linux-kernel - Re: [tip:x86/setup] x86, setup: "glove box" BIOS calls -- infrastructure

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]

Date:	Fri, 10 Apr 2009 10:19:32 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Pavel Machek <pavel@....cz>
CC:	mingo@...hat.com, linux-kernel@...r.kernel.org, tglx@...utronix.de,
	hpa@...ux.intel.com, rjw@...k.pl, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/setup] x86, setup: "glove box" BIOS calls --	infrastructure

Pavel Machek wrote:
> 
>> +	.code16
>> +	.text
>> +	.globl	intcall
>> +	.type	intcall, @function
>> +intcall:
>> +	/* Self-modify the INT instruction.  Ugly, but works. */
>> +	cmpb	%al, 3f
>> +	je	1f
>> +	movb	%al, 3f
>> +	jmp	1f		/* Synchronize pipeline */
>> +1:
> 
> There are various CPU bugs with self-modifying code, but I guess we
> are not using it heavily enough. Also we are single-threaded so that
> should be ok.
> 								Pavel
> 

This case is extremely straightforward, so I'm not worried about it. 
The final JMP is actually not required (there is a LOOP instruction 
between the modify and the invocation point) but is there for extra safety.

FWIW, we already do SMC during the transfer to protected mode 
(pmjump.S), and hopefully got the issues worked out there.

	-hpa
--
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/