[PATCH v9 6/6] riscv: export symbols needed for riscv32 EFI stub

[Charlie Jenkins]

On Fri, Apr 03, 2026 at 01:33:38PM +0300, Dmitry Antipov wrote:
> Fix the following link error observed when building EFI-enabled
> kernel with CONFIG_EFI_STUB=y and CONFIG_EFI_GENERIC_STUB=y:
> 
> riscv32-linux-gnu-ld: ./drivers/firmware/efi/libstub/lib-cmdline.stub.o: in function `__efistub_.L49':
> __efistub_cmdline.c:(.init.text+0x1f2): undefined reference to `__efistub___ashldi3'
> riscv32-linux-gnu-ld: __efistub_cmdline.c:(.init.text+0x202): undefined reference to `__efistub___lshrdi3'
> 
> Note: compile (gcc 15.2.1 and clang 21.1.8) tested only.

I attempted to boot this on riscv32 in qemu with u-boot. I used
CONFIG_EFI_ZBOOT to generate vmlinux.efi. With this option enabled,
there is the same undefined reference errors with this patch applied.
I have not found a good way to resolve this issue, so I resorted to
copying the __lshrdi3() implementation over into
drivers/firmware/efi/libstub/riscv.c and that successfully booted with
EFI.

- Charlie

> 
> Reported-by: kernel test robot <lkp at intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202603041925.KLKqpK6N-lkp@intel.com
> Suggested-by: Ard Biesheuvel <ardb at kernel.org>
> Signed-off-by: Dmitry Antipov <dmantipov at yandex.ru>
> ---
> v9: initial version to join the series
> ---
>  arch/riscv/kernel/image-vars.h | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/arch/riscv/kernel/image-vars.h b/arch/riscv/kernel/image-vars.h
> index 3bd9d06a8b8f..888bb1ddf945 100644
> --- a/arch/riscv/kernel/image-vars.h
> +++ b/arch/riscv/kernel/image-vars.h
> @@ -32,6 +32,15 @@ __efistub___init_text_end	= __init_text_end;
>  __efistub_sysfb_primary_display	= sysfb_primary_display;
>  #endif
>  
> +#ifdef CONFIG_CC_IS_GCC
> +/*
> + * Double-word integer shifts are used by the library code and so EFI stub as
> + * well. Not needed for clang and please let me know if anyone understands why.
> + */
> +PROVIDE(__efistub___lshrdi3    = __lshrdi3);
> +PROVIDE(__efistub___ashldi3    = __ashldi3);
> +#endif /* CONFIG_CC_IS_GCC */
> +
>  #endif
>  
>  #endif /* __RISCV_KERNEL_IMAGE_VARS_H */
> -- 
> 2.53.0
> 
> 
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