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[pcbios] Support arbitrary splits of the e820 memory map

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Allow for an arbitrary number of splits of the system memory map via
INT 15,e820.

Features of the new map-mangling algorithm include:

  Supports random access to e820 map entries.

  Requires only sequential access support from the underlying e820
  map, even if our caller uses random access.

  Empty regions will always be stripped.

  Always terminates with %ebx=0, even if the underlying map terminates
  with CF=1.

  Allows for an arbitrary number of hidden regions, with underlying
  regions split into as many subregions as necessary.

Total size increase to achieve this is 193 bytes.
This commit is contained in:
Michael Brown
2008-08-18 07:14:27 +01:00
parent 9737095d49
commit 320b072c7a
5 changed files with 129 additions and 366 deletions
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82
src/arch/i386/firmware/pcbios/hidemem.c
View File

@@ -15,6 +15,7 @@
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <assert.h>
#include <realmode.h>
#include <biosint.h>
#include <basemem.h>
@@ -25,7 +26,7 @@
#define ALIGN_HIDDEN 4096 /* 4kB page alignment should be enough */
/**
* A hidden region of Etherboot
* A hidden region of gPXE
*
* This represents a region that will be edited out of the system's
* memory map.
@@ -34,24 +35,23 @@
* changed.
*/
struct hidden_region {
/* Physical start address */
physaddr_t start;
/* Physical end address */
physaddr_t end;
/** Physical start address */
uint64_t start;
/** Physical end address */
uint64_t end;
};
/**
* List of hidden regions
*
* Must be terminated by a zero entry.
*/
struct hidden_region __data16_array ( hidden_regions, [] ) = {
[TEXT] = { 0, 0 },
[BASEMEM] = { ( 640 * 1024 ), ( 640 * 1024 ) },
[EXTMEM] = { 0, 0 },
{ 0, 0, } /* Terminator */
};
#define hidden_regions __use_data16 ( hidden_regions )
/** Hidden base memory */
extern struct hidden_region __data16 ( hidemem_base );
#define hidemem_base __use_data16 ( hidemem_base )
/** Hidden umalloc memory */
extern struct hidden_region __data16 ( hidemem_umalloc );
#define hidemem_umalloc __use_data16 ( hidemem_umalloc )
/** Hidden text memory */
extern struct hidden_region __data16 ( hidemem_text );
#define hidemem_text __use_data16 ( hidemem_text )
/** Assembly routine in e820mangler.S */
extern void int15();
@@ -60,14 +60,19 @@ extern void int15();
extern struct segoff __text16 ( int15_vector );
#define int15_vector __use_text16 ( int15_vector )
/* The linker defines these symbols for us */
extern char _text[];
extern char _end[];
/**
* Hide region of memory from system memory map
*
* @v region Hidden memory region
* @v start Start of region
* @v end End of region
*/
void hide_region ( unsigned int region_id, physaddr_t start, physaddr_t end ) {
struct hidden_region *region = &hidden_regions[region_id];
static void hide_region ( struct hidden_region *region,
physaddr_t start, physaddr_t end ) {
/* Some operating systems get a nasty shock if a region of the
* E820 map seems to start on a non-page boundary. Make life
@@ -76,21 +81,7 @@ void hide_region ( unsigned int region_id, physaddr_t start, physaddr_t end ) {
region->start = ( start & ~( ALIGN_HIDDEN - 1 ) );
region->end = ( ( end + ALIGN_HIDDEN - 1 ) & ~( ALIGN_HIDDEN - 1 ) );
DBG ( "Hiding region %d [%lx,%lx)\n",
region_id, region->start, region->end );
}
/**
* Hide Etherboot text
*
*/
static void hide_text ( void ) {
/* The linker defines these symbols for us */
extern char _text[];
extern char _end[];
hide_region ( TEXT, virt_to_phys ( _text ), virt_to_phys ( _end ) );
DBG ( "Hiding region [%llx,%llx)\n", region->start, region->end );
}
/**
@@ -102,7 +93,25 @@ void hide_basemem ( void ) {
* hide_region(), because we don't want this rounded to the
* nearest page boundary.
*/
hidden_regions[BASEMEM].start = ( get_fbms() * 1024 );
hidemem_base.start = ( get_fbms() * 1024 );
}
/**
* Hide umalloc() region
*
*/
void hide_umalloc ( physaddr_t start, physaddr_t end ) {
assert ( end <= virt_to_phys ( _text ) );
hide_region ( &hidemem_umalloc, start, end );
}
/**
* Hide .text and .data
*
*/
void hide_text ( void ) {
hide_region ( &hidemem_text, virt_to_phys ( _text ),
virt_to_phys ( _end ) );
}
/**
@@ -114,8 +123,9 @@ void hide_basemem ( void ) {
static void hide_etherboot ( void ) {
/* Initialise the hidden regions */
hide_text();
hide_basemem();
hide_umalloc ( virt_to_phys ( _text ), virt_to_phys ( _text ) );
hide_text();
/* Hook INT 15 */
hook_bios_interrupt ( 0x15, ( unsigned int ) int15,