From: "H. Peter Anvin" <hpa@zytor.com>
To: Yinghai Lu <yinghai@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
"Eric W. Biederman" <ebiederm@xmission.com>,
linux-kernel@vger.kernel.org,
Matt Fleming <matt.fleming@intel.com>
Subject: Re: [PATCH v2 03/13] x86: Add macro for 64bit entry startup_64
Date: Mon, 19 Nov 2012 15:13:25 -0800 [thread overview]
Message-ID: <50AABD15.1050809@zytor.com> (raw)
In-Reply-To: <CAE9FiQV=G=5zAqv7EiUnb=O7znxuieiCawfgomv9aPNwVAV4uQ@mail.gmail.com>
On 11/19/2012 02:53 PM, Yinghai Lu wrote:
>>
>> We can't change the 0x200 value, ever, because there are already things
>> that use the 64-bit entry point. As such, these macros and the bzImage
>> fields are pointless; let's not bother and instead document the 0x200 as
>> the permanently fixed address of the 64-bit entry point.
>
> ok,
>
> any other field, in header struct field that we can use to tell
> bzImage could be used that
> 0x200 directly?
>
> hardware_subarch?
>
There isn't one... this dates back all the way to the original x86-64
kernels.
Are you asking if we can tell this is a 64-bit kernel (as opposed to a
32-bit kernel, which obviously doesn't have a 64-bit entry point)?
Unfortunately there isn't an intentional one that I know of. There
might be an accidental such indicator, but we'd have to go back to look
at 8+ years of kernels. We can't even rely on a jmp instruction at the
address...
-hpa
next prev parent reply other threads:[~2012-11-19 23:13 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-18 7:09 [PATCH v2 00/13] x86, boot, 64bit: Add support for loading ramdisk and bzImage high Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 01/13] x86, boot: move verify_cpu.S after 0x200 Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 02/13] x86, boot: Move lldt/ltr out of 64bit code section Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 03/13] x86: Add macro for 64bit entry startup_64 Yinghai Lu
2012-11-19 22:42 ` H. Peter Anvin
2012-11-19 22:53 ` Yinghai Lu
2012-11-19 23:13 ` H. Peter Anvin [this message]
2012-11-19 23:46 ` Yinghai Lu
2012-11-19 23:55 ` H. Peter Anvin
2012-11-20 0:39 ` Yinghai Lu
2012-11-20 19:20 ` Yinghai Lu
2012-11-20 20:44 ` H. Peter Anvin
2012-11-20 20:55 ` Yinghai Lu
2012-11-20 21:12 ` H. Peter Anvin
2012-11-21 0:20 ` Yinghai Lu
2012-11-21 0:28 ` H. Peter Anvin
2012-11-21 0:32 ` Yinghai Lu
2012-11-21 0:34 ` Yinghai Lu
2012-11-21 0:45 ` H. Peter Anvin
2012-11-18 7:09 ` [PATCH v2 04/13] x86, 64bit: set extra ident page table for whole kernel range Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 05/13] x86, 64bit: add support for loading kernel above 512G Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 06/13] x86: Merge early_reserve_initrd for 32bit and 64bit Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 07/13] x86: add get_ramdisk_image/size Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 08/13] x86, boot: add get_cmd_line_ptr() Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 09/13] x86, boot: Don't check if cmd_line_ptr is accessible in misc/decompressor() Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 10/13] x86, boot: update cmd_line_ptr to unsigned long Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 11/13] x86: use io_remap to access real_mode_data Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 12/13] x86, boot: add fields to support load bzImage and ramdisk high Yinghai Lu
2012-11-18 7:09 ` [PATCH v2 13/13] x86: remove 1024g limitation for kexec buffer on 64bit Yinghai Lu
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