Commit c348c163 authored by Jesse Brandeburg's avatar Jesse Brandeburg Committed by Linus Torvalds
Browse files

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@intel.com


Signed-off-by: default avatarJesse Brandeburg <jesse.brandeburg@intel.com>
Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
CcL Ingo Molnar <mingo@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 63d7f816

lib/Kconfig.debug

+13 −0
Original line number Diff line number Diff line
@@ -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

lib/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -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

lib/test_bitops.c

0 → 100644
+60 −0
Original line number Diff line number Diff line 
// 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@intel.com>");

MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("Bit testing module");

tools/testing/selftests/lib/config

+1 −0
Original line number Diff line number Diff line
@@ -2,3 +2,4 @@ CONFIG_TEST_PRINTF=m 
CONFIG_TEST_BITMAP=m

CONFIG_PRIME_NUMBERS=m

CONFIG_TEST_STRSCPY=m

CONFIG_TEST_BITOPS=m

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