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

[Marc Zyngier]

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.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny.