[PATCH v1 3/6] arm: Prepare linker scripts for memory permissions

[Tom Rini]

On Wed, Feb 05, 2025 at 09:16:47AM +0200, Ilias Apalodimas wrote:

> Upcoming patches are switching the memory mappings to RW, RO, RX
> after the U-Boot binary and its data are relocated. Add
> annotations in the linker scripts to and mark text, data, rodata
> sections and align them to a page boundary.
> 
> It's worth noting that efi_runtime relocations are left untouched for
> now. The efi runtime regions can be relocated by the OS when the latter
> is calling SetVirtualAddressMap. Which means we have to configure the
> pages as RX for U-Boot but convert them to RWX just before
> ExitBootServices. It also needs extra code in efi_tuntime relocation
> code since R_AARCH64_NONE are emitted as well if we page align the
> section. Keep it out for now and we can fix it in future patches.
> 
> Acked-by: Jerome Forissier <jerome.forissier at linaro.org>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> ---
>  arch/arm/cpu/armv8/u-boot.lds  | 29 +++++++++++++++++------------
>  include/asm-generic/sections.h |  2 ++
>  2 files changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm/cpu/armv8/u-boot.lds b/arch/arm/cpu/armv8/u-boot.lds
> index 857f44412e07..35afc3cbe7ec 100644
> --- a/arch/arm/cpu/armv8/u-boot.lds
> +++ b/arch/arm/cpu/armv8/u-boot.lds
> @@ -22,7 +22,7 @@ SECTIONS
>  
>  	. = ALIGN(8);
>  	__image_copy_start = ADDR(.text);
> -	.text :
> +	.text ALIGN(4096):
>  	{
>  		CPUDIR/start.o (.text*)
>  	}

Shouldn't this be:
-	. = ALIGN(8);
-	__image_copy_start = ADDR(.text);
-	.text :
+	.text ALIGN(4096):
 	{
+		__image_copy_start = ADDR(.text); // Or even just '= .;' ?
		CPUDIR/start.o (.text*)
 	}
Or so? Something like that would also make it easier in v2 to have a
Kconfig about page align / min align for sections in the linker script
and then ALIGN(CONFIG_FOO) or #ifdef CONFIG_FOO #define MINALIGN 8 #else
4096 #endif, or so. Also I guess today we're not going to worry about
bigger than 4KiB pages?

> @@ -36,9 +36,12 @@ SECTIONS
>                  __efi_runtime_stop = .;
>  	}
>  
> -	.text_rest :
> +	.text_rest ALIGN(4096) :
>  	{
> +		__text_start = .;
>  		*(.text*)
> +		. = ALIGN(4096);
> +		__text_end = .;
>  	}

Here and elsewhere in the patch, does that really need two ALIGN(4096)
lines? Or am I totally misremembering how these symbols work in a linker
script?

-- 
Tom
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