diff --git a/clang/tools/clang-format/ClangFormat.cpp b/clang/tools/clang-format/ClangFormat.cpp
index feb733fe3c9e0..01f7c6047726e 100644
--- a/clang/tools/clang-format/ClangFormat.cpp
+++ b/clang/tools/clang-format/ClangFormat.cpp
@@ -413,8 +413,9 @@ static bool format(StringRef FileName, bool ErrorOnIncompleteFormat = false) {
   // On Windows, overwriting a file with an open file mapping doesn't work,
   // so read the whole file into memory when formatting in-place.
   ErrorOr<std::unique_ptr<MemoryBuffer>> CodeOrErr =
-      !OutputXML && Inplace ? MemoryBuffer::getFileAsStream(FileName)
-                            : MemoryBuffer::getFileOrSTDIN(FileName);
+      !OutputXML && Inplace
+          ? MemoryBuffer::getFileAsStream(FileName)
+          : MemoryBuffer::getFileOrSTDIN(FileName, /*IsText=*/true);
   if (std::error_code EC = CodeOrErr.getError()) {
     errs() << EC.message() << "\n";
     return true;
@@ -558,7 +559,7 @@ static int dumpConfig() {
     // Read in the code in case the filename alone isn't enough to detect the
     // language.
     ErrorOr<std::unique_ptr<MemoryBuffer>> CodeOrErr =
-        MemoryBuffer::getFileOrSTDIN(FileNames[0]);
+        MemoryBuffer::getFileOrSTDIN(FileNames[0], /*IsText=*/true);
     if (std::error_code EC = CodeOrErr.getError()) {
       llvm::errs() << EC.message() << "\n";
       return 1;
diff --git a/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp b/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
index c3015d895230e..40ee59c014b09 100644
--- a/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
+++ b/llvm/lib/ToolDrivers/llvm-lib/LibDriver.cpp
@@ -95,7 +95,8 @@ static std::vector<StringRef> getSearchPaths(opt::InputArgList *Args,
 
 // Opens a file. Path has to be resolved already. (used for def file)
 std::unique_ptr<MemoryBuffer> openFile(const Twine &Path) {
-  ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> MB = MemoryBuffer::getFile(Path);
+  ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> MB =
+      MemoryBuffer::getFile(Path, /*IsText=*/true);
 
   if (std::error_code EC = MB.getError()) {
     llvm::errs() << "cannot open file " << Path << ": " << EC.message() << "\n";
diff --git a/llvm/tools/llvm-cxxmap/llvm-cxxmap.cpp b/llvm/tools/llvm-cxxmap/llvm-cxxmap.cpp
index 6a5646965df2c..c5ccd64f11653 100644
--- a/llvm/tools/llvm-cxxmap/llvm-cxxmap.cpp
+++ b/llvm/tools/llvm-cxxmap/llvm-cxxmap.cpp
@@ -144,15 +144,18 @@ int main(int argc, const char *argv[]) {
   cl::HideUnrelatedOptions({&CXXMapCategory, &getColorCategory()});
   cl::ParseCommandLineOptions(argc, argv, "LLVM C++ mangled name remapper\n");
 
-  auto OldSymbolBufOrError = MemoryBuffer::getFileOrSTDIN(OldSymbolFile);
+  auto OldSymbolBufOrError =
+      MemoryBuffer::getFileOrSTDIN(OldSymbolFile, /*IsText=*/true);
   if (!OldSymbolBufOrError)
     exitWithErrorCode(OldSymbolBufOrError.getError(), OldSymbolFile);
 
-  auto NewSymbolBufOrError = MemoryBuffer::getFileOrSTDIN(NewSymbolFile);
+  auto NewSymbolBufOrError =
+      MemoryBuffer::getFileOrSTDIN(NewSymbolFile, /*IsText=*/true);
   if (!NewSymbolBufOrError)
     exitWithErrorCode(NewSymbolBufOrError.getError(), NewSymbolFile);
 
-  auto RemappingBufOrError = MemoryBuffer::getFileOrSTDIN(RemappingFile);
+  auto RemappingBufOrError =
+      MemoryBuffer::getFileOrSTDIN(RemappingFile, /*IsText=*/true);
   if (!RemappingBufOrError)
     exitWithErrorCode(RemappingBufOrError.getError(), RemappingFile);
 
diff --git a/llvm/tools/yaml2obj/yaml2obj.cpp b/llvm/tools/yaml2obj/yaml2obj.cpp
index b7f5356e22a9e..4a060e1aad427 100644
--- a/llvm/tools/yaml2obj/yaml2obj.cpp
+++ b/llvm/tools/yaml2obj/yaml2obj.cpp
@@ -130,7 +130,7 @@ int main(int argc, char **argv) {
   }
 
   ErrorOr<std::unique_ptr<MemoryBuffer>> Buf =
-      MemoryBuffer::getFileOrSTDIN(Input);
+      MemoryBuffer::getFileOrSTDIN(Input, /*IsText=*/true);
   if (!Buf)
     return 1;
 
diff --git a/llvm/utils/lit/lit/builtin_commands/cat.py b/llvm/utils/lit/lit/builtin_commands/cat.py
index 37f55c0aef210..6fb2152ef9332 100644
--- a/llvm/utils/lit/lit/builtin_commands/cat.py
+++ b/llvm/utils/lit/lit/builtin_commands/cat.py
@@ -55,10 +55,24 @@ def main(argv):
             msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
     for filename in filenames:
         try:
-            fileToCat = open(filename, "rb")
-            contents = fileToCat.read()
+            contents = None
+            is_text = False
+            try:
+                if sys.platform != "win32":
+                    fileToCat = open(filename, "r")
+                    contents = fileToCat.read()
+                    is_text = True
+            except:
+                pass
+
+            if contents is None:
+                fileToCat = open(filename, "rb")
+                contents = fileToCat.read()
+
             if show_nonprinting:
                 contents = convertToCaretAndMNotation(contents)
+            elif is_text:
+                contents = contents.encode()
             writer.write(contents)
             sys.stdout.flush()
             fileToCat.close()
diff --git a/llvm/utils/lit/lit/llvm/config.py b/llvm/utils/lit/lit/llvm/config.py
index 96b4f7bc86772..1d4babc99984b 100644
--- a/llvm/utils/lit/lit/llvm/config.py
+++ b/llvm/utils/lit/lit/llvm/config.py
@@ -57,6 +57,13 @@ def __init__(self, lit_config, config):
                 self.lit_config.note("using lit tools: {}".format(path))
                 lit_path_displayed = True
 
+        if platform.system() == "OS/390":
+            self.with_environment("_BPXK_AUTOCVT", "ON")
+            self.with_environment("_TAG_REDIR_IN", "TXT")
+            self.with_environment("_TAG_REDIR_OUT", "TXT")
+            self.with_environment("_TAG_REDIR_ERR", "TXT")
+            self.with_environment("_CEE_RUNOPTS", "FILETAG(AUTOCVT,AUTOTAG) POSIX(ON)")
+
         # Choose between lit's internal shell pipeline runner and a real shell.
         # If LIT_USE_INTERNAL_SHELL is in the environment, we use that as an
         # override.