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Message-ID: <aYN_3P6aUaBWwQYo@li-1a3e774c-28e4-11b2-a85c-acc9f2883e29.ibm.com>
Date: Wed, 4 Feb 2026 22:58:02 +0530
From: Mukesh Kumar Chaurasiya <mkchauras@...il.com>
To: "Christophe Leroy (CS GROUP)" <chleroy@...nel.org>
Cc: maddy@...ux.ibm.com, mpe@...erman.id.au, npiggin@...il.com,
peterz@...radead.org, jpoimboe@...nel.org, jbaron@...mai.com, rostedt@...dmis.org,
ardb@...nel.org, ojeda@...nel.org, boqun.feng@...il.com, gary@...yguo.net,
bjorn3_gh@...tonmail.com, lossin@...nel.org, a.hindborg@...nel.org, aliceryhl@...gle.com,
tmgross@...ch.edu, dakr@...nel.org, nathan@...nel.org,
nick.desaulniers+lkml@...il.com, morbo@...gle.com, justinstitt@...gle.com,
linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
llvm@...ts.linux.dev, Link Mauve <linkmauve@...kmauve.fr>
Subject: Re: [PATCH] powerpc: Enable Rust for ppc64le
On Wed, Feb 04, 2026 at 06:11:13PM +0100, Christophe Leroy (CS GROUP) wrote:
> Hi Mukesh, hi Link,
>
> Le 04/02/2026 à 05:24, Mukesh Kumar Chaurasiya (IBM) a écrit :
> > [Vous ne recevez pas souvent de courriers de mkchauras@...il.com. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
> >
> > Enabling rust support for ppc64 only.
>
> Link Mauve has sent a patch for rust support on PPC32 a few hours before
> you, see
> https://lore.kernel.org/r/20260204030507.8203-1-linkmauve@linkmauve.fr
> Could you coordinate together to provide something supporting both PPC32 and
> PPC64 ?
>
Hey Christophe,
Sure.
> I see the following conflicts at the time being. I also have a few comments
> down.
>
Ohk.
> diff --git a/Documentation/rust/arch-support.rst
> b/Documentation/rust/arch-support.rst
> index 6e6a515d0899..70b9e192a7a0 100644
> --- a/Documentation/rust/arch-support.rst
> +++ b/Documentation/rust/arch-support.rst
> @@ -18,6 +18,7 @@ Architecture Level of support Constraints
> ``arm`` Maintained ARMv7 Little Endian only.
> ``arm64`` Maintained Little Endian only.
> ``loongarch`` Maintained \-
> +``powerpc`` Maintained 32-bit Big Endian only.
> ``riscv`` Maintained ``riscv64`` and LLVM/Clang only.
> ``um`` Maintained \-
> ``x86`` Maintained ``x86_64`` only.
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index b8d36a261009..80b2666fc5af 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -283,8 +283,10 @@ config PPC
> select HAVE_REGS_AND_STACK_ACCESS_API
> select HAVE_RELIABLE_STACKTRACE
> select HAVE_RSEQ
> + select HAVE_RUST if PPC32
> select HAVE_SAMPLE_FTRACE_DIRECT if HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if
> HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> + select HAVE_RUST if PPC64
> select HAVE_SETUP_PER_CPU_AREA if PPC64
> select HAVE_SOFTIRQ_ON_OWN_STACK
> select HAVE_STACKPROTECTOR if PPC32 && $(cc-option,$(m32-flag)
> -mstack-protector-guard=tls -mstack-protector-guard-reg=r2
> -mstack-protector-guard-offset=0)
> diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> index a58b1029592c..ac6fe8cc4ece 100644
> --- a/arch/powerpc/Makefile
> +++ b/arch/powerpc/Makefile
> @@ -61,6 +61,8 @@ else
> KBUILD_LDFLAGS_MODULE += $(objtree)/arch/powerpc/lib/crtsavres.o
> endif
>
> +KBUILD_RUSTFLAGS += --target=powerpc-unknown-linux-gnu
> +
> ifdef CONFIG_CPU_LITTLE_ENDIAN
> KBUILD_CPPFLAGS += -mlittle-endian
> KBUILD_LDFLAGS += -EL
> @@ -172,10 +174,11 @@ CFLAGS-y += $(CONFIG_TUNE_CPU)
>
> asinstr := $(call as-instr,lis 9$(comma)foo@...h,-DHAVE_AS_ATHIGH=1)
>
> -KBUILD_CPPFLAGS += -I $(srctree)/arch/powerpc $(asinstr)
> -KBUILD_AFLAGS += $(AFLAGS-y)
> -KBUILD_CFLAGS += $(CC_FLAGS_NO_FPU)
> -KBUILD_CFLAGS += $(CFLAGS-y)
> +KBUILD_CPPFLAGS += -I $(srctree)/arch/powerpc $(asinstr)
> +KBUILD_AFLAGS += $(AFLAGS-y)
> +KBUILD_CFLAGS += $(CC_FLAGS_NO_FPU)
> +KBUILD_CFLAGS += $(CFLAGS-y)
> +KBUILD_RUSTFLAGS += -Ctarget-feature=-mma,-vsx,-hard-float,-altivec
>
> CHECKFLAGS += -m$(BITS) -D__powerpc__ -D__powerpc$(BITS)__
> ifdef CONFIG_CPU_BIG_ENDIAN
> diff --git a/arch/powerpc/include/asm/jump_label.h
> b/arch/powerpc/include/asm/jump_label.h
> index d4eaba459a0e..d2284c72d21b 100644
> --- a/arch/powerpc/include/asm/jump_label.h
> +++ b/arch/powerpc/include/asm/jump_label.h
> @@ -15,14 +15,35 @@
> #define JUMP_ENTRY_TYPE stringify_in_c(FTR_ENTRY_LONG)
> #define JUMP_LABEL_NOP_SIZE 4
>
> +<<<<<<< HEAD
> +/* This macro is also expanded on the Rust side. */
> +#define ARCH_STATIC_BRANCH_ASM(key, label) \
> + "1:\n\t" \
> + "nop # arch_static_branch\n\t" \
> + ".pushsection __jump_table, \"aw\"\n\t" \
> + ".long 1b - ., " label " - .\n\t" \
> + JUMP_ENTRY_TYPE key " - .\n\t" \
> + ".popsection \n\t"
> +
> static __always_inline bool arch_static_branch(struct static_key *key, bool
> branch)
> {
> - asm goto("1:\n\t"
> - "nop # arch_static_branch\n\t"
> - ".pushsection __jump_table, \"aw\"\n\t"
> - ".long 1b - ., %l[l_yes] - .\n\t"
> - JUMP_ENTRY_TYPE "%c0 - .\n\t"
> - ".popsection \n\t"
> + asm goto(ARCH_STATIC_BRANCH_ASM("%c0", "%l[l_yes]")
> +=======
> +#define JUMP_TABLE_ENTRY(key, label) \
> + ".pushsection __jump_table, \"aw\" \n\t" \
> + ".long 1b - ., " label " - . \n\t" \
> + JUMP_ENTRY_TYPE key " - . \n\t" \
> + ".popsection \n\t"
> +
> +#define ARCH_STATIC_BRANCH_ASM(key, label) \
> + "1: nop \n\t" \
> + JUMP_TABLE_ENTRY(key,label)
> +
> +static __always_inline bool arch_static_branch(struct static_key *key, bool
> branch)
> +{
> + asm goto(
> + ARCH_STATIC_BRANCH_ASM("%c0", "%l[l_yes]")
> +>>>>>>> rust64
> : : "i" (&((char *)key)[branch]) : : l_yes);
>
> return false;
> @@ -34,10 +55,7 @@ static __always_inline bool
> arch_static_branch_jump(struct static_key *key, bool
> {
> asm goto("1:\n\t"
> "b %l[l_yes] # arch_static_branch_jump\n\t"
> - ".pushsection __jump_table, \"aw\"\n\t"
> - ".long 1b - ., %l[l_yes] - .\n\t"
> - JUMP_ENTRY_TYPE "%c0 - .\n\t"
> - ".popsection \n\t"
> + JUMP_TABLE_ENTRY("%c0", "%l[l_yes]")
> : : "i" (&((char *)key)[branch]) : : l_yes);
>
> return false;
> diff --git a/rust/Makefile b/rust/Makefile
> index 5d357dce1704..9b72c1e96191 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -383,13 +383,19 @@ bindgen_skip_c_flags := -mno-fp-ret-in-387
> -mpreferred-stack-boundary=% \
> -fno-inline-functions-called-once -fsanitize=bounds-strict \
> -fstrict-flex-arrays=% -fmin-function-alignment=% \
> -fzero-init-padding-bits=% -mno-fdpic \
> - --param=% --param asan-% -fno-isolate-erroneous-paths-dereference
> + --param=% --param asan-% -fno-isolate-erroneous-paths-dereference \
> + -ffixed-r2 -mmultiple -mno-readonly-in-sdata
>
> # Derived from `scripts/Makefile.clang`.
> 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
> +<<<<<<< HEAD
> +BINDGEN_TARGET_powerpc := powerpc-linux-gnu
> +=======
> +BINDGEN_TARGET_powerpc := powerpc64le-linux-gnu
> +>>>>>>> rust64
> BINDGEN_TARGET_um := $(BINDGEN_TARGET_$(SUBARCH))
> BINDGEN_TARGET := $(BINDGEN_TARGET_$(SRCARCH))
>
> diff --git a/scripts/generate_rust_target.rs
> b/scripts/generate_rust_target.rs
> index 38b3416bb979..1860af50b926 100644
> --- a/scripts/generate_rust_target.rs
> +++ b/scripts/generate_rust_target.rs
> @@ -188,6 +188,16 @@ fn main() {
> panic!("arm uses the builtin rustc target");
> } else if cfg.has("ARM64") {
> panic!("arm64 uses the builtin rustc aarch64-unknown-none target");
> + } else if cfg.has("PPC32") {
> + ts.push("arch", "powerpc");
> + ts.push("data-layout", "E-m:e-p:32:32-Fn32-i64:64-n32");
> + ts.push("features", "+soft-float");
> + ts.push("llvm-target", "powerpc-unknown-eabi");
> + if cfg.rustc_version_atleast(1, 91, 0) {
> + ts.push("target-pointer-width", 32);
> + } else {
> + ts.push("target-pointer-width", "32");
> + }
> } else if cfg.has("RISCV") {
> if cfg.has("64BIT") {
> panic!("64-bit RISC-V uses the builtin rustc
> riscv64-unknown-none-elf target");
> @@ -256,6 +266,30 @@ fn main() {
> }
> } else if cfg.has("LOONGARCH") {
> panic!("loongarch uses the builtin rustc
> loongarch64-unknown-none-softfloat target");
> + } else if cfg.has("PPC64") {
> + ts.push("arch", "powerpc64");
> + ts.push(
> + "data-layout",
> + if cfg.has("CPU_LITTLE_ENDIAN") {
> + "e-m:e-Fn32-i64:64-n32:64-S128-v256:256:256-v512:512:512"
> + } else {
> + "E-m:e-Fn32-i64:64-n32:64-S128-v256:256:256-v512:512:512"
> + },
> + );
> + ts.push("features", "-mma,-altivec,-vsx,-hard-float");
> + ts.push(
> + "llvm-target",
> + if cfg.has("CPU_LITTLE_ENDIAN") {
> + "powerpc64le-linux-gnu"
> + } else {
> + "powerpc64-linux-gnu"
> + },
> + );
> + if cfg.rustc_version_atleast(1, 91, 0) {
> + ts.push("target-pointer-width", 64);
> + } else {
> + ts.push("target-pointer-width", "64");
> + }
> } else {
> panic!("Unsupported architecture");
> }
>
> [...]
>
> > ---
> > arch/powerpc/Kconfig | 1 +
> > arch/powerpc/Makefile | 9 +++++----
> > arch/powerpc/include/asm/jump_label.h | 23 +++++++++++++----------
> > rust/Makefile | 1 +
> > scripts/generate_rust_target.rs | 24 ++++++++++++++++++++++++
> > 5 files changed, 44 insertions(+), 14 deletions(-)
> >
> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > index 9537a61ebae0..e9b8d761ed52 100644
> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -285,6 +285,7 @@ config PPC
> > select HAVE_RSEQ
> > select HAVE_SAMPLE_FTRACE_DIRECT if HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> > select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> > + select HAVE_RUST if PPC64
>
> Keep in alphabetic order
>
Sure.
> > select HAVE_SETUP_PER_CPU_AREA if PPC64
> > select HAVE_SOFTIRQ_ON_OWN_STACK
> > select HAVE_STACKPROTECTOR if PPC32 && $(cc-option,$(m32-flag) -mstack-protector-guard=tls -mstack-protector-guard-reg=r2 -mstack-protector-guard-offset=0)
> > diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> > index a58b1029592c..7ad28cf0fd35 100644
> > --- a/arch/powerpc/Makefile
> > +++ b/arch/powerpc/Makefile
> > @@ -172,10 +172,11 @@ CFLAGS-y += $(CONFIG_TUNE_CPU)
> >
> > asinstr := $(call as-instr,lis 9$(comma)foo@...h,-DHAVE_AS_ATHIGH=1)
> >
> > -KBUILD_CPPFLAGS += -I $(srctree)/arch/powerpc $(asinstr)
> > -KBUILD_AFLAGS += $(AFLAGS-y)
> > -KBUILD_CFLAGS += $(CC_FLAGS_NO_FPU)
> > -KBUILD_CFLAGS += $(CFLAGS-y)
> > +KBUILD_CPPFLAGS += -I $(srctree)/arch/powerpc $(asinstr)
> > +KBUILD_AFLAGS += $(AFLAGS-y)
> > +KBUILD_CFLAGS += $(CC_FLAGS_NO_FPU)
> > +KBUILD_CFLAGS += $(CFLAGS-y)
> > +KBUILD_RUSTFLAGS += -Ctarget-feature=-mma,-vsx,-hard-float,-altivec
> >
> > CHECKFLAGS += -m$(BITS) -D__powerpc__ -D__powerpc$(BITS)__
> > ifdef CONFIG_CPU_BIG_ENDIAN
> > diff --git a/arch/powerpc/include/asm/jump_label.h b/arch/powerpc/include/asm/jump_label.h
> > index d4eaba459a0e..a6b211502bfe 100644
> > --- a/arch/powerpc/include/asm/jump_label.h
> > +++ b/arch/powerpc/include/asm/jump_label.h
> > @@ -15,14 +15,20 @@
> > #define JUMP_ENTRY_TYPE stringify_in_c(FTR_ENTRY_LONG)
> > #define JUMP_LABEL_NOP_SIZE 4
> >
> > +#define JUMP_TABLE_ENTRY(key, label) \
> > + ".pushsection __jump_table, \"aw\" \n\t" \
> > + ".long 1b - ., " label " - . \n\t" \
> > + JUMP_ENTRY_TYPE key " - . \n\t" \
> > + ".popsection \n\t"
> > +
> > +#define ARCH_STATIC_BRANCH_ASM(key, label) \
> > + "1: nop \n\t" \
> > + JUMP_TABLE_ENTRY(key,label)
> > +
> > static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
> > {
> > - asm goto("1:\n\t"
> > - "nop # arch_static_branch\n\t"
> > - ".pushsection __jump_table, \"aw\"\n\t"
> > - ".long 1b - ., %l[l_yes] - .\n\t"
> > - JUMP_ENTRY_TYPE "%c0 - .\n\t"
> > - ".popsection \n\t"
> > + asm goto(
> > + ARCH_STATIC_BRANCH_ASM("%c0", "%l[l_yes]")
> > : : "i" (&((char *)key)[branch]) : : l_yes);
> >
> > return false;
> > @@ -34,10 +40,7 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool
> > {
> > asm goto("1:\n\t"
> > "b %l[l_yes] # arch_static_branch_jump\n\t"
> > - ".pushsection __jump_table, \"aw\"\n\t"
> > - ".long 1b - ., %l[l_yes] - .\n\t"
> > - JUMP_ENTRY_TYPE "%c0 - .\n\t"
> > - ".popsection \n\t"
> > + JUMP_TABLE_ENTRY("%c0", "%l[l_yes]")
> > : : "i" (&((char *)key)[branch]) : : l_yes);
> >
> > return false;
> > diff --git a/rust/Makefile b/rust/Makefile
> > index 5d357dce1704..7a6daa822cbc 100644
> > --- a/rust/Makefile
> > +++ b/rust/Makefile
> > @@ -390,6 +390,7 @@ 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 := powerpc64le-linux-gnu
>
> This needs to depend on CONFIG_PPC64 and CONFIG_CPU_LITTLE_ENDIAN.
>
Yeah, will fix this.
>
> > BINDGEN_TARGET_um := $(BINDGEN_TARGET_$(SUBARCH))
> > BINDGEN_TARGET := $(BINDGEN_TARGET_$(SRCARCH))
> >
> > diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs
> > index 38b3416bb979..875579b37424 100644
> > --- a/scripts/generate_rust_target.rs
> > +++ b/scripts/generate_rust_target.rs
> > @@ -256,6 +256,30 @@ fn main() {
> > }
> > } else if cfg.has("LOONGARCH") {
> > panic!("loongarch uses the builtin rustc loongarch64-unknown-none-softfloat target");
> > + } else if cfg.has("PPC64") {
>
> Shouldn't this be done closer to PPC32 ?
>
Yeah, I will build the 64 support over 32 and keep them together.
> > + ts.push("arch", "powerpc64");
> > + ts.push(
> > + "data-layout",
> > + if cfg.has("CPU_LITTLE_ENDIAN") {
> > + "e-m:e-Fn32-i64:64-n32:64-S128-v256:256:256-v512:512:512"
> > + } else {
> > + "E-m:e-Fn32-i64:64-n32:64-S128-v256:256:256-v512:512:512"
> > + },
> > + );
> > + ts.push("features", "-mma,-altivec,-vsx,-hard-float");
> > + ts.push(
> > + "llvm-target",
> > + if cfg.has("CPU_LITTLE_ENDIAN") {
> > + "powerpc64le-linux-gnu"
> > + } else {
> > + "powerpc64-linux-gnu"
> > + },
> > + );
> > + if cfg.rustc_version_atleast(1, 91, 0) {
> > + ts.push("target-pointer-width", 64);
> > + } else {
> > + ts.push("target-pointer-width", "64");
> > + }
> > } else {
> > panic!("Unsupported architecture");
> > }
> > --
> > 2.52.0
> >
>
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