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/* $Id: post.c $ */
/** @file
* BIOS POST routines. Used only during initialization.
*/
/*
* Copyright (C) 2004-2023 Oracle and/or its affiliates.
*
* This file is part of VirtualBox base platform packages, as
* available from https://www.virtualbox.org.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, in version 3 of the
* License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses>.
*
* SPDX-License-Identifier: GPL-3.0-only
*/
#include <stdint.h>
#include <string.h>
#include "biosint.h"
#include "inlines.h"
#if DEBUG_POST || 0
# define DPRINT(...) BX_DEBUG(__VA_ARGS__)
#else
# define DPRINT(...)
#endif
/* In general, checksumming ROMs in a VM just wastes time. */
//#define CHECKSUM_ROMS
/* The format of a ROM is as follows:
*
* ------------------------------
* 0 | AA55h signature (word) |
* ------------------------------
* 2 | Size in 512B blocks (byte) |
* ------------------------------
* 3 | Start of executable code |
* | ....... |
* end | |
* ------------------------------
*/
typedef struct rom_hdr_tag {
uint16_t signature;
uint8_t num_blks;
uint8_t code;
} rom_hdr;
/* Calculate the checksum of a ROM. Note that the ROM might be
* larger than 64K.
*/
static inline uint8_t rom_checksum(uint8_t __far *rom, uint8_t blocks)
{
uint8_t sum = 0;
#ifdef CHECKSUM_ROMS
while (blocks--) {
int i;
for (i = 0; i < 512; ++i)
sum += rom[i];
/* Add 512 bytes (32 paragraphs) to segment. */
rom = MK_FP(FP_SEG(rom) + (512 >> 4), 0);
}
#endif
return sum;
}
/* The ROM init routine might trash register. Give the compiler a heads-up. */
typedef void __far (rom_init_rtn)(void);
#pragma aux rom_init_rtn modify [ax bx cx dx si di es /*ignored:*/ bp] /*ignored:*/ loadds;
/* The loadds bit is ignored for rom_init_rtn, the impression from the code
generator is that this is due to using a memory model where DS is fixed.
If we add DS as a modified register, we'll get run into compiler error
E1122 (BAD_REG) because FixedRegs() in cg/intel/386/c/386rgtbl.c returns
HW_DS as part of the fixed register set that cannot be modified.
The problem of the vga bios trashing DS isn't a biggie, except when
something goes sideways before we can reload it. Setting a I/O port
breakpoint on port 80h and wait a while before resuming execution
(ba i 1 80 "sleep 400 ; g") will usually trigger a keyboard init panic and
showcase the issue. The panic message is garbage because it's read from
segment 0c000h instead of 0f000h. */
static void restore_ds_as_dgroup(void);
#pragma aux restore_ds_as_dgroup = \
"mov ax, 0f000h" \
"mov ds, ax" \
modify exact [ax];
/* Scan for ROMs in the given range and execute their POST code. */
void rom_scan(uint16_t start_seg, uint16_t end_seg)
{
rom_hdr __far *rom;
uint8_t rom_blks;
DPRINT("Scanning for ROMs in %04X-%04X range\n", start_seg, end_seg);
while (start_seg < end_seg) {
rom = MK_FP(start_seg, 0);
/* Check for the ROM signature. */
if (rom->signature == 0xAA55) {
DPRINT("Found ROM at segment %04X\n", start_seg);
if (!rom_checksum((void __far *)rom, rom->num_blks)) {
rom_init_rtn *rom_init;
/* Checksum good, initialize ROM. */
rom_init = (rom_init_rtn *)&rom->code;
rom_init();
int_disable();
restore_ds_as_dgroup();
/** @todo BP is not restored. */
DPRINT("ROM initialized\n");
/* Continue scanning past the end of this ROM. */
rom_blks = (rom->num_blks + 3) & ~3; /* 4 blocks = 2K */
start_seg += rom_blks / 4;
}
} else {
/* Scanning is done in 2K steps. */
start_seg += 2048 >> 4;
}
}
}
#if VBOX_BIOS_CPU >= 80386
/* NB: The CPUID detection is generic but currently not used elsewhere. */
/* Check CPUID availability. */
int is_cpuid_supported( void )
{
uint32_t old_flags, new_flags;
old_flags = eflags_read();
new_flags = old_flags ^ (1L << 21); /* Toggle CPUID bit. */
eflags_write( new_flags );
new_flags = eflags_read();
return( old_flags != new_flags ); /* Supported if bit changed. */
}
#define APICMODE_DISABLED 0
#define APICMODE_APIC 1
#define APICMODE_X2APIC 2
#define APIC_BASE_MSR 0x1B
#define APICBASE_X2APIC 0x400 /* bit 10 */
#define APICBASE_ENABLE 0x800 /* bit 11 */
/*
* Set up APIC/x2APIC. See also DevPcBios.cpp.
*
* NB: Virtual wire compatibility is set up earlier in 32-bit protected
* mode assembler (because it needs to access MMIO just under 4GB).
* Switching to x2APIC mode or disabling the APIC is done through an MSR
* and needs no 32-bit addressing. Going to x2APIC mode does not lose the
* existing virtual wire setup.
*
* NB: This code does not assume that there is a local APIC. It is necessary
* to check CPUID whether APIC is present; the CPUID instruction might not be
* available either.
*
* NB: Destroys high bits of 32-bit registers.
*/
void BIOSCALL apic_setup(void)
{
uint64_t base_msr;
uint16_t mask_set;
uint16_t mask_clr;
uint8_t apic_mode;
uint32_t cpu_id[4];
/* If there's no CPUID, there's certainly no APIC. */
if (!is_cpuid_supported()) {
return;
}
/* Check EDX bit 9 */
cpuid(&cpu_id, 1);
BX_DEBUG("CPUID EDX: 0x%lx\n", cpu_id[3]);
if ((cpu_id[3] & (1 << 9)) == 0) {
return; /* No local APIC, nothing to do. */
}
/* APIC mode at offset 78h in CMOS NVRAM. */
apic_mode = inb_cmos(0x78);
mask_set = mask_clr = 0;
if (apic_mode == APICMODE_X2APIC)
mask_set = APICBASE_X2APIC;
else if (apic_mode == APICMODE_DISABLED)
mask_clr = APICBASE_ENABLE;
else
; /* Any other setting leaves things alone. */
if (mask_set || mask_clr) {
base_msr = msr_read(APIC_BASE_MSR);
base_msr &= ~(uint64_t)mask_clr;
base_msr |= mask_set;
msr_write(base_msr, APIC_BASE_MSR);
}
}
#endif
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