65 lines
1.4 KiB
C
65 lines
1.4 KiB
C
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#include "limits.h"
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#include "io.h"
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#include "memsizes.h"
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#include "init.h"
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#include "buffer.h"
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/*
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* Initialise a buffer in an unused portion of memory, to be used for
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* loading an image
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*
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*/
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/* Under KEEP_IT_REAL, always use 07c0:0000 as the buffer. Otherwise,
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* use a reset_fn that finds the largest available block of RAM.
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*/
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struct buffer load_buffer = {
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.start = 0x7c00,
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.end = 0xa0000,
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};
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#ifndef KEEP_IT_REAL
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extern char _text[];
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static void init_load_buffer ( void ) {
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unsigned int i;
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unsigned long size = 0;
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load_buffer.start = 0;
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load_buffer.end = 0;
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/* Find the largest usable segment in memory */
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for ( i = 0 ; i < meminfo.map_count ; i++ ) {
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unsigned long r_start, r_end;
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if ( meminfo.map[i].type != E820_RAM )
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continue;
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if ( meminfo.map[i].addr + meminfo.map[i].size > ULONG_MAX )
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continue;
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r_start = meminfo.map[i].addr;
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r_end = meminfo.map[i].size;
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/* Avoid overlap with Etherboot. Etherboot will be
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* located towards the top of a segment, so we need
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* only consider one-sided truncation.
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*/
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if ( ( r_start <= virt_to_phys ( _text ) ) &&
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( virt_to_phys ( _text ) < r_end ) ) {
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r_end = virt_to_phys ( _text );
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}
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if ( r_end - r_start > size ) {
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size = r_end - r_start;
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load_buffer.start = r_start;
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load_buffer.end = r_end;
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}
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}
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}
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INIT_FN ( INIT_HEAP, init_load_buffer, init_load_buffer, NULL );
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#endif
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