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    Subject[PATCH v2 02/11] selftests:lib:test_counters: add new test for counters
    Date
    Add a new selftest for testing counter_atomic* Counters API. This test
    load test_counters test modules and unloads.

    The test module runs tests and prints results in dmesg.

    There are a number of atomic_t usages in the kernel where atomic_t api
    is used strictly for counting and not for managing object lifetime. In
    some cases, atomic_t might not even be needed.

    The purpose of these counters is to clearly differentiate atomic_t
    counters from atomic_t usages that guard object lifetimes, hence prone
    to overflow and underflow errors. It allows tools that scan for underflow
    and overflow on atomic_t usages to detect overflow and underflows to scan
    just the cases that are prone to errors.

    Simple atomic counters api provides interfaces for simple atomic counters
    that just count, and don't guard resource lifetimes. Counter will wrap
    around to 0 when it overflows and should not be used to guard resource
    lifetimes, device usage and open counts that control state changes, and
    pm states.

    Using counter_atomic* to guard lifetimes could lead to use-after free
    when it overflows and undefined behavior when used to manage state
    changes and device usage/open states.

    Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
    ---
    MAINTAINERS | 1 +
    tools/testing/selftests/lib/Makefile | 1 +
    tools/testing/selftests/lib/config | 1 +
    tools/testing/selftests/lib/test_counters.sh | 5 +++++
    4 files changed, 8 insertions(+)
    create mode 100755 tools/testing/selftests/lib/test_counters.sh

    diff --git a/MAINTAINERS b/MAINTAINERS
    index 4e82d0ffcab0..26719b8dd48e 100644
    --- a/MAINTAINERS
    +++ b/MAINTAINERS
    @@ -15845,6 +15845,7 @@ L: linux-kernel@vger.kernel.org
    S: Maintained
    F: include/linux/counters.h
    F: lib/test_counters.c
    +F: tools/testing/selftests/lib/test_counters.sh

    SIMPLE FIRMWARE INTERFACE (SFI)
    S: Obsolete
    diff --git a/tools/testing/selftests/lib/Makefile b/tools/testing/selftests/lib/Makefile
    index a105f094676e..e8960d7934e2 100644
    --- a/tools/testing/selftests/lib/Makefile
    +++ b/tools/testing/selftests/lib/Makefile
    @@ -5,5 +5,6 @@
    all:

    TEST_PROGS := printf.sh bitmap.sh prime_numbers.sh strscpy.sh
    +TEST_PROGS += test_counters.sh

    include ../lib.mk
    diff --git a/tools/testing/selftests/lib/config b/tools/testing/selftests/lib/config
    index b80ee3f6e265..6ed25024d371 100644
    --- a/tools/testing/selftests/lib/config
    +++ b/tools/testing/selftests/lib/config
    @@ -3,3 +3,4 @@ CONFIG_TEST_BITMAP=m
    CONFIG_PRIME_NUMBERS=m
    CONFIG_TEST_STRSCPY=m
    CONFIG_TEST_BITOPS=m
    +CONFIG_TEST_COUNTERS=m
    diff --git a/tools/testing/selftests/lib/test_counters.sh b/tools/testing/selftests/lib/test_counters.sh
    new file mode 100755
    index 000000000000..c8731aef2498
    --- /dev/null
    +++ b/tools/testing/selftests/lib/test_counters.sh
    @@ -0,0 +1,5 @@
    +#!/bin/sh
    +# SPDX-License-Identifier: GPL-2.0
    +# Tests the Simple Atomic Counters interfaces using test_counters
    +# kernel module
    +$(dirname $0)/../kselftest/module.sh "test_counters" test_counters
    --
    2.25.1
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