Re: [PATCH v2 5/5] LoongArch: Abstract DYNAMIC_FTRACE_WITH_ARGS accesses

[Youling Tang]

Hi, Enze

On 04/27/2023 02:16 PM, Enze Li wrote:
> On Thu, Apr 27 2023 at 10:12:32 AM +0800, Youling Tang wrote:
>
> > From: Qing Zhang <zhangqing@xxxxxxxxxxx>
> >
> > 1. Adds new ftrace_regs_{get,set}_*() helpers which can be used to manipulate
> > ftrace_regs. When CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=y, these can always
> > be used on any ftrace_regs, and when CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=n
> > these can be used when regs are available. A new ftrace_regs_has_args(fregs)
> > helper is added which code can use to check when these are usable.
> >
> > 2. Prepare ftrace_regs_set_instruction_pointer support in advance.
> >
> > Signed-off-by: Qing Zhang <zhangqing@xxxxxxxxxxx>
> > ---
> >  arch/loongarch/include/asm/ftrace.h | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> >
> > diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
> > index f789e680f633..30ee01243416 100644
> > --- a/arch/loongarch/include/asm/ftrace.h
> > +++ b/arch/loongarch/include/asm/ftrace.h
> > @@ -54,6 +54,31 @@ static __always_inline struct pt_regs *arch_ftrace_get_regs(struct ftrace_regs *
> >  	return &fregs->regs;
> >  }
> >
> > +static __always_inline void
> > +ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs,
> > +				    unsigned long ip)
> > +{
> > +	regs_set_return_value(&fregs->regs, ip);
> > +}
> > +
> > +static __always_inline unsigned long
> > +ftrace_regs_get_instruction_pointer(struct ftrace_regs *fregs)
> > +{
> > +	return instruction_pointer(&fregs->regs);
> > +}
> > +
> > +#define ftrace_regs_get_argument(fregs, n) \
> > +	regs_get_kernel_argument(&(fregs)->regs, n)
> > +#define ftrace_regs_get_stack_pointer(fregs) \
> > +	kernel_stack_pointer(&(fregs)->regs)
> > +#define ftrace_regs_return_value(fregs) \
> > +	regs_return_value(&(fregs)->regs)
> > +#define ftrace_regs_set_return_value(fregs, ret) \
>
> Hi Youling,
>
> > +	regs_set_return_value(&(fregs)->regs, ret)
>        ^^^^^^^^^^^^^^^^^^^^^^^^
> I can not find the implementation of this function, am I missing
> something?
Note: This patch depends on regs_set_return_value() in the patch
"LoongArch: Add support for function error injection".

https://github.com/chenhuacai/linux/commit/c78e80c75b98feeb02b9a6eefb9de759f9036f42

> > +#define ftrace_override_function_with_return(fregs) \
> > +	override_function_with_return(&(fregs)->regs)
> > +#define ftrace_regs_query_register_offset(name) \
>                                                  ^^^^^^
> There seems to be a missing function here.  Otherwise, the backslash
> should be redundant.  Did I understand correctly?
Sorry for my oversight.

ftrace_regs_query_register_offset() will reuse
regs_query_register_offset(), I will modify it as follows,

#define ftrace_regs_query_register_offset(name) \
         regs_query_register_offset(name)

Thanks,
Youling.
> Best Regards,
> Enze
>
> > +
> >  #define ftrace_graph_func ftrace_graph_func
> >  void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
> >  		       struct ftrace_ops *op, struct ftrace_regs *fregs);