linux-kernel - Re: [PATCH v3 01/12] x86, boot: move verify

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Message-ID: <CAE9FiQVreVFJ5tASirYkzTUvYw1XombdArqN3N1HnAP9wLijhQ@mail.gmail.com>
Date:	Wed, 21 Nov 2012 11:45:47 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, Matt Fleming <matt.fleming@...el.com>
Subject: Re: [PATCH v3 01/12] x86, boot: move verify_cpu.S after 0x200

On Wed, Nov 21, 2012 at 9:23 AM, H. Peter Anvin <hpa@...or.com> wrote:
> On 11/20/2012 11:15 PM, Yinghai Lu wrote:
>>
>> We are short of space before 0x200 that is entry for startup_64.
>>
>> And we can not change startup_64 to other value --- ABI ?
>
>
> Here you are saying "I don't understand how this works."  It is YOUR
> responsibility to find out and write a definite statement rather than
> leaving that to the reader, or expect the maintainer to edit this.

actually, i can not find that out.
in the code of arch/x86/boot/compressed/head_64.S

        /*
         * Be careful here startup_64 needs to be at a predictable
         * address so I can export it in an ELF header.  Bootloaders
         * should look at the ELF header to find this address, as
         * it may change in the future.
         */
        .code64
        .org 0x200
ENTRY(startup_64)
        /*
         * We come here either from startup_32 or directly from a
         * 64bit bootloader.  If we come here from a bootloader we depend on
         * an identity mapped page table being provied that maps our
         * entire text+data+bss and hopefully all of memory.
         */
#ifdef CONFIG_EFI_STUB
        /*
         * The entry point for the PE/COFF executable is 0x210, so only
         * legacy boot loaders will execute this jmp.
         */
        jmp     preferred_addr

        .org 0x210
        mov     %rcx, %rdi

and it says that 0x200 will be changed later..

so you said it has to stay with 0x200, do you mean 0x210 from PE/COFF
force that?

wonder if you are considering attatched patch to move startup_64 down...
we could kill one jmp.

Thanks

Yinghai

Download attachment "new_startup_64_0x400.patch" of type "application/octet-stream" (1901 bytes)