aarch64: Fix async_fibre_swapcontext() on clang BTI builds

Reverting to using swapcontext() when compiling with clang on BTI-enabled builds fixes the BTI setjmp() failure seen when running asynctest. The issue with setjmp/longjmp is a known clang bug: see llvm/llvm-project#48888 Change-Id: I6eeaaa2e15f402789f1b3e742038f84bef846e29 Reviewed-by: Matt Caswell <matt@openssl.org> Reviewed-by: Paul Dale <pauli@openssl.org> (Merged from #17698) (cherry picked from commit d2d2401)
openssl · Feb 28, 2022 · f5ec705 · f5ec705
1 parent f609d94
commit f5ec705
Showing 1 changed file with 12 additions and 0 deletions.
diff --git a/crypto/async/arch/async_posix.h b/crypto/async/arch/async_posix.h
@@ -36,6 +36,18 @@
  */
 #   define USE_SWAPCONTEXT
 #  endif
+#  if defined(__aarch64__) && defined(__clang__) \
+    && defined(__ARM_FEATURE_BTI_DEFAULT) && __ARM_FEATURE_BTI_DEFAULT == 1
+/*
+ * setjmp/longjmp don't currently work with BTI on all libc implementations
+ * when compiled by clang. This is because clang doesn't put a BTI after the
+ * call to setjmp where it returns the second time. This then fails on libc
+ * implementations - notably glibc - which use an indirect jump to there.
+ * So use the swapcontext implementation, which does work.
+ * See https://github.com/llvm/llvm-project/issues/48888.
+ */
+#   define USE_SWAPCONTEXT
+#  endif
 #  include <ucontext.h>
 #  ifndef USE_SWAPCONTEXT
 #   include <setjmp.h>