123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175 |
- /*
- * 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 "basemem.h"
- #include "relocate.h"
- #include <gpxe/init.h>
- #include "librm.h"
-
- /*
- * This file provides functions for managing librm.
- *
- */
-
- /* Current location of librm in base memory */
- char *installed_librm = librm;
-
- /* 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 void install_librm ( char *addr ) {
- librm_base = virt_to_phys ( 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.
- *
- * We deliberately leave the old copy intact and effectively installed
- * (apart from being in unallocated memory) so that we can use it for
- * any real-mode calls required when allocating memory for the new
- * copy, or for the real-mode exit path.
- */
- static void uninstall_librm ( void ) {
-
- /* Copy installed librm back to master copy */
- memcpy ( librm, installed_librm, librm_size );
-
- /* Free but do not zero the base memory */
- if ( allocated_librm ) {
- free_base_memory ( installed_librm, librm_size );
- allocated_librm = 0;
- }
- }
-
- /*
- * If librm isn't installed (i.e. if we have librm, but weren't
- * entered via it), then install librm and a real-mode stack to a
- * fixed temporary location, just so that we can e.g. issue printf()
- *
- * [ If we were entered via librm, then the real_to_prot call will
- * have filled in librm_base. ]
- */
- static void librm_init ( void ) {
- if ( ! librm_base ) {
- install_librm ( phys_to_virt ( 0x7c00 ) );
- inst_rm_stack.segment = 0x7c0;
- inst_rm_stack.offset = 0x1000;
- }
- }
-
- /*
- * librm_post_reloc gets called immediately after relocation.
- *
- */
- static void librm_post_reloc ( void ) {
- /* Point installed_librm back at last known physical location.
- */
- installed_librm = phys_to_virt ( librm_base );
-
- /* Allocate base memory for librm and place a copy there */
- if ( ! allocated_librm ) {
- char *new_librm = alloc_base_memory ( librm_size );
- uninstall_librm ();
- install_librm ( new_librm );
- allocated_librm = 1;
- }
- }
-
- INIT_FN ( INIT_LIBRM, librm_init, NULL, uninstall_librm );
- POST_RELOC_FN ( POST_RELOC_LIBRM, librm_post_reloc );
-
- /*
- * Wrapper for initialise() when librm is being used. We have to
- * install a copy of librm to allocated base memory and return the
- * pointer to this new librm's entry point via es:di.
- *
- */
- void initialise_via_librm ( struct i386_all_regs *ix86 ) {
- /* Hand off to initialise() */
- initialise ();
-
- /* Point es:di to new librm's entry point. Fortunately, di is
- * already set up by setup16, so all we need to do is point
- * es:0000 to the start of the new librm.
- */
- ix86->segs.es = librm_base >> 4;
- }
-
- /*
- * 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 */
|