comboot_call.c

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/*
 * Copyright (C) 2008 Daniel Verkamp <daniel@drv.nu>.
 *
 * 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 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.
 */

/**
 * @file SYSLINUX COMBOOT API
 *
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <errno.h>
#include <realmode.h>
#include <biosint.h>
#include <ipxe/console.h>
#include <stdlib.h>
#include <comboot.h>
#include <bzimage.h>
#include <pxe_call.h>
#include <rmsetjmp.h>
#include <string.h>
#include <ipxe/posix_io.h>
#include <ipxe/process.h>
#include <ipxe/serial.h>
#include <ipxe/ns16550.h>
#include <ipxe/init.h>
#include <ipxe/image.h>
#include <ipxe/version.h>
#include <usr/imgmgmt.h>

/** The "SYSLINUX" version string */
static char __bss16_array ( syslinux_version, [32] );
#define syslinux_version __use_data16 ( syslinux_version )

/** The "SYSLINUX" copyright string */
static char __data16_array ( syslinux_copyright, [] ) = " https://ipxe.org";
#define syslinux_copyright __use_data16 ( syslinux_copyright )

static char __data16_array ( syslinux_configuration_file, [] ) = "";
#define syslinux_configuration_file __use_data16 ( syslinux_configuration_file )

/** Feature flags */
static uint8_t __data16 ( comboot_feature_flags ) = COMBOOT_FEATURE_IDLE_LOOP;
#define comboot_feature_flags __use_data16 ( comboot_feature_flags )

typedef union {
        syslinux_pm_regs pm; syslinux_rm_regs rm;
} syslinux_regs;

/** Initial register values for INT 22h AX=1Ah and 1Bh */
static syslinux_regs __text16 ( comboot_initial_regs );
#define comboot_initial_regs __use_text16 ( comboot_initial_regs )

static struct segoff __text16 ( int20_vector );
#define int20_vector __use_text16 ( int20_vector )

static struct segoff __text16 ( int21_vector );
#define int21_vector __use_text16 ( int21_vector )

static struct segoff __text16 ( int22_vector );
#define int22_vector __use_text16 ( int22_vector )

extern void int20_wrapper ( void );
extern void int21_wrapper ( void );
extern void int22_wrapper ( void );

/* setjmp/longjmp context buffer used to return after loading an image */
rmjmp_buf comboot_return;

/* Mode flags set by INT 22h AX=0017h */
static uint16_t comboot_graphics_mode = 0;

/**
 * Print a string with a particular terminator
 */
static void print_user_string ( unsigned int segment, unsigned int offset, char terminator ) {
        char *c;
        for ( c = real_to_virt ( segment, offset ) ; *c != terminator ; c++ ) {
                putchar ( *c );
        }
}


/**
 * Perform a series of memory copies from a list in low memory
 */
static void shuffle ( unsigned int list_segment, unsigned int list_offset, unsigned int count )
{
        comboot_shuffle_descriptor shuf[COMBOOT_MAX_SHUFFLE_DESCRIPTORS];
        unsigned int i;

        /* Copy shuffle descriptor list so it doesn't get overwritten */
        memcpy ( shuf, real_to_virt ( list_segment, list_offset ),
                 count * sizeof( comboot_shuffle_descriptor ) );

        /* Do the copies */
        for ( i = 0; i < count; i++ ) {
                const void *src = phys_to_virt ( shuf[ i ].src );
                void *dest = phys_to_virt ( shuf[ i ].dest );

                if ( shuf[ i ].src == 0xFFFFFFFF ) {
                        /* Fill with 0 instead of copying */
                        memset ( dest, 0, shuf[ i ].len );
                } else if ( shuf[ i ].dest == 0xFFFFFFFF ) {
                        /* Copy new list of descriptors */
                        count = shuf[ i ].len / sizeof( comboot_shuffle_descriptor );
                        assert ( count <= COMBOOT_MAX_SHUFFLE_DESCRIPTORS );
                        memcpy ( shuf, src, shuf[ i ].len );
                        i = -1;
                } else {
                        /* Regular copy */
                        memmove ( dest, src, shuf[ i ].len );
                }
        }
}


/**
 * Set default text mode
 */
void comboot_force_text_mode ( void ) {
        if ( comboot_graphics_mode & COMBOOT_VIDEO_VESA ) {
                /* Set VGA mode 3 via VESA VBE mode set */
                __asm__ __volatile__ (
                        REAL_CODE (
                                "mov $0x4F02, %%ax\n\t"
                                "mov $0x03, %%bx\n\t"
                                "int $0x10\n\t"
                        )
                : : );
        } else if ( comboot_graphics_mode & COMBOOT_VIDEO_GRAPHICS ) {
                /* Set VGA mode 3 via standard VGA mode set */
                __asm__ __volatile__ (
                        REAL_CODE (
                                "mov $0x03, %%ax\n\t"
                                "int $0x10\n\t"
                        )
                : : );
        }

        comboot_graphics_mode = 0;
}


/**
 * Fetch kernel and optional initrd
 */
static int comboot_fetch_kernel ( const char *kernel_file, char *cmdline ) {
        struct image *kernel;
        struct image *initrd;
        char *initrd_file;
        int rc;

        /* Find initrd= parameter, if any */
        if ( ( initrd_file = strstr ( cmdline, "initrd=" ) ) != NULL ) {
                char *initrd_end;

                /* skip "initrd=" */
                initrd_file += 7;

                /* Find terminating space, if any, and replace with NUL */
                initrd_end = strchr ( initrd_file, ' ' );
                if ( initrd_end )
                        *initrd_end = '\0';

                DBG ( "COMBOOT: fetching initrd '%s'\n", initrd_file );

                /* Fetch initrd */
                if ( ( rc = imgdownload_string ( initrd_file, 0,
                                                 &initrd ) ) != 0 ) {
                        DBG ( "COMBOOT: could not fetch initrd: %s\n",
                              strerror ( rc ) );
                        return rc;
                }

                /* Restore space after initrd name, if applicable */
                if ( initrd_end )
                        *initrd_end = ' ';
        }

        DBG ( "COMBOOT: fetching kernel '%s'\n", kernel_file );

        /* Fetch kernel */
        if ( ( rc = imgdownload_string ( kernel_file, 0, &kernel ) ) != 0 ) {
                DBG ( "COMBOOT: could not fetch kernel: %s\n",
                      strerror ( rc ) );
                return rc;
        }

        /* Replace comboot image with kernel */
        if ( ( rc = image_replace ( kernel ) ) != 0 ) {
                DBG ( "COMBOOT: could not replace with kernel: %s\n",
                      strerror ( rc ) );
                return rc;
        }

        return 0;
}


/**
 * Terminate program interrupt handler
 */
static __asmcall __used void int20 ( struct i386_all_regs *ix86 __unused ) {
        rmlongjmp ( comboot_return, COMBOOT_EXIT );
}


/**
 * DOS-compatible API
 */
static __asmcall __used void int21 ( struct i386_all_regs *ix86 ) {
        ix86->flags |= CF;

        switch ( ix86->regs.ah ) {
        case 0x00:
        case 0x4C: /* Terminate program */
                rmlongjmp ( comboot_return, COMBOOT_EXIT );
                break;

        case 0x01: /* Get Key with Echo */
        case 0x08: /* Get Key without Echo */
                /* TODO: handle extended characters? */
                ix86->regs.al = getchar( );

                /* Enter */
                if ( ix86->regs.al == 0x0A )
                        ix86->regs.al = 0x0D;

                if ( ix86->regs.ah == 0x01 )
                        putchar ( ix86->regs.al );

                ix86->flags &= ~CF;
                break;

        case 0x02: /* Write Character */
                putchar ( ix86->regs.dl );
                ix86->flags &= ~CF;
                break;

        case 0x04: /* Write Character to Serial Port */
                if ( serial_console ) {
                        uart_transmit ( serial_console, ix86->regs.dl );
                        ix86->flags &= ~CF;
                }
                break;

        case 0x09: /* Write DOS String to Console */
                print_user_string ( ix86->segs.ds, ix86->regs.dx, '$' );
                ix86->flags &= ~CF;
                break;

        case 0x0B: /* Check Keyboard */
                if ( iskey() )
                        ix86->regs.al = 0xFF;
                else
                        ix86->regs.al = 0x00;

                ix86->flags &= ~CF;
                break;

        case 0x30: /* Check DOS Version */
                /* Bottom halves all 0; top halves spell "SYSLINUX" */
                ix86->regs.eax = 0x59530000;
                ix86->regs.ebx = 0x4C530000;
                ix86->regs.ecx = 0x4E490000;
                ix86->regs.edx = 0x58550000;
                ix86->flags &= ~CF;
                break;

        default:
                DBG ( "COMBOOT unknown int21 function %02x\n", ix86->regs.ah );
                break;
        }
}


/**
 * Dispatch PXE API call weakly
 *
 * @v ix86              Registers for PXE call
 * @ret present         Zero if the PXE stack is present, nonzero if not
 *
 * A successful return only indicates that the PXE stack was available
 * for dispatching the call; it says nothing about the success of
 * whatever the call asked for.
 */
__weak int pxe_api_call_weak ( struct i386_all_regs *ix86 __unused ) {
        return -1;
}

/**
 * SYSLINUX API
 */
static __asmcall __used void int22 ( struct i386_all_regs *ix86 ) {
        ix86->flags |= CF;

        switch ( ix86->regs.ax ) {
        case 0x0001: /* Get Version */

                /* Number of INT 22h API functions available */
                ix86->regs.ax = 0x001D;

                /* SYSLINUX version number */
                ix86->regs.ch = 0; /* major */
                ix86->regs.cl = 0; /* minor */

                /* SYSLINUX derivative ID */
                ix86->regs.dl = BZI_LOADER_TYPE_IPXE;

                /* SYSLINUX version */
                snprintf ( syslinux_version, sizeof ( syslinux_version ),
                           "\r\niPXE %s", product_version );

                /* SYSLINUX version and copyright strings */
                ix86->segs.es = rm_ds;
                ix86->regs.si = ( ( unsigned ) __from_data16 ( syslinux_version ) );
                ix86->regs.di = ( ( unsigned ) __from_data16 ( syslinux_copyright ) );

                ix86->flags &= ~CF;
                break;

        case 0x0002: /* Write String */
                print_user_string ( ix86->segs.es, ix86->regs.bx, '\0' );
                ix86->flags &= ~CF;
                break;

        case 0x0003: /* Run command */
                {
                        const char *cmd = real_to_virt ( ix86->segs.es,
                                                         ix86->regs.bx );
                        DBG ( "COMBOOT: executing command '%s'\n", cmd );
                        system ( cmd );
                        DBG ( "COMBOOT: exiting after executing command...\n" );
                        rmlongjmp ( comboot_return, COMBOOT_EXIT_COMMAND );
                }
                break;

        case 0x0004: /* Run default command */
                /* FIXME: just exit for now */
                rmlongjmp ( comboot_return, COMBOOT_EXIT_COMMAND );
                break;

        case 0x0005: /* Force text mode */
                comboot_force_text_mode ( );
                ix86->flags &= ~CF;
                break;

        case 0x0006: /* Open file */
                {
                        int fd;
                        const char *file = real_to_virt ( ix86->segs.es,
                                                          ix86->regs.si );

                        if ( file[0] == '\0' ) {
                                DBG ( "COMBOOT: attempted open with empty file name\n" );
                                break;
                        }

                        DBG ( "COMBOOT: opening file '%s'\n", file );

                        fd = open ( file );

                        if ( fd < 0 ) {
                                DBG ( "COMBOOT: error opening file %s\n", file );
                                break;
                        }

                        /* This relies on the fact that a iPXE POSIX fd will
                         * always fit in 16 bits.
                         */
#if (POSIX_FD_MAX > 65535)
#error POSIX_FD_MAX too large
#endif
                        ix86->regs.si = (uint16_t) fd;

                        ix86->regs.cx = COMBOOT_FILE_BLOCKSZ;
                        ix86->regs.eax = fsize ( fd );
                        ix86->flags &= ~CF;
                }
                break;

        case 0x0007: /* Read file */
                {
                        int fd = ix86->regs.si;
                        int len = ix86->regs.cx * COMBOOT_FILE_BLOCKSZ;
                        int rc;
                        fd_set fds;
                        void *buf = real_to_virt ( ix86->segs.es,
                                                   ix86->regs.bx );

                        /* Wait for data ready to read */
                        FD_ZERO ( &fds );
                        FD_SET ( fd, &fds );

                        select ( &fds, 1 );

                        rc = read ( fd, buf, len );
                        if ( rc < 0 ) {
                                DBG ( "COMBOOT: read failed\n" );
                                ix86->regs.si = 0;
                                break;
                        }

                        ix86->regs.ecx = rc;
                        ix86->flags &= ~CF;
                }
                break;

        case 0x0008: /* Close file */
                {
                        int fd = ix86->regs.si;
                        close ( fd );
                        ix86->flags &= ~CF;
                }
                break;

        case 0x0009: /* Call PXE Stack */
                if ( pxe_api_call_weak ( ix86 ) != 0 )
                        ix86->flags |= CF;
                else
                        ix86->flags &= ~CF;
                break;

        case 0x000A: /* Get Derivative-Specific Information */

                /* iPXE has its own derivative ID, so there is no defined
                 * output here; just return AL for now */
                ix86->regs.al = BZI_LOADER_TYPE_IPXE;
                ix86->flags &= ~CF;
                break;

        case 0x000B: /* Get Serial Console Configuration */
                if ( serial_console ) {
                        struct ns16550_uart *comport = serial_console->priv;

                        ix86->regs.dx = ( ( intptr_t ) comport->base );
                        ix86->regs.cx = comport->divisor;
                        ix86->regs.bx = 0;
                        ix86->flags &= ~CF;
                }
                break;

        case 0x000C: /* Perform final cleanup */
                shutdown_boot();
                break;

        case 0x000E: /* Get configuration file name */
                /* FIXME: stub */
                ix86->segs.es = rm_ds;
                ix86->regs.bx = ( ( unsigned ) __from_data16 ( syslinux_configuration_file ) );
                ix86->flags &= ~CF;
                break;

        case 0x000F: /* Get IPAPPEND strings */
                /* FIXME: stub */
                ix86->regs.cx = 0;
                ix86->segs.es = 0;
                ix86->regs.bx = 0;
                ix86->flags &= ~CF;
                break;

        case 0x0010: /* Resolve hostname */
                {
                        const char *hostname = real_to_virt ( ix86->segs.es,
                                                              ix86->regs.bx );
                        struct in_addr addr;

                        /* TODO:
                         * "If the hostname does not contain a dot (.), the
                         * local domain name is automatically appended."
                         */

                        comboot_resolv ( hostname, &addr );

                        ix86->regs.eax = addr.s_addr;
                        ix86->flags &= ~CF;
                }
                break;

        case 0x0011: /* Maximum number of shuffle descriptors */
                ix86->regs.cx = COMBOOT_MAX_SHUFFLE_DESCRIPTORS;
                ix86->flags &= ~CF;
                break;

        case 0x0012: /* Cleanup, shuffle and boot */
                if ( ix86->regs.cx > COMBOOT_MAX_SHUFFLE_DESCRIPTORS )
                        break;

                /* Perform final cleanup */
                shutdown_boot();

                /* Perform sequence of copies */
                shuffle ( ix86->segs.es, ix86->regs.di, ix86->regs.cx );

                /* Jump to real-mode entry point */
                __asm__ __volatile__ (
                        REAL_CODE (
                                "pushw %0\n\t"
                                "popw %%ds\n\t"
                                "pushl %1\n\t"
                                "lret\n\t"
                        )
                        :
                        : "R" ( ix86->segs.ds ),
                          "R" ( ix86->regs.ebp ),
                          "d" ( ix86->regs.ebx ),
                          "S" ( ix86->regs.esi ) );

                assert ( 0 ); /* Execution should never reach this point */

                break;

        case 0x0013: /* Idle loop call */
                step ( );
                ix86->flags &= ~CF;
                break;

        case 0x0015: /* Get feature flags */
                ix86->segs.es = rm_ds;
                ix86->regs.bx = ( ( unsigned ) __from_data16 ( &comboot_feature_flags ) );
                ix86->regs.cx = 1; /* Number of feature flag bytes */
                ix86->flags &= ~CF;
                break;

        case 0x0016: /* Run kernel image */
                {
                        const char *file = real_to_virt ( ix86->segs.ds,
                                                          ix86->regs.si );
                        char *cmd = real_to_virt ( ix86->segs.es,
                                                   ix86->regs.bx );

                        DBG ( "COMBOOT: run kernel %s %s\n", file, cmd );
                        comboot_fetch_kernel ( file, cmd );
                        /* Technically, we should return if we
                         * couldn't load the kernel, but it's not safe
                         * to do that since we have just overwritten
                         * part of the COMBOOT program's memory space.
                         */
                        DBG ( "COMBOOT: exiting to run kernel...\n" );
                        rmlongjmp ( comboot_return, COMBOOT_EXIT_RUN_KERNEL );
                }
                break;

        case 0x0017: /* Report video mode change */
                comboot_graphics_mode = ix86->regs.bx;
                ix86->flags &= ~CF;
                break;

        case 0x0018: /* Query custom font */
                /* FIXME: stub */
                ix86->regs.al = 0;
                ix86->segs.es = 0;
                ix86->regs.bx = 0;
                ix86->flags &= ~CF;
                break;

        case 0x001B: /* Cleanup, shuffle and boot to real mode */
                if ( ix86->regs.cx > COMBOOT_MAX_SHUFFLE_DESCRIPTORS )
                        break;

                /* Perform final cleanup */
                shutdown_boot();

                /* Perform sequence of copies */
                shuffle ( ix86->segs.es, ix86->regs.di, ix86->regs.cx );

                /* Copy initial register values to .text16 */
                memcpy ( real_to_virt ( rm_cs, (unsigned) __from_text16 ( &comboot_initial_regs ) ),
                         real_to_virt ( ix86->segs.ds, ix86->regs.si ),
                         sizeof(syslinux_rm_regs) );

                /* Load initial register values */
                __asm__ __volatile__ (
                        REAL_CODE (
                                /* Point SS:SP at the register value structure */
                                "pushw %%cs\n\t"
                                "popw %%ss\n\t"
                                "movw $comboot_initial_regs, %%sp\n\t"

                                /* Segment registers */
                                "popw %%es\n\t"
                                "popw %%ax\n\t" /* Skip CS */
                                "popw %%ds\n\t"
                                "popw %%ax\n\t" /* Skip SS for now */
                                "popw %%fs\n\t"
                                "popw %%gs\n\t"

                                /* GP registers */
                                "popl %%eax\n\t"
                                "popl %%ecx\n\t"
                                "popl %%edx\n\t"
                                "popl %%ebx\n\t"
                                "popl %%ebp\n\t" /* Skip ESP for now */
                                "popl %%ebp\n\t"
                                "popl %%esi\n\t"
                                "popl %%edi\n\t"

                                /* Load correct SS:ESP */
                                "movw $(comboot_initial_regs + 6), %%sp\n\t"
                                "popw %%ss\n\t"
                                "movl %%cs:(comboot_initial_regs + 28), %%esp\n\t"

                                "ljmp *%%cs:(comboot_initial_regs + 44)\n\t"
                        )
                        : : );

                break;

        case 0x001C: /* Get pointer to auxilliary data vector */
                /* FIXME: stub */
                ix86->regs.cx = 0; /* Size of the ADV */
                ix86->flags &= ~CF;
                break;

        case 0x001D: /* Write auxilliary data vector */
                /* FIXME: stub */
                ix86->flags &= ~CF;
                break;

        default:
                DBG ( "COMBOOT unknown int22 function %04x\n", ix86->regs.ax );
                break;
        }
}

/**
 * Hook BIOS interrupts related to COMBOOT API (INT 20h, 21h, 22h)
 */
void hook_comboot_interrupts ( ) {

        __asm__ __volatile__ (
                TEXT16_CODE ( "\nint20_wrapper:\n\t"
                              VIRT_CALL ( int20 )
                              "clc\n\t"
                              "call patch_cf\n\t"
                              "iret\n\t" ) : );

        hook_bios_interrupt ( 0x20, ( intptr_t ) int20_wrapper, &int20_vector );

        __asm__ __volatile__ (
                TEXT16_CODE ( "\nint21_wrapper:\n\t"
                              VIRT_CALL ( int21 )
                              "clc\n\t"
                              "call patch_cf\n\t"
                              "iret\n\t" ) : );

        hook_bios_interrupt ( 0x21, ( intptr_t ) int21_wrapper, &int21_vector );

        __asm__  __volatile__ (
                TEXT16_CODE ( "\nint22_wrapper:\n\t"
                              VIRT_CALL ( int22 )
                              "clc\n\t"
                              "call patch_cf\n\t"
                              "iret\n\t" ) : );

        hook_bios_interrupt ( 0x22, ( intptr_t ) int22_wrapper, &int22_vector );
}

/**
 * Unhook BIOS interrupts related to COMBOOT API (INT 20h, 21h, 22h)
 */
void unhook_comboot_interrupts ( ) {

        unhook_bios_interrupt ( 0x20, ( intptr_t ) int20_wrapper,
                                &int20_vector );

        unhook_bios_interrupt ( 0x21, ( intptr_t ) int21_wrapper,
                                &int21_vector );

        unhook_bios_interrupt ( 0x22, ( intptr_t ) int22_wrapper,
                                &int22_vector );
}

/* Avoid dragging in serial console support unconditionally */
struct uart *serial_console __attribute__ (( weak ));