Error on invalid macho section specifier

compiler/rustc_attr_parsing/src/attributes/link_attrs.rs

@@ -14,8 +14,9 @@ use crate::attributes::cfg::parse_cfg_entry;
 use crate::session_diagnostics::{
     AsNeededCompatibility, BundleNeedsStatic, EmptyLinkName, ExportSymbolsNeedsStatic,
     ImportNameTypeRaw, ImportNameTypeX86, IncompatibleWasmLink, InvalidLinkModifier,
-    LinkFrameworkApple, LinkOrdinalOutOfRange, LinkRequiresName, MultipleModifiers,
-    NullOnLinkSection, RawDylibNoNul, RawDylibOnlyWindows, WholeArchiveNeedsStatic,
+    InvalidMachoSection, InvalidMachoSectionReason, LinkFrameworkApple, LinkOrdinalOutOfRange,
+    LinkRequiresName, MultipleModifiers, NullOnLinkSection, RawDylibNoNul, RawDylibOnlyWindows,
+    WholeArchiveNeedsStatic,
 };
 
 pub(crate) struct LinkNameParser;
@@ -460,6 +461,29 @@ impl LinkParser {
 
 pub(crate) struct LinkSectionParser;
 
+fn check_link_section_macho(name: Symbol) -> Result<(), InvalidMachoSectionReason> {
+    let mut parts = name.as_str().split(',').map(|s| s.trim());
+
+    // The segment can be empty.
+    let _segment = parts.next();
+
+    // But the section is required.
+    let section = match parts.next() {
+        None | Some("") => return Err(InvalidMachoSectionReason::MissingSection),
+        Some(section) => section,
+    };
+
+    if section.len() > 16 {
+        return Err(InvalidMachoSectionReason::SectionTooLong { section: section.to_string() });
+    }
+
+    // LLVM also checks the other components of the section specifier, but that logic is hard to
+    // keep in sync. We skip it here for now, assuming that if you got that far you'll be able
+    // to interpret the LLVM errors.
+
+    Ok(())
+}
+
 impl<S: Stage> SingleAttributeParser<S> for LinkSectionParser {
     const PATH: &[Symbol] = &[sym::link_section];
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
@@ -492,6 +516,18 @@ impl<S: Stage> SingleAttributeParser<S> for LinkSectionParser {
             return None;
         }
 
+        // We (currently) only validate macho section specifiers.
+        match cx.sess.target.binary_format {
+            BinaryFormat::MachO => match check_link_section_macho(name) {
+                Ok(()) => {}
+                Err(reason) => {
+                    cx.emit_err(InvalidMachoSection { name_span: nv.value_span, reason });
+                    return None;
+                }
+            },
+            BinaryFormat::Coff | BinaryFormat::Elf | BinaryFormat::Wasm | BinaryFormat::Xcoff => {}
+        }
+
         Some(LinkSection { name, span: cx.attr_span })
     }
 }

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -1133,3 +1133,22 @@ pub(crate) struct UnstableAttrForAlreadyStableFeature {
     #[label("the stability attribute annotates this item")]
     pub item_span: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag("invalid Mach-O section specifier")]
+pub(crate) struct InvalidMachoSection {
+    #[primary_span]
+    #[label("not a valid Mach-O section specifier")]
+    pub name_span: Span,
+    #[subdiagnostic]
+    pub reason: InvalidMachoSectionReason,
+}
+
+#[derive(Subdiagnostic)]
+pub(crate) enum InvalidMachoSectionReason {
+    #[note("a Mach-O section specifier requires a segment and a section, separated by a comma")]
+    #[help("an example of a valid Mach-O section specifier is `__TEXT,__cstring`")]
+    MissingSection,
+    #[note("section name `{$section}` is longer than 16 bytes")]
+    SectionTooLong { section: String },
+}

compiler/rustc_hir/src/attrs/data_structures.rs

@@ -1090,8 +1090,8 @@ pub enum AttributeKind {
 
     /// Represents [`#[link_section]`](https://doc.rust-lang.org/reference/abi.html#the-link_section-attribute)
     LinkSection {
-        name: Symbol,
         span: Span,
+        name: Symbol,
     },
 
     /// Represents `#[linkage]`.

tests/codegen-llvm/link_section.rs

@@ -3,14 +3,14 @@
 
 #![crate_type = "lib"]
 
-// CHECK: @VAR1 = {{(dso_local )?}}constant [4 x i8] c"\01\00\00\00", section ".test_one"
+// CHECK: @VAR1 = {{(dso_local )?}}constant [4 x i8] c"\01\00\00\00", section "__TEST,one"
 #[no_mangle]
-#[link_section = ".test_one"]
+#[link_section = "__TEST,one"]
 #[cfg(target_endian = "little")]
 pub static VAR1: u32 = 1;
 
 #[no_mangle]
-#[link_section = ".test_one"]
+#[link_section = "__TEST,one"]
 #[cfg(target_endian = "big")]
 pub static VAR1: u32 = 0x01000000;
 
@@ -19,17 +19,17 @@ pub enum E {
     B(f32),
 }
 
-// CHECK: @VAR2 = {{(dso_local )?}}constant {{.*}}, section ".test_two"
+// CHECK: @VAR2 = {{(dso_local )?}}constant {{.*}}, section "__TEST,two"
 #[no_mangle]
-#[link_section = ".test_two"]
+#[link_section = "__TEST,two"]
 pub static VAR2: E = E::A(666);
 
-// CHECK: @VAR3 = {{(dso_local )?}}constant {{.*}}, section ".test_three"
+// CHECK: @VAR3 = {{(dso_local )?}}constant {{.*}}, section "__TEST,three"
 #[no_mangle]
-#[link_section = ".test_three"]
+#[link_section = "__TEST,three"]
 pub static VAR3: E = E::B(1.);
 
-// CHECK: define {{(dso_local )?}}void @fn1() {{.*}} section ".test_four" {
+// CHECK: define {{(dso_local )?}}void @fn1() {{.*}} section "__TEST,four" {
 #[no_mangle]
-#[link_section = ".test_four"]
+#[link_section = "__TEST,four"]
 pub fn fn1() {}

tests/codegen-llvm/naked-fn/naked-functions.rs

@@ -13,7 +13,7 @@
 //@[thumb] needs-llvm-components: arm
 
 #![crate_type = "lib"]
-#![feature(no_core, lang_items, rustc_attrs)]
+#![feature(no_core, lang_items, rustc_attrs, cfg_target_object_format)]
 #![no_core]
 
 extern crate minicore;
@@ -145,13 +145,16 @@ pub extern "C" fn naked_with_args_and_return(a: isize, b: isize) -> isize {
 }
 
 // linux:            .pushsection .text.some_different_name,\22ax\22, @progbits
-// macos:            .pushsection .text.some_different_name,regular,pure_instructions
+// macos:            .pushsection __TEXT,different,regular,pure_instructions
 // win_x86,win_i686: .pushsection .text.some_different_name,\22xr\22
 // thumb:            .pushsection .text.some_different_name,\22ax\22, %progbits
 // CHECK-LABEL: test_link_section:
 #[no_mangle]
 #[unsafe(naked)]
-#[link_section = ".text.some_different_name"]
+// FIXME: configure this with `cfg(target_binary_format = "mach-o")`,
+// see https://github.com/rust-lang/rust/issues/152586.
+#[cfg_attr(not(target_object_format = "mach-o"), link_section = ".text.some_different_name")]
+#[cfg_attr(target_object_format = "mach-o", link_section = "__TEXT,different")]
 pub extern "C" fn test_link_section() {
     cfg_select! {
         all(target_arch = "arm", target_feature = "thumb-mode") => {

tests/rustdoc-html/attributes-2021-edition.rs

@@ -9,6 +9,6 @@ pub extern "C" fn f() {}
 #[export_name = "bar"]
 pub extern "C" fn g() {}
 
-//@ has foo/fn.example.html '//pre[@class="rust item-decl"]' '#[unsafe(link_section = ".text")]'
-#[link_section = ".text"]
+//@ has foo/fn.example.html '//pre[@class="rust item-decl"]' '#[unsafe(link_section = "__TEXT,__text")]'
+#[link_section = "__TEXT,__text"]
 pub extern "C" fn example() {}

tests/rustdoc-html/attributes.rs

@@ -1,4 +1,5 @@
 //@ edition: 2024
+//@ only-linux
 #![crate_name = "foo"]
 
 //@ has foo/fn.f.html '//*[@class="code-attribute"]' '#[unsafe(no_mangle)]'

tests/rustdoc-html/inline_cross/attributes.rs

@@ -9,7 +9,7 @@
 pub use attributes::no_mangle;
 
 //@ has 'user/fn.link_section.html' '//pre[@class="rust item-decl"]' \
-//                                  '#[unsafe(link_section = ".here")]'
+//                                  '#[unsafe(link_section = "__TEXT,__here")]'
 pub use attributes::link_section;
 
 //@ has 'user/fn.export_name.html' '//pre[@class="rust item-decl"]' \

tests/rustdoc-html/inline_cross/auxiliary/attributes.rs

@@ -1,7 +1,7 @@
 #[unsafe(no_mangle)]
 pub fn no_mangle() {}
 
-#[unsafe(link_section = ".here")]
+#[unsafe(link_section = "__TEXT,__here")]
 pub fn link_section() {}
 
 #[unsafe(export_name = "exonym")]

tests/rustdoc-json/attrs/link_section_2021.rs

@@ -2,6 +2,6 @@
 #![no_std]
 
 //@ count "$.index[?(@.name=='example')].attrs[*]" 1
-//@ is "$.index[?(@.name=='example')].attrs[*].link_section" '".text"'
-#[link_section = ".text"]
+//@ is "$.index[?(@.name=='example')].attrs[*].link_section" '"__TEXT,__text"'
+#[link_section = "__TEXT,__text"]
 pub extern "C" fn example() {}

tests/rustdoc-json/attrs/link_section_2024.rs

@@ -5,6 +5,6 @@
 // However, the unsafe qualification is not shown by rustdoc.
 
 //@ count "$.index[?(@.name=='example')].attrs[*]" 1
-//@ is "$.index[?(@.name=='example')].attrs[*].link_section" '".text"'
-#[unsafe(link_section = ".text")]
+//@ is "$.index[?(@.name=='example')].attrs[*].link_section" '"__TEXT,__text"'
+#[unsafe(link_section = "__TEXT,__text")]
 pub extern "C" fn example() {}

tests/ui/asm/naked-functions.rs

@@ -3,7 +3,7 @@
 //@ ignore-spirv
 //@ reference: attributes.codegen.naked.body
 
-#![feature(asm_unwind, linkage, rustc_attrs)]
+#![feature(asm_unwind, linkage, rustc_attrs, cfg_target_object_format)]
 #![crate_type = "lib"]
 
 use std::arch::{asm, naked_asm};
@@ -200,7 +200,8 @@ pub extern "C" fn compatible_must_use_attributes() -> u64 {
 }
 
 #[export_name = "exported_function_name"]
-#[link_section = ".custom_section"]
+#[cfg_attr(not(target_object_format = "mach-o"), link_section = ".custom")]
+#[cfg_attr(target_object_format = "mach-o", link_section = "__TEXT,__custom")]
 #[unsafe(naked)]
 pub extern "C" fn compatible_ffi_attributes_1() {
     naked_asm!("", options(raw));

tests/ui/attributes/attr-on-mac-call.rs

@@ -27,7 +27,7 @@ fn main() {
     #[link_name = "x"]
     //~^ WARN attribute cannot be used on macro calls
     //~| WARN previously accepted
-    #[link_section = "x"]
+    #[link_section = "__TEXT,__text"]
     //~^ WARN attribute cannot be used on macro calls
     //~| WARN previously accepted
     #[link_ordinal(42)]

tests/ui/attributes/attr-on-mac-call.stderr

@@ -78,8 +78,8 @@ LL |     #[link_name = "x"]
 warning: `#[link_section]` attribute cannot be used on macro calls
   --> $DIR/attr-on-mac-call.rs:30:5
    |
-LL |     #[link_section = "x"]
-   |     ^^^^^^^^^^^^^^^^^^^^^
+LL |     #[link_section = "__TEXT,__text"]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = help: `#[link_section]` can be applied to functions and statics

tests/ui/attributes/codegen_attr_on_required_trait_method.rs

@@ -7,7 +7,7 @@ trait Test {
     //~^ ERROR cannot be used on required trait methods [unused_attributes]
     //~| WARN previously accepted
     fn method1(&self);
-    #[link_section = ".text"]
+    #[link_section = "__TEXT,__text"]
     //~^ ERROR cannot be used on required trait methods [unused_attributes]
     //~| WARN previously accepted
     fn method2(&self);

tests/ui/attributes/codegen_attr_on_required_trait_method.stderr

@@ -15,8 +15,8 @@ LL | #![deny(unused_attributes)]
 error: `#[link_section]` attribute cannot be used on required trait methods
   --> $DIR/codegen_attr_on_required_trait_method.rs:10:5
    |
-LL |     #[link_section = ".text"]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     #[link_section = "__TEXT,__text"]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = help: `#[link_section]` can be applied to functions, inherent methods, provided trait methods, statics, and trait methods in impl blocks

tests/ui/feature-gates/issue-43106-gating-of-builtin-attrs.rs

@@ -74,7 +74,7 @@
 //~| WARN previously accepted
 //~| HELP can be applied to
 //~| HELP remove the attribute
-#![link_section = "1800"]
+#![link_section = ",1800"]
 //~^ WARN attribute cannot be used on
 //~| WARN previously accepted
 //~| HELP can be applied to
@@ -616,66 +616,66 @@ mod link_name {
     //~| HELP remove the attribute
 }
 
-#[link_section = "1800"]
+#[link_section = ",1800"]
 //~^ WARN attribute cannot be used on
 //~| WARN previously accepted
 //~| HELP can be applied to
 //~| HELP remove the attribute
 mod link_section {
-    mod inner { #![link_section="1800"] }
+    mod inner { #![link_section=",1800"] }
     //~^ WARN attribute cannot be used on
     //~| WARN previously accepted
     //~| HELP can be applied to
     //~| HELP remove the attribute
 
-    #[link_section = "1800"] fn f() { }
+    #[link_section = ",1800"] fn f() { }
 
-    #[link_section = "1800"] struct S;
+    #[link_section = ",1800"] struct S;
     //~^ WARN attribute cannot be used on
     //~| WARN previously accepted
     //~| HELP can be applied to
     //~| HELP remove the attribute
 
-    #[link_section = "1800"] type T = S;
+    #[link_section = ",1800"] type T = S;
     //~^ WARN attribute cannot be used on
     //~| WARN previously accepted
     //~| HELP can be applied to
     //~| HELP remove the attribute
 
-    #[link_section = "1800"] impl S { }
+    #[link_section = ",1800"] impl S { }
     //~^ WARN attribute cannot be used on
     //~| WARN previously accepted
     //~| HELP can be applied to
     //~| HELP remove the attribute
 
-    #[link_section = "1800"]
+    #[link_section = ",1800"]
     //~^ WARN attribute cannot be used on
     //~| WARN previously accepted
     //~| HELP can be applied to
     //~| HELP remove the attribute
     trait Tr {
-        #[link_section = "1800"]
+        #[link_section = ",1800"]
         //~^ WARN attribute cannot be used on
         //~| WARN previously accepted
         //~| HELP can be applied to
         //~| HELP remove the attribute
         fn inside_tr_no_default(&self);
 
-        #[link_section = "1800"]
+        #[link_section = ",1800"]
         fn inside_tr_default(&self) { }
     }
 
     impl S {
-        #[link_section = "1800"]
+        #[link_section = ",1800"]
         fn inside_abc_123(&self) { }
     }
 
     impl Tr for S {
-        #[link_section = "1800"]
+        #[link_section = ",1800"]
         fn inside_tr_no_default(&self) { }
     }
 
-    #[link_section = "1800"]
+    #[link_section = ",1800"]
     fn should_always_link() { }
 }