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Re: Odd gcc-6.3.0 code generation on mips64 platform causing kernel Oops
On 01/23/2017 10:34, Andrew Haley wrote:
> On 23/01/17 15:26, Joshua Kinard wrote:
>> I am not sure what this lone store-doubleword instruction is exactly doing, nor
>> can I locate where in the gcc MIPS code it is being generated from.
>
> It's a stack probe, making sure that there is enough stack space. Its
> only purpose is to provide a SEGV if there is not enough kernel stack.
>
> Look for`-fstack-check' as a GCC argument.
>
>
> Andrew.
Okay, that explains that. I rebuilt the affected kernel with
'-fno-stack-check', and that particular platform boots now (it has other
issues, but it at least gets past early init).
So now the question is why stack-probing kills this machine on generic MIPS
code that its smaller cousin is seemingly unaffected by. I do know that IP27
has a different set of memory initialization routines in the MIPS code, so is
it possible that, at the point that _raw_spin_lock_irq is called and the
stack-probe happens, that there isn't any stack space available because the
IP27-specific memory init hasn't yet completed?
--
Joshua Kinard
Gentoo/MIPS
kumba@gentoo.org
6144R/F5C6C943 2015-04-27
177C 1972 1FB8 F254 BAD0 3E72 5C63 F4E3 F5C6 C943
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