[U-Boot] [PATCH 4/8] ARMv8: PSCI: Add linker section to hold PSCI code

[Marc Zyngier]

On 2014-10-11 12:27, Albert ARIBAUD wrote:
> Hi Albert,
>
> On Fri, 19 Sep 2014 18:04:14 +0200, Albert ARIBAUD
> <albert.u.boot at aribaud.net> wrote:
>
>> Hi Marc,
>>
>> On Thu, 18 Sep 2014 16:28:52 +0100, Marc Zyngier 
>> <marc.zyngier at arm.com>
>> wrote:
>>
>> > On Thu, Sep 18 2014 at 10:12:17 AM, Albert ARIBAUD 
>> <albert.u.boot at aribaud.net> wrote:
>> > > Hi Arnab,
>> > >
>> > > On Thu, 28 Aug 2014 01:59:57 +0530, Arnab Basu
>> > > <arnab.basu at freescale.com> wrote:
>> > >
>> > >> A separate linker section makes it possible to keep this code 
>> either
>> > >> in DDR or in some secure memory location provided specifically 
>> for the
>> > >> purpose.
>> > >>
>> > >> So far no one is using this section.
>> > >>
>> > >> Signed-off-by: Arnab Basu <arnab.basu at freescale.com>
>> > >> Reviewed-by: Bhupesh Sharma <bhupesh.sharma at freescale.com>
>> > >> Cc: Marc Zyngier <marc.zyngier at arm.com>
>> > >> ---
>> > >>  arch/arm/config.mk            |    2 +-
>> > >>  arch/arm/cpu/armv8/u-boot.lds |   30 
>> ++++++++++++++++++++++++++++++
>> > >>  2 files changed, 31 insertions(+), 1 deletions(-)
>> > >>
>> > >> diff --git a/arch/arm/config.mk b/arch/arm/config.mk
>> > >> index c339e6d..9272e9c 100644
>> > >> --- a/arch/arm/config.mk
>> > >> +++ b/arch/arm/config.mk
>> > >> @@ -111,7 +111,7 @@ endif
>> > >>
>> > >>  # limit ourselves to the sections we want in the .bin.
>> > >>  ifdef CONFIG_ARM64
>> > >> -OBJCOPYFLAGS += -j .text -j .rodata -j .data -j .u_boot_list 
>> -j .rela.dyn
>> > >> +OBJCOPYFLAGS += -j .text -j .secure_text -j .rodata -j .data 
>> -j .u_boot_list -j .rela.dyn
>> > >>  else
>> > >>  OBJCOPYFLAGS += -j .text -j .secure_text -j .rodata -j .hash 
>> -j .data -j .got.plt -j .u_boot_list -j .rel.dyn
>> > >>  endif
>> > >> diff --git a/arch/arm/cpu/armv8/u-boot.lds 
>> b/arch/arm/cpu/armv8/u-boot.lds
>> > >> index 4c12222..bd95fff 100644
>> > >> --- a/arch/arm/cpu/armv8/u-boot.lds
>> > >> +++ b/arch/arm/cpu/armv8/u-boot.lds
>> > >> @@ -8,6 +8,8 @@
>> > >>   * SPDX-License-Identifier:	GPL-2.0+
>> > >>   */
>> > >>
>> > >> +#include <config.h>
>> > >> +
>> > >>  OUTPUT_FORMAT("elf64-littleaarch64", "elf64-littleaarch64", 
>> "elf64-littleaarch64")
>> > >>  OUTPUT_ARCH(aarch64)
>> > >>  ENTRY(_start)
>> > >> @@ -23,6 +25,34 @@ SECTIONS
>> > >>  		*(.text*)
>> > >>  	}
>> > >>
>> > >> +#ifdef CONFIG_ARMV8_PSCI
>> > >> +
>> > >> +#ifndef CONFIG_ARMV8_SECURE_BASE
>> > >> +#define CONFIG_ARMV8_SECURE_BASE
>> > >> +#endif
>> > >> +
>> > >> +	.__secure_start : {
>> > >> +		. = ALIGN(0x1000);
>> > >> +		*(.__secure_start)
>> > >> +	}
>> > >> +
>> > >> +	.secure_text CONFIG_ARMV8_SECURE_BASE :
>> > >> +		AT(ADDR(.__secure_start) + SIZEOF(.__secure_start))
>> > >> +	{
>> > >> +		*(._secure.text)
>> > >> +	}
>> > >> +
>> > >> +	. = LOADADDR(.__secure_start) +
>> > >> +		SIZEOF(.__secure_start) +
>> > >> +		SIZEOF(.secure_text);
>> > >> +
>> > >> +	__secure_end_lma = .;
>> > >> +	.__secure_end : AT(__secure_end_lma) {
>> > >> +		*(.__secure_end)
>> > >> +		LONG(0x1d1071c);	/* Must output something to reset LMA */
>> > >
>> > > Can you explain in more detail what issue this fixes?
>> >
>> > If you use AT to force a new load address (LMA), you must ensure 
>> that
>> > you actually output something at this address. Here, if 
>> *(.__secure_end)
>> > ends up being empty, whatever follows would be as if the AT never
>> > happened, ending up at the wrong LMA.
>> >
>> > The workaround is to force the output of a dummy value in all
>> > cases, ensuring that the rest of the text is at a sensible LMA. 
>> This is
>> > an issue that has been in GNU ld for years, and this workaround is 
>> a
>> > copy/paste of the same one in the ARMv7 ld script.
>>
>> I see. Does the ld bug have an identifier that we could mention in a
>> comment in the linker script as a reference?

The only report I'm aware of is this one:
https://sourceware.org/bugzilla/show_bug.cgi?id=948

There may be other ways to work around this, but my linker-foo is 
admittedly pretty limited.

Thanks,

         M.
-- 
Fast, cheap, reliable. Pick two.