Re: [gpio kself-test & bisect] gpio-mockup.sh kslef-test failed in v6.3-rc5

[Andy Shevchenko]

On Thu, Apr 6, 2023 at 12:15 PM Pengfei Xu <pengfei.xu@xxxxxxxxx> wrote:
>
> Hi Christophe Leroy and gpio experts,
>
> Greeting!
>
> Platform: Tigerlake-H and so on x86 platforms
>
> All detailed info is in link: https://github.com/xupengfe/syzkaller_logs/tree/main/issue_bisect/230406_gpio-mockup_kselftest_failed_bisect_v63rc5
> Bisect info: https://github.com/xupengfe/syzkaller_logs/blob/main/issue_bisect/230406_gpio-mockup_kselftest_failed_bisect_v63rc5/bisect_info.txt
>
> gpio-mockup.sh kslef-test failed in v6.3-rc5 kernel.
> gpio-mockup.sh(gpio overflow test) in kself-test could reproduce this issue:
> cd linux/tools/testing/selftests
>  1.  ./kselftest_install.sh
>  2.  cd  linux/tools/testing/selftests/kselftest_install/gpio
>  # ./gpio-mockup.sh
>  1.  Module load tests
>  1.1.  dynamic allocation of gpio
>  2.  Module load error tests
>  2.1 gpio overflow
>  test failed: unexpected chip - gpiochip1
>  GPIO gpio-mockup test FAIL
>
> And the simplified steps to reproduce this issue are as follow:
> "
> # Load gpio_mockup with overflow ranges -1,1024:
> modprobe -q gpio_mockup gpio_mockup_ranges="-1,1024"
>
> # Check is there some Call Trace generated in dmesg
> dmesg | grep -C 5 Call
>
> # Should not generate any gpiochip folder like /sys/kernel/debug/gpio-mockup/gpiochip1
> # Because load gpio_mockup with overflow ranges -1,1024
> find "/sys/kernel/debug/gpio-mockup/" -name gpiochip* -type d | sort
>
> # Unload the gpio_mockup module
> modprobe -r gpio_mockup
> # Check is there "Call Trace" generated in dmesg
> dmesg | grep -C 5 Call
> "
>
> Actually the judgement "gpio-mockup.sh" test/bisect judgement point is that:
> Should not generate any gpiochip folder like
> /sys/kernel/debug/gpio-mockup/gpiochip1 after load gpio_mockup with overflow
> ranges -1,1024.
>
> I met gpio-mockup.sh test failed but there is no any "Call Trace" dmesg info
> sometimes.
>
> So the shortest check steps are as follow:
> "
> 1. modprobe -q gpio_mockup gpio_mockup_ranges="-1,1024"
> After above gpio_mockup module loaded with overflow range "-1,1024":
> Correct behavior as previous v6.1 or older kernel:"gpio should not load "gpiochip1" due to overflow range -1,1024";
> Wrong behavior in v6.3-rc5 kernel: "gpio *load* "gpiochip1" with overflow range -1,1024 and "gpiochip1" should not be loaded".
> The underlying problem was already buried here.
>
> 2. Could use below command to check if "gpiochip1" generated:
> As before v6.1,  there was no "/sys/kernel/debug/gpio-mockup/gpiochip1" sysfs folder due to overflow range -1,1024";
> Wrong behavior in v6.3-rc5 kernel: "/sys/kernel/debug/gpio-mockup/gpiochip1" sysfs folder generated as follow command check:
> # find "/sys/kernel/debug/gpio-mockup/" -name gpiochip* -type d | sort
> /sys/kernel/debug/gpio-mockup/gpiochip1
> If there is gpiochip* generated, gpio-mockup.sh kself-test would be failed also.
> "
>
> Bisected and found the bad commit was:
> "
> 7b61212f2a07a5afd213c8876e52b5c9946441e2
> gpiolib: Get rid of ARCH_NR_GPIOS
> "
> And after reverted the above commit on top of v6.3-rc5 kernel, above
> gpio-mockup.sh kself-test could pass and this issue was gone.
>
> Now gpio-mockup.sh kself-test is failed on almost all x86 platform from
> v6.2 cycle mainline kernel.
>
> I hope above info is helpful to solve the "gpio-mockup.sh kself-test failed"
> problem.

Thank you for the report and full analysis of the root cause. I think
we may fix the test script however the gpio-mockup is obsoleted and
should be actually replaced with tests again gpio-sim.

-- 
With Best Regards,
Andy Shevchenko