Re: [PATCH 18/22] usb: gadget: serial: %pF is only for function pointers

[Scott Wood]

On Thu, 2015-03-12 at 12:51 -0300, Fabio Estevam wrote:
> On Thu, Mar 12, 2015 at 12:13 AM, Scott Wood <scottwood@xxxxxxxxxxxxx> wrote:
> > Use %pS for actual addresses, otherwise you'll get bad output
> > on arches like ppc64 where %pF expects a function descriptor.
> 
> From Documentation/printk-formats.txt:
> 
>     "On ia64, ppc64 and parisc64 architectures function pointers are
>     actually function descriptors which must first be resolved. The 'F' and
>     'f' specifiers perform this resolution and then provide the same
>     functionality as the 'S' and 's' specifiers."
> 
> ,so current code should work fine on ppc64, right?

No.  __builtin_return_address() returns a pointer to an instruction, not
a function pointer descriptor.  If you use %pF on the former, it'll
print instruction opcodes as if they were the address.

-Scott


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