linux-kernel - Re: [PATCH] pci: spear: Drop __initdata from struct platform_driver spear13xx_pcie

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Message-ID: <CAJs94EbMiX=a=bcRiprobHNK-zkXaWqq4VnHXTmrh-zpMv0QSw@mail.gmail.com>
Date:	Mon, 9 Feb 2015 22:52:30 +0400
From:	"Matwey V. Kornilov" <matwey@....msu.ru>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Mohit Kumar <mohit.kumar@...com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] pci: spear: Drop __initdata from struct platform_driver spear13xx_pcie_driver

2015-02-09 16:11 GMT+03:00 Matwey V. Kornilov <matwey@....msu.ru>:
> 2015-02-09 7:22 GMT+03:00 Viresh Kumar <viresh.kumar@...aro.org>:
>> On Sun, Feb 8, 2015 at 3:37 PM, Matwey V. Kornilov <matwey@....msu.ru> wrote:
>>> spear13xx_pcie_driver.driver is allocated in text.init section
>>> and then the pointer to it is passed futher. This patch is to avoid
>>> crashes like the following, when freed memory is used:
>>>
>>>  #0  __device_attach (drv=0xc0ed5608 <spear13xx_pcie_driver+20>, data=0xdb622610) at ../drivers/base/dd.c:409
>>>  #1  0xc07a4798 in bus_for_each_drv (bus=<optimized out>, start=<optimized out>, data=0xda0, fn=0xc07a6740 <__device_attach>)
>>>     at ../drivers/base/bus.c:463
>>>  #2  0xc07a6324 in device_attach (dev=0xdb622610) at ../drivers/base/dd.c:447
>>>  #3  0xc07a5814 in bus_probe_device (dev=0xdb622610) at ../drivers/base/bus.c:558
>>>  #4  0xc07a38d8 in device_add (dev=<optimized out>) at ../drivers/base/core.c:1058
>>>  #5  0xc08b6a5c in of_device_add (ofdev=<optimized out>) at ../drivers/of/device.c:66
>>>  #6  0xc08b742c in of_platform_device_create_pdata (np=<optimized out>, bus_id=0x0 <__vectors_start>, platform_data=0x0 <__vectors_start>,
>>>     parent=<optimized out>) at ../drivers/of/platform.c:241
>>>  #7  0xc08b7568 in of_platform_bus_create (bus=0xdfa46780, matches=0x0 <__vectors_start>, lookup=0x0 <__vectors_start>, parent=0xdb183410,
>>>     strict=true) at ../drivers/of/platform.c:414
>>>  #8  0xc08b79bc in of_platform_populate (root=0xc0ed5608 <spear13xx_pcie_driver+20>, matches=0xdb622610, lookup=0xda0,
>>>     parent=0xc07a6740 <__device_attach>) at ../drivers/of/platform.c:501
>>>  #9  0xbf000030 in am335x_child_probe (pdev=0xdb183400) at ../drivers/usb/musb/musb_am335x.c:12
>>>  #10 0xc07a83f0 in platform_drv_probe (_dev=0xdb183410) at ../drivers/base/platform.c:512
>>>  #11 0xc07a64e8 in really_probe (drv=<optimized out>, dev=<optimized out>) at ../drivers/base/dd.c:302
>>>  #12 driver_probe_device (drv=0xbf000234, dev=0xdb183410) at ../drivers/base/dd.c:399
>>>  #13 0xc07a6820 in __driver_attach (dev=0xdb183410, data=0xbf000234) at ../drivers/base/dd.c:477
>>>  #14 0xc07a46e8 in bus_for_each_dev (bus=<optimized out>, start=<optimized out>, data=0xda0, fn=0xc07a83a4 <platform_drv_probe>)
>>>     at ../drivers/base/bus.c:313
>>>  #15 0xc07a5ebc in driver_attach (drv=<optimized out>) at ../drivers/base/dd.c:496
>>>  #16 0xc07a5af0 in bus_add_driver (drv=0xbf000234) at ../drivers/base/bus.c:694
>>>  #17 0xc07a6fec in driver_register (drv=0xbf000234) at ../drivers/base/driver.c:167
>>>  #18 0xc0209c34 in do_one_initcall (fn=0xbf002000) at ../init/main.c:801
>>>  #19 0xc02e0494 in do_init_module (mod=<optimized out>) at ../kernel/module.c:3142
>>>  #20 load_module (info=0xdb6b1f54, uargs=<optimized out>, flags=<optimized out>) at ../kernel/module.c:3461
>>>  #21 0xc02e0a44 in SYSC_finit_module (flags=<optimized out>, uargs=<optimized out>, fd=<optimized out>) at ../kernel/module.c:3537
>>>  #22 SyS_finit_module (fd=7, uargs=-1225602132, flags=0) at ../kernel/module.c:3518
>>>  #23 0xc021a680 in ?? ()
>>>
>>> Fixes: 6675ef212da (PCI: spear: Fix Section mismatch compilation warning for probe())
>>
>> wouldn't this again result in the problem reported above ?
>>
>
> Frankly speaking, I don't believe that that problem ever existed.
> probe() is marked as __init, it assumes that there are/were guarantees
> that nobody will require actual probing after the driver init. This
> way there is completely no difference where .probe points to.
> If one wants just to make linker happy and not see warnings, almost
> all __init specifications should be dropped out.
>

Ok, I think I can re-implement spear13xx_pcie_init in the way using
platform_driver_probe instead of platform_driver_register and we will
not see neither kernel OOPSes nor linker warnings.

-- 
With best regards,
Matwey V. Kornilov.
Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia
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