linux-kernel - Re: [RFC 12/17] x86/xen/64: Clean up SP code in cpu_initialize

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Message-ID: <20170912200952.2r7xxgtbjwl7jp6j@treble>
Date:   Tue, 12 Sep 2017 15:09:52 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [RFC 12/17] x86/xen/64: Clean up SP code in
 cpu_initialize_context()

On Wed, Sep 06, 2017 at 02:36:57PM -0700, Andy Lutomirski wrote:
> @@ -293,12 +294,19 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
>  #endif
>  	memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
>  
> +	/*
> +	 * Bring up the CPU in cpu_bringup_and_idle() with the stack
> +	 * pointing just below where pt_regs would be if it were a normal
> +	 * kernel entry.
> +	 */
>  	ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
>  	ctxt->flags = VGCF_IN_KERNEL;
>  	ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
>  	ctxt->user_regs.ds = __USER_DS;
>  	ctxt->user_regs.es = __USER_DS;
>  	ctxt->user_regs.ss = __KERNEL_DS;
> +	ctxt->user_regs.cs = __KERNEL_CS;
> +	ctxt->user_regs.esp = task_top_of_stack(idle) - sizeof(struct pt_regs);

Isn't this the same as task_pt_regs(idle)?

-- 
Josh