kprobes: Mark ftrace mcount handler functions nokprobe

[PATCH] kprobes: Mark ftrace mcount handler functions nokprobe

Posted by Liao Chang 3 years, 6 months ago

Mark ftrace mcount handler functions nokprobe since probing on these
functions probably reaches mcount recursivly during kprobe breakpoint
handler for some architecture(tested for riscv, arm64), and reenter
kprobe is treated as a fatal error, causes kernel panic.

Pesudo code below demonstrate this problem:

  mcount
    function_trace_call (probed)
      arch_breakpoint_handler
        arch_setup_singlestep [mcount]
          function_trace_call (probed)
            arch_breakpoint_handler
              reenter_kprobe
                BUG

Signed-off-by: Liao Chang <liaochang1@huawei.com>
---
 kernel/trace/trace_functions.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 9f1bfbe105e8..440a678a8c7c 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -16,6 +16,7 @@
 #include <linux/ftrace.h>
 #include <linux/slab.h>
 #include <linux/fs.h>
+#include <linux/kprobes.h>
 
 #include "trace.h"
 
@@ -194,6 +195,7 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
 
 	ftrace_test_recursion_unlock(bit);
 }
+NOKPROBE_SYMBOL(function_trace_call);
 
 #ifdef CONFIG_UNWINDER_ORC
 /*
@@ -245,6 +247,7 @@ function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
 	atomic_dec(&data->disabled);
 	local_irq_restore(flags);
 }
+NOKPROBE_SYMBOL(function_stack_trace_call);
 
 static inline bool is_repeat_check(struct trace_array *tr,
 				   struct trace_func_repeats *last_info,
@@ -321,6 +324,7 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
 out:
 	ftrace_test_recursion_unlock(bit);
 }
+NOKPROBE_SYMBOL(function_no_repeats_trace_call);
 
 static void
 function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
@@ -363,6 +367,7 @@ function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
 	atomic_dec(&data->disabled);
 	local_irq_restore(flags);
 }
+NOKPROBE_SYMBOL(function_stack_no_repeats_trace_call);
 
 static struct tracer_opt func_opts[] = {
 #ifdef CONFIG_STACKTRACE
-- 
2.17.1

Re: [PATCH] kprobes: Mark ftrace mcount handler functions nokprobe

Posted by Steven Rostedt 3 years, 6 months ago

On Mon, 19 Sep 2022 16:45:33 +0800
Liao Chang <liaochang1@huawei.com> wrote:

> Mark ftrace mcount handler functions nokprobe since probing on these
> functions probably reaches mcount recursivly during kprobe breakpoint
> handler for some architecture(tested for riscv, arm64), and reenter
> kprobe is treated as a fatal error, causes kernel panic.

This looks to me that the affected archs should be made more robust for this
case than to add this to the generic code.

-- Steve


> 
> Pesudo code below demonstrate this problem:
> 
>   mcount
>     function_trace_call (probed)
>       arch_breakpoint_handler
>         arch_setup_singlestep [mcount]
>           function_trace_call (probed)
>             arch_breakpoint_handler
>               reenter_kprobe
>                 BUG
> 
> Signed-off-by: Liao Chang <liaochang1@huawei.com>
> ---
>  kernel/trace/trace_functions.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
> index 9f1bfbe105e8..440a678a8c7c 100644
> --- a/kernel/trace/trace_functions.c
> +++ b/kernel/trace/trace_functions.c
> @@ -16,6 +16,7 @@
>  #include <linux/ftrace.h>
>  #include <linux/slab.h>
>  #include <linux/fs.h>
> +#include <linux/kprobes.h>
>  
>  #include "trace.h"
>  
> @@ -194,6 +195,7 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
>  
>  	ftrace_test_recursion_unlock(bit);
>  }
> +NOKPROBE_SYMBOL(function_trace_call);
>  
>  #ifdef CONFIG_UNWINDER_ORC
>  /*
> @@ -245,6 +247,7 @@ function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
>  	atomic_dec(&data->disabled);
>  	local_irq_restore(flags);
>  }
> +NOKPROBE_SYMBOL(function_stack_trace_call);
>  
>  static inline bool is_repeat_check(struct trace_array *tr,
>  				   struct trace_func_repeats *last_info,
> @@ -321,6 +324,7 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
>  out:
>  	ftrace_test_recursion_unlock(bit);
>  }
> +NOKPROBE_SYMBOL(function_no_repeats_trace_call);
>  
>  static void
>  function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
> @@ -363,6 +367,7 @@ function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
>  	atomic_dec(&data->disabled);
>  	local_irq_restore(flags);
>  }
> +NOKPROBE_SYMBOL(function_stack_no_repeats_trace_call);
>  
>  static struct tracer_opt func_opts[] = {
>  #ifdef CONFIG_STACKTRACE

Re: [PATCH] kprobes: Mark ftrace mcount handler functions nokprobe

Posted by Masami Hiramatsu (Google) 3 years, 6 months ago

On Mon, 26 Sep 2022 14:37:23 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Mon, 19 Sep 2022 16:45:33 +0800
> Liao Chang <liaochang1@huawei.com> wrote:
> 
> > Mark ftrace mcount handler functions nokprobe since probing on these
> > functions probably reaches mcount recursivly during kprobe breakpoint
> > handler for some architecture(tested for riscv, arm64), and reenter
> > kprobe is treated as a fatal error, causes kernel panic.
> 
> This looks to me that the affected archs should be made more robust for this
> case than to add this to the generic code.

Yeah, kprobes (arch specific code) itself shouldn't be traced by ftrace usually.

Thank you,

> 
> -- Steve
> 
> 
> > 
> > Pesudo code below demonstrate this problem:
> > 
> >   mcount
> >     function_trace_call (probed)
> >       arch_breakpoint_handler
> >         arch_setup_singlestep [mcount]
> >           function_trace_call (probed)
> >             arch_breakpoint_handler
> >               reenter_kprobe
> >                 BUG
> > 
> > Signed-off-by: Liao Chang <liaochang1@huawei.com>
> > ---
> >  kernel/trace/trace_functions.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
> > index 9f1bfbe105e8..440a678a8c7c 100644
> > --- a/kernel/trace/trace_functions.c
> > +++ b/kernel/trace/trace_functions.c
> > @@ -16,6 +16,7 @@
> >  #include <linux/ftrace.h>
> >  #include <linux/slab.h>
> >  #include <linux/fs.h>
> > +#include <linux/kprobes.h>
> >  
> >  #include "trace.h"
> >  
> > @@ -194,6 +195,7 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
> >  
> >  	ftrace_test_recursion_unlock(bit);
> >  }
> > +NOKPROBE_SYMBOL(function_trace_call);
> >  
> >  #ifdef CONFIG_UNWINDER_ORC
> >  /*
> > @@ -245,6 +247,7 @@ function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
> >  	atomic_dec(&data->disabled);
> >  	local_irq_restore(flags);
> >  }
> > +NOKPROBE_SYMBOL(function_stack_trace_call);
> >  
> >  static inline bool is_repeat_check(struct trace_array *tr,
> >  				   struct trace_func_repeats *last_info,
> > @@ -321,6 +324,7 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
> >  out:
> >  	ftrace_test_recursion_unlock(bit);
> >  }
> > +NOKPROBE_SYMBOL(function_no_repeats_trace_call);
> >  
> >  static void
> >  function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
> > @@ -363,6 +367,7 @@ function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
> >  	atomic_dec(&data->disabled);
> >  	local_irq_restore(flags);
> >  }
> > +NOKPROBE_SYMBOL(function_stack_no_repeats_trace_call);
> >  
> >  static struct tracer_opt func_opts[] = {
> >  #ifdef CONFIG_STACKTRACE
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>

Re: [PATCH] kprobes: Mark ftrace mcount handler functions nokprobe

Posted by liaochang (A) 3 years, 6 months ago


在 2022/9/27 2:37, Steven Rostedt 写道:
> On Mon, 19 Sep 2022 16:45:33 +0800
> Liao Chang <liaochang1@huawei.com> wrote:
> 
>> Mark ftrace mcount handler functions nokprobe since probing on these
>> functions probably reaches mcount recursivly during kprobe breakpoint
>> handler for some architecture(tested for riscv, arm64), and reenter
>> kprobe is treated as a fatal error, causes kernel panic.
> 
> This looks to me that the affected archs should be made more robust for this
> case than to add this to the generic code.

OK, i will fix this problem in arch related code, thanks for feedback.

> 
> -- Steve
> 
> 
>>
>> Pesudo code below demonstrate this problem:
>>
>>   mcount
>>     function_trace_call (probed)
>>       arch_breakpoint_handler
>>         arch_setup_singlestep [mcount]
>>           function_trace_call (probed)
>>             arch_breakpoint_handler
>>               reenter_kprobe
>>                 BUG
>>
>> Signed-off-by: Liao Chang <liaochang1@huawei.com>
>> ---
>>  kernel/trace/trace_functions.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
>> index 9f1bfbe105e8..440a678a8c7c 100644
>> --- a/kernel/trace/trace_functions.c
>> +++ b/kernel/trace/trace_functions.c
>> @@ -16,6 +16,7 @@
>>  #include <linux/ftrace.h>
>>  #include <linux/slab.h>
>>  #include <linux/fs.h>
>> +#include <linux/kprobes.h>
>>  
>>  #include "trace.h"
>>  
>> @@ -194,6 +195,7 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
>>  
>>  	ftrace_test_recursion_unlock(bit);
>>  }
>> +NOKPROBE_SYMBOL(function_trace_call);
>>  
>>  #ifdef CONFIG_UNWINDER_ORC
>>  /*
>> @@ -245,6 +247,7 @@ function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
>>  	atomic_dec(&data->disabled);
>>  	local_irq_restore(flags);
>>  }
>> +NOKPROBE_SYMBOL(function_stack_trace_call);
>>  
>>  static inline bool is_repeat_check(struct trace_array *tr,
>>  				   struct trace_func_repeats *last_info,
>> @@ -321,6 +324,7 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
>>  out:
>>  	ftrace_test_recursion_unlock(bit);
>>  }
>> +NOKPROBE_SYMBOL(function_no_repeats_trace_call);
>>  
>>  static void
>>  function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
>> @@ -363,6 +367,7 @@ function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
>>  	atomic_dec(&data->disabled);
>>  	local_irq_restore(flags);
>>  }
>> +NOKPROBE_SYMBOL(function_stack_no_repeats_trace_call);
>>  
>>  static struct tracer_opt func_opts[] = {
>>  #ifdef CONFIG_STACKTRACE
> 
> 
> .

-- 
BR,
Liao, Chang