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Rollup merge of #151998 - zmodem:naked_visibility.squash, r=saethlin,bjorn3

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Set hidden visibility on naked functions in compiler-builtins

88b46460fa made builtin functions hidden, but it doesn't apply to naked functions, which are generated through a different code path.

This was discovered in rust-lang/rust#151486 where aarch64 outline atomics showed up in shared objects, overriding the symbols from compiler-rt.
This commit is contained in:
Jacob Pratt 2026-02-13 22:26:31 -05:00 • committed by GitHub
commit 4571317d32
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GPG key ID: B5690EEEBB952194
2 changed files with 29 additions and 15 deletions
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26
compiler/rustc_codegen_llvm/src/mono_item.rs
View file

@ -41,7 +41,8 @@ impl<'tcx> PreDefineCodegenMethods<'tcx> for CodegenCx<'_, 'tcx> {
});
llvm::set_linkage(g, base::linkage_to_llvm(linkage));
llvm::set_visibility(g, base::visibility_to_llvm(visibility));
self.set_visibility(g, linkage, visibility);
self.assume_dso_local(g, false);
let attrs = self.tcx.codegen_instance_attrs(instance.def);
@ -69,16 +70,7 @@ impl<'tcx> PreDefineCodegenMethods<'tcx> for CodegenCx<'_, 'tcx> {
{
llvm::SetUniqueComdat(self.llmod, lldecl);
}
// If we're compiling the compiler-builtins crate, e.g., the equivalent of
// compiler-rt, then we want to implicitly compile everything with hidden
// visibility as we're going to link this object all over the place but
// don't want the symbols to get exported.
if linkage != Linkage::Internal && self.tcx.is_compiler_builtins(LOCAL_CRATE) {
llvm::set_visibility(lldecl, llvm::Visibility::Hidden);
} else {
llvm::set_visibility(lldecl, base::visibility_to_llvm(visibility));
}
self.set_visibility(lldecl, linkage, visibility);
debug!("predefine_fn: instance = {:?}", instance);
@ -122,6 +114,18 @@ impl CodegenCx<'_, '_> {
assume
}
fn set_visibility(&self, lldecl: &llvm::Value, linkage: Linkage, visibility: Visibility) {
// If we're compiling the compiler-builtins crate, i.e., the equivalent of
// compiler-rt, then we want to implicitly compile everything with hidden
// visibility as we're going to link this object all over the place but
// don't want the symbols to get exported.
if linkage != Linkage::Internal && self.tcx.is_compiler_builtins(LOCAL_CRATE) {
llvm::set_visibility(lldecl, llvm::Visibility::Hidden);
} else {
llvm::set_visibility(lldecl, base::visibility_to_llvm(visibility));
}
}
fn should_assume_dso_local(&self, llval: &llvm::Value, is_declaration: bool) -> bool {
let linkage = llvm::get_linkage(llval);
let visibility = llvm::get_visibility(llval);

18
compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
View file

@ -1,5 +1,6 @@
use rustc_abi::{BackendRepr, Float, Integer, Primitive, RegKind};
use rustc_hir::attrs::{InstructionSetAttr, Linkage};
use rustc_hir::def_id::LOCAL_CRATE;
use rustc_middle::mir::mono::{MonoItemData, Visibility};
use rustc_middle::mir::{InlineAsmOperand, START_BLOCK};
use rustc_middle::ty::layout::{FnAbiOf, LayoutOf, TyAndLayout};
@ -128,6 +129,15 @@ fn prefix_and_suffix<'tcx>(
let is_arm = tcx.sess.target.arch == Arch::Arm;
let is_thumb = tcx.sess.unstable_target_features.contains(&sym::thumb_mode);
// If we're compiling the compiler-builtins crate, e.g., the equivalent of
// compiler-rt, then we want to implicitly compile everything with hidden
// visibility as we're going to link this object all over the place but
// don't want the symbols to get exported. For naked asm we set the visibility here.
let mut visibility = item_data.visibility;
if item_data.linkage != Linkage::Internal && tcx.is_compiler_builtins(LOCAL_CRATE) {
visibility = Visibility::Hidden;
}
let attrs = tcx.codegen_instance_attrs(instance.def);
let link_section = attrs.link_section.map(|symbol| symbol.as_str().to_string());
@ -217,7 +227,7 @@ fn prefix_and_suffix<'tcx>(
writeln!(begin, ".pushsection {section},\"ax\", {progbits}").unwrap();
writeln!(begin, ".balign {align_bytes}").unwrap();
write_linkage(&mut begin).unwrap();
match item_data.visibility {
match visibility {
Visibility::Default => {}
Visibility::Protected => writeln!(begin, ".protected {asm_name}").unwrap(),
Visibility::Hidden => writeln!(begin, ".hidden {asm_name}").unwrap(),
@ -243,7 +253,7 @@ fn prefix_and_suffix<'tcx>(
writeln!(begin, ".pushsection {},regular,pure_instructions", section).unwrap();
writeln!(begin, ".balign {align_bytes}").unwrap();
write_linkage(&mut begin).unwrap();
match item_data.visibility {
match visibility {
Visibility::Default | Visibility::Protected => {}
Visibility::Hidden => writeln!(begin, ".private_extern {asm_name}").unwrap(),
}
@ -280,7 +290,7 @@ fn prefix_and_suffix<'tcx>(
writeln!(begin, ".section {section},\"\",@").unwrap();
// wasm functions cannot be aligned, so skip
write_linkage(&mut begin).unwrap();
if let Visibility::Hidden = item_data.visibility {
if let Visibility::Hidden = visibility {
writeln!(begin, ".hidden {asm_name}").unwrap();
}
writeln!(begin, ".type {asm_name}, @function").unwrap();
@ -313,7 +323,7 @@ fn prefix_and_suffix<'tcx>(
writeln!(begin, ".align {}", align_bytes).unwrap();
write_linkage(&mut begin).unwrap();
if let Visibility::Hidden = item_data.visibility {
if let Visibility::Hidden = visibility {
// FIXME apparently `.globl {asm_name}, hidden` is valid
// but due to limitations with `.weak` (see above) we can't really use that in general yet
}