Auto merge of #98208 - ivanloz:master, r=nagisa

Add support for LLVM ShadowCallStack.

LLVMs ShadowCallStack provides backward edge control flow integrity protection by using a separate shadow stack to store and retrieve a function's return address.

LLVM currently only supports this for AArch64 targets. The x18 register is used to hold the pointer to the shadow stack, and therefore this only works on ABIs which reserve x18. Further details are available in the [LLVM ShadowCallStack](https://clang.llvm.org/docs/ShadowCallStack.html) docs.

# Usage
`-Zsanitizer=shadow-call-stack`

# Comments/Caveats
* Currently only enabled for the aarch64-linux-android target
* Requires the platform to define a runtime to initialize the shadow stack, see the [LLVM docs](https://clang.llvm.org/docs/ShadowCallStack.html) for more detail.

2 files changed, 3 insertions, 0 deletions

diff --git a/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h b/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h
index 9fe84a6309b..bca5425e728 100644
--- a/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h
+++ b/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h
@@ -85,6 +85,7 @@ enum LLVMRustAttribute {
   NoUndef = 33,
   SanitizeMemTag = 34,
   NoCfCheck = 35,
+  ShadowCallStack = 36,
 };
 
 typedef struct OpaqueRustString *RustStringRef;
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index 2d35ee8976e..4615558b912 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -232,6 +232,8 @@ static Attribute::AttrKind fromRust(LLVMRustAttribute Kind) {
     return Attribute::NoUndef;
   case SanitizeMemTag:
     return Attribute::SanitizeMemTag;
+  case ShadowCallStack:
+    return Attribute::ShadowCallStack;
   }
   report_fatal_error("bad AttributeKind");
 }