Relax restrictions on multiple sanitizers

Most combinations of LLVM sanitizers are legal-enough to enable
simultaneously. This change will allow simultaneously enabling ASAN and
shadow call stacks on supported platforms.

Author: djkoloski

compiler/rustc_session/src/session.rs

@@ -1181,9 +1181,9 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
             });
         }
     }
-    // Cannot mix and match sanitizers.
-    let mut sanitizer_iter = sess.opts.unstable_opts.sanitizer.into_iter();
-    if let (Some(first), Some(second)) = (sanitizer_iter.next(), sanitizer_iter.next()) {
+
+    // Cannot mix and match mutually-exclusive sanitizers.
+    if let Some((first, second)) = sess.opts.unstable_opts.sanitizer.mutually_exclusive() {
         sess.dcx().emit_err(errors::CannotMixAndMatchSanitizers {
             first: first.to_string(),
             second: second.to_string(),
@@ -1218,14 +1218,6 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
         sess.dcx().emit_err(errors::SanitizerCfiRequiresSingleCodegenUnit);
     }
 
-    // LLVM CFI is incompatible with LLVM KCFI.
-    if sess.is_sanitizer_cfi_enabled() && sess.is_sanitizer_kcfi_enabled() {
-        sess.dcx().emit_err(errors::CannotMixAndMatchSanitizers {
-            first: "cfi".to_string(),
-            second: "kcfi".to_string(),
-        });
-    }
-
     // Canonical jump tables requires CFI.
     if sess.is_sanitizer_cfi_canonical_jump_tables_disabled() {
         if !sess.is_sanitizer_cfi_enabled() {

compiler/rustc_target/src/spec/mod.rs

@@ -1316,6 +1316,32 @@ bitflags::bitflags! {
 rustc_data_structures::external_bitflags_debug! { SanitizerSet }
 
 impl SanitizerSet {
+    const MUTUALLY_EXCLUSIVE: &'static [(SanitizerSet, SanitizerSet)] = &[
+        (SanitizerSet::MEMORY, SanitizerSet::ADDRESS),
+        (SanitizerSet::MEMORY, SanitizerSet::LEAK),
+        (SanitizerSet::THREAD, SanitizerSet::ADDRESS),
+        (SanitizerSet::THREAD, SanitizerSet::LEAK),
+        (SanitizerSet::THREAD, SanitizerSet::MEMORY),
+        (SanitizerSet::HWADDRESS, SanitizerSet::ADDRESS),
+        (SanitizerSet::HWADDRESS, SanitizerSet::MEMORY),
+        (SanitizerSet::HWADDRESS, SanitizerSet::THREAD),
+        (SanitizerSet::MEMTAG, SanitizerSet::ADDRESS),
+        (SanitizerSet::MEMTAG, SanitizerSet::HWADDRESS),
+        (SanitizerSet::KCFI, SanitizerSet::CFI),
+        (SanitizerSet::KERNELADDRESS, SanitizerSet::ADDRESS),
+        (SanitizerSet::KERNELADDRESS, SanitizerSet::LEAK),
+        (SanitizerSet::KERNELADDRESS, SanitizerSet::MEMORY),
+        (SanitizerSet::KERNELADDRESS, SanitizerSet::THREAD),
+        (SanitizerSet::KERNELADDRESS, SanitizerSet::HWADDRESS),
+        (SanitizerSet::KERNELADDRESS, SanitizerSet::MEMTAG),
+        (SanitizerSet::SAFESTACK, SanitizerSet::ADDRESS),
+        (SanitizerSet::SAFESTACK, SanitizerSet::LEAK),
+        (SanitizerSet::SAFESTACK, SanitizerSet::MEMORY),
+        (SanitizerSet::SAFESTACK, SanitizerSet::THREAD),
+        (SanitizerSet::SAFESTACK, SanitizerSet::HWADDRESS),
+        (SanitizerSet::SAFESTACK, SanitizerSet::KERNELADDRESS),
+    ];
+
     /// Return sanitizer's name
     ///
     /// Returns none if the flags is a set of sanitizers numbering not exactly one.
@@ -1336,6 +1362,13 @@ impl SanitizerSet {
             _ => return None,
         })
     }
+
+    pub fn mutually_exclusive(self) -> Option<(SanitizerSet, SanitizerSet)> {
+        Self::MUTUALLY_EXCLUSIVE
+            .into_iter()
+            .find(|&(a, b)| self.contains(*a) && self.contains(*b))
+            .copied()
+    }
 }
 
 /// Formats a sanitizer set as a comma separated list of sanitizers' names.