365 lines
12 KiB
C
365 lines
12 KiB
C
/* PXE callback mechanisms. This file contains only the portions
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* specific to i386: i.e. the low-level mechanisms for calling in from
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* an NBP to the PXE stack and for starting an NBP from the PXE stack.
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*/
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#ifdef PXE_EXPORT
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#include "etherboot.h"
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#include "callbacks.h"
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#include "realmode.h"
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#include "pxe.h"
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#include "pxe_callbacks.h"
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#include "pxe_export.h"
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#include "hidemem.h"
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#include <stdarg.h>
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#define INSTALLED(x) ( (typeof(&x)) ( (void*)(&x) \
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- &pxe_callback_interface \
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+ (void*)&pxe_stack->arch_data ) )
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#define pxe_intercept_int1a INSTALLED(_pxe_intercept_int1a)
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#define pxe_intercepted_int1a INSTALLED(_pxe_intercepted_int1a)
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#define pxe_pxenv_location INSTALLED(_pxe_pxenv_location)
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#define INT1A_VECTOR ( (segoff_t*) ( phys_to_virt( 4 * 0x1a ) ) )
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/* The overall size of the PXE stack is ( sizeof(pxe_stack_t) +
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* pxe_callback_interface_size + rm_callback_interface_size ).
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* Unfortunately, this isn't a compile-time constant, since
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* {pxe,rm}_callback_interface_size depend on the length of the
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* assembly code in these interfaces.
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*
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* We used to have a function pxe_stack_size() which returned this
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* value. However, it actually needs to be a link-time constant, so
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* that it can appear in the UNDIROMID structure in romprefix.S. We
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* therefore export the three component sizes as absolute linker
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* symbols, get the linker to add them together and generate a new
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* absolute symbol _pxe_stack_size. We then import this value into a
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* C variable pxe_stack_size, for access from C code.
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*/
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/* gcc won't let us use extended asm outside a function (compiler
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* bug), ao we have to put these asm statements inside a dummy
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* function.
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*/
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static void work_around_gcc_bug ( void ) __attribute__ ((used));
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static void work_around_gcc_bug ( void ) {
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/* Export sizeof(pxe_stack_t) as absolute linker symbol */
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__asm__ ( ".globl _pxe_stack_t_size" );
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__asm__ ( ".equ _pxe_stack_t_size, %c0"
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: : "i" (sizeof(pxe_stack_t)) );
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}
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/* Import _pxe_stack_size absolute linker symbol into C variable */
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extern int pxe_stack_size;
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__asm__ ( "pxe_stack_size: .long _pxe_stack_size" );
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/* Utility routine: byte checksum
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*/
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uint8_t byte_checksum ( void *address, size_t size ) {
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unsigned int i, sum = 0;
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for ( i = 0; i < size; i++ ) {
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sum += ((uint8_t*)address)[i];
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}
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return (uint8_t)sum;
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}
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/* install_pxe_stack(): install PXE stack.
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*
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* Use base = NULL for auto-allocation of base memory
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*
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* IMPORTANT: no further allocation of base memory should take place
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* before the PXE stack is removed. This is to work around a small
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* but important deficiency in the PXE specification.
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*/
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pxe_stack_t * install_pxe_stack ( void *base ) {
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pxe_t *pxe;
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pxenv_t *pxenv;
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void *pxe_callback_code;
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void (*pxe_in_call_far)(void);
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void (*pxenv_in_call_far)(void);
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void *rm_callback_code;
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void *e820mangler_code;
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void *end;
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/* If already installed, just return */
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if ( pxe_stack != NULL ) return pxe_stack;
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/* Allocate base memory if requested to do so
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*/
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if ( base == NULL ) {
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base = allot_base_memory ( pxe_stack_size );
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if ( base == NULL ) return NULL;
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}
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/* Round address up to 16-byte physical alignment */
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pxe_stack = (pxe_stack_t *)
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( phys_to_virt ( ( virt_to_phys(base) + 0xf ) & ~0xf ) );
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/* Zero out allocated stack */
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memset ( pxe_stack, 0, sizeof(*pxe_stack) );
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/* Calculate addresses for portions of the stack */
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pxe = &(pxe_stack->pxe);
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pxenv = &(pxe_stack->pxenv);
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pxe_callback_code = &(pxe_stack->arch_data);
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pxe_in_call_far = _pxe_in_call_far +
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( pxe_callback_code - &pxe_callback_interface );
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pxenv_in_call_far = _pxenv_in_call_far +
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( pxe_callback_code - &pxe_callback_interface );
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rm_callback_code = pxe_callback_code + pxe_callback_interface_size;
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e820mangler_code = (void*)(((int)rm_callback_code +
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rm_callback_interface_size + 0xf ) & ~0xf);
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end = e820mangler_code + e820mangler_size;
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/* Initialise !PXE data structures */
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memcpy ( pxe->Signature, "!PXE", 4 );
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pxe->StructLength = sizeof(*pxe);
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pxe->StructRev = 0;
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pxe->reserved_1 = 0;
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/* We don't yet have an UNDI ROM ID structure */
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pxe->UNDIROMID.segment = 0;
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pxe->UNDIROMID.offset = 0;
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/* or a BC ROM ID structure */
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pxe->BaseROMID.segment = 0;
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pxe->BaseROMID.offset = 0;
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pxe->EntryPointSP.segment = SEGMENT(pxe_stack);
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pxe->EntryPointSP.offset = (void*)pxe_in_call_far - (void*)pxe_stack;
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/* No %esp-compatible entry point yet */
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pxe->EntryPointESP.segment = 0;
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pxe->EntryPointESP.offset = 0;
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pxe->StatusCallout.segment = -1;
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pxe->StatusCallout.offset = -1;
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pxe->reserved_2 = 0;
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pxe->SegDescCn = 7;
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pxe->FirstSelector = 0;
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/* PXE specification doesn't say anything about when the stack
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* space should get freed. We work around this by claiming it
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* as our data segment as well.
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*/
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pxe->Stack.Seg_Addr = pxe->UNDIData.Seg_Addr = real_mode_stack >> 4;
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pxe->Stack.Phy_Addr = pxe->UNDIData.Phy_Addr = real_mode_stack;
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pxe->Stack.Seg_Size = pxe->UNDIData.Seg_Size = real_mode_stack_size;
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/* Code segment has to be the one containing the data structures... */
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pxe->UNDICode.Seg_Addr = SEGMENT(pxe_stack);
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pxe->UNDICode.Phy_Addr = virt_to_phys(pxe_stack);
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pxe->UNDICode.Seg_Size = end - (void*)pxe_stack;
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/* No base code loaded */
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pxe->BC_Data.Seg_Addr = 0;
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pxe->BC_Data.Phy_Addr = 0;
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pxe->BC_Data.Seg_Size = 0;
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pxe->BC_Code.Seg_Addr = 0;
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pxe->BC_Code.Phy_Addr = 0;
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pxe->BC_Code.Seg_Size = 0;
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pxe->BC_CodeWrite.Seg_Addr = 0;
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pxe->BC_CodeWrite.Phy_Addr = 0;
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pxe->BC_CodeWrite.Seg_Size = 0;
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pxe->StructCksum -= byte_checksum ( pxe, sizeof(*pxe) );
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/* Initialise PXENV+ data structures */
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memcpy ( pxenv->Signature, "PXENV+", 6 );
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pxenv->Version = 0x201;
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pxenv->Length = sizeof(*pxenv);
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pxenv->RMEntry.segment = SEGMENT(pxe_stack);
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pxenv->RMEntry.offset = (void*)pxenv_in_call_far - (void*)pxe_stack;
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pxenv->PMOffset = 0; /* "Do not use" says the PXE spec */
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pxenv->PMSelector = 0; /* "Do not use" says the PXE spec */
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pxenv->StackSeg = pxenv->UNDIDataSeg = real_mode_stack >> 4;
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pxenv->StackSize = pxenv->UNDIDataSize = real_mode_stack_size;
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pxenv->BC_CodeSeg = 0;
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pxenv->BC_CodeSize = 0;
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pxenv->BC_DataSeg = 0;
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pxenv->BC_DataSize = 0;
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/* UNDIData{Seg,Size} set above */
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pxenv->UNDICodeSeg = SEGMENT(pxe_stack);
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pxenv->UNDICodeSize = end - (void*)pxe_stack;
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pxenv->PXEPtr.segment = SEGMENT(pxe);
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pxenv->PXEPtr.offset = OFFSET(pxe);
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pxenv->Checksum -= byte_checksum ( pxenv, sizeof(*pxenv) );
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/* Mark stack as inactive */
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pxe_stack->state = CAN_UNLOAD;
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/* Install PXE and RM callback code and E820 mangler */
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memcpy ( pxe_callback_code, &pxe_callback_interface,
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pxe_callback_interface_size );
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install_rm_callback_interface ( rm_callback_code, 0 );
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install_e820mangler ( e820mangler_code );
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return pxe_stack;
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}
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/* Use the UNDI data segment as our real-mode stack. This is for when
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* we have been loaded via the UNDI loader
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*/
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void use_undi_ds_for_rm_stack ( uint16_t ds ) {
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forget_real_mode_stack();
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real_mode_stack = virt_to_phys ( VIRTUAL ( ds, 0 ) );
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lock_real_mode_stack = 1;
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}
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/* Activate PXE stack (i.e. hook interrupt vectors). The PXE stack
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* *can* be used before it is activated, but it really shoudln't.
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*/
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int hook_pxe_stack ( void ) {
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if ( pxe_stack == NULL ) return 0;
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if ( pxe_stack->state >= MIDWAY ) return 1;
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/* Hook INT15 handler */
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hide_etherboot();
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/* Hook INT1A handler */
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*pxe_intercepted_int1a = *INT1A_VECTOR;
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pxe_pxenv_location->segment = SEGMENT(pxe_stack);
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pxe_pxenv_location->offset = (void*)&pxe_stack->pxenv
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- (void*)pxe_stack;
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INT1A_VECTOR->segment = SEGMENT(&pxe_stack->arch_data);
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INT1A_VECTOR->offset = (void*)pxe_intercept_int1a
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- (void*)&pxe_stack->arch_data;
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/* Mark stack as active */
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pxe_stack->state = MIDWAY;
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return 1;
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}
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/* Deactivate the PXE stack (i.e. unhook interrupt vectors).
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*/
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int unhook_pxe_stack ( void ) {
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if ( pxe_stack == NULL ) return 0;
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if ( pxe_stack->state <= CAN_UNLOAD ) return 1;
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/* Restore original INT15 and INT1A handlers */
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*INT1A_VECTOR = *pxe_intercepted_int1a;
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if ( !unhide_etherboot() ) {
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/* Cannot unhook INT15. We're up the creek without
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* even a suitable log out of which to fashion a
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* paddle. There are some very badly behaved NBPs
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* that will ignore plaintive pleas such as
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* PXENV_KEEP_UNDI and just zero out our code anyway.
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* This means they end up vapourising an active INT15
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* handler, which is generally not a good thing to do.
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*/
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return 0;
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}
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/* Mark stack as inactive */
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pxe_stack->state = CAN_UNLOAD;
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return 1;
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}
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/* remove_pxe_stack(): remove PXE stack installed by install_pxe_stack()
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*/
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void remove_pxe_stack ( void ) {
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/* Ensure stack is deactivated, then free up the memory */
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if ( ensure_pxe_state ( CAN_UNLOAD ) ) {
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forget_base_memory ( pxe_stack, pxe_stack_size );
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pxe_stack = NULL;
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} else {
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printf ( "Cannot remove PXE stack!\n" );
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}
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}
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/* xstartpxe(): start up a PXE image
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*/
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int xstartpxe ( void ) {
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int nbp_exit;
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struct {
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reg16_t bx;
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reg16_t es;
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segoff_t pxe;
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} PACKED in_stack;
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/* Set up registers and stack parameters to pass to PXE NBP */
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in_stack.es.word = SEGMENT(&(pxe_stack->pxenv));
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in_stack.bx.word = OFFSET(&(pxe_stack->pxenv));
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in_stack.pxe.segment = SEGMENT(&(pxe_stack->pxe));
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in_stack.pxe.offset = OFFSET(&(pxe_stack->pxe));
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/* Real-mode trampoline fragment used to jump to PXE NBP
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*/
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RM_FRAGMENT(jump_to_pxe_nbp,
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"popw %bx\n\t"
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"popw %es\n\t"
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"lcall $" RM_STR(PXE_LOAD_SEGMENT) ", $" RM_STR(PXE_LOAD_OFFSET) "\n\t"
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);
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/* Call to PXE image */
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gateA20_unset();
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nbp_exit = real_call ( jump_to_pxe_nbp, &in_stack, NULL );
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gateA20_set();
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return nbp_exit;
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}
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int pxe_in_call ( in_call_data_t *in_call_data, va_list params ) {
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/* i386 calling conventions; the only two defined by Intel's
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* PXE spec.
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*
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* Assembly code must pass a long containing the PXE version
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* code (i.e. 0x201 for !PXE, 0x200 for PXENV+) as the first
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* parameter after the in_call opcode. This is used to decide
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* whether to take parameters from the stack (!PXE) or from
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* registers (PXENV+).
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*/
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uint32_t api_version = va_arg ( params, typeof(api_version) );
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uint16_t opcode;
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segoff_t segoff;
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t_PXENV_ANY *structure;
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if ( api_version >= 0x201 ) {
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/* !PXE calling convention */
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pxe_call_params_t pxe_params
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= va_arg ( params, typeof(pxe_params) );
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opcode = pxe_params.opcode;
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segoff = pxe_params.segoff;
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} else {
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/* PXENV+ calling convention */
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opcode = in_call_data->pm->regs.bx;
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segoff.segment = in_call_data->rm->seg_regs.es;
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segoff.offset = in_call_data->pm->regs.di;
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}
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structure = VIRTUAL ( segoff.segment, segoff.offset );
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return pxe_api_call ( opcode, structure );
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}
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#ifdef TEST_EXCLUDE_ALGORITHM
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/* This code retained because it's a difficult algorithm to tweak with
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* confidence
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*/
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int ___test_exclude ( int start, int len, int estart, int elen, int fixbase );
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void __test_exclude ( int start, int len, int estart, int elen, int fixbase ) {
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int newrange = ___test_exclude ( start, len, estart, elen, fixbase );
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int newstart = ( newrange >> 16 ) & 0xffff;
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int newlen = ( newrange & 0xffff );
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printf ( "[%x,%x): excluding [%x,%x) %s gives [%x,%x)\n",
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start, start + len,
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estart, estart + elen,
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( fixbase == 0 ) ? " " : "fb",
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newstart, newstart + newlen );
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}
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void _test_exclude ( int start, int len, int estart, int elen ) {
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__test_exclude ( start, len, estart, elen, 0 );
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__test_exclude ( start, len, estart, elen, 1 );
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}
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void test_exclude ( void ) {
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_test_exclude ( 0x8000, 0x1000, 0x0400, 0x200 ); /* before */
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_test_exclude ( 0x8000, 0x1000, 0x9000, 0x200 ); /* after */
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_test_exclude ( 0x8000, 0x1000, 0x7f00, 0x200 ); /* before overlap */
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_test_exclude ( 0x8000, 0x1000, 0x8f00, 0x200 ); /* after overlap */
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_test_exclude ( 0x8000, 0x1000, 0x8000, 0x200 ); /* align start */
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_test_exclude ( 0x8000, 0x1000, 0x8e00, 0x200 ); /* align end */
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_test_exclude ( 0x8000, 0x1000, 0x8100, 0x200 ); /* early overlap */
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_test_exclude ( 0x8000, 0x1000, 0x8d00, 0x200 ); /* late overlap */
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_test_exclude ( 0x8000, 0x1000, 0x7000, 0x3000 ); /* total overlap */
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_test_exclude ( 0x8000, 0x1000, 0x8000, 0x1000 ); /* exact overlap */
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}
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#endif /* TEST_EXCLUDE_ALGORITHM */
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#else /* PXE_EXPORT */
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/* Define symbols used by the linker scripts, to prevent link errors */
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__asm__ ( ".globl _pxe_stack_t_size" );
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__asm__ ( ".equ _pxe_stack_t_size, 0" );
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#endif /* PXE_EXPORT */
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