Re: [PATCH v2 15/21] ARM: linker script: create separate PT_LOAD segments for text, rodata, and data

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 1/6/26 1:53 PM, Sascha Hauer wrote:
> Fix the linker scripts to generate three distinct PT_LOAD segments with
> correct permissions instead of combining .rodata with .data.
> 
> Before this fix, the linker auto-generated only two PT_LOAD segments:
> 1. Text segment (PF_R|PF_X)
> 2. Data segment (PF_R|PF_W) - containing .rodata, .data, .bss, etc.
> 
> This caused .rodata to be mapped with write permissions when
> pbl_mmu_setup_from_elf() set up MMU permissions based on ELF segments,
> defeating the W^X protection that commit d9ccb0cf14 intended to provide.
> 
> With explicit PHDRS directives, we now generate three segments:
> 1. text segment (PF_R|PF_X): .text and related code sections
> 2. rodata segment (PF_R): .rodata and unwind tables
> 3. data segment (PF_R|PF_W): .data, .bss, and related sections
> 
> This ensures pbl_mmu_setup_from_elf() correctly maps .rodata as
> read-only (MAP_CACHED_RO) instead of read-write (MAP_CACHED).
> 
> 🤖 Generated with [Claude Code](https://claude.com/claude-code)
> 
> Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  arch/arm/include/asm/barebox.lds.h |  2 +-
>  arch/arm/lib32/barebox.lds.S       | 34 ++++++++++++++++++++++------------
>  arch/arm/lib64/barebox.lds.S       | 29 +++++++++++++++++++----------
>  arch/riscv/lib/barebox.lds.S       |  1 +
>  4 files changed, 43 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/arm/include/asm/barebox.lds.h b/arch/arm/include/asm/barebox.lds.h
> index 72aabe155b5c9e8b9159c7da6c6f0fa1f7b93375..7d1811645762a2ce1f58b7d86bed188a93fdb711 100644
> --- a/arch/arm/include/asm/barebox.lds.h
> +++ b/arch/arm/include/asm/barebox.lds.h
> @@ -16,7 +16,7 @@
>  
>  #define BAREBOX_RELOCATION_TABLE					\
>  	.rel_dyn_start : { *(.__rel_dyn_start) }			\
> -	.BAREBOX_RELOCATION_TYPE.dyn : { *(.BAREBOX_RELOCATION_TYPE*) }	\
> +	.BAREBOX_RELOCATION_TYPE.dyn : { *(.BAREBOX_RELOCATION_TYPE*) } \

Stray change?

>  	.rel_dyn_end : { *(.__rel_dyn_end) }				\
>  	.__dynsym_start :  { *(.__dynsym_start) }			\
>  	.dynsym : { *(.dynsym) }					\
> diff --git a/arch/arm/lib32/barebox.lds.S b/arch/arm/lib32/barebox.lds.S
> index 17e0970ba4989e5213ed38ea5ff87bdf5bfa2740..e84118ee2f43b07bd82fcd9936398847d0a3b42f 100644
> --- a/arch/arm/lib32/barebox.lds.S
> +++ b/arch/arm/lib32/barebox.lds.S
> @@ -7,14 +7,23 @@
>  OUTPUT_FORMAT(BAREBOX_OUTPUT_FORMAT)
>  OUTPUT_ARCH(BAREBOX_OUTPUT_ARCH)
>  ENTRY(start)
> +
> +PHDRS
> +{
> +	text PT_LOAD FLAGS(5);     /* PF_R | PF_X */
> +	rodata PT_LOAD FLAGS(4);   /* PF_R */
> +	data PT_LOAD FLAGS(6);     /* PF_R | PF_W */
> +	dynamic PT_DYNAMIC FLAGS(6); /* PF_R | PF_W */
> +}

Why not map dynamic R/O as well, so it's merged with rodata?


> diff --git a/arch/riscv/lib/barebox.lds.S b/arch/riscv/lib/barebox.lds.S
> index 03b3a967193cfee1c67b96632cf972a553e8bec4..38376befe9a82ead2152f8c7fc581eb5bb35fab4 100644
> --- a/arch/riscv/lib/barebox.lds.S
> +++ b/arch/riscv/lib/barebox.lds.S
> @@ -16,6 +16,7 @@
>  OUTPUT_ARCH(BAREBOX_OUTPUT_ARCH)
>  ENTRY(start)
>  OUTPUT_FORMAT(BAREBOX_OUTPUT_FORMAT)
> +

stray change.

Cheers,
Ahmad

>  SECTIONS
>  {
>  	. = 0x0;
> 

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