linux-kernel - Re: [PATCH v3 3/4] arm64: kaslr: Fix incorrect placement of __initdata and __read_mostly

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Date:	Mon, 15 Aug 2016 12:52:14 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC:	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	"Kees Cook" <keescook@...omium.org>,
	Mark Rutland <mark.rutland@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 3/4] arm64: kaslr: Fix incorrect placement of
 __initdata and __read_mostly

Hi Ard,

On Fri, 12 Aug 2016 14:02:40 +0200 Ard Biesheuvel wrote:

> Hi Jisheng,
> 
> On 12 August 2016 at 10:01, Jisheng Zhang <jszhang@...vell.com> wrote:
> > __initdata and __read_mostly should be placed after the variable name
> > for the variable to be placed in the intended section.
> >  
> 
> Why?

include/linux/init.h says something as:

 * For initialized data:
 * You should insert __initdata or __initconst between the variable name
 * and equal sign followed by value, e.g.:
 *
 * static int init_variable __initdata = 0;
 * static const char linux_logo[] __initconst = { 0x32, 0x36, ... };

and examples in gcc manual also put __attribute__ (...) after variable name.

https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#Common-Variable-Attributes

Then I grep the source, found most lines (especially arch/arm64/*) put the
__initdata and __read_mostly after the variable name.

However, I built the code with three different gcc, the result looks identical
no matter where these markers put. So the commit msg looks wrong, what about
changes it as

"put __initdata and __read_mostly after the variable name
to keep the style consistent"?

Thanks,
Jisheng

> 
> > Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> > ---
> >  arch/arm64/kernel/kaslr.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
> > index b054691..8ebabc4 100644
> > --- a/arch/arm64/kernel/kaslr.c
> > +++ b/arch/arm64/kernel/kaslr.c
> > @@ -20,8 +20,8 @@
> >  #include <asm/pgtable.h>
> >  #include <asm/sections.h>
> >
> > -u64 __read_mostly module_alloc_base;
> > -u16 __initdata memstart_offset_seed;
> > +u64 module_alloc_base __read_mostly;
> > +u16 memstart_offset_seed __initdata;
> >
> >  static __init u64 get_kaslr_seed(void *fdt)
> >  {
> > --
> > 2.8.1
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel  

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