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

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Message-ID: <CAJs94EaCsiFkJQaohmbsFnP4qKr6u9B76=HY2H88A7TswutVHg@mail.gmail.com>
Date:	Mon, 9 Feb 2015 17:11:21 +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 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.

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