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Date: Tue, 13 Dec 2016 18:51:29 +0100
From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>, x86-ml <x86@kernel.org>,
        lkml <linux-kernel@vger.kernel.org>, Andy Lutomirski <luto@kernel.org>
Subject: Re: WARNING: kernel stack frame pointer at ffffffff82e03f40 in
 swapper:0 has bad value (null)
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On Tue, Dec 13, 2016 at 08:55:53AM -0800, Andy Lutomirski wrote:
> I want to file a GCC bug, though.  This code sucks.

Looks like it started doing that with gcc-5. gcc-4.9 output looks fine here:

        .globl  x86_64_start_kernel
        .type   x86_64_start_kernel, @function
x86_64_start_kernel:
.LFB2013:
        .loc 1 134 0
        .cfi_startproc
        pushq   %rbp    #
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp      #,
        .cfi_def_cfa_register 6
        pushq   %rbx    #
        .cfi_offset 3, -24
        .loc 1 134 0
        movq    %rdi, %rbx      # real_mode_data, real_mode_data
.LBB157:
.LBB158:
.LBB159:
.LBB160:
.LBB161:
        .loc 3 69 0
#APP
# 69 "./arch/x86/include/asm/special_insns.h" 1
        mov %cr4,%rax   # val

-- 
Regards/Gruss,
    Boris.

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