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

[Dongsheng Wang]

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.
         */

Regards,
-Dongsheng