From: Jesse Brandeburg <jesse.brandeburg@xxxxxxxxx> Subject: 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/20200310221747.2848474-2-jesse.brandeburg@xxxxxxxxx Signed-off-by: Jesse Brandeburg <jesse.brandeburg@xxxxxxxxx> Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CcL Ingo Molnar <mingo@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Wei Yang <richard.weiyang@xxxxxxxxx> Cc: Christian Brauner <christian.brauner@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/Kconfig.debug | 13 +++++ lib/Makefile | 2 lib/test_bitops.c | 60 +++++++++++++++++++++++++++ tools/testing/selftests/lib/config | 1 4 files changed, 76 insertions(+) --- a/lib/Kconfig.debug~lib-make-a-test-module-with-set-clear-bit +++ a/lib/Kconfig.debug @@ -2022,6 +2022,19 @@ config TEST_LKM 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 --- a/lib/Makefile~lib-make-a-test-module-with-set-clear-bit +++ a/lib/Makefile @@ -56,6 +56,8 @@ obj-y += kstrtox.o 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 --- /dev/null +++ a/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 <jesse.brandeburg@xxxxxxxxx>"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Bit testing module"); --- a/tools/testing/selftests/lib/config~lib-make-a-test-module-with-set-clear-bit +++ a/tools/testing/selftests/lib/config @@ -2,3 +2,4 @@ CONFIG_TEST_PRINTF=m CONFIG_TEST_BITMAP=m CONFIG_PRIME_NUMBERS=m CONFIG_TEST_STRSCPY=m +CONFIG_TEST_BITOPS=m _
