[U-Boot] [PATCH] ARM: Disable "DISCARD" for secure section if CONFIG_ARMV7_SECURE_BASE isn't defined

[Tom Rini]

On Fri, Dec 11, 2015 at 03:30:24PM +0000, Dongsheng Wang wrote:
> Hi Tom,
> 
> > On Fri, Dec 11, 2015 at 10:15:03AM +0000, Dongsheng Wang wrote:
> > > Hi Tom,
> > >
> > > Thanks for your review.
> > >
> > > > On Thu, Dec 10, 2015 at 10:49:01AM +0800, Dongsheng Wang wrote:
> > > >
> > > > > From: Wang Dongsheng <dongsheng.wang at nxp.com>
> > > > >
> > > > > Fix PSCI hang up without CONFIG_ARMV7_SECURE_BASE define.
> > > > > "DISCARD" will remove ._secure.text relocate, but PSCI framework
> > > > > has already used some absolute address those need to relocate.
> > > > >
> > > > > Use readelf -t -r u-boot show us:
> > > > > .__secure_start		addr: 601408e4
> > > > > .__secure_end		addr: 60141460
> > > > >
> > > > > 60141140  00000017 R_ARM_RELATIVE
> > > > > 46	_secure_monitor:
> > > > > 47	#ifdef CONFIG_ARMV7_PSCI
> > > > > 48      ldr     r5, =_psci_vectors
> > > > >
> > > > > 60141194  00000017 R_ARM_RELATIVE
> > > > > 6014119c  00000017 R_ARM_RELATIVE
> > > > > 601411a4  00000017 R_ARM_RELATIVE
> > > > > 601411ac  00000017 R_ARM_RELATIVE
> > > > > 64	_psci_table:
> > > > > 66	.word	psci_cpu_suspend
> > > > > ...
> > > > > 72	.word	psci_migrate
> > > > >
> > > > > 60141344  00000017 R_ARM_RELATIVE
> > > > > 6014145c  00000017 R_ARM_RELATIVE
> > > > > 202	ldr     r5, =psci_text_end
> > > > >
> > > > > Solutions:
> > > > > 1. Change absolute address to RelAdr.
> > > > >    Based on LDR (immediate, ARM), we only have 4K offset to jump.
> > > > > Now PSCI code size is close to 4K size that is LDR limit jump
> > > > > size, so even if the LDR is based on the current instruction
> > > > > address, there is also have a risk for RelAdr. If we use two jump
> > > > > steps I think we can fix this issue, but looks too hack, so give up this way.
> > > > >
> > > > > 2. Enable "DISCARD" only for CONFIG_ARMV7_SECURE_BASE has defined.
> > > > >    If CONFIG_ARMV7_SECURE_BASE is defined in platform, all of
> > > > > secure will in the BASE address that is absolute. psci_update_dt
> > > > > will relocate the PSCI code into link stage
> > > > > address(CONFIG_ARMV7_SECURE_BASE address), so using this method.
> > > > >
> > > > > Signed-off-by: Wang Dongsheng <dongsheng.wang at nxp.com>
> > > > > Reviewed-by: Peng Fan <Peng.Fan at nxp.com>
> > > > > Cc: Albert Aribaud <albert.u.boot at aribaud.net>
> > > > > Cc: Tom Warren <twarren at nvidia.com>
> > > > > Cc: York Sun <yorksun at freescale.com>
> > > > > Cc: Hans De Goede <hdegoede at redhat.com>
> > > > > Cc: Ian Campbell <ijc at hellion.org.uk>
> > > > > Cc: Tom Rini <trini at konsulko.com>
> > > > > Cc: Jan Kiszka <jan.kiszka at siemens.com>
> > > > > Cc: Stefano Babic <sbabic at denx.de>
> > > > >
> > > > > diff --git a/arch/arm/cpu/u-boot.lds b/arch/arm/cpu/u-boot.lds
> > > > > index
> > > > > d48a905..413d459 100644
> > > > > --- a/arch/arm/cpu/u-boot.lds
> > > > > +++ b/arch/arm/cpu/u-boot.lds
> > > > > @@ -14,6 +14,7 @@ OUTPUT_ARCH(arm)
> > > > >  ENTRY(_start)
> > > > >  SECTIONS
> > > > >  {
> > > > > +#if defined(CONFIG_ARMV7_SECURE_BASE) &&
> > > > defined(CONFIG_ARMV7_NONSEC)
> > > > >  	/*
> > > > >  	 * Discard the relocation entries for secure text.
> > > > >  	 * The secure code is bundled with u-boot image, so there will
> > > > > @@
> > > > > -31,6 +32,7 @@ SECTIONS
> > > > >  	 * avoid hole in the final image.
> > > > >  	 */
> > >
> > > Update this comment, not my patch's comment, right?
> > 
> > Correct.
> > 
> Not sure we hope a detailed comment or concise comment.
> Could you review my comment?
> 
> If my understanding is wrong, please correct me, thanks:
>         /*
>          * Based on the /DISCARD/ introduce by ARMv7 patch. And ARMv8 not
>          * for sure has the same issue. Based on conservative this is only for
>          * ARMv7, another point the /DISCARD/ may isn't necessary in platform.
>          * Please see below investigation:
>          *
>          * If undefine CONFIG_ARMV7_SECURE_BASE secure zone will be
>          * included in u-boot space, and some absolute address were used
>          * in secure code. Accompanied by u-boot relocation secure code
>          * also need to relocate the absolute address.
>          *
>          * If CONFIG_ARMV7_SECURE_BASE is true, secure code will not
>          * bundle with u-boot, and codes offset are fixed. Secure zone
>          * only needs to be copied from loading address to
>          * CONFIG_ARMV7_SECURE_BASE, which is the linking and running
>          * address for secure code.
>          *
>          * About below may depend on toolchain:
>          * 1. If keep the relocation entries in .rel.dyn section,
>          * "relocation offset + linking address" may locates into an
>          * address that is reserved by SoC, then will trigger data abort.
>          * The reason that move .rel._secure at the beginning, is to
>          * avoid hole in the final image.
>          *
>          * 2. .rel.dyn will not include secure code, becuase
>          * CONFIG_ARMV7_SECURE_BASE give us an real absolute address, all
>          * of codes offset has fixed on build and link stage, and the same
>          * to runtime address.
>          * e.g:
>          * NXP Layerscape platform, gcc version:
>          * crosstool-NG linaro-1.13.1-4.8-2013.12 - Linaro GCC 2013.11
>          * The secure code will not include in .rel.dyn. So /DISCARD/ is redundant.
>          *
>          * Considering the compatibility, so keep DISCARD for
>          * CONFIG_ARMV7_SECURE_BASE.
>          */

Not exactly.  We shouldn't need to mention other patches here (but you
can reference git commit hashes (git rev-parse --short HASH) for
additional clarity.  Peng, can you please also comment on the new code
comment here as this is from your patch initially?  Thanks and sorry for
the delay!

-- 
Tom
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