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. Cheers ---Dave -- 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
