From: Mathias Krause <minipli@googlemail.com>
To: Joe Perches <joe@perches.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [RFC PATCH 0/3] Mark literal strings in __init / __exit code
Date: Tue, 24 Jun 2014 22:10:29 +0200 [thread overview]
Message-ID: <CA+rthh9qGpkicfR+C7Qz1uOF4HUaVANVyq6YaH_Rx-80L_-YvQ@mail.gmail.com> (raw)
In-Reply-To: <1403638620.29061.35.camel@joe-AO725>
On 24 June 2014 21:37, Joe Perches <joe@perches.com> wrote:
> On Tue, 2014-06-24 at 21:13 +0200, Mathias Krause wrote:
>> I don't think it's that easy. You cannot simply put all strings into
>> the .init.rodata section when code currently gets emitted to
>> .init.text. The reason is because strings used in __init code might be
>> referenced later on, too. For example, the name passed to
>> class_create() won't be copied. If that one would go into the
>> .init.rodata section automatically, we would have dangling pointers
>> after the .init.* memory got freed. Therefore a compiler driven
>> approach would need to be implemented as a compiler extension, a gcc
>> plugin to handle such cases -- know when a string can safely be put
>> into the .init.rodata section and when not. But that decision is not
>> as easy as Joe might think it would be. How would the plugin know
>> which strings to put into the .init.rodata section? Would it only
>> handle the ones passed to printk()?
>
> Yes.
Well, I would like to handle the easy ones, too. E.g. strings used in
parameter parsing, i.e. strcmp()s.
>> I still strongly believe it's better to do this manually.
>
> Maybe.
>
> It'd work with any version of the compiler that way too.
That's a much stronger argument, IMHO. It'll work with gcc < 4.5 and
clang, even. And, it does not require us to maintain compatibility to
the repeating gcc plugin API breakage.
> It's a pretty simple transform.
Indeed, it is.
> I believe this will show most all of the __init
> uses of printks:
>
> $ grep-2.5.4 -rP --include=*.[ch] -n '\b__init\b[^\n][^\}]+\n}' * | \
> grep -P '^[\w\/\.]+:\d+:|\bprintk\b|\bpr_[a-z]+' | \
> grep -P -B1 '\bprintk\b|\bpr_[a-z]+'
>
> This shows a little more than a 1000 __init printks
> treewide that could be converted.
A simple awk script found additional 5399 pr_<level> calls in __init
code and 188 calls in __exit code. So it's worth it, IMHO.
>
> For example:
> arch/ia64/include/asm/cyclone.h:6:extern void __init cyclone_setup(void);
> printk(KERN_ERR "Cyclone Counter: System not configured"
> --
> arch/ia64/kernel/acpi.c:66:static unsigned long __init acpi_find_rsdp(void)
> printk(KERN_WARNING PREFIX
> --
> arch/ia64/kernel/acpi.c:366:static int __init acpi_parse_madt(struct acpi_table
> printk(KERN_INFO PREFIX "Local APIC address %p\n", ipi_base_addr);
>
Those might benefit twice from the change by being converted to
pi_<level> calls along the way. So it's a win-win on all sides, no?
> etc...
>
> There are maybe 200 or so __exit ones.
>
Yeah, the __exit ones are used less. Nonetheless, they should be
converted, too. For completeness, at least.
Thanks,
Mathias
next prev parent reply other threads:[~2014-06-24 20:10 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-22 22:46 [RFC PATCH 0/3] Mark literal strings in __init / __exit code Mathias Krause
2014-06-22 22:46 ` [RFC PATCH 1/3] init.h: Add __init_str / __exit_str macros Mathias Krause
2014-06-24 19:43 ` Joe Perches
2014-06-24 20:13 ` Mathias Krause
2014-06-22 22:46 ` [RFC PATCH 2/3] printk: Provide pi_<level> / pe_<level> macros for __init / __exit code Mathias Krause
2014-06-22 22:46 ` [RFC PATCH 3/3] x86, acpi: Mark __init strings as such Mathias Krause
2014-06-22 22:56 ` [RFC PATCH 0/3] Mark literal strings in __init / __exit code Joe Perches
2014-06-23 6:23 ` Mathias Krause
2014-06-23 6:33 ` Joe Perches
2014-06-24 14:31 ` Rasmus Villemoes
2014-06-24 19:13 ` Mathias Krause
2014-06-24 19:37 ` Joe Perches
2014-06-24 20:10 ` Mathias Krause [this message]
2014-06-24 20:30 ` Joe Perches
2014-06-24 20:41 ` Mathias Krause
2014-06-24 20:57 ` Joe Perches
2014-06-24 21:06 ` Mathias Krause
2014-06-24 21:45 ` Joe Perches
2014-06-25 5:55 ` Mathias Krause
2014-06-25 7:35 ` Rasmus Villemoes
2014-06-25 7:48 ` Joe Perches
2014-06-25 8:34 ` Mathias Krause
2014-06-25 11:22 ` Joe Perches
2014-06-25 8:17 ` Mathias Krause
2014-06-23 1:30 ` Joe Perches
2014-06-23 6:29 ` Mathias Krause
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