diff --git a/clang/test/Analysis/analyzer-checker-config.c b/clang/test/Analysis/analyzer-checker-config.c
--- a/clang/test/Analysis/analyzer-checker-config.c
+++ b/clang/test/Analysis/analyzer-checker-config.c
@@ -1,12 +1,9 @@
-// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config unix.mallo:Optimistic=true 2>&1 | FileCheck %s
-// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config uni:Optimistic=true 2>&1 | FileCheck %s
-// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config uni.:Optimistic=true 2>&1 | FileCheck %s
-// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config ..:Optimistic=true 2>&1 | FileCheck %s
-// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config unix.:Optimistic=true 2>&1 | FileCheck %s
-// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config unrelated:Optimistic=true 2>&1 | FileCheck %s
-// RUN: %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config unix.DynamicMemoryModeling:Optimistic=true
+// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config unix.mallo:Optimistic=true %s 2>&1 | FileCheck %s
+// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config uni:Optimistic=true %s 2>&1 | FileCheck %s
+// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config uni.:Optimistic=true %s 2>&1 | FileCheck %s
+// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config ..:Optimistic=true %s 2>&1 | FileCheck %s
+// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config unix.:Optimistic=true %s 2>&1 | FileCheck %s
+// RUN: not %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config unrelated:Optimistic=true %s 2>&1 | FileCheck %s
+// RUN:     %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -analyzer-config unix.DynamicMemoryModeling:Optimistic=true %s 2>&1
 
-// Just to test clang is working.
-# foo
-
-// CHECK: error:
+// CHECK: error: no analyzer checkers or packages are associated with
diff --git a/clang/test/Analysis/analyzer-config.c b/clang/test/Analysis/analyzer-config.c
--- a/clang/test/Analysis/analyzer-config.c
+++ b/clang/test/Analysis/analyzer-config.c
@@ -1,4 +1,4 @@
-// RUN: %clang_analyze_cc1 -analyzer-checker=debug.ConfigDumper > %t 2>&1
+// RUN: %clang_analyze_cc1 -analyzer-checker=debug.ConfigDumper %s > %t 2>&1
 // RUN: FileCheck --input-file=%t %s --match-full-lines
 
 // CHECK:      [config]
diff --git a/clang/test/Driver/cc1-response-files.c b/clang/test/Driver/cc1-response-files.c
--- a/clang/test/Driver/cc1-response-files.c
+++ b/clang/test/Driver/cc1-response-files.c
@@ -1,2 +1,2 @@
-// RUN: %clang @%S/Inputs/cc1-response.txt -fsyntax-only -disable-llvm-passes
+// RUN: %clang @%S/Inputs/cc1-response.txt -fsyntax-only -disable-llvm-passes %s
 int main() {}
diff --git a/clang/test/Interpreter/incremental-mode.cpp b/clang/test/Interpreter/incremental-mode.cpp
--- a/clang/test/Interpreter/incremental-mode.cpp
+++ b/clang/test/Interpreter/incremental-mode.cpp
@@ -1,3 +1,3 @@
-// RUN: clang-repl -Xcc -E
-// RUN: clang-repl -Xcc -emit-llvm 
+// RUN: clang-repl -Xcc -E %s
+// RUN: clang-repl -Xcc -emit-llvm %s
 // expected-no-diagnostics
diff --git a/clang/test/Modules/load-module-with-errors.m b/clang/test/Modules/load-module-with-errors.m
--- a/clang/test/Modules/load-module-with-errors.m
+++ b/clang/test/Modules/load-module-with-errors.m
@@ -16,14 +16,14 @@
 // RUN: mkdir %t
 // RUN: mkdir %t/prebuilt
 
-// RUN: %clang_cc1 -fmodules -fallow-pcm-with-compiler-errors \
+// RUN: echo "" | %clang_cc1 -fmodules -fallow-pcm-with-compiler-errors \
 // RUN:   -fmodule-name=error -o %t/prebuilt/error.pcm \
 // RUN:   -x objective-c -emit-module %S/Inputs/error/module.modulemap
-// RUN: %clang_cc1 -fmodules -fallow-pcm-with-compiler-errors \
+// RUN: echo "" | %clang_cc1 -fmodules -fallow-pcm-with-compiler-errors \
 // RUN:   -fmodule-file=error=%t/prebuilt/error.pcm \
 // RUN:   -fmodule-name=use_error_a -o %t/prebuilt/use_error_a.pcm \
 // RUN:   -x objective-c -emit-module %S/Inputs/error/module.modulemap
-// RUN: %clang_cc1 -fmodules -fallow-pcm-with-compiler-errors \
+// RUN: echo "" | %clang_cc1 -fmodules -fallow-pcm-with-compiler-errors \
 // RUN:   -fmodule-file=error=%t/prebuilt/error.pcm \
 // RUN:   -fmodule-name=use_error_b -o %t/prebuilt/use_error_b.pcm \
 // RUN:   -x objective-c -emit-module %S/Inputs/error/module.modulemap
@@ -60,7 +60,7 @@
 // RUN:   -fmodule-file=%t/prebuilt/error.pcm \
 // RUN:   -fmodule-file=%t/prebuilt/use_error_a.pcm \
 // RUN:   -fmodule-file=%t/prebuilt/use_error_b.pcm \
-// RUN:   -fmodules-cache-path=%t 2>&1 | \
+// RUN:   -fmodules-cache-path=%t %s 2>&1 | \
 // RUN: grep "PCH file contains compiler errors"
 
 // Shouldn't build the cached modules (that have errors) when not allowing
@@ -91,7 +91,7 @@
 
 // allow-pcm-with-compiler-errors should also allow errors in PCH
 // RUN: %clang_cc1 -fallow-pcm-with-compiler-errors -x objective-c \
-// RUN:   -o %t/check.pch -emit-pch %S/Inputs/error/error.h
+// RUN:   -o %t/check.pch -emit-pch %S/Inputs/error/error.h %s
 
 // CHECK: @interface Error
 // CHECK-NEXT: - (int)method;
diff --git a/clang/test/OpenMP/target_uses_allocators.c b/clang/test/OpenMP/target_uses_allocators.c
--- a/clang/test/OpenMP/target_uses_allocators.c
+++ b/clang/test/OpenMP/target_uses_allocators.c
@@ -1,7 +1,7 @@
 // Test host codegen.
-// RUN: %clang_cc1 -verify -fopenmp -fopenmp-version=50  -triple powerpc64le-unknown-unknown -fopenmp-targets=powerpc64le-ibm-linux-gnu -emit-llvm %s -o - | FileCheck %s --check-prefix CHECK --check-prefix CHECK-64
+// RUN: %clang_cc1 -verify -fopenmp -fopenmp-version=50 -triple powerpc64le-unknown-unknown -fopenmp-targets=powerpc64le-ibm-linux-gnu -emit-llvm %s -o - | FileCheck %s
 // RUN: %clang_cc1 -fopenmp -fopenmp-version=50 -x c++ -triple powerpc64le-unknown-unknown -fopenmp-targets=powerpc64le-ibm-linux-gnu -emit-pch -o %t %s
-// RUN: %clang_cc1 -fopenmp -fopenmp-version=50 -x c++ -triple powerpc64le-unknown-unknown -fopenmp-targets=powerpc64le-ibm-linux-gnu
+// RUN: %clang_cc1 -fopenmp -fopenmp-version=50 -x c++ -triple powerpc64le-unknown-unknown -fopenmp-targets=powerpc64le-ibm-linux-gnu %s
 
 // expected-no-diagnostics
 #ifndef HEADER
diff --git a/clang/test/Preprocessor/elfiamcu-predefines.c b/clang/test/Preprocessor/elfiamcu-predefines.c
--- a/clang/test/Preprocessor/elfiamcu-predefines.c
+++ b/clang/test/Preprocessor/elfiamcu-predefines.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -E -dM -triple i586-intel-elfiamcu | FileCheck %s
+// RUN: %clang_cc1 -E -dM -triple i586-intel-elfiamcu %s | FileCheck %s
 
 // CHECK: #define __USER_LABEL_PREFIX__ {{$}}
 // CHECK: #define __WINT_TYPE__ unsigned int
diff --git a/llvm/utils/lit/lit/TestRunner.py b/llvm/utils/lit/lit/TestRunner.py
--- a/llvm/utils/lit/lit/TestRunner.py
+++ b/llvm/utils/lit/lit/TestRunner.py
@@ -640,7 +640,7 @@
 
     procs = []
     proc_not_counts = []
-    default_stdin = subprocess.PIPE
+    default_stdin = None
     stderrTempFiles = []
     opened_files = []
     named_temp_files = []
diff --git a/llvm/utils/lit/lit/util.py b/llvm/utils/lit/lit/util.py
--- a/llvm/utils/lit/lit/util.py
+++ b/llvm/utils/lit/lit/util.py
@@ -321,7 +321,7 @@
     * working directory ``cwd`` (str), use None to use the current
       working directory
     * environment ``env`` (dict), use None for none
-    * Input to the command ``input`` (str), use string to pass
+    * Input to the command ``input`` (str), use None to pass
       no input.
     * Max execution time ``timeout`` (int) seconds. Use 0 for no timeout.
     * ``redirect_stderr`` (bool), use True if redirect stderr to stdout
@@ -339,7 +339,7 @@
         input = to_bytes(input)
     err_out = subprocess.STDOUT if redirect_stderr else subprocess.PIPE
     p = subprocess.Popen(command, cwd=cwd,
-                         stdin=subprocess.PIPE,
+                         stdin=subprocess.PIPE if input else None,
                          stdout=subprocess.PIPE,
                          stderr=err_out,
                          env=env, close_fds=kUseCloseFDs)
diff --git a/llvm/utils/lit/tests/Inputs/shtest-stdin/lit.cfg b/llvm/utils/lit/tests/Inputs/shtest-stdin/lit.cfg
new file mode 100644
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-stdin/lit.cfg
@@ -0,0 +1,26 @@
+# -*- Python -*-
+import os
+import sys
+
+import lit.formats
+
+config.name = 'shtest-stdin'
+
+externalShell = lit_config.params.get('external', '1') != '0'
+config.test_format = lit.formats.ShTest(execute_external=externalShell)
+config.suffixes = ['.py']
+
+config.test_source_root = os.path.dirname(__file__)
+config.test_exec_root = config.test_source_root
+config.target_triple = '(unused)'
+src_root = os.path.join(config.test_source_root, '..')
+
+pythonpath_list = [src_root]
+# Ensure the user's PYTHONPATH is included.
+if 'PYTHONPATH' in os.environ:
+    pythonpath_list.append(os.environ['PYTHONPATH'])
+if 'PYTHONPATH' in config.environment:
+    pythonpath_list.append(config.environment['PYTHONPATH'])
+config.environment['PYTHONPATH'] = os.pathsep.join(pythonpath_list)
+
+config.substitutions.append(('%{python}', '"%s"' % (sys.executable)))
diff --git a/llvm/utils/lit/tests/Inputs/shtest-stdin/print-stdin.py b/llvm/utils/lit/tests/Inputs/shtest-stdin/print-stdin.py
new file mode 100644
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-stdin/print-stdin.py
@@ -0,0 +1,5 @@
+# Checks that lit provides no input to stdin.
+# RUN: %{python} %s
+import sys
+
+print(sys.stdin.read())
\ No newline at end of file
diff --git a/llvm/utils/lit/tests/shtest-stdin.py b/llvm/utils/lit/tests/shtest-stdin.py
new file mode 100644
--- /dev/null
+++ b/llvm/utils/lit/tests/shtest-stdin.py
@@ -0,0 +1,28 @@
+# REQUIRES: lit-max-individual-test-time
+
+###############################################################################
+# Check tests do not receive spurious stdin input.
+###############################################################################
+# RUN: not %{lit} %{inputs}/shtest-stdin/print-stdin.py \
+# RUN:   --param external=0 --timeout 1 \
+# RUN: | FileCheck --check-prefix=CHECK-STDIN %s
+#
+# RUN: not %{lit} %{inputs}/shtest-stdin/print-stdin.py \
+# RUN:   --param external=1 --timeout 1 \
+# RUN: | FileCheck --check-prefix=CHECK-STDIN %s
+#
+# CHECK-STDIN: TIMEOUT: shtest-stdin :: print-stdin.py
+
+###############################################################################
+# Check tests do receive piped stdin input.
+###############################################################################
+# RUN: echo foobar | %{lit} %{inputs}/shtest-stdin/print-stdin.py \
+# RUN:   --param external=0 -a \
+# RUN: | FileCheck --check-prefix=CHECK-PIPE %s
+#
+# RUN: echo foobar | %{lit} %{inputs}/shtest-stdin/print-stdin.py \
+# RUN:   --param external=1 -a \
+# RUN: | FileCheck --check-prefix=CHECK-PIPE %s
+#
+# CHECK-PIPE: foobar
+
diff --git a/utils/bazel/llvm-project-overlay/llvm/utils/lit/tests/BUILD.bazel b/utils/bazel/llvm-project-overlay/llvm/utils/lit/tests/BUILD.bazel
--- a/utils/bazel/llvm-project-overlay/llvm/utils/lit/tests/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/llvm/utils/lit/tests/BUILD.bazel
@@ -33,5 +33,15 @@
             "//llvm:not",
         ] + glob(["Inputs/**"]),
     )
-    for src in glob(["*/*.py"])
+    for src in glob(
+        include = ["**/*.py"],
+        exclude = [
+            "Inputs/**",
+            # FIXME: these tests fail under bazel.
+            "discovery.py",
+            "max-time.py",
+            "selecting.py",
+            "shtest-recursive-substitution.py",
+        ]
+    )
 ]