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* [PATCH v3 10/10] LoongArch/ftrace: Fix unwind state when option func_stack_trace
@ 2022-09-07 10:06 Qing Zhang
  2022-09-07 10:40 ` Jinyang He
  2022-09-07 14:00 ` Jeff Xie
  0 siblings, 2 replies; 4+ messages in thread
From: Qing Zhang @ 2022-09-07 10:06 UTC (permalink / raw)
  To: Huacai Chen, Steven Rostedt, Ingo Molnar
  Cc: WANG Xuerui, loongarch, linux-kernel, Jiaxun Yang, hejinyang

Ftrace plays like function head exception, prologue analysis will stop soon
because PC is at entry.

   90000000004c5a54 <callee>:
   90000000004c5a54:	03400000  andi   $zero, $zero, 0x0   ==>move  t0, ra
   90000000004c5a58:	03400000  andi   $zero, $zero, 0x0   ==>bl callsite
==>90000000004c5a5c:	02fcc063  addi.d $sp, $sp, -208(0xf30)
   ...

When encountering ftrace_call, save trace function ra at PT_ERA, save parent ra
at PT_R1, At this time, pc is the position after the two nops of callee. There is
no conventional prologue operation between this position and the function entry,
so we need to resetthe first flag to make the caller continue to unwind.

testing method:
  echo path_openat > ./set_ftrace_filter
  echo 1 > ./options/func_stack_trace
  echo function > ./current_tracer

Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
---
 arch/loongarch/include/asm/unwind.h     |  2 +-
 arch/loongarch/kernel/unwind_prologue.c | 33 +++++++++++++++++++++----
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/arch/loongarch/include/asm/unwind.h b/arch/loongarch/include/asm/unwind.h
index f66b07c3e6a1..f2b52b9ea93d 100644
--- a/arch/loongarch/include/asm/unwind.h
+++ b/arch/loongarch/include/asm/unwind.h
@@ -20,7 +20,7 @@ struct unwind_state {
 	char type; /* UNWINDER_XXX */
 	struct stack_info stack_info;
 	struct task_struct *task;
-	bool first, error;
+	bool first, error, is_ftrace;
 	int graph_idx;
 	unsigned long sp, pc, ra;
 };
diff --git a/arch/loongarch/kernel/unwind_prologue.c b/arch/loongarch/kernel/unwind_prologue.c
index 03f8b31a90cc..0bb19d3ae8ba 100644
--- a/arch/loongarch/kernel/unwind_prologue.c
+++ b/arch/loongarch/kernel/unwind_prologue.c
@@ -14,9 +14,7 @@ unsigned long unwind_get_return_address(struct unwind_state *state)
 
 	if (unwind_done(state))
 		return 0;
-	else if (state->type)
-		return state->pc;
-	else if (state->first)
+	else if (state->type || state->first)
 		return state->pc;
 
 	return *(unsigned long *)(state->sp);
@@ -42,16 +40,39 @@ static bool unwind_by_guess(struct unwind_state *state)
 	return false;
 }
 
+static void unwind_state_fixup(struct unwind_state *state)
+{
+	static unsigned long ftrace_case = (unsigned long)ftrace_call + 4;
+
+	if (state->pc == ftrace_case)
+		state->is_ftrace = true;
+}
+
 static bool unwind_by_prologue(struct unwind_state *state)
 {
 	struct stack_info *info = &state->stack_info;
 	union loongarch_instruction *ip, *ip_end;
 	unsigned long frame_size = 0, frame_ra = -1;
 	unsigned long size, offset, pc = state->pc;
+	struct pt_regs *regs;
 
 	if (state->sp >= info->end || state->sp < info->begin)
 		return false;
 
+	if (state->is_ftrace) {
+		/*
+		 * As we meet ftrace_regs_entry, reset first flag like first doing
+		 * tracing, Prologue analysis will stop soon because PC is at entry.
+		 */
+		regs = (struct pt_regs *)state->sp;
+		state->pc = regs->csr_era;
+		state->ra = regs->regs[1];
+		state->sp = regs->regs[3];
+		state->first = true;
+		state->is_ftrace = false;
+		return true;
+	}
+
 	if (!kallsyms_lookup_size_offset(pc, &size, &offset))
 		return false;
 
@@ -97,7 +118,7 @@ static bool unwind_by_prologue(struct unwind_state *state)
 
 	state->pc = *(unsigned long *)(state->sp + frame_ra);
 	state->sp = state->sp + frame_size;
-	return !!__kernel_text_address(state->pc);
+	goto out;
 
 first:
 	state->first = false;
@@ -106,7 +127,9 @@ static bool unwind_by_prologue(struct unwind_state *state)
 
 	state->pc = state->ra;
 
-	return !!__kernel_text_address(state->ra);
+out:
+	unwind_state_fixup(state);
+	return !!__kernel_text_address(state->pc);
 }
 
 void unwind_start(struct unwind_state *state, struct task_struct *task,
-- 
2.20.1


^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [PATCH v3 10/10] LoongArch/ftrace: Fix unwind state when option func_stack_trace
  2022-09-07 10:06 [PATCH v3 10/10] LoongArch/ftrace: Fix unwind state when option func_stack_trace Qing Zhang
@ 2022-09-07 10:40 ` Jinyang He
  2022-09-08  1:38   ` Qing Zhang
  2022-09-07 14:00 ` Jeff Xie
  1 sibling, 1 reply; 4+ messages in thread
From: Jinyang He @ 2022-09-07 10:40 UTC (permalink / raw)
  To: Qing Zhang, Huacai Chen, Steven Rostedt, Ingo Molnar
  Cc: WANG Xuerui, loongarch, linux-kernel, Jiaxun Yang, Jeff Xie

On 2022/9/7 18:06, Qing Zhang wrote:

> Ftrace plays like function head exception, prologue analysis will stop soon
> because PC is at entry.
>
>     90000000004c5a54 <callee>:
>     90000000004c5a54:	03400000  andi   $zero, $zero, 0x0   ==>move  t0, ra
>     90000000004c5a58:	03400000  andi   $zero, $zero, 0x0   ==>bl callsite
> ==>90000000004c5a5c:	02fcc063  addi.d $sp, $sp, -208(0xf30)
>     ...
>
> When encountering ftrace_call, save trace function ra at PT_ERA, save parent ra
> at PT_R1, At this time, pc is the position after the two nops of callee. There is
> no conventional prologue operation between this position and the function entry,
> so we need to resetthe first flag to make the caller continue to unwind.
>
> testing method:
>    echo path_openat > ./set_ftrace_filter
>    echo 1 > ./options/func_stack_trace
>    echo function > ./current_tracer
>
> Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
> ---
>   arch/loongarch/include/asm/unwind.h     |  2 +-
>   arch/loongarch/kernel/unwind_prologue.c | 33 +++++++++++++++++++++----
>   2 files changed, 29 insertions(+), 6 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/unwind.h b/arch/loongarch/include/asm/unwind.h
> index f66b07c3e6a1..f2b52b9ea93d 100644
> --- a/arch/loongarch/include/asm/unwind.h
> +++ b/arch/loongarch/include/asm/unwind.h
> @@ -20,7 +20,7 @@ struct unwind_state {
>   	char type; /* UNWINDER_XXX */
>   	struct stack_info stack_info;
>   	struct task_struct *task;
> -	bool first, error;
> +	bool first, error, is_ftrace;
>   	int graph_idx;
>   	unsigned long sp, pc, ra;
>   };
> diff --git a/arch/loongarch/kernel/unwind_prologue.c b/arch/loongarch/kernel/unwind_prologue.c
> index 03f8b31a90cc..0bb19d3ae8ba 100644
> --- a/arch/loongarch/kernel/unwind_prologue.c
> +++ b/arch/loongarch/kernel/unwind_prologue.c
> @@ -14,9 +14,7 @@ unsigned long unwind_get_return_address(struct unwind_state *state)
>   
>   	if (unwind_done(state))
>   		return 0;
> -	else if (state->type)
> -		return state->pc;
> -	else if (state->first)
> +	else if (state->type || state->first)
>   		return state->pc;
>   
>   	return *(unsigned long *)(state->sp);
> @@ -42,16 +40,39 @@ static bool unwind_by_guess(struct unwind_state *state)
>   	return false;
>   }
>   
> +static void unwind_state_fixup(struct unwind_state *state)
> +{
> +	static unsigned long ftrace_case = (unsigned long)ftrace_call + 4;
> +
> +	if (state->pc == ftrace_case)
> +		state->is_ftrace = true;
> +}
> +
>   static bool unwind_by_prologue(struct unwind_state *state)
>   {
>   	struct stack_info *info = &state->stack_info;
>   	union loongarch_instruction *ip, *ip_end;
>   	unsigned long frame_size = 0, frame_ra = -1;
>   	unsigned long size, offset, pc = state->pc;
> +	struct pt_regs *regs;
>   
>   	if (state->sp >= info->end || state->sp < info->begin)
>   		return false;
>   
> +	if (state->is_ftrace) {
> +		/*
> +		 * As we meet ftrace_regs_entry, reset first flag like first doing
> +		 * tracing, Prologue analysis will stop soon because PC is at entry.
> +		 */
> +		regs = (struct pt_regs *)state->sp;
> +		state->pc = regs->csr_era;
> +		state->ra = regs->regs[1];
> +		state->sp = regs->regs[3];
> +		state->first = true;
> +		state->is_ftrace = false;
> +		return true;
> +	}
> +
>   	if (!kallsyms_lookup_size_offset(pc, &size, &offset))
>   		return false;
>   
> @@ -97,7 +118,7 @@ static bool unwind_by_prologue(struct unwind_state *state)
>   
>   	state->pc = *(unsigned long *)(state->sp + frame_ra);
>   	state->sp = state->sp + frame_size;
> -	return !!__kernel_text_address(state->pc);
> +	goto out;
>   
>   first:
>   	state->first = false;
> @@ -106,7 +127,9 @@ static bool unwind_by_prologue(struct unwind_state *state)
>   
>   	state->pc = state->ra;
>   
> -	return !!__kernel_text_address(state->ra);
> +out:
> +	unwind_state_fixup(state);
> +	return !!__kernel_text_address(state->pc);
>   }
>   
>   void unwind_start(struct unwind_state *state, struct task_struct *task,

Hi, Qing

Additional 'Reported-by: Jeff Xie <xiehuan09@gmail.com>' is welcome.

For this patch, Tested-by: Jinyang He <hejinyang@loongson.cn>.


Thanks,

Jinyang


^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH v3 10/10] LoongArch/ftrace: Fix unwind state when option func_stack_trace
  2022-09-07 10:06 [PATCH v3 10/10] LoongArch/ftrace: Fix unwind state when option func_stack_trace Qing Zhang
  2022-09-07 10:40 ` Jinyang He
@ 2022-09-07 14:00 ` Jeff Xie
  1 sibling, 0 replies; 4+ messages in thread
From: Jeff Xie @ 2022-09-07 14:00 UTC (permalink / raw)
  To: Qing Zhang
  Cc: Huacai Chen, Steven Rostedt, Ingo Molnar, WANG Xuerui, loongarch,
	linux-kernel, Jiaxun Yang, hejinyang

Hi Qing,

On Wed, Sep 7, 2022 at 7:56 PM Qing Zhang <zhangqing@loongson.cn> wrote:
>
> Ftrace plays like function head exception, prologue analysis will stop soon
> because PC is at entry.
>
>    90000000004c5a54 <callee>:
>    90000000004c5a54:    03400000  andi   $zero, $zero, 0x0   ==>move  t0, ra
>    90000000004c5a58:    03400000  andi   $zero, $zero, 0x0   ==>bl callsite
> ==>90000000004c5a5c:    02fcc063  addi.d $sp, $sp, -208(0xf30)
>    ...
>
> When encountering ftrace_call, save trace function ra at PT_ERA, save parent ra
> at PT_R1, At this time, pc is the position after the two nops of callee. There is
> no conventional prologue operation between this position and the function entry,
> so we need to resetthe first flag to make the caller continue to unwind.
>
> testing method:
>   echo path_openat > ./set_ftrace_filter
>   echo 1 > ./options/func_stack_trace
>   echo function > ./current_tracer
>
> Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
> ---
>  arch/loongarch/include/asm/unwind.h     |  2 +-
>  arch/loongarch/kernel/unwind_prologue.c | 33 +++++++++++++++++++++----
>  2 files changed, 29 insertions(+), 6 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/unwind.h b/arch/loongarch/include/asm/unwind.h
> index f66b07c3e6a1..f2b52b9ea93d 100644
> --- a/arch/loongarch/include/asm/unwind.h
> +++ b/arch/loongarch/include/asm/unwind.h
> @@ -20,7 +20,7 @@ struct unwind_state {
>         char type; /* UNWINDER_XXX */
>         struct stack_info stack_info;
>         struct task_struct *task;
> -       bool first, error;
> +       bool first, error, is_ftrace;
>         int graph_idx;
>         unsigned long sp, pc, ra;
>  };
> diff --git a/arch/loongarch/kernel/unwind_prologue.c b/arch/loongarch/kernel/unwind_prologue.c
> index 03f8b31a90cc..0bb19d3ae8ba 100644
> --- a/arch/loongarch/kernel/unwind_prologue.c
> +++ b/arch/loongarch/kernel/unwind_prologue.c
> @@ -14,9 +14,7 @@ unsigned long unwind_get_return_address(struct unwind_state *state)
>
>         if (unwind_done(state))
>                 return 0;
> -       else if (state->type)
> -               return state->pc;
> -       else if (state->first)
> +       else if (state->type || state->first)
>                 return state->pc;
>
>         return *(unsigned long *)(state->sp);
> @@ -42,16 +40,39 @@ static bool unwind_by_guess(struct unwind_state *state)
>         return false;
>  }
>
> +static void unwind_state_fixup(struct unwind_state *state)
> +{
> +       static unsigned long ftrace_case = (unsigned long)ftrace_call + 4;
> +
> +       if (state->pc == ftrace_case)
> +               state->is_ftrace = true;
> +}
> +
>  static bool unwind_by_prologue(struct unwind_state *state)
>  {
>         struct stack_info *info = &state->stack_info;
>         union loongarch_instruction *ip, *ip_end;
>         unsigned long frame_size = 0, frame_ra = -1;
>         unsigned long size, offset, pc = state->pc;
> +       struct pt_regs *regs;
>
>         if (state->sp >= info->end || state->sp < info->begin)
>                 return false;
>
> +       if (state->is_ftrace) {
> +               /*
> +                * As we meet ftrace_regs_entry, reset first flag like first doing
> +                * tracing, Prologue analysis will stop soon because PC is at entry.
> +                */
> +               regs = (struct pt_regs *)state->sp;
> +               state->pc = regs->csr_era;
> +               state->ra = regs->regs[1];
> +               state->sp = regs->regs[3];
> +               state->first = true;
> +               state->is_ftrace = false;
> +               return true;
> +       }
> +
>         if (!kallsyms_lookup_size_offset(pc, &size, &offset))
>                 return false;
>
> @@ -97,7 +118,7 @@ static bool unwind_by_prologue(struct unwind_state *state)
>
>         state->pc = *(unsigned long *)(state->sp + frame_ra);
>         state->sp = state->sp + frame_size;
> -       return !!__kernel_text_address(state->pc);
> +       goto out;
>
>  first:
>         state->first = false;
> @@ -106,7 +127,9 @@ static bool unwind_by_prologue(struct unwind_state *state)
>
>         state->pc = state->ra;
>
> -       return !!__kernel_text_address(state->ra);
> +out:
> +       unwind_state_fixup(state);
> +       return !!__kernel_text_address(state->pc);
>  }
>
>  void unwind_start(struct unwind_state *state, struct task_struct *task,
> --
> 2.20.1
>

The patch looks good.

Tested-by: Jeff Xie <xiehuan09@gmail.com>

-- 
Thanks,
JeffXie

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH v3 10/10] LoongArch/ftrace: Fix unwind state when option func_stack_trace
  2022-09-07 10:40 ` Jinyang He
@ 2022-09-08  1:38   ` Qing Zhang
  0 siblings, 0 replies; 4+ messages in thread
From: Qing Zhang @ 2022-09-08  1:38 UTC (permalink / raw)
  To: Jinyang He, Huacai Chen, Steven Rostedt, Ingo Molnar
  Cc: WANG Xuerui, loongarch, linux-kernel, Jiaxun Yang, Jeff Xie

Hi, Jinyang

On 2022/9/7 下午6:40, Jinyang He wrote:
> On 2022/9/7 18:06, Qing Zhang wrote:
> 
>> Ftrace plays like function head exception, prologue analysis will stop 
>> soon
>> because PC is at entry.
>>
>>     90000000004c5a54 <callee>:
>>     90000000004c5a54:    03400000  andi   $zero, $zero, 0x0   ==>move  
>> t0, ra
>>     90000000004c5a58:    03400000  andi   $zero, $zero, 0x0   ==>bl 
>> callsite
>> ==>90000000004c5a5c:    02fcc063  addi.d $sp, $sp, -208(0xf30)
>>     ...
>>
>> When encountering ftrace_call, save trace function ra at PT_ERA, save 
>> parent ra
>> at PT_R1, At this time, pc is the position after the two nops of 
>> callee. There is
>> no conventional prologue operation between this position and the 
>> function entry,
>> so we need to resetthe first flag to make the caller continue to unwind.
>>
>> testing method:
>>    echo path_openat > ./set_ftrace_filter
>>    echo 1 > ./options/func_stack_trace
>>    echo function > ./current_tracer
>>
>> Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
>> ---
>>   arch/loongarch/include/asm/unwind.h     |  2 +-
>>   arch/loongarch/kernel/unwind_prologue.c | 33 +++++++++++++++++++++----
>>   2 files changed, 29 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/loongarch/include/asm/unwind.h 
>> b/arch/loongarch/include/asm/unwind.h
>> index f66b07c3e6a1..f2b52b9ea93d 100644
>> --- a/arch/loongarch/include/asm/unwind.h
>> +++ b/arch/loongarch/include/asm/unwind.h
>> @@ -20,7 +20,7 @@ struct unwind_state {
>>       char type; /* UNWINDER_XXX */
>>       struct stack_info stack_info;
>>       struct task_struct *task;
>> -    bool first, error;
>> +    bool first, error, is_ftrace;
>>       int graph_idx;
>>       unsigned long sp, pc, ra;
>>   };
>> diff --git a/arch/loongarch/kernel/unwind_prologue.c 
>> b/arch/loongarch/kernel/unwind_prologue.c
>> index 03f8b31a90cc..0bb19d3ae8ba 100644
>> --- a/arch/loongarch/kernel/unwind_prologue.c
>> +++ b/arch/loongarch/kernel/unwind_prologue.c
>> @@ -14,9 +14,7 @@ unsigned long unwind_get_return_address(struct 
>> unwind_state *state)
>>       if (unwind_done(state))
>>           return 0;
>> -    else if (state->type)
>> -        return state->pc;
>> -    else if (state->first)
>> +    else if (state->type || state->first)
>>           return state->pc;
>>       return *(unsigned long *)(state->sp);
>> @@ -42,16 +40,39 @@ static bool unwind_by_guess(struct unwind_state 
>> *state)
>>       return false;
>>   }
>> +static void unwind_state_fixup(struct unwind_state *state)
>> +{
>> +    static unsigned long ftrace_case = (unsigned long)ftrace_call + 4;
>> +
>> +    if (state->pc == ftrace_case)
>> +        state->is_ftrace = true;
>> +}
>> +
>>   static bool unwind_by_prologue(struct unwind_state *state)
>>   {
>>       struct stack_info *info = &state->stack_info;
>>       union loongarch_instruction *ip, *ip_end;
>>       unsigned long frame_size = 0, frame_ra = -1;
>>       unsigned long size, offset, pc = state->pc;
>> +    struct pt_regs *regs;
>>       if (state->sp >= info->end || state->sp < info->begin)
>>           return false;
>> +    if (state->is_ftrace) {
>> +        /*
>> +         * As we meet ftrace_regs_entry, reset first flag like first 
>> doing
>> +         * tracing, Prologue analysis will stop soon because PC is at 
>> entry.
>> +         */
>> +        regs = (struct pt_regs *)state->sp;
>> +        state->pc = regs->csr_era;
>> +        state->ra = regs->regs[1];
>> +        state->sp = regs->regs[3];
>> +        state->first = true;
>> +        state->is_ftrace = false;
>> +        return true;
>> +    }
>> +
>>       if (!kallsyms_lookup_size_offset(pc, &size, &offset))
>>           return false;
>> @@ -97,7 +118,7 @@ static bool unwind_by_prologue(struct unwind_state 
>> *state)
>>       state->pc = *(unsigned long *)(state->sp + frame_ra);
>>       state->sp = state->sp + frame_size;
>> -    return !!__kernel_text_address(state->pc);
>> +    goto out;
>>   first:
>>       state->first = false;
>> @@ -106,7 +127,9 @@ static bool unwind_by_prologue(struct unwind_state 
>> *state)
>>       state->pc = state->ra;
>> -    return !!__kernel_text_address(state->ra);
>> +out:
>> +    unwind_state_fixup(state);
>> +    return !!__kernel_text_address(state->pc);
>>   }
>>   void unwind_start(struct unwind_state *state, struct task_struct *task,
> 
> Hi, Qing
> 
> Additional 'Reported-by: Jeff Xie <xiehuan09@gmail.com>' is welcome.
> 
> For this patch, Tested-by: Jinyang He <hejinyang@loongson.cn>.
> 
ok, I will add relevant Reported and Tested tags, wait for other
people's comments on the series before this. ping Steven manually. :)

Thanks,
-Qing
> 
> Thanks,
> 
> Jinyang
> 


^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-09-08  1:39 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-09-07 10:06 [PATCH v3 10/10] LoongArch/ftrace: Fix unwind state when option func_stack_trace Qing Zhang
2022-09-07 10:40 ` Jinyang He
2022-09-08  1:38   ` Qing Zhang
2022-09-07 14:00 ` Jeff Xie

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