Message-ID: <aYSgjPD5KRcNN0j4@luna>
Date: Thu, 5 Feb 2026 14:52:12 +0100
From: Link Mauve <linkmauve@...kmauve.fr>
To: "Mukesh Kumar Chaurasiya (IBM)" <mkchauras@...il.com>
Cc: linkmauve@...kmauve.fr, ojeda@...nel.org, boqun.feng@...il.com,
	gary@...yguo.net, bjorn3_gh@...tonmail.com, lossin@...nel.org,
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	peterz@...radead.org, jpoimboe@...nel.org, jbaron@...mai.com,
	rostedt@...dmis.org, ardb@...nel.org,
	rust-for-linux@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH V2 3/3] powerpc: Enable Rust for ppc64le

On Thu, Feb 05, 2026 at 02:31:25AM +0530, Mukesh Kumar Chaurasiya (IBM) wrote:
[…]
> diff --git a/rust/Makefile b/rust/Makefile
> index ae22f2c5f0b3..c3961fd0d9a4 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -392,10 +392,17 @@ BINDGEN_TARGET_x86	:= x86_64-linux-gnu
>  BINDGEN_TARGET_arm64	:= aarch64-linux-gnu
>  BINDGEN_TARGET_arm	:= arm-linux-gnueabi
>  BINDGEN_TARGET_loongarch	:= loongarch64-linux-gnusf
> -BINDGEN_TARGET_powerpc	:= powerpc-linux-gnu
>  BINDGEN_TARGET_um	:= $(BINDGEN_TARGET_$(SUBARCH))
>  BINDGEN_TARGET		:= $(BINDGEN_TARGET_$(SRCARCH))
>  
> +ifdef CONFIG_PPC64
> +ifdef CONFIG_CPU_LITTLE_ENDIAN
> +BINDGEN_TARGET_powerpc	:= powerpc64le-linux-gnu
> +endif
> +else
> +BINDGEN_TARGET_powerpc	:= powerpc-linux-gnu
> +endif

You define BINDGEN_TARGET_powerpc after BINDGEN_TARGET has been set to
the value of $(BINDGEN_TARGET_$(SRCARCH)), so it is empty and bindgen
then gets passed --target= which makes it fail here, with this error
message:
```
bindgen ../rust/bindings/bindings_helper.h --blocklist-type __kernel_s?size_t --blocklist-type __kernel_ptrdiff_t --opaque-type xregs_state --opaque-type desc_struct --opaque-type arch_lbr_state --opaque-type local_apic --opaque-type alt_instr --opaque-type x86_msi_data --opaque-type x86_msi_addr_lo --opaque-type kunit_try_catch --opaque-type spinlock --no-doc-comments --blocklist-function __list_.*_report --blocklist-item ARCH_SLAB_MINALIGN --blocklist-item ARCH_KMALLOC_MINALIGN --with-derive-custom-struct .*=MaybeZeroable --with-derive-custom-union .*=MaybeZeroable --rust-target 1.68 --use-core --with-derive-default --ctypes-prefix ffi --no-layout-tests --no-debug '.*' --enable-function-attribute-detection -o rust/bindings/bindings_generated.rs -- -Wp,-MMD,rust/bindings/.bindings_generated.rs.d -nostdinc -I../arch/powerpc/include -I./arch/powerpc/include/generated -I../include -I./include -I../arch/powerpc/include/uapi -I./arch/powerpc/include/generated/uapi -I../include/uapi -I./include/generated/uapi -include ../include/linux/compiler-version.h -include ../include/linux/kconfig.h -include ../include/linux/compiler_types.h -D__KERNEL__ -mbig-endian -m32 -I ../arch/powerpc -fmacro-prefix-map=../= -std=gnu11 -fshort-wchar -funsigned-char -fno-common -fno-PIE -fno-strict-aliasing -msoft-float -mcpu=powerpc -mno-prefixed -mno-pcrel -mno-altivec -mno-vsx -mno-mma -fno-asynchronous-unwind-tables -mbig-endian -fno-delete-null-pointer-checks -Os -fno-stack-protector -fomit-frame-pointer -ftrivial-auto-var-init=zero -fno-strict-overflow -fno-stack-check -fno-builtin-wcslen -Wall -Wextra -Wundef -Werror=implicit-function-declaration -Werror=implicit-int -Werror=return-type -Werror=strict-prototypes -Wno-format-security -Wno-trigraphs -Wno-frame-address -Wno-address-of-packed-member -Wmissing-declarations -Wmissing-prototypes -Wframe-larger-than=1280 -Wno-main -Wno-dangling-pointer -Wvla-larger-than=1 -Wno-pointer-sign -Wcast-function-type -Wno-array-bounds -Wno-stringop-overflow -Wno-alloc-size-larger-than -Wimplicit-fallthrough=5 -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -Wenum-conversion -Wunused -Wno-unused-but-set-variable -Wno-unused-const-variable -Wno-packed-not-aligned -Wno-format-overflow -Wno-format-truncation -Wno-stringop-truncation -Wno-override-init -Wno-missing-field-initializers -Wno-type-limits -Wno-shift-negative-value -Wno-maybe-uninitialized -Wno-sign-compare -Wno-unused-parameter -DGCC_PLUGINS -I../rust -Irust -DKBUILD_MODFILE='"rust/bindings_generated"' -DKBUILD_BASENAME='"bindings_generated"' -DKBUILD_MODNAME='"bindings_generated"' -D__KBUILD_MODNAME=kmod_bindings_generated -w --target= -fno-builtin -D__BINDGEN__ -DMODULE  ; sed -Ei 's/pub const RUST_CONST_HELPER_([a-zA-Z0-9_]*)/pub const /g' rust/bindings/bindings_generated.rs
error: unsupported option '-mbig-endian' for target ''
error: unsupported option '-mcpu=' for target ''
error: unsupported option '-mno-prefixed' for target ''
error: unsupported option '-mno-pcrel' for target ''
error: unsupported option '-mno-altivec' for target ''
error: unsupported option '-mno-vsx' for target ''
error: unsupported option '-mno-mma' for target ''
error: unsupported option '-mbig-endian' for target ''
error: unknown target triple 'unknown'
panicked at bindgen/ir/context.rs:562:15:
libclang error; possible causes include:
- Invalid flag syntax
- Unrecognized flags
- Invalid flag arguments
- File I/O errors
- Host vs. target architecture mismatch
If you encounter an error missing from this list, please file an issue or a PR!
```

Did this work on PPC64?

> +
>  # All warnings are inhibited since GCC builds are very experimental,
>  # many GCC warnings are not supported by Clang, they may only appear in
>  # some configurations, with new GCC versions, etc.
> -- 
> 2.52.0
> 

With this fixed:
Reviewed-by: Link Mauve <linkmauve@...kmauve.fr>
Tested-by: Link Mauve <linkmauve@...kmauve.fr>

-- 
Link Mauve

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