lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <1210827473.23707.133.camel@caritas-dev.intel.com>
Date:	Thu, 15 May 2008 12:57:53 +0800
From:	"Huang, Ying" <ying.huang@...el.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Vivek Goyal <vgoyal@...hat.com>, Pavel Machek <pavel@....cz>,
	nigel@...el.suspend2.net, "Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [PATCH] kexec based hibernation: a prototype of kexec
	multi-stage load

On Wed, 2008-05-14 at 14:43 -0700, Eric W. Biederman wrote:
[...]
> Then as a preliminary design let's plan on this.
> 
> - Pass the rentry point as the return address (using the C ABI).
>   We may want to load the stack pointer etc so we can act as
>   a direct entry point for new code.

There are some issues about passing entry point as return address. The
kexec jump (or kexec with return) is used for

- Switching between original kernel (A) and kexeced kernel (B)
- Call some code (such as BIOS code) in physical mode

1) When call some code in physical mode, the called code can use a
simple return to return to kernel A. So there is no return address on
stack after return to kernel A. Instead, argument 1 is on stack top.

2) When switch back from kernel B to kernel A, kernel B will call the
jump back entry of kernel A with C ABI. So, the return address is on
stack top. And kernel A get jump back entry of kernel B via the return
address.

Because the stack state is different between 1) and 2), the jump back
entry of kernel A should distinguish them. Possible solution can be as
follow:

a) Before kernel A call some physical mode code or kernel B, it set
argument 1 to be a magic number that can not be return address (such as
-1). Jump back entry of kernel A can check whether the stack top is
argument 1 or return address.

b) Distinguish by return address. Such as, called physical mode code
must return 0, while kernel B must set %eax to some other number.

c) Use different entry point for 1) and 2). Two entry points are deduced
from return address. Such as:

entry1 = return_address;
entry2 = return_address & ~0xfff;	/* page aligned */

entry1 is used by physical mode code. entry2 is used by kernel B.


Which one is better? Or some other solution?

Best Regards,
Huang Ying

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ