arch_stack_walk() is called intensively in function_graph when the
kernel is compiled with CONFIG_TRACE_IRQFLAGS. As a result, the kernel
logs a lot of arch_stack_walk and its sub-functions into the ftrace
buffer. However, these functions should not appear on the trace log
because they are part of the ftrace itself. This patch references what
arm64 does for the smae function. So it further prevent the re-enter
kprobe issue, which is also possible on riscv.

Related-to: commit 0fbcd8abf337 ("arm64: Prohibit instrumentation on arch_stack_walk()")
Fixes: 680341382da5 ("riscv: add CALLER_ADDRx support")
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
---
 arch/riscv/kernel/stacktrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index 528ec7cc9a62..0d3f00eb0bae 100644
--- a/arch/riscv/kernel/stacktrace.c
+++ b/arch/riscv/kernel/stacktrace.c
@@ -156,7 +156,7 @@ unsigned long __get_wchan(struct task_struct *task)
 	return pc;
 }
 
-noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
+noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
 		     struct task_struct *task, struct pt_regs *regs)
 {
 	walk_stackframe(task, regs, consume_entry, cookie);

-- 
2.43.0

Hi Andy,

On 13/06/2024 09:11, Andy Chiu wrote:
> arch_stack_walk() is called intensively in function_graph when the
> kernel is compiled with CONFIG_TRACE_IRQFLAGS. As a result, the kernel
> logs a lot of arch_stack_walk and its sub-functions into the ftrace
> buffer. However, these functions should not appear on the trace log
> because they are part of the ftrace itself. This patch references what
> arm64 does for the smae function. So it further prevent the re-enter
> kprobe issue, which is also possible on riscv.
>
> Related-to: commit 0fbcd8abf337 ("arm64: Prohibit instrumentation on arch_stack_walk()")
> Fixes: 680341382da5 ("riscv: add CALLER_ADDRx support")
> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> ---
>   arch/riscv/kernel/stacktrace.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
> index 528ec7cc9a62..0d3f00eb0bae 100644
> --- a/arch/riscv/kernel/stacktrace.c
> +++ b/arch/riscv/kernel/stacktrace.c
> @@ -156,7 +156,7 @@ unsigned long __get_wchan(struct task_struct *task)
>   	return pc;
>   }
>   
> -noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
> +noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
>   		     struct task_struct *task, struct pt_regs *regs)
>   {
>   	walk_stackframe(task, regs, consume_entry, cookie);
>

Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>

I'll try to make this go into -fixes, this is in my fixes branch at least.

Thanks,

Alex

On Tue, 18 Jun 2024 02:55:32 PDT (-0700), alex@ghiti.fr wrote:
> Hi Andy,
>
> On 13/06/2024 09:11, Andy Chiu wrote:
>> arch_stack_walk() is called intensively in function_graph when the
>> kernel is compiled with CONFIG_TRACE_IRQFLAGS. As a result, the kernel
>> logs a lot of arch_stack_walk and its sub-functions into the ftrace
>> buffer. However, these functions should not appear on the trace log
>> because they are part of the ftrace itself. This patch references what
>> arm64 does for the smae function. So it further prevent the re-enter
>> kprobe issue, which is also possible on riscv.
>>
>> Related-to: commit 0fbcd8abf337 ("arm64: Prohibit instrumentation on arch_stack_walk()")
>> Fixes: 680341382da5 ("riscv: add CALLER_ADDRx support")
>> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
>> ---
>>   arch/riscv/kernel/stacktrace.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
>> index 528ec7cc9a62..0d3f00eb0bae 100644
>> --- a/arch/riscv/kernel/stacktrace.c
>> +++ b/arch/riscv/kernel/stacktrace.c
>> @@ -156,7 +156,7 @@ unsigned long __get_wchan(struct task_struct *task)
>>   	return pc;
>>   }
>>
>> -noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
>> +noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
>>   		     struct task_struct *task, struct pt_regs *regs)
>>   {
>>   	walk_stackframe(task, regs, consume_entry, cookie);
>>
>
> Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
>
> I'll try to make this go into -fixes, this is in my fixes branch at least.

Looks like there's some comments on the rest of the patch set.

Andy: aree you going to send a v2, or do you want me to just pick this 
one up onto fixes now and then handle the rest later?

>
> Thanks,
>
> Alex