Re: [PATCH] Use medany instead of large model for RISCV

[Yao Zi via Grub-devel <grub-devel@gnu.org>]

On Fri, Mar 20, 2026 at 10:44:15AM -0400, Trevor Gamblin wrote:
> From: Jason Montleon <jason@montleon.com>
> 
> Upstream-Status: Submitted [https://savannah.gnu.org/bugs/?65909]
> 
> Signed-off-by: Jason Montleon <jason@montleon.com>
> Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>
> ---
> We have recently added this to the openembedded-core layer to help with RISC-V
> builds on certain platforms (e.g. the VisionFive 2). I have left the patch as it
> is there, including the link to the original bug submission and the author's
> attribution. Jason, if you would like to change the attribution or anything
> about the patch, let me know and I can re-submit.

However on riscv64, medany memory model only allows addressing in +-2GiB
range, while large memory model could index the whole 64-bit address
space. This patch would break cases that grub core and dynamically
loaded modules (i.e. EFI memory allocated with type EFI_LOADER_CODE) are
located too far away to address each other with medany code model.

The issue reported in your link is related to handling of R_RISCV_ALIGN
relocations, which shouldn't happen anymore in Grub 2.14+ as commit
8fef533cf695 ("configure: Add -mno-relax on riscv*") is a fix for it.

Thanks,
Yao Zi

>  configure.ac | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/configure.ac b/configure.ac
> index d19fb625d..2a070c577 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -1675,7 +1675,7 @@ fi]
>  
>  CFLAGS="$TARGET_CFLAGS"
>  
> -if test "$target_cpu" = x86_64 || test "$target_cpu" = sparc64 || test "$target_cpu" = riscv64 ; then
> +if test "$target_cpu" = x86_64 || test "$target_cpu" = sparc64 ; then
>    # Use large model to support 4G memory
>    AC_CACHE_CHECK([whether option -mcmodel=large works], grub_cv_cc_mcmodel, [
>      CFLAGS="$TARGET_CFLAGS -mcmodel=large"
> @@ -1685,9 +1685,11 @@ if test "$target_cpu" = x86_64 || test "$target_cpu" = sparc64 || test "$target_
>    ])
>    if test "x$grub_cv_cc_mcmodel" = xyes; then
>      TARGET_CFLAGS="$TARGET_CFLAGS -mcmodel=large"
> -  elif test "$target_cpu" = sparc64 || test "$target_cpu" = riscv64; then
> +  elif test "$target_cpu" = sparc64; then
>      TARGET_CFLAGS="$TARGET_CFLAGS -mcmodel=medany"
>    fi
> +elif test "$target_cpu" = riscv64 ; then
> +    TARGET_CFLAGS="$TARGET_CFLAGS -mcmodel=medany"
>  fi
>  
>  # Stack smashing protector.
> -- 
> 2.53.0
> 
> 
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