote:
>> When DYNAMIC_FTRACE is enabled, we put four instructions in front of the
>> function for ftrace use, not five.
>>
>> Signed-off-by: Li Huafei <lihuafei1@huawei.com>
>> ---
>>   arch/riscv/kernel/ftrace.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
>> index 4716f4cdc038..63f457650fa4 100644
>> --- a/arch/riscv/kernel/ftrace.c
>> +++ b/arch/riscv/kernel/ftrace.c
>> @@ -73,7 +73,7 @@ static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
>>   }
>>
>>   /*
>> - * Put 5 instructions with 16 bytes at the front of function within
>> + * Put 4 instructions with 16 bytes at the front of function within
> Yeah, 5 instructions are for mcount, -fpatchable-function-entry=8
> cause 8 16bit instructions.
I misunderstood, thanks for the clarification.
>
> Fixes: afc76b8b8011 ("riscv: Using PATCHABLE_FUNCTION_ENTRY instead of MCOUNT")
There is no functional fix here, do we need to add the fix tag?
>
> I recommend just delete "4 instructions with"
> - * Put 5 instructions with 16 bytes at the front of function within
> - * patchable function entry nops' area.
> + * Put 16 bytes at the front of the function within the patchable
> + * function entry nops' area.

I agree and will use this modification for the next version, thanks!


Huafei
>
>>    * patchable function entry nops' area.
>>    *
>>    * 0: REG_S  ra, -SZREG(sp)
>> --
>> 2.17.1
>>
>