From: Link Mauve <linkmauve@linkmauve•fr>
To: David Laight <david.laight.linux@gmail•com>
Cc: "Mukesh Kumar Chaurasiya (IBM)" <mkchauras@gmail•com>,
maddy@linux•ibm.com, mpe@ellerman•id.au, npiggin@gmail•com,
chleroy@kernel•org, peterz@infradead•org, jpoimboe@kernel•org,
jbaron@akamai•com, aliceryhl@google•com, rostedt@goodmis•org,
ardb@kernel•org, sumit.semwal@linaro•org,
christian.koenig@amd•com, ojeda@kernel•org, boqun@kernel•org,
gary@garyguo•net, bjorn3_gh@protonmail•com, lossin@kernel•org,
a.hindborg@kernel•org, tmgross@umich•edu, dakr@kernel•org,
nathan@kernel•org, nick.desaulniers+lkml@gmail•com,
morbo@google•com, justinstitt@google•com, tamird@kernel•org,
arnd@arndb•de, nsc@kernel•org, simona.vetter@ffwll•ch,
linuxppc-dev@lists•ozlabs.org, linux-kernel@vger•kernel.org,
linux-media@vger•kernel.org, dri-devel@lists•freedesktop.org,
linaro-mm-sig@lists•linaro.org, rust-for-linux@vger•kernel.org,
llvm@lists•linux.dev, Link Mauve <linkmauve@linkmauve•fr>
Subject: Re: [PATCH V13 5/7] rust: Make __udivdi3() and __umoddi3() panic
Date: Fri, 24 Apr 2026 11:43:11 +0200 [thread overview]
Message-ID: <aes7L3M1d_LvvGKa@luna> (raw)
In-Reply-To: <20260424101425.6bde0e17@pumpkin>
On Fri, Apr 24, 2026 at 10:14:25AM +0100, David Laight wrote:
> On Fri, 24 Apr 2026 11:17:40 +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.
>
> Ugg.
> Surely you can make it a link-time failure?
> Or change the underlying code to avoid the divide.
This is currently a link-time failure, which means if any of the core
crate or drm_panic_qr are linked in, the kernel will fail to link.
And since we rely on core, that means no kernel can be built on PowerPC
without this patch.
A possible solution would be to change the core crate to not divide
u64s, but the last time I tried to do that I couldn’t quite figure out
how to do formatting without it, maybe I will just open an issue against
Rust.
>
> David
>
> >
> > 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.
> >
> > 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 2a5428a5503d..ee11fba7a03d 100644
> > --- a/rust/Makefile
> > +++ b/rust/Makefile
> > @@ -616,6 +616,10 @@ 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`.
>
>
--
Link Mauve
next prev parent reply other threads:[~2026-04-24 9:43 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-24 5:47 [PATCH V13 0/7] Rust support for powerpc Mukesh Kumar Chaurasiya (IBM)
2026-04-24 5:47 ` [PATCH V13 1/7] rust: Fix "multiple candidates for rmeta dependency core" error Mukesh Kumar Chaurasiya (IBM)
2026-04-24 5:47 ` [PATCH V13 2/7] dma-resv: Fix undefined symbol when CONFIG_DMA_SHARED_BUFFER is disabled Mukesh Kumar Chaurasiya (IBM)
2026-04-24 7:56 ` Christian König
2026-04-24 8:06 ` Mukesh Kumar Chaurasiya
2026-04-24 8:25 ` Christian König
2026-04-24 8:34 ` Mukesh Kumar Chaurasiya
2026-04-24 8:44 ` Christian König
2026-04-24 5:47 ` [PATCH V13 3/7] powerpc/jump_label: adjust inline asm to be consistent Mukesh Kumar Chaurasiya (IBM)
2026-04-24 5:47 ` [PATCH V13 4/7] rust/powerpc: Set min rustc version for powerpc Mukesh Kumar Chaurasiya (IBM)
2026-04-24 5:47 ` [PATCH V13 5/7] rust: Make __udivdi3() and __umoddi3() panic Mukesh Kumar Chaurasiya (IBM)
2026-04-24 8:59 ` Arnd Bergmann
2026-04-24 9:14 ` David Laight
2026-04-24 9:43 ` Link Mauve [this message]
2026-04-24 10:20 ` Arnd Bergmann
2026-04-24 10:34 ` Miguel Ojeda
2026-04-24 10:26 ` Miguel Ojeda
2026-04-24 11:09 ` David Laight
2026-04-27 16:05 ` [Linaro-mm-sig] " Arnd Bergmann
2026-04-24 11:54 ` Segher Boessenkool
2026-04-24 11:57 ` Segher Boessenkool
2026-04-24 12:53 ` Segher Boessenkool
2026-04-24 12:43 ` Gary Guo
2026-04-26 7:52 ` Mukesh Kumar Chaurasiya
2026-04-26 14:20 ` Gary Guo
2026-04-26 22:04 ` David Laight
2026-04-27 13:04 ` Gary Guo
2026-04-24 5:47 ` [PATCH V13 6/7] rust: Add PowerPC support Mukesh Kumar Chaurasiya (IBM)
2026-04-24 5:47 ` [PATCH V13 7/7] powerpc: Enable Rust for ppc64le Mukesh Kumar Chaurasiya (IBM)
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