Add ShadowCallStack Support

Adds support for the LLVM ShadowCallStack sanitizer.

Author: ivanloz

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -69,6 +69,9 @@ pub fn sanitize_attrs<'ll>(
     if enabled.contains(SanitizerSet::HWADDRESS) {
         attrs.push(llvm::AttributeKind::SanitizeHWAddress.create_attr(cx.llcx));
     }
+    if enabled.contains(SanitizerSet::SHADOWCALLSTACK) {
+        attrs.push(llvm::AttributeKind::ShadowCallStack.create_attr(cx.llcx));
+    }
     if enabled.contains(SanitizerSet::MEMTAG) {
         // Check to make sure the mte target feature is actually enabled.
         let features = cx.tcx.global_backend_features(());

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -192,6 +192,7 @@ pub enum AttributeKind {
     NoUndef = 33,
     SanitizeMemTag = 34,
     NoCfCheck = 35,
+    ShadowCallStack = 36,
 }
 
 /// LLVMIntPredicate

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;

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");
 }

compiler/rustc_session/src/options.rs

@@ -377,7 +377,7 @@ mod desc {
     pub const parse_opt_panic_strategy: &str = parse_panic_strategy;
     pub const parse_oom_strategy: &str = "either `panic` or `abort`";
     pub const parse_relro_level: &str = "one of: `full`, `partial`, or `off`";
-    pub const parse_sanitizers: &str = "comma separated list of sanitizers: `address`, `cfi`, `hwaddress`, `leak`, `memory`, `memtag`, or `thread`";
+    pub const parse_sanitizers: &str = "comma separated list of sanitizers: `address`, `cfi`, `hwaddress`, `leak`, `memory`, `memtag`, `shadow-call-stack`, or `thread`";
     pub const parse_sanitizer_memory_track_origins: &str = "0, 1, or 2";
     pub const parse_cfguard: &str =
         "either a boolean (`yes`, `no`, `on`, `off`, etc), `checks`, or `nochecks`";
@@ -683,6 +683,7 @@ mod parse {
                     "leak" => SanitizerSet::LEAK,
                     "memory" => SanitizerSet::MEMORY,
                     "memtag" => SanitizerSet::MEMTAG,
+                    "shadow-call-stack" => SanitizerSet::SHADOWCALLSTACK,
                     "thread" => SanitizerSet::THREAD,
                     "hwaddress" => SanitizerSet::HWADDRESS,
                     _ => return false,

compiler/rustc_span/src/symbol.rs

@@ -1282,6 +1282,7 @@ symbols! {
         self_in_typedefs,
         self_struct_ctor,
         semitransparent,
+        shadow_call_stack,
         shl,
         shl_assign,
         should_panic,

compiler/rustc_target/src/spec/aarch64_linux_android.rs

@@ -17,6 +17,7 @@ pub fn target() -> Target {
             supported_sanitizers: SanitizerSet::CFI
                 | SanitizerSet::HWADDRESS
                 | SanitizerSet::MEMTAG
+                | SanitizerSet::SHADOWCALLSTACK
                 | SanitizerSet::ADDRESS,
             ..super::android_base::opts()
         },

compiler/rustc_target/src/spec/mod.rs

@@ -618,6 +618,7 @@ bitflags::bitflags! {
         const HWADDRESS = 1 << 4;
         const CFI     = 1 << 5;
         const MEMTAG  = 1 << 6;
+        const SHADOWCALLSTACK = 1 << 7;
     }
 }
 
@@ -632,6 +633,7 @@ impl SanitizerSet {
             SanitizerSet::LEAK => "leak",
             SanitizerSet::MEMORY => "memory",
             SanitizerSet::MEMTAG => "memtag",
+            SanitizerSet::SHADOWCALLSTACK => "shadow-call-stack",
             SanitizerSet::THREAD => "thread",
             SanitizerSet::HWADDRESS => "hwaddress",
             _ => return None,
@@ -666,6 +668,7 @@ impl IntoIterator for SanitizerSet {
             SanitizerSet::LEAK,
             SanitizerSet::MEMORY,
             SanitizerSet::MEMTAG,
+            SanitizerSet::SHADOWCALLSTACK,
             SanitizerSet::THREAD,
             SanitizerSet::HWADDRESS,
         ]
@@ -1960,6 +1963,7 @@ impl Target {
                                 Some("leak") => SanitizerSet::LEAK,
                                 Some("memory") => SanitizerSet::MEMORY,
                                 Some("memtag") => SanitizerSet::MEMTAG,
+                                Some("shadow-call-stack") => SanitizerSet::SHADOWCALLSTACK,
                                 Some("thread") => SanitizerSet::THREAD,
                                 Some("hwaddress") => SanitizerSet::HWADDRESS,
                                 Some(s) => return Err(format!("unknown sanitizer {}", s)),

compiler/rustc_typeck/src/collect.rs

@@ -2939,14 +2939,16 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: DefId) -> CodegenFnAttrs {
                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
                     } else if item.has_name(sym::memtag) {
                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMTAG;
+                    } else if item.has_name(sym::shadow_call_stack) {
+                        codegen_fn_attrs.no_sanitize |= SanitizerSet::SHADOWCALLSTACK;
                     } else if item.has_name(sym::thread) {
                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
                     } else if item.has_name(sym::hwaddress) {
                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
                     } else {
                         tcx.sess
                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
-                            .note("expected one of: `address`, `cfi`, `hwaddress`, `memory`, `memtag`, or `thread`")
+                            .note("expected one of: `address`, `cfi`, `hwaddress`, `memory`, `memtag`, `shadow-call-stack`, or `thread`")
                             .emit();
                     }
                 }

src/doc/unstable-book/src/compiler-flags/sanitizer.md

@@ -18,11 +18,13 @@ This feature allows for use of one of following sanitizers:
 * [MemorySanitizer][clang-msan] a detector of uninitialized reads.
 * [MemTagSanitizer][clang-memtag] fast memory error detector based on
   Armv8.5-A Memory Tagging Extension.
+* [ShadowCallStack][clang-scs] provides backward-edge control flow protection.
 * [ThreadSanitizer][clang-tsan] a fast data race detector.
 
 To enable a sanitizer compile with `-Zsanitizer=address`,`-Zsanitizer=cfi`,
 `-Zsanitizer=hwaddress`, `-Zsanitizer=leak`, `-Zsanitizer=memory`,
-`-Zsanitizer=memtag`, or `-Zsanitizer=thread`. You might also need the `--target` and `build-std` flags. Example:
+`-Zsanitizer=memtag`, `-Zsanitizer=shadow-call-stack`, or `-Zsanitizer=thread`.
+You might also need the `--target` and `build-std` flags. Example:
 ```shell
 $ RUSTFLAGS=-Zsanitizer=address cargo build -Zbuild-std --target x86_64-unknown-linux-gnu
 ```
@@ -513,6 +515,18 @@ To enable this target feature compile with `-C target-feature="+mte"`.
 
 More information can be found in the associated [LLVM documentation](https://llvm.org/docs/MemTagSanitizer.html).
 
+# ShadowCallStack
+
+ShadowCallStack provides backward edge control flow protection by storing a function's return address in a separately allocated 'shadow call stack' and loading the return address from that shadow call stack.
+
+ShadowCallStack requires a platform ABI which reserves `x18` as the instrumentation makes use of this register.
+
+ShadowCallStack can be enabled with `-Zsanitizer=shadow-call-stack` option and is supported on the following targets:
+
+* `aarch64-linux-android`
+
+A runtime must be provided by the application or operating system. See the [LLVM documentation][clang-scs] for further details.
+
 # ThreadSanitizer
 
 ThreadSanitizer is a data race detection tool. It is supported on the following
@@ -610,4 +624,5 @@ Sanitizers produce symbolized stacktraces when llvm-symbolizer binary is in `PAT
 [clang-hwasan]: https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
 [clang-lsan]: https://clang.llvm.org/docs/LeakSanitizer.html
 [clang-msan]: https://clang.llvm.org/docs/MemorySanitizer.html
+[clang-scs]: https://clang.llvm.org/docs/ShadowCallStack.html
 [clang-tsan]: https://clang.llvm.org/docs/ThreadSanitizer.html