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 regions.
This commit is contained in:
Michael Brown
parent
d0f4e9a54b
commit
aaed3d50a8
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@ -16,12 +16,41 @@
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*/
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#include <realmode.h>
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#include <bios.h>
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#include <biosint.h>
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#include <gpxe/hidemem.h>
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/* Linker-defined symbols */
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extern char _text[];
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extern char _end[];
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/** Alignment for hidden memory regions */
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#define ALIGN_HIDDEN 4096 /* 4kB page alignment should be enough */
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/**
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* A hidden region of Etherboot
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*
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* This represents a region that will be edited out of the system's
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* memory map.
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*
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* This structure is accessed by assembly code, so must not be
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* changed.
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*/
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struct hidden_region {
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/* Physical start address */
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physaddr_t start;
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/* Physical end address */
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physaddr_t end;
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};
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/**
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* List of hidden regions
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*
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* Must be terminated by a zero entry.
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*/
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struct hidden_region __data16_array ( hidden_regions, [] ) = {
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[TEXT] = { 0, 0 },
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[BASEMEM] = { ( 640 * 1024 ), ( 640 * 1024 ) },
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[EXTMEM] = { 0, 0 },
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{ 0, 0, } /* Terminator */
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};
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#define hidden_regions __use_data16 ( hidden_regions )
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/** Assembly routine in e820mangler.S */
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extern void int15();
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@ -31,16 +60,50 @@ extern struct segoff __text16 ( int15_vector );
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#define int15_vector __use_text16 ( int15_vector )
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/**
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* List of hidden regions
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* Hide region of memory from system memory map
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*
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* Must be terminated by a zero entry.
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* @v start Start of region
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* @v end End of region
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*/
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struct hidden_region __data16_array ( hidden_regions, [] ) = {
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[TEXT] = { 0, 0 },
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[BASEMEM] = { 0, ( 640 * 1024 ) },
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[EXTMEM] = { 0, 0 },
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{ 0, 0, } /* Terminator */
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};
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void hide_region ( unsigned int region_id, physaddr_t start, physaddr_t end ) {
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struct hidden_region *region = &hidden_regions[region_id];
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/* Some operating systems get a nasty shock if a region of the
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* E820 map seems to start on a non-page boundary. Make life
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* safer by rounding out our edited region.
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*/
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region->start = ( start & ~( ALIGN_HIDDEN - 1 ) );
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region->end = ( ( end + ALIGN_HIDDEN - 1 ) & ~( ALIGN_HIDDEN - 1 ) );
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DBG ( "Hiding [%lx,%lx)\n", region->start, region->end );
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}
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/**
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* Hide Etherboot text
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*
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*/
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static void hide_text ( void ) {
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/* The linker defines these symbols for us */
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extern char _text[];
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extern char _end[];
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hide_region ( TEXT, virt_to_phys ( _text ), virt_to_phys ( _end ) );
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}
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/**
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* Hide used base memory
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*
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*/
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static void hide_basemem ( void ) {
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uint16_t fbms;
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/* Hide from the top of free base memory to 640kB. Don't use
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* hide_region(), because we don't want this rounded to the
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* nearest page boundary.
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*/
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get_real ( fbms, BDA_SEG, BDA_FBMS );
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hidden_regions[BASEMEM].start = ( fbms * 1024 );
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}
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/**
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* Hide Etherboot
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@ -49,16 +112,12 @@ struct hidden_region __data16_array ( hidden_regions, [] ) = {
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* returned by the BIOS.
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*/
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void hide_etherboot ( void ) {
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hidden_regions[TEXT].start = virt_to_phys ( _text );
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hidden_regions[TEXT].end = virt_to_phys ( _end );
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hidden_regions[BASEMEM].start = ( rm_cs << 4 );
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DBG ( "Hiding [%lx,%lx) and [%lx,%lx)\n",
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( unsigned long ) hidden_regions[TEXT].start,
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( unsigned long ) hidden_regions[TEXT].end,
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( unsigned long ) hidden_regions[BASEMEM].start,
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( unsigned long ) hidden_regions[BASEMEM].end );
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/* Initialise the hidden regions */
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hide_text();
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hide_basemem();
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/* Hook INT 15 */
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hook_bios_interrupt ( 0x15, ( unsigned int ) int15,
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&int15_vector );
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}
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@ -8,38 +8,16 @@
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*
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*/
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/**
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* A hidden region of Etherboot
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*
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* This represents a region that will be edited out of the system's
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* memory map.
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*
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* This structure is accessed by assembly code, so must not be
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* changed.
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*/
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struct hidden_region {
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/* Physical start address */
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physaddr_t start;
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/* Physical end address */
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physaddr_t end;
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};
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/**
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* Unique IDs for hidden regions
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*/
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enum {
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enum hidemem_region_id {
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TEXT = 0,
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BASEMEM,
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EXTMEM,
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};
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extern struct hidden_region __data16_array ( hidden_regions, [] );
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#define hidden_regions __use_data16 ( hidden_regions )
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static inline void hide_region ( unsigned int region,
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physaddr_t start, physaddr_t end ) {
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hidden_regions[region].start = start;
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hidden_regions[region].end = end;
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}
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extern void hide_region ( unsigned int region_id, physaddr_t start,
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physaddr_t end );
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#endif /* _GPXE_HIDEMEM_H */
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