linux-kernel - Re: [PATCH v3 11/12] x86, boot: add fields to support load bzImage and ramdisk high

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Message-ID: <CAE9FiQVDbR4d3-SgQ0O3hOWqApN241Pxd7fvF7-wwPWbdX75ug@mail.gmail.com>
Date:	Thu, 22 Nov 2012 12:18:15 -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, Rob Landley <rob@...dley.net>,
	Matt Fleming <matt.fleming@...el.com>
Subject: Re: [PATCH v3 11/12] x86, boot: add fields to support load bzImage
 and ramdisk high

On Thu, Nov 22, 2012 at 10:51 AM, H. Peter Anvin <hpa@...or.com> wrote:
> On 11/22/2012 10:50 AM, Yinghai Lu wrote:
>>
>>
>> ok, I will use 0xc0 instead, and at the same time try to fix that from
>> kexec.
>>
>> then user will still have chance to use old kexec tools without enable
>> CONFIG_EFI_STUB in kernel.
>>
>
> If we can get the sentinel hack to work that would probably be useful, but
> we need to understand the exact pathology.

for kexec bzImage --real-mode-entry, code after setup_header will be executed.

so we could clear value before setup_header after copy 16bit section
from bzImage...

Index: kexec-tools/kexec/arch/i386/kexec-bzImage.c
===================================================================
--- kexec-tools.orig/kexec/arch/i386/kexec-bzImage.c
+++ kexec-tools/kexec/arch/i386/kexec-bzImage.c
@@ -212,6 +212,16 @@ int do_bzImage_load(struct kexec_info *i
 	setup_size = kern16_size + command_line_len + PURGATORY_CMDLINE_SIZE;
 	real_mode = xmalloc(setup_size);
 	memcpy(real_mode, kernel, kern16_size);
+	/*
+	 * clear value before header
+	 * not not clear value after header, --real-mode-entry
+	 * need code after header.
+	 */
+	memset(real_mode, 0, 0x1f1);
+	if (!real_mode_entry) {
+		/* clear value after setup_header  */
+		memset((unsigned char *)real_mode + 0x290, 0, kern16_size - 0x290);
+	}

 	if (info->kexec_flags & (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT)) {
 		/* If using bzImage for capture kernel, then we will not be
--
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