diff --git a/compiler-rt/include/sanitizer/linux_syscall_hooks.h b/compiler-rt/include/sanitizer/linux_syscall_hooks.h
--- a/compiler-rt/include/sanitizer/linux_syscall_hooks.h
+++ b/compiler-rt/include/sanitizer/linux_syscall_hooks.h
@@ -3077,6 +3077,8 @@
                                                long oldact, long sz);
 void __sanitizer_syscall_post_impl_rt_sigaction(long res, long signum, long act,
                                                 long oldact, long sz);
+void __sanitizer_syscall_pre_impl_sigaltstack(long ss, long oss);
+void __sanitizer_syscall_post_impl_sigaltstack(long res, long ss, long oss);
 #ifdef __cplusplus
 }  // extern "C"
 #endif
diff --git a/compiler-rt/test/msan/Linux/syscalls.cpp b/compiler-rt/test/msan/Linux/syscalls.cpp
--- a/compiler-rt/test/msan/Linux/syscalls.cpp
+++ b/compiler-rt/test/msan/Linux/syscalls.cpp
@@ -8,6 +8,7 @@
 #include <string.h>
 
 #include <linux/aio_abi.h>
+#include <signal.h>
 #include <sys/ptrace.h>
 #include <sys/stat.h>
 #include <sys/uio.h>
@@ -123,5 +124,9 @@
   __sanitizer_syscall_post_socketpair(0, 0, 0, 0, (int *)buf);
   assert(__msan_test_shadow(buf, sizeof(buf)) == 2 * sizeof(int));
 
+  __msan_poison(buf, sizeof(buf));
+  __sanitizer_syscall_post_sigaltstack(0, nullptr, (stack_t *)buf);
+  assert(__msan_test_shadow(buf, sizeof(buf)) == sizeof(stack_t));
+
   return 0;
 }