Hi,
On 1/5/26 12:26 PM, Sascha Hauer wrote:
> Implement architecture-specific ELF relocation handlers for ARM32 and ARM64.
>
> ARM32 implementation (arch/arm/lib32/elf_reloc.c):
> - Handles REL-format relocations (no explicit addend)
> - Supports R_ARM_RELATIVE and R_ARM_ABS32 relocation types
> - Addend is read from the target location
>
> ARM64 implementation (arch/arm/lib64/elf_reloc.c):
> - Handles RELA-format relocations (with explicit addend)
> - Supports R_AARCH64_RELATIVE and R_AARCH64_ABS64 relocation types
> - Addend is provided in relocation entry
>
> Both implementations:
> - Parse PT_DYNAMIC segment to locate relocation tables
> - Validate relocation table format and entry sizes
> - Apply relocations based on the computed load offset
> - Return appropriate errors for unsupported relocation types
>
> Signed-off-by: Sascha Hauer <[email protected]>
> Co-Authored-By: Claude Sonnet 4.5 <[email protected]>
> ---
> arch/arm/include/asm/elf.h | 11 +++++
> arch/arm/lib32/Makefile | 1 +
> arch/arm/lib32/elf_reloc.c | 105
> +++++++++++++++++++++++++++++++++++++++++++++
> arch/arm/lib64/Makefile | 1 +
> arch/arm/lib64/elf_reloc.c | 105
> +++++++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 223 insertions(+)
>
> diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h
> index
> 4043e6fd5b991eb5cccb3fa0ea28d208006ee1fc..cceb92ee1a5f63c37b0e981c263676bd35a261c0
> 100644
> --- a/arch/arm/include/asm/elf.h
> +++ b/arch/arm/include/asm/elf.h
> @@ -36,6 +36,17 @@ typedef struct user_fp elf_fpregset_t;
> #define R_ARM_THM_CALL 10
> #define R_ARM_THM_JUMP24 30
>
> +/* Additional relocation types for dynamic linking */
> +#define R_ARM_RELATIVE 23
This is already defined in arch/arm/cpu/common.c, you can guess where
this is going ;)
> +#define R_ARM_GLOB_DAT 21
> +#define R_ARM_JUMP_SLOT 22
These two are not used.
> +
> +#define R_AARCH64_NONE 0
> +#define R_AARCH64_ABS64 257
> +#define R_AARCH64_RELATIVE 1027
> +#define R_AARCH64_GLOB_DAT 1025
> +#define R_AARCH64_JUMP_SLOT 1026
Likewise, only R_AARCH64_JUMP_SLOT and R_AARCH64_GLOB_DAT are not used.
> +/*
> + * Parse dynamic section and extract relocation info for ARM32
> + */
> +static int parse_dynamic_section(struct elf_image *elf, Elf32_Dyn *dyn,
> + Elf32_Rel **rel_out, u64 *relsz_out)
> +{
> + Elf32_Rel *rel = NULL;
If we define ELF_CLASS depending on CONFIG_ARM32/CONFIG_ARM64, we can
write a generic parse_dynamic_section() that applies to all architectures.
In this case, we would just collect both REL and RELA in the switch and
just use what's available.
> +int elf_apply_relocations(struct elf_image *elf, void *dyn_seg)
> +{
We already have relocate_to_current_adr(). If we change it to call
a new relocate_image():
relocate_image(get_runtime_offset(),
runtime_addr(__rel_dyn_start),
runtime_addr(__rel_dyn_end),
runtime_addr(__dynsym_start),
runtime_addr(__dynsym_end));
Then we could use relocate_image() in generic code instead of
duplicating it per architecture.
> +/*
> + * Parse dynamic section and extract relocation info for ARM64
> + */
> +static int parse_dynamic_section(struct elf_image *elf, Elf64_Dyn *dyn,
> + Elf64_Rela **rela_out, u64 *relasz_out)
Same comment as for ARM32. I believe this can go into generic code.
> + case R_AARCH64_ABS64:
> + /* B(P) = S + A */
> + *fixup_addr = base + rela->r_addend;
> + break;
What did you do to get R_AARCH64_ABS64 relocations? We don't handle them
in relocate_to_current_adr() and they shouldn't have been generated.
Thanks,
Ahmad
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