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Some operating systems get a nasty shock if a region of the E820 map seems

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to start on a non-page boundary.  Make life safer by rounding out our
edited regions.
This commit is contained in:
Michael Brown 2007-01-13 23:38:33 +00:00
parent d0f4e9a54b
commit aaed3d50a8
2 changed files with 81 additions and 44 deletions
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97
src/arch/i386/firmware/pcbios/hidemem.c
View File

@ -16,12 +16,41 @@
*/
#include <realmode.h>
#include <bios.h>
#include <biosint.h>
#include <gpxe/hidemem.h>
/* Linker-defined symbols */
extern char _text[];
extern char _end[];
/** Alignment for hidden memory regions */
#define ALIGN_HIDDEN 4096 /* 4kB page alignment should be enough */
/**
* A hidden region of Etherboot
*
* This represents a region that will be edited out of the system's
* memory map.
*
* This structure is accessed by assembly code, so must not be
* changed.
*/
struct hidden_region {
/* Physical start address */
physaddr_t start;
/* Physical end address */
physaddr_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 )
/** Assembly routine in e820mangler.S */
extern void int15();
@ -31,16 +60,50 @@ extern struct segoff __text16 ( int15_vector );
#define int15_vector __use_text16 ( int15_vector )
/**
* List of hidden regions
* Hide region of memory from system memory map
*
* Must be terminated by a zero entry.
* @v start Start of region
* @v end End of region
*/
struct hidden_region __data16_array ( hidden_regions, [] ) = {
[TEXT] = { 0, 0 },
[BASEMEM] = { 0, ( 640 * 1024 ) },
[EXTMEM] = { 0, 0 },
{ 0, 0, } /* Terminator */
};
void hide_region ( unsigned int region_id, physaddr_t start, physaddr_t end ) {
struct hidden_region *region = &hidden_regions[region_id];
/* Some operating systems get a nasty shock if a region of the
* E820 map seems to start on a non-page boundary. Make life
* safer by rounding out our edited region.
*/
region->start = ( start & ~( ALIGN_HIDDEN - 1 ) );
region->end = ( ( end + ALIGN_HIDDEN - 1 ) & ~( ALIGN_HIDDEN - 1 ) );
DBG ( "Hiding [%lx,%lx)\n", 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 ) );
}
/**
* Hide used base memory
*
*/
static void hide_basemem ( void ) {
uint16_t fbms;
/* Hide from the top of free base memory to 640kB. Don't use
* hide_region(), because we don't want this rounded to the
* nearest page boundary.
*/
get_real ( fbms, BDA_SEG, BDA_FBMS );
hidden_regions[BASEMEM].start = ( fbms * 1024 );
}
/**
* Hide Etherboot
@ -49,16 +112,12 @@ struct hidden_region __data16_array ( hidden_regions, [] ) = {
* returned by the BIOS.
*/
void hide_etherboot ( void ) {
hidden_regions[TEXT].start = virt_to_phys ( _text );
hidden_regions[TEXT].end = virt_to_phys ( _end );
hidden_regions[BASEMEM].start = ( rm_cs << 4 );
DBG ( "Hiding [%lx,%lx) and [%lx,%lx)\n",
( unsigned long ) hidden_regions[TEXT].start,
( unsigned long ) hidden_regions[TEXT].end,
( unsigned long ) hidden_regions[BASEMEM].start,
( unsigned long ) hidden_regions[BASEMEM].end );
/* Initialise the hidden regions */
hide_text();
hide_basemem();
/* Hook INT 15 */
hook_bios_interrupt ( 0x15, ( unsigned int ) int15,
&int15_vector );
}

28
src/include/gpxe/hidemem.h
View File

@ -8,38 +8,16 @@
*
*/
/**
* A hidden region of Etherboot
*
* This represents a region that will be edited out of the system's
* memory map.
*
* This structure is accessed by assembly code, so must not be
* changed.
*/
struct hidden_region {
/* Physical start address */
physaddr_t start;
/* Physical end address */
physaddr_t end;
};
/**
* Unique IDs for hidden regions
*/
enum {
enum hidemem_region_id {
TEXT = 0,
BASEMEM,
EXTMEM,
};
extern struct hidden_region __data16_array ( hidden_regions, [] );
#define hidden_regions __use_data16 ( hidden_regions )
static inline void hide_region ( unsigned int region,
physaddr_t start, physaddr_t end ) {
hidden_regions[region].start = start;
hidden_regions[region].end = end;
}
extern void hide_region ( unsigned int region_id, physaddr_t start,
physaddr_t end );
#endif /* _GPXE_HIDEMEM_H */