Auto merge of #112000 - wesleywiser:safestack, r=Amanieu

Add support for LLVM SafeStack

Adds support for LLVM [SafeStack] which provides backward edge control
flow protection by separating the stack into two parts: data which is
only accessed in provable safe ways is allocated on the normal stack
(the "safe stack") and all other data is placed in a separate allocation
(the "unsafe stack").

SafeStack support is enabled by passing `-Zsanitizer=safestack`.

[SafeStack]: https://clang.llvm.org/docs/SafeStack.html

cc `@rcvalle` #39699

2 files changed, 4 insertions, 0 deletions

diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs
index 651d644ebb6..6d00464e0a0 100644
--- a/compiler/rustc_codegen_llvm/src/attributes.rs
+++ b/compiler/rustc_codegen_llvm/src/attributes.rs
@@ -88,6 +88,9 @@ pub fn sanitize_attrs<'ll>(
 
         attrs.push(llvm::AttributeKind::SanitizeMemTag.create_attr(cx.llcx));
     }
+    if enabled.contains(SanitizerSet::SAFESTACK) {
+        attrs.push(llvm::AttributeKind::SanitizeSafeStack.create_attr(cx.llcx));
+    }
     attrs
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index de93a64c0d6..6ef3418cc5f 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -196,6 +196,7 @@ pub enum AttributeKind {
     AllocSize = 37,
     AllocatedPointer = 38,
     AllocAlign = 39,
+    SanitizeSafeStack = 40,
 }
 
 /// LLVMIntPredicate