Can you add a comment to compiler_builtins.rs reminding people that if
they add an additional intrinsic, they may also need to add it to
redirect-intrinsics in the Makefile?
Alex
On Sun, Dec 4, 2022 at 5:44 PM Gary Guo <[email protected]> wrote:
>
> Currently we define a number of stubs for compiler-builtin intrinsics
> that compiled libcore generates. The defined stubs are weak so they will
> not conflict with genuine implementation of these intrinsics, but their
> effect is global and will cause non-libcore code that accidently
> generate these intrinsics calls compile and bug on runtime.
>
> Instead of defining a stub that can affect all code, this patch uses
> objcopy's `--redefine-sym` flag to redirect these calls (from libcore
> only) to a prefixed version (e.g. redirect `__multi3` to `__rust_multi3`),
> so we can define panciking stubs that are only visible to libcore.
>
> Signed-off-by: Gary Guo <[email protected]>
> ---
> This patch was previous discussed on GitHub.
>
> Link: https://github.com/Rust-for-Linux/linux/pull/779
>
> To: Miguel Ojeda <[email protected]>
> To: Alex Gaynor <[email protected]>
> To: Wedson Almeida Filho <[email protected]>
> To: Boqun Feng <[email protected]>
> To: Björn Roy Baron <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> ---
> rust/Makefile | 14 ++++++++++++++
> rust/compiler_builtins.rs | 2 +-
> 2 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/rust/Makefile b/rust/Makefile
> index ff70c4c916f8..aed6f7eca36f 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -359,8 +359,22 @@ rust-analyzer:
> $(Q)$(srctree)/scripts/generate_rust_analyzer.py $(srctree) $(objtree) \
> $(RUST_LIB_SRC) > $(objtree)/rust-project.json
>
> +redirect-intrinsics = \
> + __eqsf2 __gesf2 __lesf2 __nesf2 __unordsf2 \
> + __unorddf2 \
> + __muloti4 __multi3 \
> + __udivmodti4 __udivti3 __umodti3
> +
> +ifneq ($(or $(CONFIG_ARM64),$(and $(CONFIG_RISCV),$(CONFIG_64BIT))),)
> + # These intrinsics are defined for ARM64 and RISCV64
> + redirect-intrinsics += \
> + __ashrti3 \
> + __ashlti3 __lshrti3
> +endif
> +
> $(obj)/core.o: private skip_clippy = 1
> $(obj)/core.o: private skip_flags = -Dunreachable_pub
> +$(obj)/core.o: private rustc_objcopy = $(foreach sym,$(redirect-intrinsics),--redefine-sym $(sym)=__rust$(sym))
> $(obj)/core.o: private rustc_target_flags = $(core-cfgs)
> $(obj)/core.o: $(RUST_LIB_SRC)/core/src/lib.rs $(obj)/target.json FORCE
> $(call if_changed_dep,rustc_library)
> diff --git a/rust/compiler_builtins.rs b/rust/compiler_builtins.rs
> index f8f39a3e6855..1f05f93f2187 100644
> --- a/rust/compiler_builtins.rs
> +++ b/rust/compiler_builtins.rs
> @@ -28,7 +28,7 @@ macro_rules! define_panicking_intrinsics(
> ($reason: tt, { $($ident: ident, )* }) => {
> $(
> #[doc(hidden)]
> - #[no_mangle]
> + #[export_name = concat!("__rust", stringify!($ident))]
> pub extern "C" fn $ident() {
> panic!($reason);
> }
>
> ---
> base-commit: b9ecf9b9ac5969d7b7ea786ce5c76e24246df2c5
> change-id: 20221204-compiler-builtin-bb03aa6c4400
>
> Best regards,
> --
> Gary Guo <[email protected]>
--
All that is necessary for evil to succeed is for good people to do nothing.