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/* Callout/callback interface for Etherboot
*
* This file provides the mechanisms for making calls from Etherboot
* to external programs and vice-versa.
*
* Initial version by Michael Brown <mbrown@fensystems.co.uk>, January 2004.
*/
#include "etherboot.h"
#include "callbacks.h"
#include "realmode.h"
#include <stdarg.h>
/* Maximum amount of stack data that prefix may request to be passed
* to its exit routine
*/
#define MAX_PREFIX_STACK_DATA 16
/* Prefix exit routine is defined in prefix object */
extern void prefix_exit ( void );
extern void prefix_exit_end ( void );
/*****************************************************************************
*
* IN_CALL INTERFACE
*
*****************************************************************************
*/
/* in_call(): entry point for calls in to Etherboot from external code.
*
* Parameters: some set up by assembly code _in_call(), others as
* passed from external code.
*/
uint32_t i386_in_call ( va_list ap, i386_pm_in_call_data_t pm_data,
uint32_t opcode ) {
uint32_t ret;
i386_rm_in_call_data_t rm_data;
in_call_data_t in_call_data = { &pm_data, NULL };
struct {
int data[MAX_PREFIX_STACK_DATA/4];
} in_stack;
/* Fill out rm_data if we were called from real mode */
if ( opcode & EB_CALL_FROM_REAL_MODE ) {
in_call_data.rm = &rm_data;
rm_data = va_arg ( ap, typeof(rm_data) );
/* Null return address indicates to use the special
* prefix exit mechanism, and that there are
* parameters on the stack that the prefix wants
* handed to its exit routine.
*/
if ( rm_data.ret_addr.offset == 0 ) {
int n = va_arg ( ap, int ) / 4;
int i;
for ( i = 0; i < n; i++ ) {
in_stack.data[i] = va_arg ( ap, int );
}
}
}
/* Hand off to main in_call() routine */
ret = in_call ( &in_call_data, opcode, ap );
/* If real-mode return address is null, it means that we
* should exit via the prefix's exit path, which is part of
* our image. (This arrangement is necessary since the prefix
* code itself may have been vapourised by the time we want to
* return.)
*/
if ( ( opcode & EB_CALL_FROM_REAL_MODE ) &&
( rm_data.ret_addr.offset == 0 ) ) {
real_call ( prefix_exit, &in_stack, NULL );
/* Should never return */
}
return ret;
}
#ifdef CODE16
/* install_rm_callback_interface(): install real-mode callback
* interface at specified address.
*
* Real-mode code may then call to this address (or lcall to this
* address plus RM_IN_CALL_FAR) in order to make an in_call() to
* Etherboot.
*
* Returns the size of the installed code, or 0 if the code could not
* be installed.
*/
int install_rm_callback_interface ( void *address, size_t available ) {
if ( available &&
( available < rm_callback_interface_size ) ) return 0;
/* Inform RM code where to find Etherboot */
rm_etherboot_location = virt_to_phys(_text);
/* Install callback interface */
memcpy ( address, &rm_callback_interface,
rm_callback_interface_size );
return rm_callback_interface_size;
}
#endif /* CODE16 */
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