selftests: add new kallsyms selftests

We lack find_symbol() selftests, so add one. This let's us stress test
improvements easily on find_symbol() or optimizations. It also inherently
allows us to test the limits of kallsyms on Linux today.

We test a pathalogical use case for kallsyms by introducing modules
which are automatically written for us with a larger number of symbols.
We have 4 kallsyms test modules:

A: has KALLSYSMS_NUMSYMS exported symbols
B: uses one of A's symbols
C: adds KALLSYMS_SCALE_FACTOR * KALLSYSMS_NUMSYMS exported
D: adds 2 * the symbols than C

By using anything much larger than KALLSYSMS_NUMSYMS as 10,000 and
KALLSYMS_SCALE_FACTOR of 8 we segfault today. So we're capped at
around 160000 symbols somehow today. We can inpsect that issue at
our leasure later, but for now the real value to this test is that
this will easily allow us to test improvements on find_symbol().

We want to enable this test on allyesmodconfig builds so we can't
use this combination, so instead just use a safe value for now and
be informative on the Kconfig symbol documentation about where our
thresholds are for testers. We default then to KALLSYSMS_NUMSYMS of
just 100 and KALLSYMS_SCALE_FACTOR of 8.

On x86_64 we can use perf, for other architectures we just use 'time'
and allow for customizations. For example a future enhancements could
be done for parisc to check for unaligned accesses which triggers a
special special exception handler assembler code inside the kernel.
The negative impact on performance is so large on parisc that it
keeps track of its accesses on /proc/cpuinfo as UAH:

IRQ:       CPU0       CPU1
3:       1332          0         SuperIO  ttyS0
7:    1270013          0         SuperIO  pata_ns87415
64:  320023012  320021431             CPU  timer
65:   17080507   20624423             CPU  IPI
UAH:   10948640      58104   Unaligned access handler traps

While at it, this tidies up lib/ test modules to allow us to have
a new directory for them. The amount of test modules under lib/
is insane.

This should also hopefully showcase how to start doing basic
self module writing code, which may be more useful for more complex
cases later in the future.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

3 files changed, 96 insertions, 0 deletions

diff --git a/tools/testing/selftests/module/Makefile b/tools/testing/selftests/module/Makefile
new file mode 100644
index 000000000000..6132d7ddb08b
--- /dev/null
+++ b/tools/testing/selftests/module/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# Makefile for module loading selftests
+
+# No binaries, but make sure arg-less "make" doesn't trigger "run_tests"
+all:
+
+TEST_PROGS := find_symbol.sh
+
+include ../lib.mk
+
+# Nothing to clean up.
+clean:
diff --git a/tools/testing/selftests/module/config b/tools/testing/selftests/module/config
new file mode 100644
index 000000000000..b0c206b1ad47
--- /dev/null
+++ b/tools/testing/selftests/module/config
@@ -0,0 +1,3 @@
+CONFIG_TEST_RUNTIME=y
+CONFIG_TEST_RUNTIME_MODULE=y
+CONFIG_TEST_KALLSYMS=m
diff --git a/tools/testing/selftests/module/find_symbol.sh b/tools/testing/selftests/module/find_symbol.sh
new file mode 100755
index 000000000000..140364d3c49f
--- /dev/null
+++ b/tools/testing/selftests/module/find_symbol.sh
@@ -0,0 +1,81 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-or-later OR copyleft-next-0.3.1
+# Copyright (C) 2023 Luis Chamberlain <mcgrof@kernel.org>
+#
+# This is a stress test script for kallsyms through find_symbol()
+
+set -e
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+test_reqs()
+{
+	if ! which modprobe 2> /dev/null > /dev/null; then
+		echo "$0: You need modprobe installed" >&2
+		exit $ksft_skip
+	fi
+
+	if ! which kmod 2> /dev/null > /dev/null; then
+		echo "$0: You need kmod installed" >&2
+		exit $ksft_skip
+	fi
+
+	if ! which perf 2> /dev/null > /dev/null; then
+		echo "$0: You need perf installed" >&2
+		exit $ksft_skip
+	fi
+
+	uid=$(id -u)
+	if [ $uid -ne 0 ]; then
+		echo $msg must be run as root >&2
+		exit $ksft_skip
+	fi
+}
+
+load_mod()
+{
+	local STATS="-e duration_time"
+	STATS="$STATS -e user_time"
+	STATS="$STATS -e system_time"
+	STATS="$STATS -e page-faults"
+	local MOD=$1
+
+	local ARCH="$(uname -m)"
+	case "${ARCH}" in
+	x86_64)
+		perf stat $STATS $MODPROBE test_kallsyms_b
+		;;
+	*)
+		time $MODPROBE test_kallsyms_b
+		exit 1
+		;;
+	esac
+}
+
+remove_all()
+{
+	$MODPROBE -r test_kallsyms_b
+	for i in a b c d; do
+		$MODPROBE -r test_kallsyms_$i
+	done
+}
+test_reqs
+
+MODPROBE=$(</proc/sys/kernel/modprobe)
+
+remove_all
+load_mod test_kallsyms_b
+remove_all
+
+# Now pollute the namespace
+$MODPROBE test_kallsyms_c
+load_mod test_kallsyms_b
+
+# Now pollute the namespace with twice the number of symbols than the last time
+remove_all
+$MODPROBE test_kallsyms_c
+$MODPROBE test_kallsyms_d
+load_mod test_kallsyms_b
+
+exit 0