linux-kernel - Re: [PATCH 00/14] Fix wrong %pF and %pS printk format specifier usages

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Date:   Thu, 7 Sep 2017 18:51:19 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Helge Deller <deller@....de>, linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH 00/14] Fix wrong %pF and %pS printk format specifier
 usages

On (09/07/17 18:36), Sergey Senozhatsky wrote:
[..]
> > I can look into adding such check-code, but even then the warning will
> > only show up if you run on ia64, ppc64 and parisc64.

sorry, not sure I understand the "warning" part.

what I'm thinking about is:

- every platform that needs descriptor dereference defines its own
  function. otherwise dereference_descriptor(p) is just (p).

- so it's something like

  arch/platform_abc/include/asm/sections.h

#undef dereference_function_descriptor
static inline void *dereference_function_descriptor(void *ptr)
{
	if (not_a_function_descriptor(ptr))
		return ptr;

	if (!probe_kernel_address(....))
		return function_ip;
	return ptr;
}

- so then in lib/vsprintf.c we can do unconditionally

  case F:
  case f:
  case S:
  case s:
  case B:
	ptr = dereference_function_descriptor(ptr);
	return symbol_string(....);

  because platforms will take care of proper descriptor dereference,
  when needed.

- and ideally we even can drop %pF-%pf. because there won't
  be any difference between `S' and `F'.

something like this.
let's see if this is possible.

any thoughts?

	-ss