Index: compiler-rt/trunk/cmake/config-ix.cmake
===================================================================
--- compiler-rt/trunk/cmake/config-ix.cmake
+++ compiler-rt/trunk/cmake/config-ix.cmake
@@ -109,6 +109,7 @@
   check_symbol_exists(__i386__ "" __I386)
   check_symbol_exists(__mips__ "" __MIPS)
   check_symbol_exists(__mips64__ "" __MIPS64)
+  check_symbol_exists(__s390x__ "" __S390X)
   check_symbol_exists(__wasm32__ "" __WEBASSEMBLY32)
   check_symbol_exists(__wasm64__ "" __WEBASSEMBLY64)
   if(__ARM)
@@ -125,6 +126,8 @@
     add_default_target_arch(mips64)
   elseif(__MIPS)
     add_default_target_arch(mips)
+  elseif(__S390X)
+    add_default_target_arch(s390x)
   elseif(__WEBASSEMBLY32)
     add_default_target_arch(wasm32)
   elseif(__WEBASSEMBLY64)
@@ -188,6 +191,8 @@
     else()
       test_target_arch(powerpc64le "" "-m64")
     endif()
+  elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "s390x")
+    test_target_arch(s390x "" "")
   elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "mipsel|mips64el")
     # Gcc doesn't accept -m32/-m64 so we do the next best thing and use
     # -mips32r2/-mips64r2. We don't use -mips1/-mips3 because we want to match
@@ -238,6 +243,7 @@
 set(MIPS32 mips mipsel)
 set(MIPS64 mips64 mips64el)
 set(PPC64 powerpc64 powerpc64le)
+set(S390X s390x)
 set(WASM32 wasm32)
 set(WASM64 wasm64)
 
@@ -250,7 +256,7 @@
 set(ALL_BUILTIN_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64}
     ${MIPS32} ${MIPS64} ${WASM32} ${WASM64})
 set(ALL_SANITIZER_COMMON_SUPPORTED_ARCH ${X86} ${X86_64} ${PPC64}
-    ${ARM32} ${ARM64} ${MIPS32} ${MIPS64})
+    ${ARM32} ${ARM64} ${MIPS32} ${MIPS64} ${S390X})
 set(ALL_ASAN_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64}
     ${MIPS32} ${MIPS64} ${PPC64})
 set(ALL_DFSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64})
@@ -260,7 +266,7 @@
     ${MIPS32} ${MIPS64})
 set(ALL_TSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64} ${PPC64})
 set(ALL_UBSAN_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64}
-    ${MIPS32} ${MIPS64} ${PPC64})
+    ${MIPS32} ${MIPS64} ${PPC64} ${S390X})
 set(ALL_SAFESTACK_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM64} ${MIPS32} ${MIPS64})
 set(ALL_CFI_SUPPORTED_ARCH ${X86} ${X86_64})
 
Index: compiler-rt/trunk/lib/ubsan/ubsan_platform.h
===================================================================
--- compiler-rt/trunk/lib/ubsan/ubsan_platform.h
+++ compiler-rt/trunk/lib/ubsan/ubsan_platform.h
@@ -16,7 +16,8 @@
 // Other platforms should be easy to add, and probably work as-is.
 #if (defined(__linux__) || defined(__FreeBSD__) || defined(__APPLE__)) && \
     (defined(__x86_64__) || defined(__i386__) || defined(__arm__) || \
-     defined(__aarch64__) || defined(__mips__) || defined(__powerpc64__))
+     defined(__aarch64__) || defined(__mips__) || defined(__powerpc64__) || \
+     defined(__s390__))
 # define CAN_SANITIZE_UB 1
 #elif defined(_WIN32)
 # define CAN_SANITIZE_UB 1