5 files changed, 216 insertions, 0 deletions
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 32487ed18354..e66e710cc595 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -10,6 +10,7 @@ TARGETS += timers
 TARGETS += vm
 TARGETS += powerpc
 TARGETS += user
+TARGETS += sysctl
 
 all:
 	for TARGET in $(TARGETS); do \
diff --git a/tools/testing/selftests/sysctl/Makefile b/tools/testing/selftests/sysctl/Makefile
new file mode 100644
index 000000000000..0a92adaf0865
--- /dev/null
+++ b/tools/testing/selftests/sysctl/Makefile
@@ -0,0 +1,19 @@
+# Makefile for sysctl selftests.
+# Expects kernel.sysctl_writes_strict=1.
+
+# No binaries, but make sure arg-less "make" doesn't trigger "run_tests".
+all:
+
+# Allow specific tests to be selected.
+test_num:
+	@/bin/sh ./run_numerictests
+
+test_string:
+	@/bin/sh ./run_stringtests
+
+run_tests: all test_num test_string
+
+# Nothing to clean up.
+clean:
+
+.PHONY: all run_tests clean test_num test_string
diff --git a/tools/testing/selftests/sysctl/common_tests b/tools/testing/selftests/sysctl/common_tests
new file mode 100644
index 000000000000..17d534b1b7b4
--- /dev/null
+++ b/tools/testing/selftests/sysctl/common_tests
@@ -0,0 +1,109 @@
+#!/bin/sh
+
+TEST_FILE=$(mktemp)
+
+echo "== Testing sysctl behavior against ${TARGET} =="
+
+set_orig()
+{
+	echo "${ORIG}" > "${TARGET}"
+}
+
+set_test()
+{
+	echo "${TEST_STR}" > "${TARGET}"
+}
+
+verify()
+{
+	local seen
+	seen=$(cat "$1")
+	if [ "${seen}" != "${TEST_STR}" ]; then
+		return 1
+	fi
+	return 0
+}
+
+trap 'set_orig; rm -f "${TEST_FILE}"' EXIT
+
+rc=0
+
+echo -n "Writing test file ... "
+echo "${TEST_STR}" > "${TEST_FILE}"
+if ! verify "${TEST_FILE}"; then
+	echo "FAIL" >&2
+	exit 1
+else
+	echo "ok"
+fi
+
+echo -n "Checking sysctl is not set to test value ... "
+if verify "${TARGET}"; then
+	echo "FAIL" >&2
+	exit 1
+else
+	echo "ok"
+fi
+
+echo -n "Writing sysctl from shell ... "
+set_test
+if ! verify "${TARGET}"; then
+	echo "FAIL" >&2
+	exit 1
+else
+	echo "ok"
+fi
+
+echo -n "Resetting sysctl to original value ... "
+set_orig
+if verify "${TARGET}"; then
+	echo "FAIL" >&2
+	exit 1
+else
+	echo "ok"
+fi
+
+# Now that we've validated the sanity of "set_test" and "set_orig",
+# we can use those functions to set starting states before running
+# specific behavioral tests.
+
+echo -n "Writing entire sysctl in single write ... "
+set_orig
+dd if="${TEST_FILE}" of="${TARGET}" bs=4096 2>/dev/null
+if ! verify "${TARGET}"; then
+	echo "FAIL" >&2
+	rc=1
+else
+	echo "ok"
+fi
+
+echo -n "Writing middle of sysctl after synchronized seek ... "
+set_test
+dd if="${TEST_FILE}" of="${TARGET}" bs=1 seek=1 skip=1 2>/dev/null
+if ! verify "${TARGET}"; then
+	echo "FAIL" >&2
+	rc=1
+else
+	echo "ok"
+fi
+
+echo -n "Writing beyond end of sysctl ... "
+set_orig
+dd if="${TEST_FILE}" of="${TARGET}" bs=20 seek=2 2>/dev/null
+if verify "${TARGET}"; then
+        echo "FAIL" >&2
+        rc=1
+else
+        echo "ok"
+fi
+
+echo -n "Writing sysctl with multiple long writes ... "
+set_orig
+(perl -e 'print "A" x 50;'; echo "${TEST_STR}") | \
+	dd of="${TARGET}" bs=50 2>/dev/null
+if verify "${TARGET}"; then
+	echo "FAIL" >&2
+	rc=1
+else
+	echo "ok"
+fi
diff --git a/tools/testing/selftests/sysctl/run_numerictests b/tools/testing/selftests/sysctl/run_numerictests
new file mode 100644
index 000000000000..8510f93f2d14
--- /dev/null
+++ b/tools/testing/selftests/sysctl/run_numerictests
@@ -0,0 +1,10 @@
+#!/bin/sh
+
+SYSCTL="/proc/sys"
+TARGET="${SYSCTL}/vm/swappiness"
+ORIG=$(cat "${TARGET}")
+TEST_STR=$(( $ORIG + 1 ))
+
+. ./common_tests
+
+exit $rc
diff --git a/tools/testing/selftests/sysctl/run_stringtests b/tools/testing/selftests/sysctl/run_stringtests
new file mode 100644
index 000000000000..90a9293d520c
--- /dev/null
+++ b/tools/testing/selftests/sysctl/run_stringtests
@@ -0,0 +1,77 @@
+#!/bin/sh
+
+SYSCTL="/proc/sys"
+TARGET="${SYSCTL}/kernel/domainname"
+ORIG=$(cat "${TARGET}")
+TEST_STR="Testing sysctl"
+
+. ./common_tests
+
+# Only string sysctls support seeking/appending.
+MAXLEN=65
+
+echo -n "Writing entire sysctl in short writes ... "
+set_orig
+dd if="${TEST_FILE}" of="${TARGET}" bs=1 2>/dev/null
+if ! verify "${TARGET}"; then
+	echo "FAIL" >&2
+	rc=1
+else
+	echo "ok"
+fi
+
+echo -n "Writing middle of sysctl after unsynchronized seek ... "
+set_test
+dd if="${TEST_FILE}" of="${TARGET}" bs=1 seek=1 2>/dev/null
+if verify "${TARGET}"; then
+	echo "FAIL" >&2
+	rc=1
+else
+	echo "ok"
+fi
+
+echo -n "Checking sysctl maxlen is at least $MAXLEN ... "
+set_orig
+perl -e 'print "A" x ('"${MAXLEN}"'-2), "B";' | \
+	dd of="${TARGET}" bs="${MAXLEN}" 2>/dev/null
+if ! grep -q B "${TARGET}"; then
+	echo "FAIL" >&2
+	rc=1
+else
+	echo "ok"
+fi
+
+echo -n "Checking sysctl keeps original string on overflow append ... "
+set_orig
+perl -e 'print "A" x ('"${MAXLEN}"'-1), "B";' | \
+	dd of="${TARGET}" bs=$(( MAXLEN - 1 )) 2>/dev/null
+if grep -q B "${TARGET}"; then
+	echo "FAIL" >&2
+	rc=1
+else
+	echo "ok"
+fi
+
+echo -n "Checking sysctl stays NULL terminated on write ... "
+set_orig
+perl -e 'print "A" x ('"${MAXLEN}"'-1), "B";' | \
+	dd of="${TARGET}" bs="${MAXLEN}" 2>/dev/null
+if grep -q B "${TARGET}"; then
+	echo "FAIL" >&2
+	rc=1
+else
+	echo "ok"
+fi
+
+echo -n "Checking sysctl stays NULL terminated on overwrite ... "
+set_orig
+perl -e 'print "A" x ('"${MAXLEN}"'-1), "BB";' | \
+	dd of="${TARGET}" bs=$(( $MAXLEN + 1 )) 2>/dev/null
+if grep -q B "${TARGET}"; then
+	echo "FAIL" >&2
+	rc=1
+else
+	echo "ok"
+fi
+
+exit $rc