From cb7d9defdafba4c1d463a09c9b09876066f81ee4 Mon Sep 17 00:00:00 2001 From: Gary Guo Date: Mon, 5 Dec 2022 21:50:00 +0000 Subject: [PATCH] rust: compiler_builtins: make stubs non-global 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. This patch was previously discussed on GitHub [1]. This approach was also independently proposed by Nick Desaulniers in [2]. Link: https://github.com/Rust-for-Linux/linux/pull/779 [1] Link: https://lore.kernel.org/lkml/CAKwvOdkc0Qhwu=gfe1+H23TnAa6jnO6A3ZCO687dH6mSrATmDA@mail.gmail.com/ Suggested-by: Nick Desaulniers Acked-by: Nick Desaulniers Signed-off-by: Gary Guo Reviewed-by: Wei Liu Signed-off-by: Miguel Ojeda --- rust/Makefile | 14 ++++++++++++++ rust/compiler_builtins.rs | 5 ++++- 2 files changed, 18 insertions(+), 1 deletion(-) diff --git a/rust/Makefile b/rust/Makefile index d7621fad5b56..8a521f2b6422 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -360,8 +360,22 @@ 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 $(call if_changed_dep,rustc_library) diff --git a/rust/compiler_builtins.rs b/rust/compiler_builtins.rs index f8f39a3e6855..43378357ece9 100644 --- a/rust/compiler_builtins.rs +++ b/rust/compiler_builtins.rs @@ -28,7 +28,7 @@ macro_rules! define_panicking_intrinsics( ($reason: tt, { $($ident: ident, )* }) => { $( #[doc(hidden)] - #[no_mangle] + #[export_name = concat!("__rust", stringify!($ident))] pub extern "C" fn $ident() { panic!($reason); } @@ -61,3 +61,6 @@ define_panicking_intrinsics!("`u128` should not be used", { __udivti3, __umodti3, }); + +// NOTE: if you are adding a new intrinsic here, you should also add it to +// `redirect-intrinsics` in `rust/Makefile`.