Add LLVM CFI support to the Rust compiler

This commit adds LLVM Control Flow Integrity (CFI) support to the Rust
compiler. It initially provides forward-edge control flow protection for
Rust-compiled code only by aggregating function pointers in groups
identified by their number of arguments.

Forward-edge control flow protection for C or C++ and Rust -compiled
code "mixed binaries" (i.e., for when C or C++ and Rust -compiled code
share the same virtual address space) will be provided in later work as
part of this project by defining and using compatible type identifiers
(see Type metadata in the design document in the tracking issue #89653).

LLVM CFI can be enabled with -Zsanitizer=cfi and requires LTO (i.e.,
-Clto).

2 files changed, 15 insertions, 2 deletions

diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index b3d36b396c5..6f8f8b8f27e 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -351,8 +351,7 @@ mod desc {
     pub const parse_panic_strategy: &str = "either `unwind` or `abort`";
     pub const parse_opt_panic_strategy: &str = parse_panic_strategy;
     pub const parse_relro_level: &str = "one of: `full`, `partial`, or `off`";
-    pub const parse_sanitizers: &str =
-        "comma separated list of sanitizers: `address`, `hwaddress`, `leak`, `memory` or `thread`";
+    pub const parse_sanitizers: &str = "comma separated list of sanitizers: `address`, `cfi`, `hwaddress`, `leak`, `memory` 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`";
@@ -584,6 +583,7 @@ mod parse {
             for s in v.split(',') {
                 *slot |= match s {
                     "address" => SanitizerSet::ADDRESS,
+                    "cfi" => SanitizerSet::CFI,
                     "leak" => SanitizerSet::LEAK,
                     "memory" => SanitizerSet::MEMORY,
                     "thread" => SanitizerSet::THREAD,
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index b6ba6cc1dd6..0f6a3ddccba 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -672,6 +672,9 @@ impl Session {
     pub fn is_nightly_build(&self) -> bool {
         self.opts.unstable_features.is_nightly_build()
     }
+    pub fn is_sanitizer_cfi_enabled(&self) -> bool {
+        self.opts.debugging_opts.sanitizer.contains(SanitizerSet::CFI)
+    }
     pub fn overflow_checks(&self) -> bool {
         self.opts
             .cg
@@ -1398,6 +1401,16 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
                                 disable it using `-C target-feature=-crt-static`",
         );
     }
+
+    // LLVM CFI requires LTO.
+    if sess.is_sanitizer_cfi_enabled() {
+        if sess.opts.cg.lto == config::LtoCli::Unspecified
+            || sess.opts.cg.lto == config::LtoCli::No
+            || sess.opts.cg.lto == config::LtoCli::Thin
+        {
+            sess.err("`-Zsanitizer=cfi` requires `-Clto`");
+        }
+    }
 }
 
 /// Holds data on the current incremental compilation session, if there is one.