Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932106Ab1FPTTH (ORCPT ); Thu, 16 Jun 2011 15:19:07 -0400 Received: from mail-pw0-f46.google.com ([209.85.160.46]:37014 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757099Ab1FPTTF convert rfc822-to-8bit (ORCPT ); Thu, 16 Jun 2011 15:19:05 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=AbPOncUSly8/2oM4pXBzmlYmhvKocLxu43xkI9mgK5W+jtnOB6TP/jaMFCa+nVFI0d aPAApyxN/hbb10cv4yIkFNQbLZJLZankDNvIcaLsflt/pQozIBuoFWXlmmhYhxbknhlz ul+Nie89vdwzHdb9/XXXrOXvaE2n1XCXTHaHU= MIME-Version: 1.0 In-Reply-To: <4DFA4672.5080307@lwfinger.net> References: <4DFA4672.5080307@lwfinger.net> Date: Thu, 16 Jun 2011 21:19:04 +0200 Message-ID: Subject: Re: Faking MMIO ops? Fooling a driver From: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= To: Larry Finger Cc: linux-wireless@vger.kernel.org, Linux Kernel Mailing List , Pekka Paalanen Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2696 Lines: 82 W dniu 16 czerwca 2011 20:07 użytkownik Larry Finger napisał: > On 06/16/2011 12:20 PM, Rafał Miłecki wrote: >> >> W dniu 16 czerwca 2011 16:44 użytkownik Rafał Miłecki >>  napisał: >>> >>> I analyze MMIO dumps of closed source driver and found such a place: >>> W 2 3855.911536 9 0xb06003fc 0x810 0x0 0 >>> R 2 3855.911540 9 0xb06003fe 0x0 0x0 0 >>> W 2 3855.911541 9 0xb06003fe 0x0 0x0 0 >>> >>> After translation: >>>  phy_read(0x0810) ->  0x0000 >>> phy_write(0x0810)<- 0x0000 >>> >>> So it's quite obvious, the driver is reading PHY register, masking it >>> and writing masked value. Unfortunately from just looking at such >>> place we can not guess the mask driver uses. >>> >>> I'd like to fake value read from 0xb06003fe to be 0xFFFF. >>> Is there some ready method for doing such a trick? >>> >>> Dump comes from Kernel hacking → Tracers → MMIO and ndiswrapper. >> >> I can see values in MMIO trace struct are filled in >> arch/x86/mm/mmio-mod.c in "pre" and "post". However still no idea how >> to hack the returned value. >> >> Should I try hacking read[bwl] instead? :| > > Probably. I do not see any way to trace and modify the results for a > particular address without special code. Did you success with writing some special code? Following patch does not seem to work for me: diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h index e0ffa3d..448e4ff 100644 --- a/include/asm-generic/io.h +++ b/include/asm-generic/io.h @@ -23,6 +23,8 @@ #define mmiowb() do {} while (0) #endif +static int zajec = 0; + /*****************************************************************************/ /* * readX/writeX() are used to access memory mapped devices. On some @@ -40,6 +42,11 @@ static inline u8 __raw_readb(const volatile void __iomem *addr) #ifndef __raw_readw static inline u16 __raw_readw(const volatile void __iomem *addr) { + if (zajec++ < 10) + printk(KERN_INFO "[ZAJEC] %d\n", *addr); + if (*addr == 0xfaafc000) + printk(KERN_INFO "[ZAJEC] Bingo!\n"); + //0x1381a8d8 return *(const volatile u16 __force *) addr; } #endif Should I modify different readw? Path include/asm-generic/io.h sounds sane to me, so I modified this one. > FYI, my reference driver for reverse engineering has no instance of a > read/modify/write for PHY register 0x810. Is the code in question for a PHY > type > 6? This is for PHY type 7, AKA "HT". -- Rafał -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/