Added (not yet tested) PXE API entry point and support functions.

src/arch/i386/interface/pxe/pxe_call.c

@@ -18,6 +18,7 @@
 
 #include <gpxe/uaccess.h>
 #include <registers.h>
+#include <biosint.h>
 #include <pxe.h>
 
 /** @file
@@ -25,6 +26,21 @@
  * PXE API entry point
  */
 
+/** Vector for chaining INT 1A */
+extern struct segoff __text16 ( pxe_int_1a_vector );
+#define pxe_int_1a_vector __use_text16 ( pxe_int_1a_vector )
+
+/** INT 1A handler */
+extern void pxe_int_1a ( void );
+
+/** !PXE structure */
+extern struct s_PXE __text16 ( pxe );
+#define pxe __use_text16 ( pxe )
+
+/** PXENV+ structure */
+extern struct s_PXENV __text16 ( pxenv );
+#define pxenv __use_text16 ( pxenv )
+
 /** A function pointer to hold any PXE API call
  *
  * Used by pxe_api_call() to avoid large swathes of duplicated code.
@@ -288,3 +304,95 @@ void pxe_api_call ( struct i386_all_regs *ix86 ) {
 	copy_to_user ( parameters, 0, &pxenv_any, param_len );
 	ix86->regs.ax = ret;
 }
+
+/**
+ * Hook INT 1A for PXE
+ *
+ */
+void pxe_hook_int ( void ) {
+	hook_bios_interrupt ( 0x1a, ( unsigned int ) pxe_int_1a,
+			      &pxe_int_1a_vector );
+}
+
+/**
+ * Unhook INT 1A for PXE
+ *
+ * @ret rc		Return status code
+ */
+int pxe_unhook_int ( void ) {
+	return unhook_bios_interrupt ( 0x1a, ( unsigned int ) pxe_int_1a,
+				       &pxe_int_1a_vector );
+}
+
+/**
+ * Calculate byte checksum as used by PXE
+ *
+ * @v data		Data
+ * @v size		Length of data
+ * @ret sum		Checksum
+ */
+static uint8_t pxe_checksum ( void *data, size_t size ) {
+	uint8_t *bytes = data;
+	uint8_t sum = 0;
+
+	while ( size-- ) {
+		sum += *bytes++;
+	}
+	return sum;
+}
+
+/**
+ * Initialise PXE stack
+ *
+ */
+void init_pxe ( void ) {
+	uint32_t rm_cs_phys = ( rm_cs << 4 );
+	uint32_t rm_ds_phys = ( rm_ds << 4 );
+
+	/* Fill in missing segment fields */
+	pxe.EntryPointSP.segment = rm_cs;
+	pxe.EntryPointESP.segment = rm_cs;
+	pxe.Stack.segment_address = rm_ds;
+	pxe.Stack.Physical_address = rm_ds_phys;
+	pxe.UNDIData.segment_address = rm_ds;
+	pxe.UNDIData.Physical_address = rm_ds_phys;
+	pxe.UNDICode.segment_address = rm_cs;
+	pxe.UNDICode.Physical_address = rm_cs_phys;
+	pxe.UNDICodeWrite.segment_address = rm_cs;
+	pxe.UNDICodeWrite.Physical_address = rm_cs_phys;
+	pxenv.RMEntry.segment = rm_cs;
+	pxenv.StackSeg = rm_ds;
+	pxenv.UNDIDataSeg = rm_ds;
+	pxenv.UNDICodeSeg = rm_cs;
+	pxenv.PXEPtr.segment = rm_cs;
+
+	/* Update checksums */
+	pxe.StructCksum -= pxe_checksum ( &pxe, sizeof ( pxe ) );
+	pxenv.Checksum -= pxe_checksum ( &pxenv, sizeof ( pxenv ) );
+}
+
+/**
+ * Boot via PXE NBP
+ *
+ * @ret rc		Return status code
+ */
+int pxe_boot ( void ) {
+	int discard_b, discard_c;
+	uint16_t rc;
+
+	/* Ensure that PXE stack is ready to use */
+	init_pxe();
+	pxe_hook_int();
+
+	/* Far call to PXE NBP */
+	__asm__ __volatile__ ( REAL_CODE ( "pushw %%cx\n\t"
+					   "pushw %%ax\n\t"
+					   "movw %%cx, %%es\n\t"
+					   "lcall $0, $0x7c00\n\t" )
+			       : "=a" ( rc ), "=b" ( discard_b ),
+			         "=c" ( discard_c )
+			       :  "a" ( &pxe ), "b" ( &pxenv ), "c" ( rm_cs )
+			       : "edx", "esi", "edi", "ebp", "memory" );
+
+	return rc;
+}

src/arch/i386/interface/pxe/pxe_entry.S

@@ -0,0 +1,192 @@
+/*
+ * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+	.arch i386
+	.section ".text16", "awx", @progbits
+	.section ".text16.data", "aw", @progbits
+	.section ".data16", "aw", @progbits
+
+/****************************************************************************
+ * !PXE structure
+ ****************************************************************************
+ */
+	.section ".text16.data"
+	.globl pxe
+pxe:
+	.ascii "!PXE"			/* Signature */
+	.byte pxe_length		/* StructLength */
+	.byte 0				/* StructCksum */
+	.byte 0				/* StructRev */
+	.byte 0				/* reserved_1 */
+	.word 0, 0			/* UNDIROMID */
+	.word 0, 0			/* BaseROMID */
+	.word pxe_entry_sp, 0		/* EntryPointSP */
+	.word pxe_entry_esp, 0		/* EntryPointESP */
+	.word -1, -1			/* StatusCallout */
+	.byte 0				/* reserved_2 */
+	.byte SegDescCnt		/* SegDescCnt */
+	.word 0				/* FirstSelector */
+pxe_segments:
+	.word 0, 0, 0, _data16_size	/* Stack */
+	.word 0, 0, 0, _data16_size	/* UNDIData */
+	.word 0, 0, 0, _text16_size	/* UNDICode */
+	.word 0, 0, 0, _text16_size	/* UNDICodeWrite */
+	.word 0, 0, 0, 0		/* BC_Data */
+	.word 0, 0, 0, 0		/* BC_Code */
+	.word 0, 0, 0, 0		/* BC_CodeWrite */
+	.equ	SegDescCnt, ( ( . - pxe_segments ) / 8 )
+	.equ	pxe_length, . - pxe
+	.size	pxe, . - pxe
+
+/****************************************************************************
+ * PXENV+ structure
+ ****************************************************************************
+ */
+	.section ".text16.data"
+	.globl pxenv
+pxenv:
+	.ascii "PXENV+"			/* Signature */
+	.word 0x0201			/* Version */
+	.byte pxenv_length		/* Length */
+	.byte 0				/* Checksum */
+	.word pxenv_entry, 0		/* RMEntry */
+	.long 0				/* PMEntry */
+	.word 0				/* PMSelector */
+	.word 0				/* StackSeg */
+	.word _data16_size		/* StackSize */
+	.word 0				/* BC_CodeSeg */
+	.word 0				/* BC_CodeSize */
+	.word 0				/* BC_DataSeg */
+	.word 0				/* BC_DataSize */
+	.word 0				/* UNDIDataSeg */
+	.word _data16_size		/* UNDIDataSize */
+	.word 0				/* UNDICodeSeg */
+	.word _text16_size		/* UNDICodeSize */
+	.word pxe, 0			/* PXEPtr */
+	.equ	pxenv_length, . - pxenv
+	.size	pxenv, . - pxenv
+ 
+/****************************************************************************
+ * pxenv_entry (16-bit far call)
+ *
+ * PXE API call PXENV+ entry point
+ *
+ * Parameters:
+ *   %es:di : Far pointer to PXE parameter structure
+ *   %bx : PXE API call
+ * Returns:
+ *   %ax : PXE exit status
+ * Corrupts:
+ *   none
+ ****************************************************************************
+ */
+	.section ".text16"
+	.code16
+pxenv_entry:
+	pushl	$pxe_api_call
+	pushw	%cs
+	call	prot_call
+	addl	$4, %esp
+	lret
+	.size	pxenv_entry, . - pxenv_entry
+
+/****************************************************************************
+ * pxe_entry
+ *
+ * PXE API call !PXE entry point
+ *
+ * Parameters:
+ *   stack : Far pointer to PXE parameter structure
+ *   stack : PXE API call
+ * Returns:
+ *   %ax : PXE exit status
+ * Corrupts:
+ *   none
+ ****************************************************************************
+ */
+	.section ".text16"
+	.code16
+pxe_entry:
+pxe_entry_sp:
+	/* Preserve original %esp */
+	pushl	%esp
+	/* Zero high word of %esp to allow use of common code */
+	movzwl	%sp, %esp
+	jmp	pxe_entry_common
+pxe_entry_esp:
+	/* Preserve %esp to match behaviour of pxe_entry_sp */
+	pushl	%esp
+pxe_entry_common:
+	/* Save PXENV+ API call registers */
+	pushw	%es
+	pushw	%di
+	pushw	%bx
+	/* Load !PXE parameters from stack into PXENV+ registers */
+	movw	16(%esp), %bx
+	movw	%bx, %es
+	movw	14(%esp), %di
+	movw	12(%esp), %bx
+	/* Make call as for PXENV+ */
+	pushw	%cs
+	call	pxenv_entry
+	/* Restore PXENV+ registers */
+	popw	%bx
+	popw	%di
+	popw	%es
+	/* Restore original %esp and return */
+	popl	%esp
+	lret
+	.size	pxe_entry, . - pxe_entry
+
+/****************************************************************************
+ * pxe_int_1a
+ *
+ * PXE INT 1A handler
+ *
+ * Parameters:
+ *   %ax : 0x5650
+ * Returns:
+ *   %ax : 0x564e
+ *   %es:bx : Far pointer to the PXENV+ structure
+ *   CF cleared
+ * Corrupts:
+ *   none
+ ****************************************************************************
+ */
+	.section ".text16"
+	.code16
+pxe_int_1a:
+	pushfw
+	cmpw	$0x5650, %ax
+	jne	1f
+	/* INT 1A,5650 - PXE installation check */
+	pushw	%cs
+	popw	%es
+	movw	$pxenv, %bx
+	movw	$0x564e, %ax
+	popfw
+	clc
+	lret	$2
+1:	/* INT 1A,other - pass through */
+	popfw
+	ljmp	*%cs:pxe_int_1a_vector
+
+	.section ".text16.data"
+	.globl	pxe_int_1a_vector
+pxe_int_1a_vector:	.long 0