linux-kernel - RE: [patch V2 03/13] x86/irq/64: Adjust the per CPU irq stack pointer by 8

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Message-ID: <c7d8e27f99a5410dac934925e0f89a7c@AcuMS.aculab.com>
Date:   Wed, 10 Feb 2021 11:41:34 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Thomas Gleixner' <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
CC:     "x86@...nel.org" <x86@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Helge Deller <deller@....de>,
        "David S. Miller" <davem@...emloft.net>,
        Michael Ellerman <mpe@...erman.id.au>,
        Rich Felker <dalias@...c.org>,
        "Heiko Carstens" <hca@...ux.ibm.com>,
        Kees Cook <keescook@...omium.org>,
        "Lai Jiangshan" <jiangshanlai+lkml@...il.com>
Subject: RE: [patch V2 03/13] x86/irq/64: Adjust the per CPU irq stack pointer
 by 8

From: Thomas Gleixner
> Sent: 09 February 2021 23:41
> From: Thomas Gleixner <tglx@...utronix.de>
> 
> The per CPU hardirq_stack_ptr contains the pointer to the irq stack in the
> form that it is ready to be assigned to [ER]SP so that the first push ends
> up on the top entry of the stack.
...
> Do the -8 adjustment right when storing the pointer and make the data type
> a void pointer to avoid confusion vs. the struct irq_stack data type which
> is on 64bit only used to declare the backing store...

It might be better to make it a pointer to an undefined struct.
That will stop all accidental assignments - except those that
are already 'void *'.

	David

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