linux-kernel - Re: [PATCH v2 5/5] LoongArch: Abstract DYNAMIC_FTRACE_WITH

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Message-ID: <b52aff74-17a6-3a91-62b3-d11477645e81@loongson.cn>
Date:   Thu, 27 Apr 2023 14:47:53 +0800
From:   Youling Tang <tangyouling@...ngson.cn>
To:     Enze Li <lienze@...inos.cn>
Cc:     Huacai Chen <chenhuacai@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        WANG Xuerui <kernel@...0n.name>, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, loongarch@...ts.linux.dev,
        loongson-kernel@...ts.loongnix.cn,
        Qing Zhang <zhangqing@...ngson.cn>
Subject: Re: [PATCH v2 5/5] LoongArch: Abstract DYNAMIC_FTRACE_WITH_ARGS
 accesses

Hi, Enze

On 04/27/2023 02:16 PM, Enze Li wrote:
> On Thu, Apr 27 2023 at 10:12:32 AM +0800, Youling Tang wrote:
>
>> From: Qing Zhang <zhangqing@...ngson.cn>
>>
>> 1. Adds new ftrace_regs_{get,set}_*() helpers which can be used to manipulate
>> ftrace_regs. When CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=y, these can always
>> be used on any ftrace_regs, and when CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=n
>> these can be used when regs are available. A new ftrace_regs_has_args(fregs)
>> helper is added which code can use to check when these are usable.
>>
>> 2. Prepare ftrace_regs_set_instruction_pointer support in advance.
>>
>> Signed-off-by: Qing Zhang <zhangqing@...ngson.cn>
>> ---
>>  arch/loongarch/include/asm/ftrace.h | 25 +++++++++++++++++++++++++
>>  1 file changed, 25 insertions(+)
>>
>> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
>> index f789e680f633..30ee01243416 100644
>> --- a/arch/loongarch/include/asm/ftrace.h
>> +++ b/arch/loongarch/include/asm/ftrace.h
>> @@ -54,6 +54,31 @@ static __always_inline struct pt_regs *arch_ftrace_get_regs(struct ftrace_regs *
>>  	return &fregs->regs;
>>  }
>>
>> +static __always_inline void
>> +ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs,
>> +				    unsigned long ip)
>> +{
>> +	regs_set_return_value(&fregs->regs, ip);
>> +}
>> +
>> +static __always_inline unsigned long
>> +ftrace_regs_get_instruction_pointer(struct ftrace_regs *fregs)
>> +{
>> +	return instruction_pointer(&fregs->regs);
>> +}
>> +
>> +#define ftrace_regs_get_argument(fregs, n) \
>> +	regs_get_kernel_argument(&(fregs)->regs, n)
>> +#define ftrace_regs_get_stack_pointer(fregs) \
>> +	kernel_stack_pointer(&(fregs)->regs)
>> +#define ftrace_regs_return_value(fregs) \
>> +	regs_return_value(&(fregs)->regs)
>> +#define ftrace_regs_set_return_value(fregs, ret) \
>
> Hi Youling,
>
>> +	regs_set_return_value(&(fregs)->regs, ret)
>        ^^^^^^^^^^^^^^^^^^^^^^^^
> I can not find the implementation of this function, am I missing
> something?
Note: This patch depends on regs_set_return_value() in the patch
"LoongArch: Add support for function error injection".

https://github.com/chenhuacai/linux/commit/c78e80c75b98feeb02b9a6eefb9de759f9036f42

>
>> +#define ftrace_override_function_with_return(fregs) \
>> +	override_function_with_return(&(fregs)->regs)
>> +#define ftrace_regs_query_register_offset(name) \
>                                                  ^^^^^^
> There seems to be a missing function here.  Otherwise, the backslash
> should be redundant.  Did I understand correctly?
Sorry for my oversight.

ftrace_regs_query_register_offset() will reuse
regs_query_register_offset(), I will modify it as follows,

#define ftrace_regs_query_register_offset(name) \
          regs_query_register_offset(name)

Thanks,
Youling.
>
> Best Regards,
> Enze
>
>> +
>>  #define ftrace_graph_func ftrace_graph_func
>>  void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
>>  		       struct ftrace_ops *op, struct ftrace_regs *fregs);