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- /*
- * librm: a library for interfacing to real-mode code
- *
- * Michael Brown <mbrown@fensystems.co.uk>
- *
- */
-
- #ifdef KEEP_IT_REAL
- /* Build a null object under -DKEEP_IT_REAL */
- #else
-
- #include "stdint.h"
- #include "stddef.h"
- #include "string.h"
- #include "init.h"
- #include "basemem.h"
- #include "librm.h"
-
- /*
- * This file provides functions for managing librm.
- *
- */
-
- /* Current location of librm in base memory */
- char *installed_librm = librm;
- static uint32_t installed_librm_phys;
-
- /* Whether or not we have base memory currently allocated for librm.
- * Note that we *can* have a working librm present in unallocated base
- * memory; this is the situation at startup for all real-mode
- * prefixes.
- */
- static int allocated_librm = 0;
-
- /*
- * Allocate space on the real-mode stack and copy data there.
- *
- */
- uint16_t copy_to_rm_stack ( void *data, size_t size ) {
- #ifdef DEBUG_LIBRM
- if ( inst_rm_stack.offset <= size ) {
- printf ( "librm: out of space in RM stack\n" );
- lockup();
- }
- #endif
- inst_rm_stack.offset -= size;
- copy_to_real ( inst_rm_stack.segment, inst_rm_stack.offset,
- data, size );
- return inst_rm_stack.offset;
- };
-
- /*
- * Deallocate space on the real-mode stack, optionally copying back
- * data.
- *
- */
- void remove_from_rm_stack ( void *data, size_t size ) {
- if ( data ) {
- copy_from_real ( data,
- inst_rm_stack.segment, inst_rm_stack.offset,
- size );
- }
- inst_rm_stack.offset += size;
- };
-
- /*
- * Install librm to base memory
- *
- */
- static inline void install_librm ( char *addr ) {
- memcpy ( addr, librm, librm_size );
- installed_librm = addr;
- }
-
- /*
- * Uninstall librm from base memory. This copies librm back to the
- * "master" copy, so that it can be reinstalled to a new location,
- * preserving the values for rm_ss and rm_sp from the old installed
- * copy.
- *
- */
- static inline void uninstall_librm ( void ) {
- memcpy ( librm, installed_librm, librm_size );
- }
-
- /*
- * On entry, record the physical location of librm. Do this so that
- * we can update installed_librm after relocation.
- *
- * Doing this is probably more efficient than making installed_librm
- * be a physical address, because of the number of times that
- * installed_librm gets referenced in the remainder of the code.
- *
- */
- static void librm_init ( void ) {
- installed_librm_phys = virt_to_phys ( installed_librm );
- }
-
- /*
- * On exit, we want to leave a copy of librm in *unallocated* base
- * memory. It must be there so that we can exit via a 16-bit exit
- * path, but it must not be allocated because nothing will ever
- * deallocate it once we exit.
- *
- */
- static void librm_exit ( void ) {
- /* Free but do not zero the base memory */
- if ( allocated_librm ) {
- free_base_memory ( installed_librm, librm_size );
- allocated_librm = 0;
- }
- }
-
- /*
- * On reset, we want to free up our old installed copy of librm, if
- * any, then allocate a new base memory block and install there.
- *
- */
-
- static void librm_reset ( void ) {
- char *new_librm;
-
- /* Point installed_librm back at last known physical location */
- installed_librm = phys_to_virt ( installed_librm_phys );
-
- /* Uninstall old librm */
- uninstall_librm();
-
- /* Free allocated base memory, if applicable */
- librm_exit();
-
- /* Allocate space for new librm */
- new_librm = alloc_base_memory ( librm_size );
- allocated_librm = 1;
-
- /* Install new librm */
- install_librm ( new_librm );
- }
-
- INIT_FN ( INIT_LIBRM, librm_init, librm_reset, librm_exit );
-
-
-
-
- /*
- * Increment lock count of librm
- *
- */
- void lock_librm ( void ) {
- inst_librm_ref_count++;
- }
-
- /*
- * Decrement lock count of librm
- *
- */
- void unlock_librm ( void ) {
- #ifdef DEBUG_LIBRM
- if ( inst_librm_ref_count == 0 ) {
- printf ( "librm: ref count gone negative\n" );
- lockup();
- }
- #endif
- inst_librm_ref_count--;
- }
-
- #endif /* KEEP_IT_REAL */
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