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Subject: Re: tboot: non-0 tboot_addr but it is not of type E820_RESERVED
To: "Elliott, Robert (Persistent Memory)" <elliott@hpe.com>,
        "joseph.cihula@intel.com" <joseph.cihula@intel.com>,
        "richard.l.maliszewski@intel.com" <richard.l.maliszewski@intel.com>,
        "gang.wei@intel.com" <gang.wei@intel.com>,
        "shane.wang@intel.com" <shane.wang@intel.com>
References: <94D0CD8314A33A4D9D801C0FE68B40295BE5000E@G9W0745.americas.hpqcorp.net>
 <94D0CD8314A33A4D9D801C0FE68B40295BE775BC@G4W3202.americas.hpqcorp.net>
Cc: "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "tboot-devel@lists.sourceforge.net" 
	<tboot-devel@lists.sourceforge.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Knippers, Linda" <linda.knippers@hpe.com>,
        "Kani, Toshimitsu" <toshi.kani@hpe.com>
From: "H. Peter Anvin" <hpa@zytor.com>
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Date: Tue, 1 Dec 2015 18:20:06 -0800
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On 12/01/15 17:26, Elliott, Robert (Persistent Memory) wrote:
>
> Per an hpa suggestion, I compared two versions of grub:
>
> upstream grub (with "linux" in grub.cfg):
> tboot_probe boot_params[0] = 0000008000000000 0000000000000070
> tboot_probe boot_params[16] = 1000000400032000 0000009100003000
> tboot_probe boot_params[32] = 3fa3001000100810 0808080008180000
> tboot_probe boot_params[48] = 0000000000000000 0000000000000000
> tboot probe boot_params[64] = 0000000000000000 0000000000000000
> tboot_probe boot_params[80] = 0000000000000000 0000000000000000
> tboot_probe boot_params[96] = 0000000000000000 0000000000000000
> tboot_probe boot_params[112] = 0000000000000000 0000000000000000
> tboot_probe boot_params[128] = 0000000000000000 0000000000000000
> tboot_probe boot_params[144] = 0000000000000000 0000000000000000
> tboot_probe boot_params[160] = 0000000000000000 0000000000000000
> tboot_probe boot_params[176] = 0000000000000000 0000000000000000
> tboot_probe boot_params[192] = 0000000000000000 0000000000000000
> ...
> <no complaint about tboot_addr>
>
> Fedora 22 grub (with "linuxefi" in grub.cfg):
> tboot_probe boot_params[0] = 0000000000000000 0000000000000070
> tboot_probe boot_params[16] = 0000000400032000 0000009100003000
> tboot_probe boot_params[32] = 0000000000100810 0808080008180000
> tboot_probe boot_params[48] = 0000010000000100 0000000000000000
> tboot_probe boot_params[64] = 557365206120626f 6f74206c6f616465
> tboot_probe boot_params[80] = 722e0d0a0a52656d 6f7665206469736b
> tboot_probe boot_params[96] = 20616e6420707265 737320616e79206b
> tboot_probe boot_params[112] = 657920746f207265 626f6f742e2e2e0d
> tboot_probe boot_params[128] = 0a00504500006486 0400000000000000
> tboot_probe boot_params[144] = 000001000000a000 06020b020214f017
> tboot_probe boot_params[160] = 5c00000000001076 d200104600000002
> tboot_probe boot_params[176] = 0000000000000000 0000200000002000
> tboot_probe boot_params[192] = 0000000000000000 0000000000000000
> ...
> [    0.000000] tboot: non-0 tboot_addr 0x6b7369642065766f but it is not of type E820_RESERVED
>
> In both cases, the kernel is compiled with CONFIG_EFI_STUB=y.
>
> tboot_addr is at offset 88.  Offset 64 is an ASCII string that says:
> "Use a boot loader.
>
> Remove disk and press any key to reboot..."
>
> and is from arch/x86/boot/header.S, which is placing that string
> at offset 64 (0x3c + 4) from .bstext (which precedes .bsdata) if
> CONFIG_EFI_STUB is true.
>
> #ifdef CONFIG_EFI_STUB
>          .org    0x3c
>          #
>          # Offset to the PE header.
>          #
>          .long   pe_header
> #endif /* CONFIG_EFI_STUB */
>
>          .section ".bsdata", "a"
> bugger_off_msg:
>          .ascii  "Use a boot loader.\r\n"
>          .ascii  "\n"
>          .ascii  "Remove disk and press any key to reboot...\r\n"
>          .byte   0
>

Most likely the "linuxefi" boot method uses the EFI handover protocol, 
however.  It looks like they don't start with a properly zeroed structure...

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