[RFC RESEND 0/2] RISC-V: enable rust

[RFC RESEND 0/2] RISC-V: enable rust

[Conor Dooley]

This is a somewhat blind (and maybe foolish) attempt at enabling Rust
for RISC-V. I've tested this on Icicle, and the modules seem to work.
I'd like to play around with Rust on RISC-V, but I'm not interested in
using downstream kernels, so figured I should try and see what's
missing...
I've tagged this as RFC in case I've missed some "WAaaaa you can't do
this" somewhere :)

Thanks,
Conor.

Changes in RFC-RESEND:
- fixed the asymmetrical additions in the Makefile bits
- added cc-cover to my git send-email command...

CC: Miguel Ojeda <ojeda@kernel.org>
CC: Alex Gaynor <alex.gaynor@gmail.com>
CC: Wedson Almeida Filho <wedsonaf@gmail.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: Gary Guo <gary@garyguo.net>
CC: Björn Roy Baron <bjorn3_gh@protonmail.com>
CC: Jonathan Corbet <corbet@lwn.net>
CC: Paul Walmsley <paul.walmsley@sifive.com>
CC: Palmer Dabbelt <palmer@dabbelt.com>
CC: Nathan Chancellor <nathan@kernel.org>
CC: Nick Desaulniers <ndesaulniers@google.com>
CC: Tom Rix <trix@redhat.com>
CC: rust-for-linux@vger.kernel.org
CC: linux-doc@vger.kernel.org
CC: linux-kernel@vger.kernel.org
CC: linux-riscv@lists.infradead.org
CC: llvm@lists.linux.dev

Miguel Ojeda (2):
  scripts: generate_rust_target: enable building on RISC-V
  RISC-V: enable building the 64-bit kernels with rust support

 Documentation/rust/arch-support.rst |  2 ++
 arch/riscv/Kconfig                  |  1 +
 arch/riscv/Makefile                 |  3 ++-
 scripts/generate_rust_target.rs     | 19 +++++++++++++++++++
 4 files changed, 24 insertions(+), 1 deletion(-)

-- 
2.39.2

[RFC RESEND 1/2] scripts: generate_rust_target: enable building on RISC-V

[Conor Dooley]

From: Miguel Ojeda <ojeda@kernel.org>

Add the required bits from rust-for-linux to enable generating a RISC-V
target for rust.

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 scripts/generate_rust_target.rs | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs
index 3c6cbe2b278d..72428fc66502 100644
--- a/scripts/generate_rust_target.rs
+++ b/scripts/generate_rust_target.rs
@@ -161,6 +161,25 @@ fn main() {
         ts.push("features", features);
         ts.push("llvm-target", "x86_64-linux-gnu");
         ts.push("target-pointer-width", "64");
+    } else if cfg.has("RISCV") {
+        if cfg.has("64BIT") {
+            ts.push("arch", "riscv64");
+            ts.push("data-layout", "e-m:e-p:64:64-i64:64-i128:128-n64-S128");
+            ts.push("llvm-target", "riscv64-linux-gnu");
+            ts.push("target-pointer-width", "64");
+        } else {
+            ts.push("arch", "riscv32");
+            ts.push("data-layout", "e-m:e-p:32:32-i64:64-n32-S128");
+            ts.push("llvm-target", "riscv32-linux-gnu");
+            ts.push("target-pointer-width", "32");
+        }
+        ts.push("code-model", "medium");
+        ts.push("disable-redzone", true);
+        let mut features = "+m,+a".to_string();
+        if cfg.has("RISCV_ISA_C") {
+            features += ",+c";
+        }
+        ts.push("features", features);
     } else {
         panic!("Unsupported architecture");
     }
-- 
2.39.2

[RFC RESEND 2/2] RISC-V: enable building the 64-bit kernels with rust support

[Conor Dooley]

From: Miguel Ojeda <ojeda@kernel.org>

The rust modules work on 64-bit RISC-V, with no twiddling required.
Select HAS_RUST and provide the required flags to kbuild so that the
modules can be used.
32-bit is broken in core rust code, so support is limited to 64-bit
only: ld.lld: error: undefined symbol: __udivdi3

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 Documentation/rust/arch-support.rst | 2 ++
 arch/riscv/Kconfig                  | 1 +
 arch/riscv/Makefile                 | 3 ++-
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst
index 6982b63775da..197919158596 100644
--- a/Documentation/rust/arch-support.rst
+++ b/Documentation/rust/arch-support.rst
@@ -15,5 +15,7 @@ support corresponds to ``S`` values in the ``MAINTAINERS`` file.
 ============  ================  ==============================================
 Architecture  Level of support  Constraints
 ============  ================  ==============================================
+``riscv``     Maintained        ``rv64`` only.
+============  ================  ==============================================
 ``x86``       Maintained        ``x86_64`` only.
 ============  ================  ==============================================
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 81eb031887d2..73174157212d 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -115,6 +115,7 @@ config RISCV
 	select HAVE_POSIX_CPU_TIMERS_TASK_WORK
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_RSEQ
+	select HAVE_RUST if 64BIT
 	select HAVE_STACKPROTECTOR
 	select HAVE_SYSCALL_TRACEPOINTS
 	select IRQ_DOMAIN
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 76989561566b..0d6fc4e25221 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -29,8 +29,8 @@ ifeq ($(CONFIG_ARCH_RV64I),y)
 
 	KBUILD_CFLAGS += -mabi=lp64
 	KBUILD_AFLAGS += -mabi=lp64
-
 	KBUILD_LDFLAGS += -melf64lriscv
+	KBUILD_RUSTFLAGS += -Ctarget-cpu=generic-rv64
 else
 	BITS := 32
 	UTS_MACHINE := riscv32
@@ -38,6 +38,7 @@ else
 	KBUILD_CFLAGS += -mabi=ilp32
 	KBUILD_AFLAGS += -mabi=ilp32
 	KBUILD_LDFLAGS += -melf32lriscv
+	KBUILD_RUSTFLAGS += -Ctarget-cpu=generic-rv32
 endif
 
 ifeq ($(CONFIG_LD_IS_LLD),y)
-- 
2.39.2

Re: [RFC RESEND 2/2] RISC-V: enable building the 64-bit kernels with rust support

[Nathan Chancellor]

Hi Conor,

On Fri, Feb 24, 2023 at 01:50:44PM +0000, Conor Dooley wrote:
> From: Miguel Ojeda <ojeda@kernel.org>
> 
> The rust modules work on 64-bit RISC-V, with no twiddling required.
> Select HAS_RUST and provide the required flags to kbuild so that the
> modules can be used.
> 32-bit is broken in core rust code, so support is limited to 64-bit
> only: ld.lld: error: undefined symbol: __udivdi3
> 
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>  Documentation/rust/arch-support.rst | 2 ++
>  arch/riscv/Kconfig                  | 1 +
>  arch/riscv/Makefile                 | 3 ++-
>  3 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst
> index 6982b63775da..197919158596 100644
> --- a/Documentation/rust/arch-support.rst
> +++ b/Documentation/rust/arch-support.rst
> @@ -15,5 +15,7 @@ support corresponds to ``S`` values in the ``MAINTAINERS`` file.
>  ============  ================  ==============================================
>  Architecture  Level of support  Constraints
>  ============  ================  ==============================================
> +``riscv``     Maintained        ``rv64`` only.
> +============  ================  ==============================================
>  ``x86``       Maintained        ``x86_64`` only.
>  ============  ================  ==============================================
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 81eb031887d2..73174157212d 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -115,6 +115,7 @@ config RISCV
>  	select HAVE_POSIX_CPU_TIMERS_TASK_WORK
>  	select HAVE_REGS_AND_STACK_ACCESS_API
>  	select HAVE_RSEQ
> +	select HAVE_RUST if 64BIT

Just a small drive by comment, you have 'if 64BIT' here...

>  	select HAVE_STACKPROTECTOR
>  	select HAVE_SYSCALL_TRACEPOINTS
>  	select IRQ_DOMAIN
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index 76989561566b..0d6fc4e25221 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -29,8 +29,8 @@ ifeq ($(CONFIG_ARCH_RV64I),y)
>  
>  	KBUILD_CFLAGS += -mabi=lp64
>  	KBUILD_AFLAGS += -mabi=lp64
> -
>  	KBUILD_LDFLAGS += -melf64lriscv
> +	KBUILD_RUSTFLAGS += -Ctarget-cpu=generic-rv64
>  else
>  	BITS := 32
>  	UTS_MACHINE := riscv32
> @@ -38,6 +38,7 @@ else
>  	KBUILD_CFLAGS += -mabi=ilp32
>  	KBUILD_AFLAGS += -mabi=ilp32
>  	KBUILD_LDFLAGS += -melf32lriscv
> +	KBUILD_RUSTFLAGS += -Ctarget-cpu=generic-rv32

but also add KBUILD_RUSTFLAGS for the !64BIT case. Seems like one of
those can be removed.

>  endif
>  
>  ifeq ($(CONFIG_LD_IS_LLD),y)
> -- 
> 2.39.2
> 

Cheers,
Nathan

Re: [RFC RESEND 2/2] RISC-V: enable building the 64-bit kernels with rust support

[Conor Dooley]

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On Fri, Feb 24, 2023 at 07:57:13AM -0700, Nathan Chancellor wrote:
> Hi Conor,
> 
> On Fri, Feb 24, 2023 at 01:50:44PM +0000, Conor Dooley wrote:
> > From: Miguel Ojeda <ojeda@kernel.org>
> > 
> > The rust modules work on 64-bit RISC-V, with no twiddling required.
> > Select HAS_RUST and provide the required flags to kbuild so that the
> > modules can be used.
> > 32-bit is broken in core rust code, so support is limited to 64-bit
> > only: ld.lld: error: undefined symbol: __udivdi3
> > 
> > Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> > ---
> >  Documentation/rust/arch-support.rst | 2 ++
> >  arch/riscv/Kconfig                  | 1 +
> >  arch/riscv/Makefile                 | 3 ++-
> >  3 files changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst
> > index 6982b63775da..197919158596 100644
> > --- a/Documentation/rust/arch-support.rst
> > +++ b/Documentation/rust/arch-support.rst
> > @@ -15,5 +15,7 @@ support corresponds to ``S`` values in the ``MAINTAINERS`` file.
> >  ============  ================  ==============================================
> >  Architecture  Level of support  Constraints
> >  ============  ================  ==============================================
> > +``riscv``     Maintained        ``rv64`` only.
> > +============  ================  ==============================================
> >  ``x86``       Maintained        ``x86_64`` only.
> >  ============  ================  ==============================================
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 81eb031887d2..73174157212d 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -115,6 +115,7 @@ config RISCV
> >  	select HAVE_POSIX_CPU_TIMERS_TASK_WORK
> >  	select HAVE_REGS_AND_STACK_ACCESS_API
> >  	select HAVE_RSEQ
> > +	select HAVE_RUST if 64BIT
> 
> Just a small drive by comment, you have 'if 64BIT' here...
> 
> >  	select HAVE_STACKPROTECTOR
> >  	select HAVE_SYSCALL_TRACEPOINTS
> >  	select IRQ_DOMAIN
> > diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> > index 76989561566b..0d6fc4e25221 100644
> > --- a/arch/riscv/Makefile
> > +++ b/arch/riscv/Makefile
> > @@ -29,8 +29,8 @@ ifeq ($(CONFIG_ARCH_RV64I),y)
> >  
> >  	KBUILD_CFLAGS += -mabi=lp64
> >  	KBUILD_AFLAGS += -mabi=lp64
> > -
> >  	KBUILD_LDFLAGS += -melf64lriscv
> > +	KBUILD_RUSTFLAGS += -Ctarget-cpu=generic-rv64
> >  else
> >  	BITS := 32
> >  	UTS_MACHINE := riscv32
> > @@ -38,6 +38,7 @@ else
> >  	KBUILD_CFLAGS += -mabi=ilp32
> >  	KBUILD_AFLAGS += -mabi=ilp32
> >  	KBUILD_LDFLAGS += -melf32lriscv
> > +	KBUILD_RUSTFLAGS += -Ctarget-cpu=generic-rv32
> 
> but also add KBUILD_RUSTFLAGS for the !64BIT case. Seems like one of
> those can be removed.

Yeah & it's ditto for the rv32 handling in 1/2 as well. Ideally there
wouldn't be implicit 64-bit division and the "if 64BIT" could go
away. I just left things as-lifted, but I'll go drop anything 32-bit
related if this series looses the RFC prefix ;)

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Re: [RFC RESEND 2/2] RISC-V: enable building the 64-bit kernels with rust support

[Miguel Ojeda]

On Fri, Feb 24, 2023 at 2:51 PM Conor Dooley <conor.dooley@microchip.com> wrote:
>
> The rust modules work on 64-bit RISC-V, with no twiddling required.
> Select HAS_RUST and provide the required flags to kbuild so that the

HAS -> HAVE

> diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst
> index 6982b63775da..197919158596 100644
> --- a/Documentation/rust/arch-support.rst
> +++ b/Documentation/rust/arch-support.rst
> @@ -15,5 +15,7 @@ support corresponds to ``S`` values in the ``MAINTAINERS`` file.
>  ============  ================  ==============================================
>  Architecture  Level of support  Constraints
>  ============  ================  ==============================================
> +``riscv``     Maintained        ``rv64`` only.
> +============  ================  ==============================================
>  ``x86``       Maintained        ``x86_64`` only.

I think this separator between rows should not be here (it is not in
`rust-for-linux/rust`). Please see
https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#simple-tables.

Cheers,
Miguel

Re: [RFC RESEND 2/2] RISC-V: enable building the 64-bit kernels with rust support

[Conor Dooley]

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On Fri, Feb 24, 2023 at 09:45:05PM +0100, Miguel Ojeda wrote:
> On Fri, Feb 24, 2023 at 2:51 PM Conor Dooley <conor.dooley@microchip.com> wrote:

> > diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst
> > index 6982b63775da..197919158596 100644
> > --- a/Documentation/rust/arch-support.rst
> > +++ b/Documentation/rust/arch-support.rst
> > @@ -15,5 +15,7 @@ support corresponds to ``S`` values in the ``MAINTAINERS`` file.
> >  ============  ================  ==============================================
> >  Architecture  Level of support  Constraints
> >  ============  ================  ==============================================
> > +``riscv``     Maintained        ``rv64`` only.
> > +============  ================  ==============================================
> >  ``x86``       Maintained        ``x86_64`` only.
> 
> I think this separator between rows should not be here (it is not in
> `rust-for-linux/rust`). Please see
> https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#simple-tables.

That's what the "let the automation tell me if I messed up rst" approach
gets you ;)


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