Re: [RFT PATCH -next ] [BUGFIX] kprobes: Fix "Failed to find blacklist" error on ia64 and ppc64

Ananth N Mavinakayanahalli
2014-05-08T06:28:58Z

On Thu, May 08, 2014 at 02:40:00PM +0900, Masami Hiramatsu wrote:
> (2014/05/08 13:47), Ananth N Mavinakayanahalli wrote:
> > On Wed, May 07, 2014 at 08:55:51PM +0900, Masami Hiramatsu wrote:
> >
> > ...
> >
> >> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF = 1)
> >> +/*
> >> + * On PPC64 ABIv1 the function pointer actually points to the
> >> + * function's descriptor. The first entry in the descriptor is the
> >> + * address of the function text.
> >> + */
> >> +#define constant_function_entry(fn) (((func_descr_t *)(fn))->entry)
> >> +#else
> >> +#define constant_function_entry(fn) ((unsigned long)(fn))
> >> +#endif
> >> +
> >> #endif /* __ASSEMBLY__ */
> >
> > Hi Masami,
> >
> > You could just use ppc_function_entry() instead.
>
> No, I think ppc_function_entry() has two problems (on the latest -next kernel)
>
> At first, that is an inlined functions which is not applied in build time.
> Since the NOKPROBE_SYMBOL() is used outside of any functions as like as
> EXPORT_SYMBOL(), we can only use preprocessed macros.
> Next, on PPC64 ABI*v2*, ppc_function_entry() returns local function entry,
> which seems global function entry + 2 insns. I'm not sure about implementation
> of the kallsyms on PPC64 ABIv2, but I guess we need global function entry
> for kallsyms.

ABIv2 does away with function descriptors and Anton fixed up that
routine to handle the change (the +2 is an artefact of that).

> BTW, could you test this patch on the latest -next tree on PPC64 if possible?

I'll test it, but it may take a bit.

Ananth