[U-Boot] crash in usb_stor_get_info using pre-relocation address for ss->transport

[Chris Packham]

On Thu, Jun 13, 2013 at 11:24 PM, Albert ARIBAUD
<albert.u.boot at aribaud.net> wrote:
> Hi Chris,
>
> On Thu, 13 Jun 2013 22:19:54 +1200, Chris Packham
> <judge.packham at gmail.com> wrote:
>
>> Hi Albert,
>>
>> On 13/06/13 17:43, Albert ARIBAUD wrote:
>> > Hi Chris,
>> >
>> > On Thu, 13 Jun 2013 13:16:17 +1200, Chris Packham
>> > <judge.packham at gmail.com> wrote:
>> >
>> >> On Thu, Jun 13, 2013 at 12:02 PM, Chris Packham <judge.packham at gmail.com> wrote:
>> >>> Hi,
>> >>>
>> >>> I've just found a crash in usb_stor_get_info (actually usb_inquiry
>> >>> which gets auto-inlined). The cause seems to be that ss->transport is
>> >>> set to the pre-relocation address of usb_stor_BBB_transport. Yet
>> >>> ss->transport_reset is set to the correct relocated address of.
>> >>>
>> >>> The difference between the two is that usb_stor_BBB_reset is declared
>> >>> static and usb_stor_BBB_transport is not. Changing
>> >>> usb_stor_BBB_transport to a static makes things work but I notice that
>> >>> none of the other transport functions are static either so I'm
>> >>> thinking I haven't actually fixed the problem rather just masked it.
>> >>
>> >> Actually I see commit 199adb60 (common/misc: sparse fixes) does change
>> >> the transport functions to static. Which is the change I was looking
>> >> at. I still don't know if it is fixing a problem or masking a
>> >> different one but this is probably why no-one else is complaining that
>> >> their usb mass storage devices are causing crashes. I'll cherry-pick
>> >> this to fix my problem.
>> >>
>> >>>
>> >>> I did  some poking with a lauterbach and from the disassembly it looks
>> >>> like there is a translation table being used when the function
>> >>> pointers are setup by usb_storage_probe and when declared normally
>> >>> usb_stor_BBB_transport ends up at the end. Everything else has the
>> >>> correct relocated address so I wonder if there is an off-by-one error
>> >>> in whatever creates that table.
>> >
>> > Can you elaborate? The only relocation-related table that I know of is
>> > the one used in relocate_code(), and no other relocation-fix table
>> > exists or is used anywhere else.
>> >
>> >>> Does this sound familiar to anyone.
>> >
>> > Familiar, no, but it does set in my mind, if not a blaring alarm with
>> > flashing beacons, at least a blinking red light with a beep, so let's
>> > analyize this.
>> >
>> > Amicalement,
>> >
>>
>> I'm at home right now so I don't have the board in front of me. Here's
>> some disassembly that gdb gives me
>>
>> int usb_stor_BBB_transport(); (without 199adb60)
>>
>> 1272            case US_PR_BULK:
>> 1273                    USB_STOR_PRINTF("Bulk/Bulk/Bulk\n");
>> 1274                    ss->transport = usb_stor_BBB_transport;
>>    0xfffa9780 <+208>:   lwz     r0,-4(r30)
>>    0xfffa9784 <+212>:   stw     r0,48(r31)
>>
>> 1275                    ss->transport_reset = usb_stor_BBB_reset;
>>    0xfffa9788 <+216>:   lwz     r0,-4268(r30)
>>    0xfffa978c <+220>:   b       0xfffa9770 <usb_storage_probe+192>
>>
>> 1276                    break;
>>
>> static int usb_stor_BBB_transport(); (with 199adb60)
>>
>> 1261            case US_PR_CB:
>> 1262                    USB_STOR_PRINTF("Control/Bulk\n");
>> 1263                    ss->transport = usb_stor_CB_transport;
>>    0xfffa9608 <+180>:   lwz     r0,-4240(r30)
>>    0xfffa960c <+184>:   stw     r0,48(r31)
>>
>> 1264                    ss->transport_reset = usb_stor_CB_reset;
>>    0xfffa9610 <+188>:   lwz     r0,-4248(r30)
>>    0xfffa9614 <+192>:   stw     r0,44(r31)
>>
>> 1265                    break;
>>
>> So r30 is the table thing I was talking about. I'm assuming it's
>> something maintained by the compiler/linker. From memory -4(r30) was
>> 0xfffaabcd everything else (including -4268(r30)) seemed to be the
>> relocated address for various symbols, hence my comment about a possible
>> off-by-one in whatever maintains that table.
>>
>> Because it's probably relevant here are my compiler details
>>   $ powerpc-e500-linux-gnu-gcc --version
>>   powerpc-e500-linux-gnu-gcc (Gentoo 4.6.3-r1 p1.9, pie-0.5.2) 4.6.3
>>
>> When I get back to work tomorrow I can post a dump of r30 from a running
>> system.
>
> So that's PPC. Maybe PPC does manual fixing -- I was being ARM-centric
> there.
>
> Amicalement,
> --
> Albert.

Another relevant detail that I left out is that I'm booting via the
CPC (from SPI or NOR). So the pre-relocation address is definitely
invalid for me, but it might be valid for others (problems with
re-flashing the board aside).

Here's some info I was able to extract using the lauterbach.

R(R30) = 7FF9AE00
R(R30) - 0x4    7FF9ADFC = FFFA94A8
R(R30) - 0x10AC 7FF99D54 = 7FF586E8
.u-boot\usb_storage\usb_stor_BBB_reset
R(R30) - 0x8    7FF9ADF8 = 7FFB017C  .u-boot\Global\NetArpWaitTimerStart


And fom u-boot.map
 .got           0x00000000fffe8024     0x2de8 arch/powerpc/cpu/mpc85xx/start.o
                0x00000000fffeae00                _GLOBAL_OFFSET_TABLE_
                0x00000000fffeae10                PROVIDE
(_GLOBAL_OFFSET_TABLE_, (. + 0x4))
                0x00000000fffeae0c                _FIXUP_TABLE_ = .

so 7FF9AE00 is the relocated address of _GLOBAL_OFFSET_TABLE_