5 files changed, 60 insertions, 6 deletions

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 4ac1d1c7ce5b..64699f59b95f 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -178,6 +178,7 @@ ifdef INSTALL_PATH
         @# Ask all targets to install their files
         mkdir -p $(INSTALL_PATH)/kselftest
         install -m 744 kselftest/runner.sh $(INSTALL_PATH)/kselftest/
+        install -m 744 kselftest/prefix.pl $(INSTALL_PATH)/kselftest/
         @for TARGET in $(TARGETS); do \
                 BUILD_TARGET=$$BUILD/$$TARGET;  \
                 make OUTPUT=$$BUILD_TARGET -C $$TARGET INSTALL_PATH=$(INSTALL_PATH)/$$TARGET install; \
diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h
index 9f4147a6fdbc..7f078e79a9fa 100644
--- a/tools/testing/selftests/kselftest.h
+++ b/tools/testing/selftests/kselftest.h
@@ -63,7 +63,7 @@ static inline void ksft_print_header(void)
 
 static inline void ksft_print_cnts(void)
 {
-        printf("Pass %d Fail %d Xfail %d Xpass %d Skip %d Error %d\n",
+        printf("# Pass %d Fail %d Xfail %d Xpass %d Skip %d Error %d\n",
                 ksft_cnt.ksft_pass, ksft_cnt.ksft_fail,
                 ksft_cnt.ksft_xfail, ksft_cnt.ksft_xpass,
                 ksft_cnt.ksft_xskip, ksft_cnt.ksft_error);
diff --git a/tools/testing/selftests/kselftest/prefix.pl b/tools/testing/selftests/kselftest/prefix.pl
new file mode 100755
index 000000000000..ec7e48118183
--- /dev/null
+++ b/tools/testing/selftests/kselftest/prefix.pl
@@ -0,0 +1,23 @@
+#!/usr/bin/perl
+# SPDX-License-Identifier: GPL-2.0
+# Prefix all lines with "# ", unbuffered. Command being piped in may need
+# to have unbuffering forced with "stdbuf -i0 -o0 -e0 $cmd".
+use strict;
+
+binmode STDIN;
+binmode STDOUT;
+
+STDOUT->autoflush(1);
+
+my $needed = 1;
+while (1) {
+        my $char;
+        my $bytes = sysread(STDIN, $char, 1);
+        exit 0 if ($bytes == 0);
+        if ($needed) {
+                print "# ";
+                $needed = 0;
+        }
+        print $char;
+        $needed = 1 if ($char eq "\n");
+}
diff --git a/tools/testing/selftests/kselftest/runner.sh b/tools/testing/selftests/kselftest/runner.sh
index a66fb64e61e9..b9f74e5a2ee5 100644
--- a/tools/testing/selftests/kselftest/runner.sh
+++ b/tools/testing/selftests/kselftest/runner.sh
@@ -7,6 +7,34 @@ export skip_rc=4
 export logfile=/dev/stdout
 export per_test_logging=
 
+# There isn't a shell-agnostic way to find the path of a sourced file,
+# so we must rely on BASE_DIR being set to find other tools.
+if [ -z "$BASE_DIR" ]; then
+        echo "Error: BASE_DIR must be set before sourcing." >&2
+        exit 1
+fi
+
+# If Perl is unavailable, we must fall back to line-at-a-time prefixing
+# with sed instead of unbuffered output.
+tap_prefix()
+{
+        if [ ! -x /usr/bin/perl ]; then
+                sed -e 's/^/# /'
+        else
+                "$BASE_DIR"/kselftest/prefix.pl
+        fi
+}
+
+# If stdbuf is unavailable, we must fall back to line-at-a-time piping.
+tap_unbuffer()
+{
+        if ! which stdbuf >/dev/null ; then
+                "$@"
+        else
+                stdbuf -i0 -o0 -e0 "$@"
+        fi
+}
+
 run_one()
 {
         DIR="$1"
@@ -16,10 +44,9 @@ run_one()
         BASENAME_TEST=$(basename $TEST)
 
         TEST_HDR_MSG="selftests: $DIR: $BASENAME_TEST"
-        echo "$TEST_HDR_MSG"
-        echo "========================================"
+        echo "# $TEST_HDR_MSG"
         if [ ! -x "$TEST" ]; then
-                echo -n "$TEST_HDR_MSG: Warning: file $TEST is "
+                echo -n "# Warning: file $TEST is "
                 if [ ! -e "$TEST" ]; then
                         echo "missing!"
                 else
@@ -28,7 +55,9 @@ run_one()
                 echo "not ok $test_num $TEST_HDR_MSG"
         else
                 cd `dirname $TEST` > /dev/null
-                (./$BASENAME_TEST >> "$logfile" 2>&1 &&
+                (((((tap_unbuffer ./$BASENAME_TEST 2>&1; echo $? >&3) |
+                        tap_prefix >&4) 3>&1) |
+                        (read xs; exit $xs)) 4>>"$logfile" &&
                 echo "ok $test_num $TEST_HDR_MSG") ||
                 (if [ $? -eq $skip_rc ]; then   \
                         echo "not ok $test_num $TEST_HDR_MSG # SKIP"
diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk
index 28b8ffedfdf1..098dd0065fb1 100644
--- a/tools/testing/selftests/lib.mk
+++ b/tools/testing/selftests/lib.mk
@@ -67,7 +67,8 @@ endif
 
 .ONESHELL:
 define RUN_TESTS
-        @. $(selfdir)/kselftest/runner.sh;      \
+        @BASE_DIR="$(selfdir)";                 \
+        . $(selfdir)/kselftest/runner.sh;       \
         if [ "X$(summary)" != "X" ]; then       \
                 per_test_logging=1;             \
         fi;                                     \