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Date:   Mon, 26 Jul 2021 15:26:19 -0500
From:   Jeff LaBundy <jeff@labundy.com>
To:     kernel test robot <lkp@intel.com>, natechancellor@gmail.com,
        ndesaulniers@google.com, mpe@ellerman.id.au
Cc:     clang-built-linux@googlegroups.com, kbuild-all@lists.01.org,
        linux-kernel@vger.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>
Subject: Re: drivers/input/misc/iqs626a.c:1645:12: warning: stack frame size
 (2384) exceeds limit (2048) in function 'iqs626_probe'
Message-ID: <20210726202619.GA1915@nixie72>
References: <202107261431.ugRM3oKP-lkp@intel.com>
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+ Nathan, Nick and Michael

Hi all,

On Mon, Jul 26, 2021 at 02:20:40PM +0800, kernel test robot wrote:
> Hi Jeff,
> 
> FYI, the error/warning still remains.
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   ff1176468d368232b684f75e82563369208bc371
> commit: f1d2809de97adc422967b6de59f0f6199769eb93 Input: Add support for Azoteq IQS626A
> date:   4 months ago
> config: powerpc-randconfig-r011-20210718 (attached as .config)
> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 5d5b08761f944d5b9822d582378333cc4b36a0a7)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # install powerpc cross compiling tool for clang build
>         # apt-get install binutils-powerpc-linux-gnu
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f1d2809de97adc422967b6de59f0f6199769eb93
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout f1d2809de97adc422967b6de59f0f6199769eb93
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All warnings (new ones prefixed by >>):
> 
>    __do_insb
>    ^
>    arch/powerpc/include/asm/io.h:556:56: note: expanded from macro '__do_insb'
>    #define __do_insb(p, b, n)      readsb((PCI_IO_ADDR)_IO_BASE+(p), (b), (n))
>                                           ~~~~~~~~~~~~~~~~~~~~~^
>    In file included from drivers/input/misc/iqs626a.c:20:
>    In file included from include/linux/interrupt.h:11:
>    In file included from include/linux/hardirq.h:10:
>    In file included from arch/powerpc/include/asm/hardirq.h:6:
>    In file included from include/linux/irq.h:20:
>    In file included from include/linux/io.h:13:
>    In file included from arch/powerpc/include/asm/io.h:619:
>    arch/powerpc/include/asm/io-defs.h:45:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>    DEF_PCI_AC_NORET(insw, (unsigned long p, void *b, unsigned long c),
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    arch/powerpc/include/asm/io.h:616:3: note: expanded from macro 'DEF_PCI_AC_NORET'
>                    __do_##name al;                                 \
>                    ^~~~~~~~~~~~~~
>    <scratch space>:12:1: note: expanded from here
>    __do_insw
>    ^
>    arch/powerpc/include/asm/io.h:557:56: note: expanded from macro '__do_insw'
>    #define __do_insw(p, b, n)      readsw((PCI_IO_ADDR)_IO_BASE+(p), (b), (n))
>                                           ~~~~~~~~~~~~~~~~~~~~~^
>    In file included from drivers/input/misc/iqs626a.c:20:
>    In file included from include/linux/interrupt.h:11:
>    In file included from include/linux/hardirq.h:10:
>    In file included from arch/powerpc/include/asm/hardirq.h:6:
>    In file included from include/linux/irq.h:20:
>    In file included from include/linux/io.h:13:
>    In file included from arch/powerpc/include/asm/io.h:619:
>    arch/powerpc/include/asm/io-defs.h:47:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>    DEF_PCI_AC_NORET(insl, (unsigned long p, void *b, unsigned long c),
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    arch/powerpc/include/asm/io.h:616:3: note: expanded from macro 'DEF_PCI_AC_NORET'
>                    __do_##name al;                                 \
>                    ^~~~~~~~~~~~~~
>    <scratch space>:16:1: note: expanded from here
>    __do_insl
>    ^
>    arch/powerpc/include/asm/io.h:558:56: note: expanded from macro '__do_insl'
>    #define __do_insl(p, b, n)      readsl((PCI_IO_ADDR)_IO_BASE+(p), (b), (n))
>                                           ~~~~~~~~~~~~~~~~~~~~~^
>    In file included from drivers/input/misc/iqs626a.c:20:
>    In file included from include/linux/interrupt.h:11:
>    In file included from include/linux/hardirq.h:10:
>    In file included from arch/powerpc/include/asm/hardirq.h:6:
>    In file included from include/linux/irq.h:20:
>    In file included from include/linux/io.h:13:
>    In file included from arch/powerpc/include/asm/io.h:619:
>    arch/powerpc/include/asm/io-defs.h:49:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>    DEF_PCI_AC_NORET(outsb, (unsigned long p, const void *b, unsigned long c),
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    arch/powerpc/include/asm/io.h:616:3: note: expanded from macro 'DEF_PCI_AC_NORET'
>                    __do_##name al;                                 \
>                    ^~~~~~~~~~~~~~
>    <scratch space>:20:1: note: expanded from here
>    __do_outsb
>    ^
>    arch/powerpc/include/asm/io.h:559:58: note: expanded from macro '__do_outsb'
>    #define __do_outsb(p, b, n)     writesb((PCI_IO_ADDR)_IO_BASE+(p),(b),(n))
>                                            ~~~~~~~~~~~~~~~~~~~~~^
>    In file included from drivers/input/misc/iqs626a.c:20:
>    In file included from include/linux/interrupt.h:11:
>    In file included from include/linux/hardirq.h:10:
>    In file included from arch/powerpc/include/asm/hardirq.h:6:
>    In file included from include/linux/irq.h:20:
>    In file included from include/linux/io.h:13:
>    In file included from arch/powerpc/include/asm/io.h:619:
>    arch/powerpc/include/asm/io-defs.h:51:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>    DEF_PCI_AC_NORET(outsw, (unsigned long p, const void *b, unsigned long c),
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    arch/powerpc/include/asm/io.h:616:3: note: expanded from macro 'DEF_PCI_AC_NORET'
>                    __do_##name al;                                 \
>                    ^~~~~~~~~~~~~~
>    <scratch space>:24:1: note: expanded from here
>    __do_outsw
>    ^
>    arch/powerpc/include/asm/io.h:560:58: note: expanded from macro '__do_outsw'
>    #define __do_outsw(p, b, n)     writesw((PCI_IO_ADDR)_IO_BASE+(p),(b),(n))
>                                            ~~~~~~~~~~~~~~~~~~~~~^
>    In file included from drivers/input/misc/iqs626a.c:20:
>    In file included from include/linux/interrupt.h:11:
>    In file included from include/linux/hardirq.h:10:
>    In file included from arch/powerpc/include/asm/hardirq.h:6:
>    In file included from include/linux/irq.h:20:
>    In file included from include/linux/io.h:13:
>    In file included from arch/powerpc/include/asm/io.h:619:
>    arch/powerpc/include/asm/io-defs.h:53:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>    DEF_PCI_AC_NORET(outsl, (unsigned long p, const void *b, unsigned long c),
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    arch/powerpc/include/asm/io.h:616:3: note: expanded from macro 'DEF_PCI_AC_NORET'
>                    __do_##name al;                                 \
>                    ^~~~~~~~~~~~~~
>    <scratch space>:28:1: note: expanded from here
>    __do_outsl
>    ^
>    arch/powerpc/include/asm/io.h:561:58: note: expanded from macro '__do_outsl'
>    #define __do_outsl(p, b, n)     writesl((PCI_IO_ADDR)_IO_BASE+(p),(b),(n))
>                                            ~~~~~~~~~~~~~~~~~~~~~^
> >> drivers/input/misc/iqs626a.c:1645:12: warning: stack frame size (2384) exceeds limit (2048) in function 'iqs626_probe' [-Wframe-larger-than]
>    static int iqs626_probe(struct i2c_client *client)
>               ^
>    14 warnings generated.
> 
> 
> vim +/iqs626_probe +1645 drivers/input/misc/iqs626a.c
> 
>   1644	
> > 1645	static int iqs626_probe(struct i2c_client *client)
>   1646	{
>   1647		struct iqs626_ver_info ver_info;
>   1648		struct iqs626_private *iqs626;
>   1649		int error;
>   1650	
>   1651		iqs626 = devm_kzalloc(&client->dev, sizeof(*iqs626), GFP_KERNEL);
>   1652		if (!iqs626)
>   1653			return -ENOMEM;
>   1654	
>   1655		i2c_set_clientdata(client, iqs626);
>   1656		iqs626->client = client;
>   1657	
>   1658		iqs626->regmap = devm_regmap_init_i2c(client, &iqs626_regmap_config);
>   1659		if (IS_ERR(iqs626->regmap)) {
>   1660			error = PTR_ERR(iqs626->regmap);
>   1661			dev_err(&client->dev, "Failed to initialize register map: %d\n",
>   1662				error);
>   1663			return error;
>   1664		}
>   1665	
>   1666		init_completion(&iqs626->ati_done);
>   1667	
>   1668		error = regmap_raw_read(iqs626->regmap, IQS626_VER_INFO, &ver_info,
>   1669					sizeof(ver_info));
>   1670		if (error)
>   1671			return error;
>   1672	
>   1673		if (ver_info.prod_num != IQS626_VER_INFO_PROD_NUM) {
>   1674			dev_err(&client->dev, "Unrecognized product number: 0x%02X\n",
>   1675				ver_info.prod_num);
>   1676			return -EINVAL;
>   1677		}
>   1678	
>   1679		error = iqs626_parse_prop(iqs626);
>   1680		if (error)
>   1681			return error;
>   1682	
>   1683		error = iqs626_input_init(iqs626);
>   1684		if (error)
>   1685			return error;
>   1686	
>   1687		error = devm_request_threaded_irq(&client->dev, client->irq,
>   1688						  NULL, iqs626_irq, IRQF_ONESHOT,
>   1689						  client->name, iqs626);
>   1690		if (error) {
>   1691			dev_err(&client->dev, "Failed to request IRQ: %d\n", error);
>   1692			return error;
>   1693		}
>   1694	
>   1695		if (!wait_for_completion_timeout(&iqs626->ati_done,
>   1696						 msecs_to_jiffies(2000))) {
>   1697			dev_err(&client->dev, "Failed to complete ATI\n");
>   1698			return -ETIMEDOUT;
>   1699		}
>   1700	
>   1701		/*
>   1702		 * The keypad may include one or more switches and is not registered
>   1703		 * until ATI is complete and the initial switch states are read.
>   1704		 */
>   1705		error = input_register_device(iqs626->keypad);
>   1706		if (error)
>   1707			dev_err(&client->dev, "Failed to register keypad: %d\n", error);
>   1708	
>   1709		return error;
>   1710	}
>   1711	
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

This function has elicited previous stack frame warnings using clang with
powerpc, the last being [1]. In each case the warning is preceded by many
others in arch/powerpc/include/asm/ so I'm curious if the warning here is
simply fallout from something else.

Do you have any insight? The stack size should be well under 2 kB in this
case. I see some other similar warnings throughout the mailing list which
are preceded by DEF_PCI_AC_NORET as well. If I have misunderstood or this
driver is indeed doing something nefarious, please let me know.

Kind regards,
Jeff LaBundy

[1] https://lkml.org/lkml/2021/6/6/10