Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 18 Oct 2001 05:57:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 18 Oct 2001 05:57:16 -0400 Received: from [195.66.192.167] ([195.66.192.167]:21772 "EHLO Port.imtp.ilyichevsk.odessa.ua") by vger.kernel.org with ESMTP id ; Thu, 18 Oct 2001 05:56:53 -0400 Date: Thu, 18 Oct 2001 12:56:29 +0200 From: vda X-Mailer: The Bat! (v1.44) Reply-To: vda Organization: IMTP X-Priority: 3 (Normal) Message-ID: <741181208.20011018125629@port.imtp.ilyichevsk.odessa.ua> To: linux-kernel@vger.kernel.org Subject: [PATCH] setup.S: fix for BIOS/DOS not reporting ext mem size Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Linus, Alan, This patch to i386 setup.S resulted from my attempts to load big bzImages from DOS. Loadlin fails at aroung 1020000 bytes, I didn't want to mess with that much asm in loadlin src and wrote new loader from scratch mostly in c. I had a problem booting from DOS on pc with 196 mb or ram. It turned out int15/e801 and int15/88 reported zero ext mem -> "Less than 4MB" type hang. Digging in loadlin sources turned out some horrors (loadlin hooks itself on int 15/88 and reads CMOS) I think it's cleaner to do this in setup.S rather than jump thru the hoops in DOS loader. Attached patch does that *only if* int15 methods fail. It does not break existing practice, only adds just another fallback in case of brain damage. I couldn't resist and fixed some typos, cleaned up some label names and replaced some instructions with shorter code :-) Tested on three boxes. Works for me. :-) -- Best regards, vda mailto:vda@port.imtp.ilyichevsk.odessa.ua diff -ubB --expand-tabs setup.S.orig setup.S --- setup.S.orig Mon Sep 24 00:58:58 2001 +++ setup.S Thu Oct 18 11:36:24 2001 @@ -39,9 +39,13 @@ * from Ralf Brown interrupt list seem to indicate AX/BX should be used * anyway. So to avoid breaking many machines (presumably there was a reason * to orginally use CX/DX instead of AX/BX), we do a kludge to see - * if CX/DX have been changed in the e801 call and if so use AX/BX . + * if CX/DX have been changed in the e801 call and if so use AX/BX. * Michael Miller, April 2001 * + * Even more fixes for memory detection when started from DOS + * TODO: maybe we can just resort to memory scan on our own + * to stop using int15/e820,int15/e801,int15/88,cmos once and for all? + * october 2001 */ #include @@ -297,13 +301,13 @@ #define SMAP 0x534d4150 -meme820: +mem_e820: xorl %ebx, %ebx # continuation counter movw $E820MAP, %di # point into the whitelist # so we can have the bios # directly write into it. -jmpe820: +jmp820: movl $0x0000e820, %eax # e820, upper word zeroed movl $SMAP, %edx # ascii 'SMAP' movl $20, %ecx # size of the e820rec @@ -327,12 +331,10 @@ jnl bail820 incb (E820NR) - movw %di, %ax - addw $20, %ax - movw %ax, %di + addw $20, %di again820: - cmpl $0, %ebx # check to see if - jne jmpe820 # %ebx is set to EOF + testl %ebx, %ebx # check to see if + jnz jmp820 # %ebx is set to EOF bail820: @@ -344,10 +346,10 @@ # alternative new memory detection scheme, and it's sensible # to write everything into the same place.) -meme801: +mem_e801: stc # fix to work around buggy - xorw %cx,%cx # BIOSes which dont clear/set - xorw %dx,%dx # carry on pass/error of + xorw %cx, %cx # BIOSes which dont clear/set + xorw %dx, %dx # carry on pass/error of # e801h memory size call # or merely pass cx,dx though # without changing them. @@ -355,28 +357,62 @@ int $0x15 jc mem88 - cmpw $0x0, %cx # Kludge to handle BIOSes - jne e801usecxdx # which report their extended - cmpw $0x0, %dx # memory in AX/BX rather than - jne e801usecxdx # CX/DX. The spec I have read + testw %cx, %cx # Kludge to handle BIOSes + jnz e801use_cxdx # which report their extended + testw %dx, %dx # memory in AX/BX rather than + jnz e801use_cxdx # CX/DX. The spec I have read movw %ax, %cx # seems to indicate AX/BX movw %bx, %dx # are more reasonable anyway... -e801usecxdx: - andl $0xffff, %edx # clear sign extend +e801use_cxdx: + movzwl %dx, %edx # clear sign extend shll $6, %edx # and go from 64k to 1k chunks - movl %edx, (0x1e0) # store extended memory size - andl $0xffff, %ecx # clear sign extend - addl %ecx, (0x1e0) # and add lower memory into - # total size. + movzwl %cx, %ecx # clear sign extend + addl %ecx, %edx # add lower memory to + movl %edx, (0x1e0) # extended, store # Ye Olde Traditional Methode. Returns the memory size (up to 16mb or # 64mb, depending on the bios) in ax. mem88: #endif + #stc # guard against brain damage - + # int 15 must clear cf to indicate success + clc # unbelievable: some BIOSes/DOSes can leave + # cf as is so I had to abandon stc trick movb $0x88, %ah int $0x15 + jc mem_cmos + testw %ax, %ax + jnz mem_store + +# Fallback: if int15/88 fails, get same data from CMOS +# this works around extremely stupid case I had with PC not booting +# from DOS when I put 196 megs of RAM in it +# (it reported 0 via int15/e801 and int15/88) +# Also this makes unnecessary for loadlin to jump thru the hoops +# just in order to let us know ext mem size +# (it hooks itself on int 15/88 and does CMOS reads for us) +mem_cmos: + pushf + cli + movb $0x18, %al + outb %al, $0x70 + #iodelay? + inb $0x71, %al + movb %al, %ah + #iodelay? + movb $0x17, %al + outb %al, $0x70 + #iodelay? + inb $0x71, %al + popf + +mem_store: + cmpw $0xffff-0x400, %ax # We want to be sure it won't roll over + jbe mem_store2 # 16 bit value when low 1024k gets added + movw $0xffff-0x400, %ax # thus max memtop is 0xffff*1k = 64m-1k +mem_store2: movw %ax, (2) # Set the keyboard repeat rate to the max - 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/