linux-kernel - [PATCH v2] arm: Fix rustgcc unknown argument '-mno-fdpic'

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Message-Id: <20250522-rust-mno-fdpic-arm-fix-v2-1-a6f691d9c198@gmail.com>
Date: Thu, 22 May 2025 05:02:31 -0700
From: Rudraksha Gupta <guptarud@...il.com>
To: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
 Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
 Benno Lossin <benno.lossin@...ton.me>, 
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, 
 Nathan Chancellor <nathan@...nel.org>, 
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
 llvm@...ts.linux.dev, torvalds@...ux-foundation.org, 
 Ben Wolsieffer <ben.wolsieffer@...ring.com>, 
 Naresh Kamboju <naresh.kamboju@...aro.org>, 
 Christian Schrrefl <chrisi.schrefl@...il.com>, 
 Russell King <rmk+kernel@...linux.org.uk>, 
 Rudraksha Gupta <guptarud@...il.com>, Ard Biesheuvel <ardb@...nel.org>, 
 anders.roxell@...aro.org, arnd@...db.de, dan.carpenter@...aro.org, 
 laura.nao@...labora.com, lkft-triage@...ts.linaro.org, 
 regressions@...ts.linux.dev, Nick Clifton <nickc@...hat.com>, 
 Richard Earnshaw <richard.earnshaw@....com>, 
 Ramana Radhakrishnan <ramanara@...dia.com>, Miguel Ojeda <ojeda@...nel.org>, 
 Linux Kernel Functional Testing <lkft@...aro.org>
Subject: [PATCH v2] arm: Fix rustgcc unknown argument '-mno-fdpic'

Currently rust on arm fails to compile due to '-mno-fdpic'. This flag
disables a GCC feature that we don't want for kernel builds, so let's
skip it as it doesn't apply to Clang.

    UPD     include/generated/asm-offsets.h
    CALL    scripts/checksyscalls.sh
    RUSTC L rust/core.o
    BINDGEN rust/bindings/bindings_generated.rs
    BINDGEN rust/bindings/bindings_helpers_generated.rs
    CC      rust/helpers/helpers.o
    Unable to generate bindings: clang diagnosed error: error: unknown argument: '-mno-fdpic'
    make[2]: *** [rust/Makefile:369: rust/bindings/bindings_helpers_generated.rs] Error 1
    make[2]: *** Deleting file 'rust/bindings/bindings_helpers_generated.rs'
    make[2]: *** Waiting for unfinished jobs....
    Unable to generate bindings: clang diagnosed error: error: unknown argument: '-mno-fdpic'
    make[2]: *** [rust/Makefile:349: rust/bindings/bindings_generated.rs] Error 1
    make[2]: *** Deleting file 'rust/bindings/bindings_generated.rs'
    make[1]: *** [/home/pmos/build/src/linux-next-next-20250521/Makefile:1285: prepare] Error 2
    make: *** [Makefile:248: __sub-make] Error 2

Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
Closes: https://lore.kernel.org/all/CA+G9fYvOanQBYXKSg7C6EU30k8sTRC0JRPJXYu7wWK51w38QUQ@mail.gmail.com/
Suggested-by: Miguel Ojeda <ojeda@...nel.org>
Tested-by: Rudraksha Gupta <guptarud@...il.com>
Acked-by: Naresh Kamboju <naresh.kamboju@...aro.org>
Signed-off-by: Rudraksha Gupta <guptarud@...il.com>
---
Changes in v2:
- Fixed patch formatting issues
- Link to v1: https://lore.kernel.org/r/20250520-rust-mno-fdpic-arm-fix-v1-1-44e77fe6b2a1@gmail.com
---
 rust/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/Makefile b/rust/Makefile
index 3aca903a7d08..f207ba0ed466 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -273,7 +273,7 @@ bindgen_skip_c_flags := -mno-fp-ret-in-387 -mpreferred-stack-boundary=% \
 	-fzero-call-used-regs=% -fno-stack-clash-protection \
 	-fno-inline-functions-called-once -fsanitize=bounds-strict \
 	-fstrict-flex-arrays=% -fmin-function-alignment=% \
-	-fzero-init-padding-bits=% \
+	-fzero-init-padding-bits=% -mno-fdpic \
 	--param=% --param asan-%
 
 # Derived from `scripts/Makefile.clang`.

---
base-commit: a5806cd506af5a7c19bcd596e4708b5c464bfd21
change-id: 20250520-rust-mno-fdpic-arm-fix-940a58bf9433

Best regards,
-- 
Rudraksha Gupta <guptarud@...il.com>