Re: [PATCH RFC 1/8] stacktrace: Change callback prototype to pass more information

2022-04-19 Thread He Zhe 



On 4/19/22 21:09, Mark Rutland wrote:
> On Mon, Apr 18, 2022 at 09:22:10PM +0800, He Zhe wrote:
>> Currently stack_trace_consume_fn can only have pc of each frame of the
>> stack. Copying-beyond-the-frame-detection also needs fp of current and
>> previous frame. Other detection algorithm in the future may need more
>> information of the frame.
>>
>> We define a frame_info to include them all.
>>
>>
>> Signed-off-by: He Zhe 
>> ---
>>  include/linux/stacktrace.h |  9 -
>>  kernel/stacktrace.c| 10 +-
>>  2 files changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
>> index 97455880ac41..5a61bfafe6f0 100644
>> --- a/include/linux/stacktrace.h
>> +++ b/include/linux/stacktrace.h
>> @@ -10,15 +10,22 @@ struct pt_regs;
>>  
>>  #ifdef CONFIG_ARCH_STACKWALK
>>  
>> +struct frame_info {
>> +unsigned long pc;
>> +unsigned long fp;
>> +unsigned long prev_fp;
>> +};
> I don't think this should be exposed through a generic interface; the `fp` and
> `prev_fp` values are only meaningful with arch-specific knowledge, and they're
> *very* easy to misuse (e.g. when transitioning from one stack to another).
> There's also a bunch of other information one may or may not want, depending 
> on
> what you're trying to achieve.
>
> I am happy to have an arch-specific internal unwinder where we can access this
> information, and *maybe* it makes sense to have a generic API that passes some
> opaque token, but I don't think we should make the structure generic.

Thanks for thoughts. I saw unwind_frame and etc was made private earlier and
took that as a hint that all further stack walk things should be based on those
functions and came up with this. But OK, good to know that arch-specific unwind
would be fine, I'll redo this series in that way.

Thanks,
Zhe

>
> Thanks,
> Mark.
>
>> +
>>  /**
>>   * stack_trace_consume_fn - Callback for arch_stack_walk()
>>   * @cookie: Caller supplied pointer handed back by arch_stack_walk()
>>   * @addr:   The stack entry address to consume
>> + * @fi: The frame information to consume
>>   *
>>   * Return:  True, if the entry was consumed or skipped
>>   *  False, if there is no space left to store
>>   */
>> -typedef bool (*stack_trace_consume_fn)(void *cookie, unsigned long addr);
>> +typedef bool (*stack_trace_consume_fn)(void *cookie, struct frame_info *fi);
>>  /**
>>   * arch_stack_walk - Architecture specific function to walk the stack
>>   * @consume_entry:  Callback which is invoked by the architecture code for
>> diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
>> index 9ed5ce989415..2d0a2812e92b 100644
>> --- a/kernel/stacktrace.c
>> +++ b/kernel/stacktrace.c
>> @@ -79,7 +79,7 @@ struct stacktrace_cookie {
>>  unsigned intlen;
>>  };
>>  
>> -static bool stack_trace_consume_entry(void *cookie, unsigned long addr)
>> +static bool stack_trace_consume_entry(void *cookie, struct frame_info *fi)
>>  {
>>  struct stacktrace_cookie *c = cookie;
>>  
>> @@ -90,15 +90,15 @@ static bool stack_trace_consume_entry(void *cookie, 
>> unsigned long addr)
>>  c->skip--;
>>  return true;
>>  }
>> -c->store[c->len++] = addr;
>> +c->store[c->len++] = fi->pc;
>>  return c->len < c->size;
>>  }
>>  
>> -static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long 
>> addr)
>> +static bool stack_trace_consume_entry_nosched(void *cookie, struct 
>> frame_info *fi)
>>  {
>> -if (in_sched_functions(addr))
>> +if (in_sched_functions(fi->pc))
>>  return true;
>> -return stack_trace_consume_entry(cookie, addr);
>> +return stack_trace_consume_entry(cookie, fi);
>>  }
>>  
>>  /**
>> -- 
>> 2.25.1
>>

Re: [PATCH RFC 1/8] stacktrace: Change callback prototype to pass more information

2022-04-19 Thread Mark Rutland 
On Mon, Apr 18, 2022 at 09:22:10PM +0800, He Zhe wrote:
> Currently stack_trace_consume_fn can only have pc of each frame of the
> stack. Copying-beyond-the-frame-detection also needs fp of current and
> previous frame. Other detection algorithm in the future may need more
> information of the frame.
> 
> We define a frame_info to include them all.
> 
> 
> Signed-off-by: He Zhe 
> ---
>  include/linux/stacktrace.h |  9 -
>  kernel/stacktrace.c| 10 +-
>  2 files changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
> index 97455880ac41..5a61bfafe6f0 100644
> --- a/include/linux/stacktrace.h
> +++ b/include/linux/stacktrace.h
> @@ -10,15 +10,22 @@ struct pt_regs;
>  
>  #ifdef CONFIG_ARCH_STACKWALK
>  
> +struct frame_info {
> + unsigned long pc;
> + unsigned long fp;
> + unsigned long prev_fp;
> +};

I don't think this should be exposed through a generic interface; the `fp` and
`prev_fp` values are only meaningful with arch-specific knowledge, and they're
*very* easy to misuse (e.g. when transitioning from one stack to another).
There's also a bunch of other information one may or may not want, depending on
what you're trying to achieve.

I am happy to have an arch-specific internal unwinder where we can access this
information, and *maybe* it makes sense to have a generic API that passes some
opaque token, but I don't think we should make the structure generic.

Thanks,
Mark.

> +
>  /**
>   * stack_trace_consume_fn - Callback for arch_stack_walk()
>   * @cookie:  Caller supplied pointer handed back by arch_stack_walk()
>   * @addr:The stack entry address to consume
> + * @fi:  The frame information to consume
>   *
>   * Return:   True, if the entry was consumed or skipped
>   *   False, if there is no space left to store
>   */
> -typedef bool (*stack_trace_consume_fn)(void *cookie, unsigned long addr);
> +typedef bool (*stack_trace_consume_fn)(void *cookie, struct frame_info *fi);
>  /**
>   * arch_stack_walk - Architecture specific function to walk the stack
>   * @consume_entry:   Callback which is invoked by the architecture code for
> diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
> index 9ed5ce989415..2d0a2812e92b 100644
> --- a/kernel/stacktrace.c
> +++ b/kernel/stacktrace.c
> @@ -79,7 +79,7 @@ struct stacktrace_cookie {
>   unsigned intlen;
>  };
>  
> -static bool stack_trace_consume_entry(void *cookie, unsigned long addr)
> +static bool stack_trace_consume_entry(void *cookie, struct frame_info *fi)
>  {
>   struct stacktrace_cookie *c = cookie;
>  
> @@ -90,15 +90,15 @@ static bool stack_trace_consume_entry(void *cookie, 
> unsigned long addr)
>   c->skip--;
>   return true;
>   }
> - c->store[c->len++] = addr;
> + c->store[c->len++] = fi->pc;
>   return c->len < c->size;
>  }
>  
> -static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long 
> addr)
> +static bool stack_trace_consume_entry_nosched(void *cookie, struct 
> frame_info *fi)
>  {
> - if (in_sched_functions(addr))
> + if (in_sched_functions(fi->pc))
>   return true;
> - return stack_trace_consume_entry(cookie, addr);
> + return stack_trace_consume_entry(cookie, fi);
>  }
>  
>  /**
> -- 
> 2.25.1
>

[PATCH RFC 1/8] stacktrace: Change callback prototype to pass more information

2022-04-18 Thread He Zhe 
Currently stack_trace_consume_fn can only have pc of each frame of the
stack. Copying-beyond-the-frame-detection also needs fp of current and
previous frame. Other detection algorithm in the future may need more
information of the frame.

We define a frame_info to include them all.


Signed-off-by: He Zhe 
---
 include/linux/stacktrace.h |  9 -
 kernel/stacktrace.c| 10 +-
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index 97455880ac41..5a61bfafe6f0 100644
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -10,15 +10,22 @@ struct pt_regs;
 
 #ifdef CONFIG_ARCH_STACKWALK
 
+struct frame_info {
+   unsigned long pc;
+   unsigned long fp;
+   unsigned long prev_fp;
+};
+
 /**
  * stack_trace_consume_fn - Callback for arch_stack_walk()
  * @cookie:Caller supplied pointer handed back by arch_stack_walk()
  * @addr:  The stack entry address to consume
+ * @fi:The frame information to consume
  *
  * Return: True, if the entry was consumed or skipped
  * False, if there is no space left to store
  */
-typedef bool (*stack_trace_consume_fn)(void *cookie, unsigned long addr);
+typedef bool (*stack_trace_consume_fn)(void *cookie, struct frame_info *fi);
 /**
  * arch_stack_walk - Architecture specific function to walk the stack
  * @consume_entry: Callback which is invoked by the architecture code for
diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index 9ed5ce989415..2d0a2812e92b 100644
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -79,7 +79,7 @@ struct stacktrace_cookie {
unsigned intlen;
 };
 
-static bool stack_trace_consume_entry(void *cookie, unsigned long addr)
+static bool stack_trace_consume_entry(void *cookie, struct frame_info *fi)
 {
struct stacktrace_cookie *c = cookie;
 
@@ -90,15 +90,15 @@ static bool stack_trace_consume_entry(void *cookie, 
unsigned long addr)
c->skip--;
return true;
}
-   c->store[c->len++] = addr;
+   c->store[c->len++] = fi->pc;
return c->len < c->size;
 }
 
-static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr)
+static bool stack_trace_consume_entry_nosched(void *cookie, struct frame_info 
*fi)
 {
-   if (in_sched_functions(addr))
+   if (in_sched_functions(fi->pc))
return true;
-   return stack_trace_consume_entry(cookie, addr);
+   return stack_trace_consume_entry(cookie, fi);
 }
 
 /**
-- 
2.25.1