int13con.c

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/*
 * Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * 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; either version 2 of the
 * License, or (at your option) any later version.
 *
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <ipxe/console.h>
#include <ipxe/init.h>
#include <realmode.h>
#include <int13.h>
#include <config/console.h>

/** @file
 *
 * INT13 disk log console
 *
 */

/* Set default console usage if applicable */
#if ! ( defined ( CONSOLE_INT13 ) && CONSOLE_EXPLICIT ( CONSOLE_INT13 ) )
#undef CONSOLE_INT13
#define CONSOLE_INT13 ( CONSOLE_USAGE_ALL & ~CONSOLE_USAGE_LOG )
#endif

/** Disk drive number */
#define INT13CON_DRIVE 0x80

/** Log partition type */
#define INT13CON_PARTITION_TYPE 0xe0

/** Maximum number of outstanding unwritten characters */
#define INT13CON_MAX_UNWRITTEN 64

/** Log partition header */
struct int13con_header {
        /** Magic signature */
        char magic[10];
} __attribute__ (( packed ));

/** Log partition magic signature */
#define INT13CON_MAGIC "iPXE LOG\n\n"

/** Original INT13 vector */
static struct segoff __bss16 ( int13con_vector );
#define int13con_vector __use_data16 ( int13con_vector )

/** Sector buffer */
static uint8_t __bss16_array ( int13con_buffer, [INT13_BLKSIZE] );
#define int13con_buffer __use_data16 ( int13con_buffer )

/** Disk address packet */
static struct int13_disk_address __bss16 ( int13con_address );
#define int13con_address __use_data16 ( int13con_address )

/** Current LBA */
static uint64_t int13con_lba;

/** Maximum LBA */
static uint64_t int13con_max_lba;

/** Current offset within sector */
static size_t int13con_offset;

/** Number of unwritten characters */
static size_t int13con_unwritten;

struct console_driver int13con __console_driver;

/**
 * Read/write disk sector
 *
 * @v op                Operation
 * @v lba               Logical block address
 * @ret rc              Return status code
 */
static int int13con_rw ( unsigned int op, uint64_t lba ) {
        uint8_t error;

        /* Construct disk address packet */
        int13con_address.bufsize = sizeof ( int13con_address );
        int13con_address.count = 1;
        int13con_address.buffer.segment = rm_ds;
        int13con_address.buffer.offset = __from_data16 ( int13con_buffer );
        int13con_address.lba = lba;

        /* Emulate INT13 via original vector.  We do this since iPXE
         * (or another subsequent bootloader) may hook INT13 and remap
         * drive numbers.
         */
        __asm__ ( REAL_CODE ( "pushfw\n\t"
                              "cli\n\t"
                              "lcall *int13con_vector\n\t" )
                  : "=a" ( error )
                  : "0" ( op << 8 ), "d" ( INT13CON_DRIVE ),
                    "S" ( __from_data16 ( &int13con_address ) ) );
        if ( error ) {
                DBG ( "INT13CON operation %04x failed: %02x\n",
                      op, error );
                return -EIO;
        }

        return 0;
}

/**
 * Write character to console
 *
 * @v character         Character
 */
static void int13con_putchar ( int character ) {
        static int busy;
        int rc;

        /* Ignore if we are already mid-logging */
        if ( busy )
                return;
        busy = 1;

        /* Write character to buffer */
        int13con_buffer[int13con_offset++] = character;
        int13con_unwritten++;

        /* Write sector to disk, if applicable */
        if ( ( int13con_offset == INT13_BLKSIZE ) ||
             ( int13con_unwritten == INT13CON_MAX_UNWRITTEN ) ||
             ( character == '\n' ) ) {

                /* Write sector to disk */
                if ( ( rc = int13con_rw ( INT13_EXTENDED_WRITE,
                                          int13con_lba ) ) != 0 ) {
                        DBG ( "INT13CON could not write log\n" );
                        /* Ignore and continue; there's nothing we can do */
                }

                /* Reset count of unwritten characters */
                int13con_unwritten = 0;
        }

        /* Move to next sector, if applicable */
        if ( int13con_offset == INT13_BLKSIZE ) {

                /* Disable console if we have run out of space */
                if ( int13con_lba >= int13con_max_lba )
                        int13con.disabled = 1;

                /* Clear log buffer */
                memset ( int13con_buffer, 0, sizeof ( int13con_buffer ) );
                int13con_offset = 0;

                /* Move to next sector */
                int13con_lba++;
        }

        /* Clear busy flag */
        busy = 0;
}

/**
 * Find log partition
 *
 * @ret rc              Return status code
 */
static int int13con_find ( void ) {
        struct master_boot_record *mbr =
                ( ( struct master_boot_record * ) int13con_buffer );
        struct int13con_header *hdr =
                ( ( struct int13con_header * ) int13con_buffer );
        struct partition_table_entry part[4];
        unsigned int i;
        int rc;

        /* Read MBR */
        if ( ( rc = int13con_rw ( INT13_EXTENDED_READ, 0 ) ) != 0 ) {
                DBG ( "INT13CON could not read MBR: %s\n", strerror ( rc ) );
                return rc;
        }

        /* Check MBR magic */
        if ( mbr->magic != INT13_MBR_MAGIC ) {
                DBG ( "INT13CON incorrect MBR magic\n" );
                DBG2_HDA ( 0, mbr, sizeof ( *mbr ) );
                return -EINVAL;
        }

        /* Look for magic partition */
        memcpy ( part, mbr->partitions, sizeof ( part ) );
        for ( i = 0 ; i < ( sizeof ( part ) / sizeof ( part[0] ) ) ; i++ ) {

                /* Skip partitions of the wrong type */
                if ( part[i].type != INT13CON_PARTITION_TYPE )
                        continue;

                /* Read partition header */
                if ( ( rc = int13con_rw ( INT13_EXTENDED_READ,
                                          part[i].start ) ) != 0 ) {
                        DBG ( "INT13CON partition %d could not read header: "
                              "%s\n", ( i + 1 ), strerror ( rc ) );
                        continue;
                }

                /* Check partition header */
                if ( memcmp ( hdr->magic, INT13CON_MAGIC,
                              sizeof ( hdr->magic ) ) != 0 ) {
                        DBG ( "INT13CON partition %d bad magic\n", ( i + 1 ) );
                        DBG2_HDA ( 0, hdr, sizeof ( *hdr ) );
                        continue;
                }

                /* Found log partition */
                DBG ( "INT13CON partition %d at [%08x,%08x)\n", ( i + 1 ),
                      part[i].start, ( part[i].start + part[i].length ) );
                int13con_lba = part[i].start;
                int13con_max_lba = ( part[i].start + part[i].length - 1 );

                /* Initialise log buffer */
                memset ( &int13con_buffer[ sizeof ( *hdr ) ], 0,
                         ( sizeof ( int13con_buffer ) - sizeof ( *hdr ) ) );
                int13con_offset = sizeof ( hdr->magic );

                return 0;
        }

        DBG ( "INT13CON found no log partition\n" );
        return -ENOENT;
}

/**
 * Initialise INT13 console
 *
 */
static void int13con_init ( void ) {
        uint8_t error;
        uint16_t check;
        unsigned int discard_c;
        unsigned int discard_d;
        int rc;

        /* Check for INT13 extensions */
        __asm__ __volatile__ ( REAL_CODE ( "int $0x13\n\t"
                                           "setc %%al\n\t" )
                               : "=a" ( error ), "=b" ( check ),
                                 "=c" ( discard_c ), "=d" ( discard_d )
                               : "0" ( INT13_EXTENSION_CHECK << 8 ),
                                 "1" ( 0x55aa ), "3" ( INT13CON_DRIVE ) );
        if ( error || ( check != 0xaa55 ) ) {
                DBG ( "INT13CON missing extensions (%02x,%04x)\n",
                      error, check );
                return;
        }

        /* Store original INT13 vector */
        copy_from_real ( &int13con_vector, 0, ( 0x13 * 4 ),
                         sizeof ( int13con_vector ) );
        DBG ( "INT13CON using original INT13 vector %04x:%04x\n",
              int13con_vector.segment, int13con_vector.offset );

        /* Locate log partition */
        if ( ( rc = int13con_find() ) != 0)
                return;

        /* Enable console */
        int13con.disabled = 0;
}

/**
 * INT13 console initialisation function
 */
struct init_fn int13con_init_fn __init_fn ( INIT_CONSOLE ) = {
        .initialise = int13con_init,
};

/** INT13 console driver */
struct console_driver int13con __console_driver = {
        .putchar = int13con_putchar,
        .disabled = CONSOLE_DISABLED,
        .usage = CONSOLE_INT13,
};