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Date:   Thu, 6 Apr 2023 17:17:16 +0800
From:   Pengfei Xu <pengfei.xu@intel.com>
To:     <christophe.leroy@csgroup.eu>
CC:     <andy.shevchenko@gmail.com>, <linux-kernel@vger.kernel.org>,
        <heng.su@intel.com>, <linux-kselftest@vger.kernel.org>,
        <lkp@intel.com>, <linux-gpio@vger.kernel.org>,
        <john.fastabend@gmail.com>, <edumazet@google.com>
Subject: [gpio kself-test & bisect] gpio-mockup.sh kslef-test failed in
 v6.3-rc5
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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.

Thanks!
BR.