From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752899AbbGBD5H (ORCPT ); Wed, 1 Jul 2015 23:57:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42460 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751293AbbGBD46 (ORCPT ); Wed, 1 Jul 2015 23:56:58 -0400 Message-ID: <5594B68A.3000205@redhat.com> Date: Wed, 01 Jul 2015 20:56:58 -0700 From: Dan Mick User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Subject: failing while writing to disk with BIOS in realmode setup Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org What might I be doing wrong? Why won't this code succeed to write to the (otherwise empty) drive 1 from kernel setup's main? I'm 100% certain this is the code I'm booting (with grub/bzImage); it's as though the intcalls just never happen (or fail for some reason I can't get telemetry on, which is why I'm trying this technique in the first place). --- /var/tmp/main.c 2015-06-30 14:08:52.435618099 -0700 +++ arch/x86/boot/main.c 2015-07-01 20:33:32.227506260 -0700 @@ -132,6 +131,8 @@ } } +char block[512] = "DJM WAS HERE "; + void main(void) { /* First, copy the boot header into the "zeropage" */ @@ -142,6 +143,22 @@ if (cmdline_find_option_bool("debug")) puts("early console in setup code\n"); + struct biosregs ireg, oreg; + initregs(&ireg); + ireg.ah = 0; // reset drive 81 + ireg.dl = 0x81; + intcall(0x13, &ireg, &oreg); + + initregs(&ireg); + ireg.ah = 0x03; // write AL sectors to drive DL CHS CH/DH/CL + ireg.al = 1; + ireg.dl = 0x81; + ireg.cl = 1; + ireg.dh = 0; + ireg.es = ds(); + ireg.bx = (uint)(uintptr_t)█ + + intcall(0x13, &ireg, &oreg); /* End of heap check */ init_heap();