[PATCH v2] powerpc: mpc: Put U-Boot version string at correct place by linker script

[Christophe Leroy]

Le 08/08/2021 à 13:20, Pali Rohár a écrit :
> It is unknown why version string is placed at specific position on these
> powerpc mpc platforms. But there is no need to overload version_string
> symbol. Just use common definition of version_string and modify linker
> script to put it at "correct place".

What's the benefit of this change ? I see more insertions than deletions, it doesn't remove any 
redundancy either it seems. And it provides a strange look to u-boot.lds

I think we should probably investigate the reason for the version at that specific place if other 
architectures don't do the same.

> 
> Signed-off-by: Pali Rohár <pali at kernel.org>
> 
> ---
> Changes in v2:
> * Put explicit ".section" keyword before declaring ".text_pre" section as
>    some gcc versions cannot recognize specifying custom section without it.
> * Tested compilation for:
>    $ make CROSS_COMPILE=powerpc-linux-gnu- MCR3000_defconfig u-boot.bin
>    and checked that u-boot.bin header is same with and without this patch
> ---
>   arch/powerpc/cpu/mpc83xx/start.S         | 10 +++-------
>   arch/powerpc/cpu/mpc83xx/u-boot.lds      |  3 +++
>   arch/powerpc/cpu/mpc85xx/start.S         | 10 ++++------
>   arch/powerpc/cpu/mpc85xx/u-boot-nand.lds |  4 ++++
>   arch/powerpc/cpu/mpc85xx/u-boot-spl.lds  |  4 ++++
>   arch/powerpc/cpu/mpc85xx/u-boot.lds      |  4 ++++
>   arch/powerpc/cpu/mpc8xx/start.S          |  9 ++++-----
>   board/cssi/MCR3000/u-boot.lds            |  2 ++
>   8 files changed, 28 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/powerpc/cpu/mpc8xx/start.S b/arch/powerpc/cpu/mpc8xx/start.S
> index ed735cdee005..09628a0d60f0 100644
> --- a/arch/powerpc/cpu/mpc8xx/start.S
> +++ b/arch/powerpc/cpu/mpc8xx/start.S
> @@ -23,7 +23,6 @@
>   #include <asm-offsets.h>
>   #include <config.h>
>   #include <mpc8xx.h>
> -#include <version.h>
>   
>   #include <ppc_asm.tmpl>
>   #include <ppc_defs.h>
> @@ -60,12 +59,12 @@
>    * r3 - 1st arg to board_init(): IMMP pointer
>    * r4 - 2nd arg to board_init(): boot flag
>    */
> -	.text
> +	.section .text_pre
>   	.long	0x27051956		/* U-Boot Magic Number			*/

Instead of creating a new artificial section, maybe you can add the magic number in front of the 
version string directly in u-boot.lds ?

> -	.globl	version_string
> -version_string:
> -	.ascii U_BOOT_VERSION_STRING, "\0"
>   
> +/* U-Boot version string is filled at this place by linker script */
> +
> +	.text
>   	. = EXC_OFF_SYS_RESET
>   	.globl	_start
>   _start:
> diff --git a/board/cssi/MCR3000/u-boot.lds b/board/cssi/MCR3000/u-boot.lds
> index 70aef3241c8e..9b2ead29b4a5 100644
> --- a/board/cssi/MCR3000/u-boot.lds
> +++ b/board/cssi/MCR3000/u-boot.lds
> @@ -16,6 +16,8 @@ SECTIONS
>   	. = + SIZEOF_HEADERS;
>   	.text          :
>   	{
> +		arch/powerpc/cpu/mpc8xx/start.o	(.text_pre)
> +		*(.text_version_string)
>   		arch/powerpc/cpu/mpc8xx/start.o	(.text)
>   		arch/powerpc/cpu/mpc8xx/traps.o	(.text*)
>   		arch/powerpc/lib/built-in.o		(.text*)
>