diff --git a/compiler-rt/lib/msan/msan_interceptors.cpp b/compiler-rt/lib/msan/msan_interceptors.cpp
--- a/compiler-rt/lib/msan/msan_interceptors.cpp
+++ b/compiler-rt/lib/msan/msan_interceptors.cpp
@@ -401,11 +401,25 @@
   __msan_unpoison(endptr, sizeof(*endptr));         \
   return res;
 
+// On s390x, long double return values are passed via implicit reference,
+// which needs to be unpoisoned.  We make the implicit pointer explicit.
+#define INTERCEPTOR_STRTO_SRET_BODY(func, sret, ...) \
+  ENSURE_MSAN_INITED();                              \
+  REAL(func)(sret, __VA_ARGS__);                     \
+  __msan_unpoison(sret, sizeof(*sret));              \
+  __msan_unpoison(endptr, sizeof(*endptr));
+
 #define INTERCEPTOR_STRTO(ret_type, func, char_type)                       \
   INTERCEPTOR(ret_type, func, const char_type *nptr, char_type **endptr) { \
     INTERCEPTOR_STRTO_BODY(ret_type, func, nptr, endptr);                  \
   }
 
+#define INTERCEPTOR_STRTO_SRET(ret_type, func, char_type)                \
+  INTERCEPTOR(void, func, ret_type *sret, const char_type *nptr,         \
+              char_type **endptr) {                                      \
+    INTERCEPTOR_STRTO_SRET_BODY(func, sret, nptr, endptr);               \
+  }
+
 #define INTERCEPTOR_STRTO_BASE(ret_type, func, char_type)                \
   INTERCEPTOR(ret_type, func, const char_type *nptr, char_type **endptr, \
               int base) {                                                \
@@ -418,6 +432,12 @@
     INTERCEPTOR_STRTO_BODY(ret_type, func, nptr, endptr, loc);           \
   }
 
+#define INTERCEPTOR_STRTO_SRET_LOC(ret_type, func, char_type)            \
+  INTERCEPTOR(void, func, ret_type *sret, const char_type *nptr,         \
+              char_type **endptr, void *loc) {                           \
+    INTERCEPTOR_STRTO_SRET_BODY(func, sret, nptr, endptr, loc);          \
+  }
+
 #define INTERCEPTOR_STRTO_BASE_LOC(ret_type, func, char_type)            \
   INTERCEPTOR(ret_type, func, const char_type *nptr, char_type **endptr, \
               int base, void *loc) {                                     \
@@ -429,6 +449,10 @@
   INTERCEPTOR_STRTO(ret_type, func, char_type)             \
   INTERCEPTOR_STRTO_LOC(ret_type, func##_l, char_type)
 
+#define INTERCEPTORS_STRTO_SRET(ret_type, func, char_type)      \
+  INTERCEPTOR_STRTO_SRET(ret_type, func, char_type)             \
+  INTERCEPTOR_STRTO_SRET_LOC(ret_type, func##_l, char_type)
+
 #define INTERCEPTORS_STRTO_BASE(ret_type, func, char_type)      \
   INTERCEPTOR_STRTO_BASE(ret_type, func, char_type)             \
   INTERCEPTOR_STRTO_BASE_LOC(ret_type, func##_l, char_type)
@@ -440,6 +464,12 @@
   INTERCEPTOR_STRTO_LOC(ret_type, __##func##_l, char_type) \
   INTERCEPTOR_STRTO_LOC(ret_type, __##func##_internal, char_type)
 
+#define INTERCEPTORS_STRTO_SRET(ret_type, func, char_type)      \
+  INTERCEPTOR_STRTO_SRET(ret_type, func, char_type)             \
+  INTERCEPTOR_STRTO_SRET_LOC(ret_type, func##_l, char_type)     \
+  INTERCEPTOR_STRTO_SRET_LOC(ret_type, __##func##_l, char_type) \
+  INTERCEPTOR_STRTO_SRET_LOC(ret_type, __##func##_internal, char_type)
+
 #define INTERCEPTORS_STRTO_BASE(ret_type, func, char_type)      \
   INTERCEPTOR_STRTO_BASE(ret_type, func, char_type)             \
   INTERCEPTOR_STRTO_BASE_LOC(ret_type, func##_l, char_type)     \
@@ -449,7 +479,11 @@
 
 INTERCEPTORS_STRTO(double, strtod, char)
 INTERCEPTORS_STRTO(float, strtof, char)
+#ifdef __s390x__
+INTERCEPTORS_STRTO_SRET(long double, strtold, char)
+#else
 INTERCEPTORS_STRTO(long double, strtold, char)
+#endif
 INTERCEPTORS_STRTO_BASE(long, strtol, char)
 INTERCEPTORS_STRTO_BASE(long long, strtoll, char)
 INTERCEPTORS_STRTO_BASE(unsigned long, strtoul, char)
@@ -458,7 +492,11 @@
 
 INTERCEPTORS_STRTO(double, wcstod, wchar_t)
 INTERCEPTORS_STRTO(float, wcstof, wchar_t)
+#ifdef __s390x__
+INTERCEPTORS_STRTO_SRET(long double, wcstold, wchar_t)
+#else
 INTERCEPTORS_STRTO(long double, wcstold, wchar_t)
+#endif
 INTERCEPTORS_STRTO_BASE(long, wcstol, wchar_t)
 INTERCEPTORS_STRTO_BASE(long long, wcstoll, wchar_t)
 INTERCEPTORS_STRTO_BASE(unsigned long, wcstoul, wchar_t)
@@ -467,7 +505,11 @@
 #if SANITIZER_GLIBC
 INTERCEPTORS_STRTO(double, __isoc23_strtod, char)
 INTERCEPTORS_STRTO(float, __isoc23_strtof, char)
+#ifdef __s390x__
+INTERCEPTORS_STRTO_SRET(long double, __isoc23_strtold, char)
+#else
 INTERCEPTORS_STRTO(long double, __isoc23_strtold, char)
+#endif
 INTERCEPTORS_STRTO_BASE(long, __isoc23_strtol, char)
 INTERCEPTORS_STRTO_BASE(long long, __isoc23_strtoll, char)
 INTERCEPTORS_STRTO_BASE(unsigned long, __isoc23_strtoul, char)
@@ -476,7 +518,11 @@
 
 INTERCEPTORS_STRTO(double, __isoc23_wcstod, wchar_t)
 INTERCEPTORS_STRTO(float, __isoc23_wcstof, wchar_t)
+#ifdef __s390x__
+INTERCEPTORS_STRTO_SRET(long double, __isoc23_wcstold, wchar_t)
+#else
 INTERCEPTORS_STRTO(long double, __isoc23_wcstold, wchar_t)
+#endif
 INTERCEPTORS_STRTO_BASE(long, __isoc23_wcstol, wchar_t)
 INTERCEPTORS_STRTO_BASE(long long, __isoc23_wcstoll, wchar_t)
 INTERCEPTORS_STRTO_BASE(unsigned long, __isoc23_wcstoul, wchar_t)
@@ -493,6 +539,12 @@
   INTERCEPT_FUNCTION(func##_l); \
   INTERCEPT_FUNCTION(__##func##_l); \
   INTERCEPT_FUNCTION(__##func##_internal);
+
+#define INTERCEPT_STRTO_VER(func, ver) \
+  INTERCEPT_FUNCTION_VER(func, ver); \
+  INTERCEPT_FUNCTION_VER(func##_l, ver); \
+  INTERCEPT_FUNCTION_VER(__##func##_l, ver); \
+  INTERCEPT_FUNCTION_VER(__##func##_internal, ver);
 #endif
 
 
@@ -1754,7 +1806,11 @@
   INTERCEPT_FUNCTION(strncat);
   INTERCEPT_STRTO(strtod);
   INTERCEPT_STRTO(strtof);
+#ifdef SANITIZER_NLDBL_VERSION
+  INTERCEPT_STRTO_VER(strtold, SANITIZER_NLDBL_VERSION);
+#else
   INTERCEPT_STRTO(strtold);
+#endif
   INTERCEPT_STRTO(strtol);
   INTERCEPT_STRTO(strtoul);
   INTERCEPT_STRTO(strtoll);
@@ -1762,7 +1818,11 @@
   INTERCEPT_STRTO(strtouq);
   INTERCEPT_STRTO(wcstod);
   INTERCEPT_STRTO(wcstof);
+#ifdef SANITIZER_NLDBL_VERSION
+  INTERCEPT_STRTO_VER(wcstold, SANITIZER_NLDBL_VERSION);
+#else
   INTERCEPT_STRTO(wcstold);
+#endif
   INTERCEPT_STRTO(wcstol);
   INTERCEPT_STRTO(wcstoul);
   INTERCEPT_STRTO(wcstoll);