biosint.c File Reference

#include <string.h>
#include <errno.h>
#include <realmode.h>
#include <biosint.h>

Go to the source code of this file.

Functions
	FILE_LICENCE (GPL2_OR_LATER_OR_UBDL)
void	hook_bios_interrupt (unsigned int interrupt, unsigned int handler, struct segoff *chain_vector)
	Hook INT vector. More...
int	unhook_bios_interrupt (unsigned int interrupt, unsigned int handler, struct segoff *chain_vector)
	Unhook INT vector. More...
void	check_bios_interrupts (void)
	Dump changes to interrupt vector table (for debugging) More...

Function Documentation

FILE_LICENCE()

FILE_LICENCE

(

GPL2_OR_LATER_OR_UBDL

)

hook_bios_interrupt()

void hook_bios_interrupt	(	unsigned int	interrupt,
		unsigned int	handler,
		struct segoff *	chain_vector
	)

Hook INT vector.

Parameters

interrupt	INT number
handler	Offset within .text16 to interrupt handler
chain_vector	Vector for chaining to previous handler

Hooks in an i386 INT handler. The handler itself must reside within the .text16 segment. chain_vector will be filled in with the address of the previously-installed handler for this interrupt; the handler should probably exit by ljmping via this vector.

Definition at line 25 of file biosint.c.

                                                         {
        struct segoff vector = {
                .segment = rm_cs,
                .offset = handler,
        };

        DBG ( "Hooking INT %#02x to %04x:%04x\n",
              interrupt, rm_cs, handler );

        if ( ( chain_vector->segment != 0 ) ||
             ( chain_vector->offset != 0 ) ) {
                /* Already hooked; do nothing */
                DBG ( "...already hooked\n" );
                return;
        }

        copy_from_real ( chain_vector, 0, ( interrupt * 4 ),
                         sizeof ( *chain_vector ) );
        DBG ( "...chaining to %04x:%04x\n",
              chain_vector->segment, chain_vector->offset );
        if ( DBG_LOG ) {
                char code[64];
                copy_from_real ( code, chain_vector->segment,
                                 chain_vector->offset, sizeof ( code ) );
                DBG_HDA ( *chain_vector, code, sizeof ( code ) );
        }

        copy_to_real ( 0, ( interrupt * 4 ), &vector, sizeof ( vector ) );
        hooked_bios_interrupts++;
}

References code, copy_from_real, copy_to_real, DBG, DBG_HDA, DBG_LOG, hooked_bios_interrupts, interrupt(), segoff::offset, rm_cs, segoff::segment, and vector.

Referenced by bios_inject_startup(), call_bootsector(), fake_e820(), hide_etherboot(), hook_comboot_interrupts(), int13_hook_vector(), pxe_activate(), rtc_hook_isr(), and undinet_hook_isr().

unhook_bios_interrupt()

int unhook_bios_interrupt	(	unsigned int	interrupt,
		unsigned int	handler,
		struct segoff *	chain_vector
	)

Unhook INT vector.

Parameters

interrupt	INT number
handler	Offset within .text16 to interrupt handler
chain_vector	Vector containing address of previous handler

Unhooks an i386 interrupt handler hooked by hook_i386_vector(). Note that this operation may fail, if some external code has hooked the vector since we hooked in our handler. If it fails, it means that it is not possible to unhook our handler, and we must leave it (and its chaining vector) resident in memory.

Definition at line 70 of file biosint.c.

                                                          {
        struct segoff vector;

        DBG ( "Unhooking INT %#02x from %04x:%04x\n",
              interrupt, rm_cs, handler );

        copy_from_real ( &vector, 0, ( interrupt * 4 ), sizeof ( vector ) );
        if ( ( vector.segment != rm_cs ) || ( vector.offset != handler ) ) {
                DBG ( "...cannot unhook; vector points to %04x:%04x\n",
                      vector.segment, vector.offset );
                return -EBUSY;
        }

        DBG ( "...restoring to %04x:%04x\n",
              chain_vector->segment, chain_vector->offset );
        copy_to_real ( 0, ( interrupt * 4 ), chain_vector,
                       sizeof ( *chain_vector ) );

        chain_vector->segment = 0;
        chain_vector->offset = 0;
        hooked_bios_interrupts--;
        return 0;
}

References copy_from_real, copy_to_real, DBG, EBUSY, hooked_bios_interrupts, interrupt(), segoff::offset, rm_cs, segoff::segment, and vector.

Referenced by bios_inject_shutdown(), call_bootsector(), int13_unhook_vector(), pxe_deactivate(), rtc_unhook_isr(), undinet_unhook_isr(), unfake_e820(), unhide_etherboot(), and unhook_comboot_interrupts().

check_bios_interrupts()

void check_bios_interrupts

(

void

)

Dump changes to interrupt vector table (for debugging)

Definition at line 99 of file biosint.c.

                                    {
        static struct segoff vectors[256];
        static uint8_t initialised;
        struct segoff vector;
        unsigned int i;

        /* Print any changed interrupt vectors */
        for ( i = 0; i < ( sizeof ( vectors ) / sizeof ( vectors[0] ) ); i++ ) {
                copy_from_real ( &vector, 0, ( i * sizeof ( vector ) ),
                                 sizeof ( vector ) );
                if ( memcmp ( &vector, &vectors[i], sizeof ( vector ) ) == 0 )
                        continue;
                if ( initialised ) {
                        dbg_printf ( "INT %02x changed %04x:%04x => "
                                     "%04x:%04x\n", i, vectors[i].segment,
                                     vectors[i].offset, vector.segment,
                                     vector.offset );
                }
                memcpy ( &vectors[i], &vector, sizeof ( vectors[i] ) );
        }
        initialised = 1;
}

References copy_from_real, dbg_printf(), memcmp(), memcpy(), offset, segment, and vector.