linux-kernel - Re: [PATCH] MIPS: IRQ Stack: Unwind IRQ stack onto task stack

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Date:   Tue, 4 Apr 2017 13:18:58 +0100
From:   Matt Redfearn <matt.redfearn@...tec.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
CC:     Ralf Baechle <ralf@...ux-mips.org>, <linux-mips@...ux-mips.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Marcin Nowakowski <marcin.nowakowski@...tec.com>,
        Masanari Iida <standby24x7@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        LKML <linux-kernel@...r.kernel.org>,
        James Hogan <james.hogan@...tec.com>,
        Paul Burton <paul.burton@...tec.com>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] MIPS: IRQ Stack: Unwind IRQ stack onto task stack

Hi Jason,


On 04/04/17 12:58, Jason A. Donenfeld wrote:
> This indeed is useful. Out of curiosity, are other archs using a
> similar technique? In anycase,
>
> Acked-by: Jason A. Donenfeld <Jason@...c4.com>

Yes, at least x86 and ARM64 do the same thing (probably more)

x86 saves the previous stack pointer on the IRQ stack in 
http://lxr.free-electrons.com/source/arch/x86/kernel/irq_32.c#L70
which is then unwound in 
http://lxr.free-electrons.com/source/arch/x86/kernel/dumpstack.c#L51

ARM64 saves the task SP in 
http://lxr.free-electrons.com/source/arch/arm64/kernel/entry.S#L249
And unwinds it in 
http://lxr.free-electrons.com/source/arch/arm64/kernel/traps.c#L140

Thanks,
Matt