From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stas Sergeev Subject: Re: Using Linux+dosemu to install Windows Date: Fri, 26 Jul 2002 18:02:19 +0400 Sender: linux-msdos-owner@vger.kernel.org Message-ID: <3D41566B.5030903@yahoo.com> Reply-To: stas.orel@mailcity.com, stas.orel@mailcity.com Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------040509000006080707030309" Return-path: List-Id: To: linux-msdos@vger.kernel.org This is a multi-part message in MIME format. --------------040509000006080707030309 Content-Type: text/plain; charset=KOI8-R; format=flowed Content-Transfer-Encoding: 7bit Hello. Patrick J. LoPresti wrote: > By instrumenting the code a bit, I learned > that winnt.exe is attempting to invoke the pushfd and popfd > instructions (opcodes 0x9c and 0x9d, respectively), which > dosemu does not support. Good investigation but actually you are hacking the wrong place. These instructions are handled in handle_vm86_fault() which is in /usr/src/linux/arch/i386/kernel/vm86.c The attached patch must be a good start for fixing the problem. It is against the latest 2.4.19-pre-ac kernels and probably can't be applied to 2.4.18 because -ac tree have a lot of changes in vm86. > All winnt.exe is really doing is trying to determine whether the > processor is a 486 or higher. It does this by using pushfd and popfd > to attempt to alter the next-to-highest bit of the EFLAGS register. No, it tries to alter the AC flag which is a bit 2 of the higher word of eflags. But dosemu explicitly clears this flag because due to some unknown bugs it sometimes sets spuriously. grep the do_vm86.c for the string "BUG:" and comment the relevant code, then winnt.exe will work. > So, my question boils down to this: How can I modify the EFLAGS > register from within vm86_GP_fault()? If someone will tell me this, I > will submit a patch to add support for emulating the pushf/pushfd and > popf/popfd opcodes. Well, but this won't solve the AC problem... --------------040509000006080707030309 Content-Type: text/plain; name="vm86_pref.diff" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="vm86_pref.diff" --- linux/arch/i386/kernel/vm86.c Sat Jun 15 19:46:46 2002 +++ linux/arch/i386/kernel/vm86.c Fri Jul 26 14:25:35 2002 @@ -502,8 +502,9 @@ void handle_vm86_fault(struct kernel_vm86_regs * regs, long error_code) { - unsigned char *csp, *ssp; + unsigned char *csp, *ssp, opcode; unsigned short ip, sp; + int prefix66, pref_done; #define CHECK_IF_IN_TRAP \ if (VMPI.vm86dbg_active && VMPI.vm86dbg_TFpendig) \ @@ -518,63 +519,61 @@ sp = SP(regs); ip = IP(regs); - switch (popb(csp, ip, simulate_sigsegv)) { - - /* operand size override */ - case 0x66: - switch (popb(csp, ip, simulate_sigsegv)) { + prefix66 = 0; + pref_done = 0; + do { + switch (opcode = popb(csp, ip, simulate_sigsegv)) { + case 0x66: /* operand prefix */ prefix66=1; break; + case 0x67: /* address prefix */ break; + case 0x2e: /* CS */ break; + case 0x3e: /* DS */ break; + case 0x26: /* ES */ break; + case 0x36: /* SS */ break; + case 0x65: /* GS */ break; + case 0x64: /* FS */ break; + case 0xf2: /* repnz */ break; + case 0xf3: /* rep */ break; + default: pref_done = 1; + } - /* pushfd */ - case 0x9c: - pushl(ssp, sp, get_vflags(regs), simulate_sigsegv); - SP(regs) -= 4; - IP(regs) += 2; - VM86_FAULT_RETURN; + if (!pref_done) + IP(regs)++; /* prefix found, adjust IP */ + else + break; /* no more prefixes */ + } while (1); - /* popfd */ - case 0x9d: - { - unsigned long newflags=popl(ssp, sp, simulate_sigsegv); - SP(regs) += 4; - IP(regs) += 2; - CHECK_IF_IN_TRAP; - set_vflags_long(newflags, regs); - VM86_FAULT_RETURN; - } - - /* iretd */ - case 0xcf: - { - unsigned long newip=popl(ssp, sp, simulate_sigsegv); - unsigned long newcs=popl(ssp, sp, simulate_sigsegv); - unsigned long newflags=popl(ssp, sp, simulate_sigsegv); - SP(regs) += 12; - IP(regs) = (unsigned short)newip; - regs->cs = (unsigned short)newcs; - CHECK_IF_IN_TRAP; - set_vflags_long(newflags, regs); - VM86_FAULT_RETURN; - } - /* need this to avoid a fallthrough */ - default: - return_to_32bit(regs, VM86_UNKNOWN); - } + switch (opcode) { /* pushf */ case 0x9c: - pushw(ssp, sp, get_vflags(regs), simulate_sigsegv); - SP(regs) -= 2; + if (prefix66) { + pushl(ssp, sp, get_vflags(regs), simulate_sigsegv); + SP(regs) -= 4; + } else { + pushw(ssp, sp, get_vflags(regs), simulate_sigsegv); + SP(regs) -= 2; + } IP(regs)++; VM86_FAULT_RETURN; /* popf */ case 0x9d: { - unsigned short newflags=popw(ssp, sp, simulate_sigsegv); - SP(regs) += 2; + unsigned long newflags; + if (prefix66) { + newflags=popl(ssp, sp, simulate_sigsegv); + SP(regs) += 4; + } else { + newflags = popw(ssp, sp, simulate_sigsegv); + SP(regs) += 2; + } IP(regs)++; CHECK_IF_IN_TRAP; - set_vflags_short(newflags, regs); + if (prefix66) { + set_vflags_long(newflags, regs); + } else { + set_vflags_short(newflags, regs); + } VM86_FAULT_RETURN; } @@ -593,14 +592,28 @@ /* iret */ case 0xcf: { - unsigned short newip=popw(ssp, sp, simulate_sigsegv); - unsigned short newcs=popw(ssp, sp, simulate_sigsegv); - unsigned short newflags=popw(ssp, sp, simulate_sigsegv); - SP(regs) += 6; + unsigned long newip; + unsigned long newcs; + unsigned long newflags; + if (prefix66) { + newip=popl(ssp, sp, simulate_sigsegv); + newcs=popl(ssp, sp, simulate_sigsegv); + newflags=popl(ssp, sp, simulate_sigsegv); + SP(regs) += 12; + } else { + newip = popw(ssp, sp, simulate_sigsegv); + newcs = popw(ssp, sp, simulate_sigsegv); + newflags = popw(ssp, sp, simulate_sigsegv); + SP(regs) += 6; + } IP(regs) = newip; regs->cs = newcs; CHECK_IF_IN_TRAP; - set_vflags_short(newflags, regs); + if (prefix66) { + set_vflags_long(newflags, regs); + } else { + set_vflags_short(newflags, regs); + } VM86_FAULT_RETURN; } --------------040509000006080707030309--