error on invalid macho section specifier

Author: folkertdev

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;
@@ -465,6 +466,29 @@ 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;
@@ -497,6 +521,18 @@ 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

@@ -1149,3 +1149,22 @@ pub(crate) struct UnknownToolInScopedLint {
     #[help("add `#![register_tool({$tool_name})]` to the crate root")]
     pub is_nightly_build: bool,
 }
+
+#[derive(Diagnostic)]
+#[diag("invalid macho section specifier")]
+pub(crate) struct InvalidMachoSection {
+    #[primary_span]
+    #[label("not a valid macho section specifier")]
+    pub name_span: Span,
+    #[subdiagnostic]
+    pub reason: InvalidMachoSectionReason,
+}
+
+#[derive(Subdiagnostic)]
+pub(crate) enum InvalidMachoSectionReason {
+    #[note("a macho section specifier requires a segment and a section, separated by a comma")]
+    #[help("an example of a valid macho section specifier is `__TEXT,__cstring`")]
+    MissingSection,
+    #[note("section name `{$section}` is longer than 16 bytes")]
+    SectionTooLong { section: String },
+}

compiler/rustc_hir/src/attrs/data_structures.rs

@@ -1229,8 +1229,8 @@ 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/naked-fn/naked-functions.rs

@@ -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_vendor = "apple"), link_section = ".text.some_different_name")]
+#[cfg_attr(target_vendor = "apple", link_section = "__TEXT,different")]
 pub extern "C" fn test_link_section() {
     cfg_select! {
         all(target_arch = "arm", target_feature = "thumb-mode") => {

tests/ui/linkage-attr/link-section-macho.rs

@@ -0,0 +1,58 @@
+//@ add-minicore
+//@ compile-flags: --target aarch64-apple-darwin
+//@ needs-llvm-components: aarch64
+//@ ignore-backends: gcc
+#![feature(no_core, rustc_attrs, lang_items)]
+#![no_core]
+#![crate_type = "lib"]
+
+extern crate minicore;
+use minicore::*;
+
+#[unsafe(link_section = "foo")]
+//~^ ERROR invalid macho section specifier
+#[unsafe(no_mangle)]
+fn missing_section() {}
+
+#[unsafe(link_section = "foo,")]
+//~^ ERROR invalid macho section specifier
+#[unsafe(no_mangle)]
+fn empty_section() {}
+
+#[unsafe(link_section = "foo, ")]
+//~^ ERROR invalid macho section specifier
+#[unsafe(no_mangle)]
+fn whitespace_section() {}
+
+#[unsafe(link_section = "foo,somelongwindedthing")]
+//~^ ERROR invalid macho section specifier
+#[unsafe(no_mangle)]
+fn section_too_long() {}
+
+#[unsafe(link_section = "foo,bar")]
+#[unsafe(no_mangle)]
+fn segment_and_section() {}
+
+#[unsafe(link_section = "foo,bar,")]
+#[unsafe(no_mangle)]
+fn segment_and_section_and_comma() {}
+
+#[unsafe(link_section = ",foo")]
+#[unsafe(no_mangle)]
+fn missing_segment_is_fine() {}
+
+#[unsafe(link_section = "__TEXT,__stubs,symbol_stubs,none,16")]
+#[unsafe(no_mangle)]
+fn stub_size_decimal() {}
+
+#[unsafe(link_section = "__TEXT,__stubs,symbol_stubs,none,0x10")]
+#[unsafe(no_mangle)]
+fn stub_size_hex() {}
+
+#[unsafe(link_section = "__TEXT,__stubs,symbol_stubs,none,020")]
+#[unsafe(no_mangle)]
+fn stub_size_oct() {}
+
+#[unsafe(link_section = "__TEXT,__stubs,symbol_stubs,none,020,rest,is,ignored")]
+#[unsafe(no_mangle)]
+fn rest_is_ignored() {}

tests/ui/linkage-attr/link-section-macho.stderr

@@ -0,0 +1,37 @@
+error: invalid macho section specifier
+  --> $DIR/link-section-macho.rs:12:25
+   |
+LL | #[unsafe(link_section = "foo")]
+   |                         ^^^^^ not a valid macho section specifier
+   |
+   = note: a macho section specifier requires a segment and a section, separated by a comma
+   = help: an example of a valid macho section specifier is `__TEXT,__cstring`
+
+error: invalid macho section specifier
+  --> $DIR/link-section-macho.rs:17:25
+   |
+LL | #[unsafe(link_section = "foo,")]
+   |                         ^^^^^^ not a valid macho section specifier
+   |
+   = note: a macho section specifier requires a segment and a section, separated by a comma
+   = help: an example of a valid macho section specifier is `__TEXT,__cstring`
+
+error: invalid macho section specifier
+  --> $DIR/link-section-macho.rs:22:25
+   |
+LL | #[unsafe(link_section = "foo, ")]
+   |                         ^^^^^^^ not a valid macho section specifier
+   |
+   = note: a macho section specifier requires a segment and a section, separated by a comma
+   = help: an example of a valid macho section specifier is `__TEXT,__cstring`
+
+error: invalid macho section specifier
+  --> $DIR/link-section-macho.rs:27:25
+   |
+LL | #[unsafe(link_section = "foo,somelongwindedthing")]
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^ not a valid macho section specifier
+   |
+   = note: section name `somelongwindedthing` is longer than 16 bytes
+
+error: aborting due to 4 previous errors
+