lib: make a test module with set/clear bit
Test some bit clears/sets to make sure assembly doesn't change, and that
the set_bit and clear_bit functions work and don't cause sparse warnings.
Instruct Kbuild to build this file with extra warning level -Wextra, to
catch new issues, and also doesn't hurt to build with C=1.
This was used to test changes to arch/x86/include/asm/bitops.h.
In particular, sparse (C=1) was very concerned when the last bit before a
natural boundary, like 7, or 31, was being tested, as this causes sign
extension (0xffffff7f) for instance when clearing bit 7.
Recommended usage:
make defconfig
scripts/config -m CONFIG_TEST_BITOPS
make modules_prepare
make C=1 W=1 lib/test_bitops.ko
objdump -S -d lib/test_bitops.ko
insmod lib/test_bitops.ko
rmmod lib/test_bitops.ko
<check dmesg>, there should be no compiler/sparse warnings and no
error messages in log.
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Jesse Brandeburg <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Cc: Thomas Gleixner <[email protected]>
CcL Ingo Molnar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Rasmus Villemoes <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Wei Yang <[email protected]>
Cc: Christian Brauner <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 30302c9..b9a450b 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2022,6 +2022,19 @@
If unsure, say N.
+config TEST_BITOPS
+ tristate "Test module for compilation of clear_bit/set_bit operations"
+ depends on m
+ help
+ This builds the "test_bitops" module that is much like the
+ TEST_LKM module except that it does a basic exercise of the
+ clear_bit and set_bit macros to make sure there are no compiler
+ warnings from C=1 sparse checker or -Wextra compilations. It has
+ no dependencies and doesn't run or load unless explicitly requested
+ by name. for example: modprobe test_bitops.
+
+ If unsure, say N.
+
config TEST_VMALLOC
tristate "Test module for stress/performance analysis of vmalloc allocator"
default n
diff --git a/lib/Makefile b/lib/Makefile
index 5adf894..32f19b4 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -56,6 +56,8 @@
obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o
obj-$(CONFIG_TEST_BPF) += test_bpf.o
obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o
+obj-$(CONFIG_TEST_BITOPS) += test_bitops.o
+CFLAGS_test_bitops.o += -Werror
obj-$(CONFIG_TEST_SYSCTL) += test_sysctl.o
obj-$(CONFIG_TEST_HASH) += test_hash.o test_siphash.o
obj-$(CONFIG_TEST_IDA) += test_ida.o
diff --git a/lib/test_bitops.c b/lib/test_bitops.c
new file mode 100644
index 0000000..fd50b3a
--- /dev/null
+++ b/lib/test_bitops.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 Intel Corporation
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+
+/* a tiny module only meant to test set/clear_bit */
+
+/* use an enum because thats the most common BITMAP usage */
+enum bitops_fun {
+ BITOPS_4 = 4,
+ BITOPS_7 = 7,
+ BITOPS_11 = 11,
+ BITOPS_31 = 31,
+ BITOPS_88 = 88,
+ BITOPS_LAST = 255,
+ BITOPS_LENGTH = 256
+};
+
+static DECLARE_BITMAP(g_bitmap, BITOPS_LENGTH);
+
+static int __init test_bitops_startup(void)
+{
+ pr_warn("Loaded test module\n");
+ set_bit(BITOPS_4, g_bitmap);
+ set_bit(BITOPS_7, g_bitmap);
+ set_bit(BITOPS_11, g_bitmap);
+ set_bit(BITOPS_31, g_bitmap);
+ set_bit(BITOPS_88, g_bitmap);
+ return 0;
+}
+
+static void __exit test_bitops_unstartup(void)
+{
+ int bit_set;
+
+ clear_bit(BITOPS_4, g_bitmap);
+ clear_bit(BITOPS_7, g_bitmap);
+ clear_bit(BITOPS_11, g_bitmap);
+ clear_bit(BITOPS_31, g_bitmap);
+ clear_bit(BITOPS_88, g_bitmap);
+
+ bit_set = find_first_bit(g_bitmap, BITOPS_LAST);
+ if (bit_set != BITOPS_LAST)
+ pr_err("ERROR: FOUND SET BIT %d\n", bit_set);
+
+ pr_warn("Unloaded test module\n");
+}
+
+module_init(test_bitops_startup);
+module_exit(test_bitops_unstartup);
+
+MODULE_AUTHOR("Jesse Brandeburg <[email protected]>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Bit testing module");
diff --git a/tools/testing/selftests/lib/config b/tools/testing/selftests/lib/config
index 14a77ea..b80ee3f 100644
--- a/tools/testing/selftests/lib/config
+++ b/tools/testing/selftests/lib/config
@@ -2,3 +2,4 @@
CONFIG_TEST_BITMAP=m
CONFIG_PRIME_NUMBERS=m
CONFIG_TEST_STRSCPY=m
+CONFIG_TEST_BITOPS=m
