From c348c16305280fe3e6c1186378f96c8634c149f9 Mon Sep 17 00:00:00 2001 From: Jesse Brandeburg Date: Thu, 4 Jun 2020 16:50:27 -0700 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 , there should be no compiler/sparse warnings and no error messages in log. Link: http://lkml.kernel.org/r/20200310221747.2848474-2-jesse.brandeburg@intel.com Signed-off-by: Jesse Brandeburg Reviewed-by: Andy Shevchenko Cc: Thomas Gleixner CcL Ingo Molnar Signed-off-by: Andrew Morton Cc: Borislav Petkov Cc: Rasmus Villemoes Cc: Dan Williams Cc: Peter Zijlstra Cc: Wei Yang Cc: Christian Brauner Signed-off-by: Linus Torvalds --- lib/test_bitops.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 60 insertions(+) create mode 100644 lib/test_bitops.c (limited to 'lib/test_bitops.c') diff --git a/lib/test_bitops.c b/lib/test_bitops.c new file mode 100644 index 000000000000..fd50b3ae4a14 --- /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 +#include +#include + +/* 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 "); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Bit testing module"); -- cgit v1.2.3