[yocto] Fix for kernel 3.8/gcc-4.8 segfault on qemuarm

[Khem Raj]

On Jun 17, 2013, at 9:37 PM, Bruce Ashfield <bruce.ashfield at windriver.com> wrote:

> On 13-06-17 11:30 PM, Khem Raj wrote:
>> Hi Bruce and All
>> 
>> Finally after a long innings I have diagnosed the mystery behind the below segfault that we see on kernel 3.8 which compiled with gcc 4.8 but don't show when compiled with gcc 4.7
>> 
>> 
> 
> There also seems to be a follow up patch:
> 
> commit 418df63adac56841ef6b0f1fcf435bc64d4ed177
> Author: Nicolas Pitre <nicolas.pitre at linaro.org>
> Date:   Tue Mar 12 13:00:42 2013 +0100
> 
>    ARM: 7670/1: fix the memset fix
> 
>    Commit 455bd4c430b0 ("ARM: 7668/1: fix memset-related crashes caused by
>    recent GCC (4.7.2) optimizations") attempted to fix a compliance issue
>    with the memset return value.  However the memset itself became broken
>    by that patch for misaligned pointers.
> 
>    This fixes the above by branching over the entry code from the
>    misaligned fixup code to avoid reloading the original pointer.
> 
>    Also, because the function entry alignment is wrong in the Thumb mode
>    compilation, that fixup code is moved to the end.
> 
>    While at it, the entry instructions are slightly reworked to help dual
>    issue pipelines.
> 
>    Signed-off-by: Nicolas Pitre <nico at linaro.org>
>    Tested-by: Alexander Holler <holler at ahsoftware.de>
>    Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
> 
> :100644 100644 d912e73... 94b0650... M  arch/arm/lib/memset.S
> 
> --------
> 
> I've staged it as well, and will do a boot test in the morning once
> my build has completed. Time to call it a night here.

I did not need anything other than the first patch to get over the segfault. but yes it completes the fix
so having both is better

> 
> Bruce
> 
>> Unable to handle kernel paging request at virtual address ffffffff
>> pgd = c0004000
>> [ffffffff] *pgd=07ffe831, *pte=00000000, *ppte=00000000
>> Internal error: Oops: 17 [#1] PREEMPT ARM
>> Modules linked in:
>> CPU: 0    Not tainted  (3.8.0-yocto-standard+ #32)
>> PC is at kmem_cache_alloc+0x38/0x154
>> LR is at subsys_system_register+0x34/0xd8
>> pc : [<c00bd4d8>]    lr : [<c0327244>]    psr: a0000153
>> sp : c7835ef0  ip : c7904590  fp : 00000000
>> r10: c0688dc4  r9 : c06db900  r8 : c0327244
>> r7 : 00000000  r6 : 000080d0  r5 : c7801380  r4 : ffffffff
>> r3 : 00000000  r2 : 00000078  r1 : 000080d0  r0 : c7801380
>> Flags: NzCv  IRQs on  FIQs off  Mode SVC_32  ISA ARM  Segment kernel
>> Control: 00093177  Table: 00004000  DAC: 00000017
>> Process swapper (pid: 1, stack limit = 0xc78341b8)
>> Stack: (0xc7835ef0 to 0xc7836000)
>> 5ee0:                                     c06a5564 c06b8b8c c7834028 00000000
>> 5f00: c0680218 c0327244 c7835f28 c06a5564 00000006 c7834028 c06db900 c0688dd4
>> 5f20: c7835f28 c00089a0 c0657f44 00000006 c086e561 00000006 00000000 c06a5534
>> 5f40: c06a5564 00000006 c06db900 c0680218 c069fd68 0000008e c069fd5c c0680924
>> 5f60: 00000006 00000006 c0680218 00000000 00000000 00000000 00000000 00000000
>> 5f80: c04f5e68 00000000 00000000 00000000 00000000 00000000 00000000 c04f5e70
>> 5fa0: 00000000 00000000 c04f5e68 c000deb0 00000000 00000000 00000000 00000000
>> 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>> 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
>> [<c00bd4d8>] (kmem_cache_alloc+0x38/0x154) from [<c0327244>] (subsys_system_register+0x34/0xd8)
>> [<c0327244>] (subsys_system_register+0x34/0xd8) from [<c0688dd4>] (init_clocksource_sysfs+0x10/0x54)
>> [<c0688dd4>] (init_clocksource_sysfs+0x10/0x54) from [<c00089a0>] (do_one_initcall+0x10c/0x17c)
>> [<c00089a0>] (do_one_initcall+0x10c/0x17c) from [<c0680924>] (kernel_init_freeable+0x164/0x224)
>> [<c0680924>] (kernel_init_freeable+0x164/0x224) from [<c04f5e70>] (kernel_init+0x8/0x150)
>> [<c04f5e70>] (kernel_init+0x8/0x150) from [<c000deb0>] (ret_from_fork+0x14/0x24)
>> Code: e5934000 e3540000 0a00001a e5953014 (e7941003)
>> ---[ end trace f4d187650e17fc5c ]---
>> Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
>> 
>> 
>> Please apply the patch below to linux-yocto-3.8
>> 
>> http://sakrah.dontexist.org/files/patches/0001-ARM-7668-1-fix-memset-related-crashes-caused-by-rece.patch
>> 
>> This is a back port from 3.9 therefore safe. The problem is not limited to linux-yocto it also impacts upstream 3.8 stable
>> but 3.8 stable is end of life so why bother. If linux-yocto upgrades to 3.9 or 3.10 and drops 3.8 in 1.5 then we are ok too.
>> 
>> Let me know how it goes
>> 
>> Thanks
>> 
>> -Khem
>> 
>