linux-kernel - Re: [PATCH] printk-formats.txt: Add examples for %pS and %pF

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Message-ID: <20170811001521.GA520@jagdpanzerIV.localdomain>
Date:   Fri, 11 Aug 2017 09:15:21 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Helge Deller <deller@....de>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org, linux-parisc@...r.kernel.org
Subject: Re: [PATCH] printk-formats.txt: Add examples for %pS and %pF

On (08/10/17 19:35), Helge Deller wrote:
> Sometimes people seems unclear when to use the %pS or %pF printk format.
> Adding some examples may help to avoid such mistakes.
> 
> See for example commit 51d96dc2e2dc ("random: fix warning message on ia64 and
> parisc") which fixed such a wrong format string.
> 
> Signed-off-by: Helge Deller <deller@....de>
> 
> diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
> index 65ea591..be8c05b 100644
> --- a/Documentation/printk-formats.txt
> +++ b/Documentation/printk-formats.txt
> @@ -73,6 +73,12 @@ 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.
>  
> +Examples::
> +
> +	printk("Called from %pS.\n", __builtin_return_address(0));
> +	printk("Called from %pS.\n", (void *)regs->ip);
> +	printk("Called from %pF.\n", &gettimeofday);

sorry, but how does it help?


there is this paragraph

: 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.

which supposed to explain everything in details. the examples
don't make it any `clearer', IMHO.


*may be* on "ia64, ppc64 and parisc64" we can somehow check
that the pointer, which we pass as %pS, belongs to .text and
print some build-time warnings. well, if it's actually a
problem. dunno.

	-ss