Allow disabling ASan instrumentation for globals

AddressSanitizer adds instrumentation to global variables unless the
[`no_sanitize_address`](https://llvm.org/docs/LangRef.html#global-attributes)
attribute is set on them.

This commit extends the existing `#[no_sanitize(address)]` attribute to
set this; previously it only had the desired effect on functions.

Author: BertalanD

compiler/rustc_codegen_llvm/src/base.rs

@@ -150,6 +150,15 @@ pub fn set_link_section(llval: &Value, attrs: &CodegenFnAttrs) {
     }
 }
 
+pub fn set_variable_sanitizer_attrs(llval: &Value, attrs: &CodegenFnAttrs) {
+    if attrs.no_sanitize.contains(SanitizerSet::ADDRESS) {
+        unsafe { llvm::LLVMRustSetNoSanitizeAddress(llval); }
+    }
+    if attrs.no_sanitize.contains(SanitizerSet::HWADDRESS) {
+        unsafe { llvm::LLVMRustSetNoSanitizeHWAddress(llval); }
+    }
+}
+
 pub fn linkage_to_llvm(linkage: Linkage) -> llvm::Linkage {
     match linkage {
         Linkage::External => llvm::Linkage::ExternalLinkage,

compiler/rustc_codegen_llvm/src/consts.rs

@@ -525,6 +525,8 @@ impl<'ll> CodegenCx<'ll, '_> {
                 base::set_link_section(g, attrs);
             }
 
+            base::set_variable_sanitizer_attrs(g, attrs);
+
             if attrs.flags.contains(CodegenFnAttrFlags::USED) {
                 // `USED` and `USED_LINKER` can't be used together.
                 assert!(!attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER));

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -2440,4 +2440,7 @@ extern "C" {
         callback: GetSymbolsCallback,
         error_callback: GetSymbolsErrorCallback,
     ) -> *mut c_void;
+
+    pub fn LLVMRustSetNoSanitizeAddress(Global: &Value);
+    pub fn LLVMRustSetNoSanitizeHWAddress(Global: &Value);
 }

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -2179,6 +2179,25 @@ extern "C" bool LLVMRustLLVMHasZstdCompressionForDebugSymbols() {
   return llvm::compression::zstd::isAvailable();
 }
 
+extern "C" void LLVMRustSetNoSanitizeAddress(LLVMValueRef Global) {
+  GlobalValue &GV = *unwrap<GlobalValue>(Global);
+  GlobalValue::SanitizerMetadata MD;
+  if (GV.hasSanitizerMetadata())
+    MD = GV.getSanitizerMetadata();
+  MD.NoAddress = true;
+  MD.IsDynInit = false;
+  GV.setSanitizerMetadata(MD);
+}
+
+extern "C" void LLVMRustSetNoSanitizeHWAddress(LLVMValueRef Global) {
+  GlobalValue &GV = *unwrap<GlobalValue>(Global);
+  GlobalValue::SanitizerMetadata MD;
+  if (GV.hasSanitizerMetadata())
+    MD = GV.getSanitizerMetadata();
+  MD.NoHWAddress = true;
+  GV.setSanitizerMetadata(MD);
+}
+
 // Operations on composite constants.
 // These are clones of LLVM api functions that will become available in future
 // releases. They can be removed once Rust's minimum supported LLVM version

tests/codegen/sanitizer/no-sanitize.rs

@@ -7,6 +7,16 @@
 #![crate_type = "lib"]
 #![feature(no_sanitize)]
 
+// CHECK:     @UNSANITIZED = constant{{.*}} no_sanitize_address
+// CHECK-NOT: @__asan_global_UNSANITIZED
+#[no_mangle]
+#[no_sanitize(address)]
+pub static UNSANITIZED: u32 = 0;
+
+// CHECK: @__asan_global_SANITIZED
+#[no_mangle]
+pub static SANITIZED: u32 = 0;
+
 // CHECK-LABEL: ; no_sanitize::unsanitized
 // CHECK-NEXT:  ; Function Attrs:
 // CHECK-NOT:   sanitize_address