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Date: Tue, 12 Aug 2014 10:50:02 +0100
From: "Jan Beulich" <JBeulich@suse.com>
To: "Denys Vlasenko" <dvlasenk@redhat.com>
Cc: "Andy Lutomirski" <luto@amacapital.net>,
        "Kees Cook" <keescook@chromium.org>, "Will Drewry" <wad@chromium.org>,
        "Frederic Weisbecker" <fweisbec@gmail.com>,
        "Denys Vlasenko" <vda.linux@googlemail.com>, "X86 ML" <x86@kernel.org>,
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        "Oleg Nesterov" <oleg@redhat.com>,
        "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 4/5] x86: entry_64.S: always allocate complete
 "struct pt_regs"
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>>> On 12.08.14 at 11:31, <dvlasenk@redhat.com> wrote:
> Jan, Pater, does this look correct _and_ human-understandable?
> 
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -652,10 +652,14 @@ END(interrupt)
>         cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp
>         CFI_DEF_CFA_REGISTER    rsi
>         pushq %rsi
> +       /*
> +        * For debugger:
> +        * "CFA (Current Frame Address) is the value on stack + offset"
> +        */
>         CFI_ESCAPE      0x0f /* DW_CFA_def_cfa_expression */, 6, \
> -                       0x77 /* DW_OP_breg7 */, 0, \
> +                       0x77 /* DW_OP_breg7 (rsp) */, 0, \

I'm fine with the changes above.

>                         0x06 /* DW_OP_deref */, \
> -                       0x08 /* DW_OP_const1u */, SS+8-RBP, \
> +                       0x08 /* DW_OP_const1u */, SIZEOF_PTREGS-RBP, \

But I'd rather not see this one alone changed - either change all
similar uses of SS, or leave the one here alone.

Jan