Re: Ftrace broken on parisc

[Helge Deller <deller@gmx.de>]

Hi Guy,

On 01/29/2014 08:59 PM, Guy Martin wrote:
> It seems that the ftrace subsystem has not been maintained for a few
> years.

Yes.
 
> So far I have the diff at the bottom that attempts to fix it bug there
> is still an issue while linking :

I'm not sure I tested 64bit at that time.

> arch/parisc/kernel/built-in.o: In function `return_to_handler':
> (.text+0xb2a8): undefined reference to `ftrace_return_to_handler'
> hppa64-linux-ld: arch/parisc/kernel/built-in.o(.text+0xllx): cannot
> reach (null)
> arch/parisc/kernel/built-in.o: In function `return_to_handler':
> (.text+0xb2a8): relocation truncated to fit: R_PARISC_PCREL17F against
> undefined symbol `ftrace_return_to_handler'
> make: *** [vmlinux] Error 1
> 
> I'm not sure how this can be fixed, the problems comes from the
> assembly in entry.S, it uses a 'b' to jump to ftrace_return_to_handler.
> I guess 'be' needs to be used but not sure how that'd works with the
> linker.

Can you try
BL ftrace_return_to_handler, %r0
(I'm not good in hppa assembly - as you can see if you take a look at this assembly code section :-)).

> Moreover, there is probably more than this to be fixed.
> 
> For the background story, I'm trying to fix this to audit irq handlers
> for my pata_sil680 issue.
> 
> Adding some printk for irq == 71 in handle_percpu_irq(), I see and odd
> behavior. The printk at the end of the function is displayed a lot more
> than the printk at the begining of the function. I know printk isn't
> the best for irq handlers that's why I was investigating the ftrace way.
> 
> Any tip/help is very much welcome !

Helge


> 
>   Guy
> 
> ---
> diff --git a/arch/parisc/Kconfig.debug b/arch/parisc/Kconfig.debug
> index bc989e5..6d23a1a 100644
> --- a/arch/parisc/Kconfig.debug
> +++ b/arch/parisc/Kconfig.debug
> @@ -1,5 +1,8 @@
>  menu "Kernel hacking"
> 
> +config TRACE_IRQFLAGS_SUPPORT
> +       def_bool y
> +
>  source "lib/Kconfig.debug"
> 
>  config DEBUG_RODATA
> diff --git a/arch/parisc/kernel/ftrace.c b/arch/parisc/kernel/ftrace.c
> index 5beb97b..8c9f757 100644
> --- a/arch/parisc/kernel/ftrace.c
> +++ b/arch/parisc/kernel/ftrace.c
> @@ -156,7 +156,7 @@ void ftrace_function_trampoline(unsigned long
>  parent, return;
> 
>         if (ftrace_trace_function != ftrace_stub) {
> -               ftrace_trace_function(parent, self_addr);
> +               ftrace_trace_function(parent, self_addr, NULL, NULL);
>                 return;
>         }
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
> 
> --
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