linux-kernel - Re: [PATCH] ARM: alignment: Use is_wide_instruction() to check wide instruction

Open Source and information security mailing list archives

Message-ID: <1428936444.7514.66.camel@mtksdaap41>
Date:	Mon, 13 Apr 2015 22:47:24 +0800
From:	Yingjoe Chen <yingjoe.chen@...iatek.com>
To:	Dave Martin <Dave.Martin@....com>
CC:	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	<srv_heupstream@...iatek.com>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] ARM: alignment: Use is_wide_instruction() to check
 wide instruction

On Mon, 2015-04-13 at 13:48 +0100, Dave Martin wrote:
> On Fri, Apr 10, 2015 at 10:05:41PM +0800, Yingjoe Chen wrote:
> > 
> > I first notice the comment is incorrect, then I realize there's another
> > macro which do exactly the same thing.
> > Tested with hand written userspace program with a few wide instructions
> > to make sure this still work as expect.
> > 
> > 8<-------------------------------------------------
> > do_alignment() is using locally added IS_T32() macro to check if an
> > instruction is a Thumb-2 32 bit instruction. The macro
> > is_wide_instruction() is doing the same thing, with slightly faster
> > implementation.
> > Change to use is_wide_instruction() in do_alignment() and remove
> > IS_T32().
> 
> Reviewed-by: Dave Martin <Dave.Martin@....com>
> 
> The existing code is correct, but the comment is indeed wrong.
> Consolidating this with one of the other existing macros makes sense.
> 
> 
> !__opcode_is_thumb16() could also be used here (or is_wide_instruction()
> redefined in terms of it), but that's not essential.

Hi Dave,

Thanks for your review.

I did notice there are __opcode_is_thumb16/32. They need to handle
32bits instruction instead of 16bits only for is_wide_instruction, so I
think using same implementation for them is a different story.

Joe.C

> 
> Cheers
> ---Dave
> 
> > 
> > Signed-off-by: Yingjoe Chen <yingjoe.chen@...iatek.com>
> > ---
> >  arch/arm/mm/alignment.c | 6 +-----
> >  1 file changed, 1 insertion(+), 5 deletions(-)
> > 
> > diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c
> > index 2c0c541..f8e82f5 100644
> > --- a/arch/arm/mm/alignment.c
> > +++ b/arch/arm/mm/alignment.c
> > @@ -71,10 +71,6 @@
> >  
> >  #define BAD_INSTR 	0xdeadc0de
> >  
> > -/* Thumb-2 32 bit format per ARMv7 DDI0406A A6.3, either f800h,e800h,f800h */
> > -#define IS_T32(hi16) \
> > -	(((hi16) & 0xe000) == 0xe000 && ((hi16) & 0x1800))
> > -
> >  static unsigned long ai_user;
> >  static unsigned long ai_sys;
> >  static void *ai_sys_last_pc;
> > @@ -770,7 +766,7 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
> >  		tinstr = __mem_to_opcode_thumb16(tinstr);
> >  		if (!fault) {
> >  			if (cpu_architecture() >= CPU_ARCH_ARMv7 &&
> > -			    IS_T32(tinstr)) {
> > +			    is_wide_instruction(tinstr)) {
> >  				/* Thumb-2 32-bit */
> >  				u16 tinst2 = 0;
> >  				fault = probe_kernel_address(ptr + 1, tinst2);
> > -- 
> > 1.8.1.1.dirty
> > 
> > 
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives