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SubjectRe: [PATCH] riscv/efistub: Ensure GP-relative addressing is not used
Hi Jan,

On Fri, 12 Jan 2024 at 19:37, Jan Kiszka <jan.kiszka@siemens.com> wrote:
>
> From: Jan Kiszka <jan.kiszka@siemens.com>
>
> The cflags for the RISC-V efistub were missing -mno-relax, thus were
> under the risk that the compiler could use GP-relative addressing. That
> happened for _edata with binutils-2.41 and kernel 6.1, causing the
> relocation to fail due to an invalid kernel_size in handle_kernel_image.
> It was not yet observed with newer versions, but that may just be luck.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>
> Something like this should go to stable as well, but we will need
> rebased patches.
>
> drivers/firmware/efi/libstub/Makefile | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index 06964a3c130f..d561d7de46a9 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -28,7 +28,7 @@ cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \
> -DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \
> -DEFI_HAVE_STRCMP -fno-builtin -fpic \
> $(call cc-option,-mno-single-pic-base)
> -cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE
> +cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax

Can we detect the presence of these references (via the relocation
type)? We already do something similar for ordinary absolute
references too.

> cflags-$(CONFIG_LOONGARCH) += -fpie
>
> cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt
> --
> 2.35.3

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