130 lines
3.4 KiB
C
130 lines
3.4 KiB
C
#include <ipxe/io.h>
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#include <registers.h>
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/*
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* Originally by Eric Biederman
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*
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* Heavily modified by Michael Brown
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*
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*/
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FILE_LICENCE ( GPL2_OR_LATER );
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/*
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* The linker passes in the symbol _max_align, which is the alignment
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* that we must preserve, in bytes.
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*
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*/
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extern char _max_align[];
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#define max_align ( ( unsigned int ) _max_align )
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/* Linker symbols */
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extern char _textdata[];
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extern char _etextdata[];
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/* within 1MB of 4GB is too close.
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* MAX_ADDR is the maximum address we can easily do DMA to.
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*
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* Not sure where this constraint comes from, but kept it from Eric's
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* old code - mcb30
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*/
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#define MAX_ADDR (0xfff00000UL)
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/**
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* Relocate iPXE
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*
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* @v ix86 x86 register dump from prefix
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* @ret ix86 x86 registers to return to prefix
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*
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* This finds a suitable location for iPXE near the top of 32-bit
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* address space, and returns the physical address of the new location
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* to the prefix in %edi.
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*/
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__asmcall void relocate ( struct i386_all_regs *ix86 ) {
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struct memory_map memmap;
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unsigned long start, end, size, padded_size;
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unsigned long new_start, new_end;
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unsigned i;
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/* Get memory map and current location */
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get_memmap ( &memmap );
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start = virt_to_phys ( _textdata );
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end = virt_to_phys ( _etextdata );
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size = ( end - start );
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padded_size = ( size + max_align - 1 );
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DBG ( "Relocate: currently at [%lx,%lx)\n"
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"...need %lx bytes for %d-byte alignment\n",
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start, end, padded_size, max_align );
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/* Walk through the memory map and find the highest address
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* below 4GB that iPXE will fit into.
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*/
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new_end = end;
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for ( i = 0 ; i < memmap.count ; i++ ) {
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struct memory_region *region = &memmap.regions[i];
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unsigned long r_start, r_end;
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DBG ( "Considering [%llx,%llx)\n", region->start, region->end);
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/* Truncate block to MAX_ADDR. This will be less than
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* 4GB, which means that we can get away with using
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* just 32-bit arithmetic after this stage.
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*/
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if ( region->start > MAX_ADDR ) {
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DBG ( "...starts after MAX_ADDR=%lx\n", MAX_ADDR );
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continue;
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}
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r_start = region->start;
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if ( region->end > MAX_ADDR ) {
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DBG ( "...end truncated to MAX_ADDR=%lx\n", MAX_ADDR );
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r_end = MAX_ADDR;
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} else {
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r_end = region->end;
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}
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DBG ( "...usable portion is [%lx,%lx)\n", r_start, r_end );
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/* If we have rounded down r_end below r_ start, skip
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* this block.
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*/
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if ( r_end < r_start ) {
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DBG ( "...truncated to negative size\n" );
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continue;
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}
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/* Check that there is enough space to fit in iPXE */
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if ( ( r_end - r_start ) < size ) {
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DBG ( "...too small (need %lx bytes)\n", size );
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continue;
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}
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/* If the start address of the iPXE we would
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* place in this block is higher than the end address
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* of the current highest block, use this block.
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*
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* Note that this avoids overlaps with the current
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* iPXE, as well as choosing the highest of all viable
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* blocks.
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*/
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if ( ( r_end - size ) > new_end ) {
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new_end = r_end;
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DBG ( "...new best block found.\n" );
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}
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}
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/* Calculate new location of iPXE, and align it to the
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* required alignemnt.
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*/
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new_start = new_end - padded_size;
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new_start += ( start - new_start ) & ( max_align - 1 );
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new_end = new_start + size;
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DBG ( "Relocating from [%lx,%lx) to [%lx,%lx)\n",
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start, end, new_start, new_end );
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/* Let prefix know what to copy */
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ix86->regs.esi = start;
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ix86->regs.edi = new_start;
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ix86->regs.ecx = size;
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}
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