KCFI: Require -C panic=abort

While the KCFI scheme is not incompatible with unwinding, LLVM's
`invoke` instruction does not currently support KCFI bundles. While it
likely will in the near future, we won't be able to assume that in Rust
for a while.

compiler/rustc_session/messages.ftl

@@ -96,6 +96,8 @@ session_sanitizer_cfi_requires_lto = `-Zsanitizer=cfi` requires `-Clto` or `-Cli
 
 session_sanitizer_cfi_requires_single_codegen_unit = `-Zsanitizer=cfi` with `-Clto` requires `-Ccodegen-units=1`
 
+session_sanitizer_kcfi_requires_panic_abort = `-Z sanitizer=kcfi` requires `-C panic=abort`
+
 session_sanitizer_not_supported = {$us} sanitizer is not supported for this target
 
 session_sanitizers_not_supported = {$us} sanitizers are not supported for this target

compiler/rustc_session/src/errors.rs

@@ -145,6 +145,10 @@ pub(crate) struct CannotMixAndMatchSanitizers {
 #[diag(session_sanitizer_cfi_normalize_integers_requires_cfi)]
 pub(crate) struct SanitizerCfiNormalizeIntegersRequiresCfi;
 
+#[derive(Diagnostic)]
+#[diag(session_sanitizer_kcfi_requires_panic_abort)]
+pub(crate) struct SanitizerKcfiRequiresPanicAbort;
+
 #[derive(Diagnostic)]
 #[diag(session_split_lto_unit_requires_lto)]
 pub(crate) struct SplitLtoUnitRequiresLto;

compiler/rustc_session/src/session.rs

@@ -1234,6 +1234,11 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
         sess.dcx().emit_err(errors::SanitizerCfiRequiresLto);
     }
 
+    // KCFI requires panic=abort
+    if sess.is_sanitizer_kcfi_enabled() && sess.panic_strategy() != PanicStrategy::Abort {
+        sess.dcx().emit_err(errors::SanitizerKcfiRequiresPanicAbort);
+    }
+
     // LLVM CFI using rustc LTO requires a single codegen unit.
     if sess.is_sanitizer_cfi_enabled()
         && sess.lto() == config::Lto::Fat

tests/ui/sanitizer/cfg.rs

@@ -11,6 +11,7 @@
 //@[cfi]compile-flags:     -Clto -Ccodegen-units=1
 //@[kcfi]needs-llvm-components: x86
 //@[kcfi]compile-flags:    -Zsanitizer=kcfi    --cfg kcfi --target x86_64-unknown-none
+//@[kcfi]compile-flags:    -C panic=abort
 //@[leak]needs-sanitizer-leak
 //@[leak]compile-flags:    -Zsanitizer=leak    --cfg leak
 //@[memory]needs-sanitizer-memory

tests/ui/sanitizer/cfi-closure-fn-ptr-cast.rs

@@ -14,6 +14,7 @@
 //@ [cfi] compile-flags: -C codegen-units=1 -C lto -C prefer-dynamic=off -C opt-level=0
 //@ [cfi] compile-flags: -Z sanitizer=cfi
 //@ [kcfi] compile-flags: -Z sanitizer=kcfi
+//@ [kcfi] compile-flags: -C panic=abort -C prefer-dynamic=off
 //@ run-pass
 
 pub fn main() {

tests/ui/sanitizer/cfi-complex-receiver.rs

@@ -11,6 +11,7 @@
 //@ [cfi] compile-flags: -C codegen-units=1 -C lto -C prefer-dynamic=off -C opt-level=0
 //@ [cfi] compile-flags: -Z sanitizer=cfi
 //@ [kcfi] compile-flags: -Z sanitizer=kcfi
+//@ [kcfi] compile-flags: -C panic=abort -C prefer-dynamic=off
 //@ run-pass
 
 use std::sync::Arc;

tests/ui/sanitizer/cfi-self-ref.rs

@@ -9,6 +9,7 @@
 //@ [cfi] compile-flags: -C codegen-units=1 -C lto -C prefer-dynamic=off -C opt-level=0
 //@ [cfi] compile-flags: -Z sanitizer=cfi
 //@ [kcfi] compile-flags: -Z sanitizer=kcfi
+//@ [kcfi] compile-flags: -C panic=abort -C prefer-dynamic=off
 //@ run-pass
 
 use std::marker::PhantomData;

tests/ui/sanitizer/cfi-virtual-auto.rs

@@ -9,6 +9,7 @@
 //@ [cfi] compile-flags: -C codegen-units=1 -C lto -C prefer-dynamic=off -C opt-level=0
 //@ [cfi] compile-flags: -Z sanitizer=cfi
 //@ [kcfi] compile-flags: -Z sanitizer=kcfi
+//@ [kcfi] compile-flags: -C panic=abort -C prefer-dynamic=off
 //@ run-pass
 
 trait Foo {