Re: [PATCH V14 5/7] rust: Make __udivdi3() and __umoddi3() panic

David Laight
2026-04-26T11:49:30Z

On Sun, 26 Apr 2026 14:27:23 +0530
"Mukesh Kumar Chaurasiya (IBM)" <mkchauras@gmail.com> wrote:

> From: Link Mauve <linkmauve@linkmauve.fr>
>
> The core crate currently depends on these two functions for i64/u64/
> i128/u128/core::time::Duration formatting, but we shouldn’t use that in
> the kernel so let’s panic if they are ever called.
>
> This doesn’t yet fix drm_panic_qr.rs, which also uses __udivdi3 when
> CONFIG_CC_OPTIMIZE_FOR_SIZE=y, but at least makes the rest of the kernel
> build on PPC32.

This needs resolving properly.

>
> Signed-off-by: Link Mauve <linkmauve@linkmauve.fr>
> Signed-off-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
> ---
> rust/Makefile | 4 ++++
> rust/compiler_builtins.rs | 6 ++++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/rust/Makefile b/rust/Makefile
> index f6369d121c50..9aa18cff2fae 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -615,6 +615,10 @@ ifneq ($(or $(CONFIG_ARM64),$(and $(CONFIG_RISCV),$(CONFIG_64BIT))),)
> __ashrti3 \
> __ashlti3 __lshrti3
> endif
> +ifdef CONFIG_PPC32
> + redirect-intrinsics += \
> + __udivdi3 __umoddi3
> +endif
>
> ifdef CONFIG_MODVERSIONS
> cmd_gendwarfksyms = $(if $(skip_gendwarfksyms),, \
> diff --git a/rust/compiler_builtins.rs b/rust/compiler_builtins.rs
> index dd16c1dc899c..fc6b54636dd5 100644
> --- a/rust/compiler_builtins.rs
> +++ b/rust/compiler_builtins.rs
> @@ -97,5 +97,11 @@ pub extern "C" fn $ident() {
> __aeabi_uldivmod,
> });
>
> +#[cfg(target_arch = "powerpc")]
> +define_panicking_intrinsics!("`u64` division/modulo should not be used", {
> + __udivdi3,
> + __umoddi3,
> +});
> +
> // NOTE: if you are adding a new intrinsic here, you should also add it to
> // `redirect-intrinsics` in `rust/Makefile`.