On 04/17/2013 04:30 AM, Dave Martin wrote: > On Tue, Apr 16, 2013 at 10:20:11AM -0600, Stephen Warren wrote: >> On 04/16/2013 08:13 AM, Dave Martin wrote: >>> On Mon, Apr 15, 2013 at 04:50:55PM -0600, Stephen Warren wrote: >>>> From: Joseph Lo <josephl@xxxxxxxxxx> >>>> >>>> When building kernel with CONFIG_THUMB2_KERNEL, the data pointer in the >>>> assembly may not on the 4 byte alignment. Then causing a data abort when >>>> accessing the pointer. This patch add a ".align" flag in the head of the >>>> pointer. And always using 32-bit ADR Thumb instruction to make sure it >>>> won't build failure. >>>> >>>> Signed-off-by: Joseph Lo <josephl@xxxxxxxxxx> >>>> Signed-off-by: Stephen Warren <swarren@xxxxxxxxxx> >>>> --- >>>> arch/arm/mach-tegra/reset-handler.S | 1 + >>>> arch/arm/mach-tegra/sleep.h | 3 ++- >>>> 2 files changed, 3 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/arch/arm/mach-tegra/reset-handler.S b/arch/arm/mach-tegra/reset-handler.S >>>> index e6de88a..519a8c5 100644 >>>> --- a/arch/arm/mach-tegra/reset-handler.S >>>> +++ b/arch/arm/mach-tegra/reset-handler.S >>>> @@ -83,6 +83,7 @@ ENDPROC(tegra_resume) >>>> >>>> #ifdef CONFIG_CACHE_L2X0 >>>> .globl l2x0_saved_regs_addr >>>> + .align >>>> l2x0_saved_regs_addr: >>>> .long 0 >>>> #endif >>>> diff --git a/arch/arm/mach-tegra/sleep.h b/arch/arm/mach-tegra/sleep.h >>>> index 4ffae54..8e9b6af 100644 >>>> --- a/arch/arm/mach-tegra/sleep.h >>>> +++ b/arch/arm/mach-tegra/sleep.h >>>> @@ -92,7 +92,8 @@ >>>> >>>> #ifdef CONFIG_CACHE_L2X0 >>>> .macro l2_cache_resume, tmp1, tmp2, tmp3, phys_l2x0_saved_regs >>>> - adr \tmp1, \phys_l2x0_saved_regs >>>> + ARM( adr \tmp1, \phys_l2x0_saved_regs ) >>>> + THUMB( adr.w \tmp1, \phys_l2x0_saved_regs ) >>> >>> Can you give an example of the assembler error you get without this? >> >> arch/arm/mach-tegra/reset-handler.S: Assembler messages: >> arch/arm/mach-tegra/reset-handler.S:78: Error: invalid immediate for >> address calculation (value = 0x00000004) > > The immediate in the 16-bit form of ADR is alignment-sensitive, and > can't address anything that's not on a word boundary. What if you just > have the .align, without adr.w? > >> This is with gcc-4.5.3, as: >> GNU assembler (crosstool-NG hg_unknown@20110628.165246) 2.20.1.20100303 >> >>> The target symbol is local and the assembler can see where it is, >>> so it should choose the correct variant for the adr instruction >>> with no need for the ".w" suffix. >>> >>> If not, it could mean that there is a bug in the version of the >>> assembler you're using. >> >> True. Switching to the Ubuntu-packaged ARM cross-compiler that ships >> with Ubuntu 12.10, I do not see this problem. >> >> Still, many people probably still use older compilers. >> >>> If it's definitely needed, you can append a Thumb-only .w suffix with >>> >>> W(adr) \tmp1, \phys_l2x0_saved_regs >>> >>> ...which is slightly neater. >> >> Yes, that certainly works too, even without the .align change in >> reset-handler.S. > > Sure, although the unaligned access is not such a good idea anyway. > > Keeping the adr fix is harmless, I just wanted to understand why it's > needed. With just the following, and no adr.w: > diff --git a/arch/arm/mach-tegra/reset-handler.S b/arch/arm/mach-tegra/reset-handler.S > index e6de88a..519a8c5 100644 > --- a/arch/arm/mach-tegra/reset-handler.S > +++ b/arch/arm/mach-tegra/reset-handler.S > @@ -83,6 +83,7 @@ ENDPROC(tegra_resume) > > #ifdef CONFIG_CACHE_L2X0 > .globl l2x0_saved_regs_addr > + .align > l2x0_saved_regs_addr: > .long 0 > #endif I still get: > arch/arm/mach-tegra/reset-handler.S: Assembler messages: > arch/arm/mach-tegra/reset-handler.S:78: Error: invalid immediate for address calculation (value = 0x00000004) That's with GNU assembler (crosstool-NG hg_unknown@20110628.165246) 2.20.1.20100303. BTW, I'm on vacation for the next 2 weeks starting this afternoon. Hopefully Joseph can keep this thread alive while I'm gone if needed. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
