tools: new dir for basic tools for the switch

tools/Makefile

+
+CFLAGS = -Wall -ggdb $(EXTRA_CFLAGS)
+
+ifdef LINUX
+    CFLAGS += -I$(LINUX)/include \
+		-I$(LINUX)/arch/arm/mach-at91/include
+endif
+
+AS              = $(CROSS_COMPILE)as
+LD              = $(CROSS_COMPILE)ld
+CC              = $(CROSS_COMPILE)gcc
+CPP             = $(CC) -E
+AR              = $(CROSS_COMPILE)ar
+NM              = $(CROSS_COMPILE)nm
+STRIP           = $(CROSS_COMPILE)strip
+OBJCOPY         = $(CROSS_COMPILE)objcopy
+OBJDUMP         = $(CROSS_COMPILE)objdump

tools/devmem2.c

+/*
+ * devmem2.c: Simple program to read/write from/to any location in memory.
+ *
+ *  Copyright (C) 2000, Jan-Derk Bakker (J.D.Bakker@its.tudelft.nl)
+ *  modified 2005 by Alessandro Rubini, to make it less verbose
+ *
+ *
+ * This software has been developed for the LART computing board
+ * (http://www.lart.tudelft.nl/). The development has been sponsored by
+ * the Mobile MultiMedia Communications (http://www.mmc.tudelft.nl/)
+ * and Ubiquitous Communications (http://www.ubicom.tudelft.nl/)
+ * projects.
+ *
+ * The author can be reached at:
+ *
+ *  Jan-Derk Bakker
+ *  Information and Communication Theory Group
+ *  Faculty of Information Technology and Systems
+ *  Delft University of Technology
+ *  P.O. Box 5031
+ *  2600 GA Delft
+ *  The Netherlands
+ *
+ *
+ * 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
+ * (at your option) 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <signal.h>
+#include <fcntl.h>
+#include <ctype.h>
+#include <termios.h>
+#include <sys/types.h>
+#include <sys/mman.h>
+  
+#define FATAL do { fprintf(stderr, "Error at line %d, file %s (%d) [%s]\n", \
+  __LINE__, __FILE__, errno, strerror(errno)); exit(1); } while(0)
+ 
+#define MAP_SIZE 4096UL
+#define MAP_MASK (MAP_SIZE - 1)
+
+int verbose = 0;
+int main(int argc, char **argv) {
+     int fd;
+     void *map_base, *virt_addr; 
+     unsigned long read_result, writeval;
+     int wid;
+     char format[16];
+     off_t target;
+     int access_type = 'w';
+	
+
+     setuid(0); /* try */
+
+     if(argc < 2) {
+	  fprintf(stderr, "\nUsage:\t%s { address } [ type [ data ] ]\n"
+		  "\taddress : memory address to act upon\n"
+		  "\ttype    : access operation type : [b]yte, [h]alfword, [w]ord\n"
+		  "\tdata    : data to be written\n\n",
+		  argv[0]);
+	  exit(1);
+     }
+     target = strtoul(argv[1], 0, 0);
+
+     if(argc > 2)
+	  access_type = tolower(argv[2][0]);
+
+
+     if((fd = open("/dev/mem", O_RDWR | O_SYNC)) == -1) FATAL;
+     if (verbose) {
+	  printf("/dev/mem opened.\n"); 
+	  fflush(stdout);
+     }
+    
+     /* Map one page */
+     map_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, target & ~MAP_MASK);
+     if(map_base == (void *) -1) FATAL;
+     if (verbose) {
+	  printf("Memory mapped at address %p.\n", map_base); 
+	  fflush(stdout);
+     }
+    
+     virt_addr = map_base + (target & MAP_MASK);
+     if (argc <= 3) {
+     switch(access_type) {
+     case 'b':
+	  read_result = *((unsigned char *) virt_addr);
+	  wid = 2;
+	  break;
+     case 'h':
+	  read_result = *((unsigned short *) virt_addr);
+	  wid = 4;
+	  break;
+     case 'w':
+	  read_result = *((unsigned long *) virt_addr);
+	  wid = 8;
+	  break;
+     default:
+	  fprintf(stderr, "Illegal data type '%c'.\n", access_type);
+	  exit(2);
+     }
+     sprintf(format, "0x%%0%ix\n", wid);
+     printf(format, read_result); 
+     fflush(stdout);
+     }
+
+     if(argc > 3) {
+	  writeval = strtoul(argv[3], 0, 0);
+	  switch(access_type) {
+	  case 'b':
+	       *((unsigned char *) virt_addr) = writeval;
+	       break;
+	  case 'h':
+	       *((unsigned short *) virt_addr) = writeval;
+	       break;
+	  case 'w':
+	       *((unsigned long *) virt_addr) = writeval;
+	       break;
+	  }
+     }
+	
+     if(munmap(map_base, MAP_SIZE) == -1) FATAL;
+     close(fd);
+     return 0;
+}
+

tools/load-fpga.c

+/*
+ * Trivial gpio bit banger.
+ * Alessandro Rubini, 2011, for CERN.
+ * Released to the public domain.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+#include <errno.h>
+#include <time.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <sys/time.h>
+
+#include <linux/types.h>
+
+#include <mach/at91_pio.h> /* -I$LINUX/arch/arm/mach-at91/include/ */
+
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(a) (sizeof(a)/sizeof(a[0]))
+#endif
+
+unsigned char bstream[10*1000*1000]; /* me lazy bastard */
+
+void *pio[5]; /* from mmap(/dev/mem) */
+
+/* describe the g45 memory layout */
+unsigned char *piobase = (void *)0xfffff000;
+
+int offsets[] = {0x200, 0x400, 0x600, 0x800, 0xa00};
+
+void *pio[5]; /* from mmap(/dev/mem) plus offsets above */
+
+enum {
+	PIOA = 0,
+	PIOB = 1,
+	PIOC = 2,
+	PIOD = 3,
+	PIOE = 4
+};
+
+/* macro to access 32-bit registers */
+#define __PIO(port, regname) (*(volatile __u32 *)(pio[port] + regname))
+
+/* This sets a bit. To clear output se set ODR (output disable register) */
+static inline void pio_set(int regname, int port, int bit)
+{
+	__PIO(port, regname)  |= (1 << bit);
+}
+
+/* This only reads input data, returns 0 or non-0 */
+static int pio_get(int port, int bit)
+{
+	return __PIO(port, PIO_PDSR) & (1 << bit);
+}
+
+/* our bits */
+#define TK0		PIOD, 0 //out
+#define TD0		PIOD, 2 //out
+
+#define LED0		PIOA, 0
+#define LED1		PIOA, 1
+#define DONE		PIOA, 2 //in -- inverted
+#define INITB		PIOA, 3 //in
+#define PROGRAMB	PIOA, 4 //out
+#define FPGA_RESET	PIOA, 5 //out
+
+
+void ud(int usecs) /* horrible udelay thing without scheduling */
+{
+	struct timeval tv1, tv2;
+	gettimeofday(&tv1, NULL);
+	do
+		gettimeofday(&tv2, NULL);
+	while ((tv2.tv_sec - tv1.tv_sec) * 1000*1000
+	       + tv2.tv_usec - tv1.tv_usec < usecs);
+}
+
+
+int main(int argc, char **argv)
+{
+	int pagesize, bs_size, i;
+	int fdmem;
+
+	if (argc != 2) {
+		fprintf(stderr, "%s: Use: \"%s <bitstream>\"\n", argv[0],
+			argv[0]);
+		exit(1);
+	}
+
+	{
+		/* read the bisstream file */
+		FILE *f = fopen(argv[1], "r");
+
+		if (!f) {
+			fprintf(stderr, "%s: %s: %s\n", argv[0], argv[1],
+				strerror(errno));
+			exit(1);
+		}
+		bs_size = fread(bstream, 1, sizeof(bstream), f);
+		if (bs_size < 0) {
+			fprintf(stderr, "%s: read(%s): %s\n", argv[0],
+				argv[1], strerror(errno));
+			exit(1);
+		}
+		if (bs_size == sizeof(bstream)) {
+			fprintf(stderr, "%s: %s: too big\n", argv[0], argv[1]);
+			exit(1);
+		}
+		fclose(f);
+	}
+
+	pagesize = getpagesize(); /* can't fail */
+
+	/* /dev/mem for mmap of both gpio and spi1 */
+	if ((fdmem = open("/dev/mem", O_RDWR | O_SYNC)) < 0) {
+		fprintf(stderr, "%s: /dev/mem: %s\n", argv[0], strerror(errno));
+		exit(1);
+	}
+
+	/* map a whole page (4kB, but we called getpagesize to know it) */
+	piobase = mmap(0, pagesize, PROT_READ | PROT_WRITE,
+		       MAP_SHARED, fdmem,
+		       (int)piobase & (~(pagesize-1)));
+	if (piobase == MAP_FAILED) {
+		fprintf(stderr, "%s: mmap(/dev/mem): %s\n",
+			argv[0], strerror(errno));
+		exit(1);
+	}
+
+	/* ok, now move the pointers within the page, we won't munmap anyways */
+	for (i = 0; i < ARRAY_SIZE(pio); i++) {
+		pio[i] = piobase + offsets[i];
+	}
+
+	/*
+	 * all of this stuff is working on gpio so enable pio, out or in
+	 */
+
+	/* clock and data are output, low by now */
+	pio_set(PIO_PER, TK0);
+	pio_set(PIO_CODR, TK0);
+	pio_set(PIO_OER, TK0);
+
+	pio_set(PIO_PER, TD0);
+	pio_set(PIO_CODR, TD0);
+	pio_set(PIO_OER, TD0);
+
+	/* fpga_reset is high */
+	pio_set(PIO_PER, FPGA_RESET);
+	pio_set(PIO_SODR, FPGA_RESET);
+	pio_set(PIO_OER, FPGA_RESET);
+
+	/* program_b is output high: is is pulsed low to start programming */
+	pio_set(PIO_PER, PROGRAMB);
+	pio_set(PIO_SODR, PROGRAMB);
+	pio_set(PIO_OER, PROGRAMB);
+
+	/* init_b is input: it's the fpga telling us it's done initializing */
+	pio_set(PIO_PER, INITB);
+	pio_set(PIO_ODR, INITB);
+
+	/* done is input */
+	pio_set(PIO_PER, DONE);
+	pio_set(PIO_ODR, DONE);
+
+	/* flip the leds for 0.1 secs to show we are alive and well */
+	pio_set(PIO_PER, LED0);
+	pio_set(PIO_OER, LED0);
+	pio_set(PIO_CODR, LED0);
+	pio_set(PIO_PER, LED1);
+	pio_set(PIO_OER, LED1);
+	pio_set(PIO_CODR, LED1);
+	ud(100*1000);
+	pio_set(PIO_SODR, LED0);
+	pio_set(PIO_SODR, LED1);
+
+	/*
+	 * What follows is based on information from
+	 * www.xilinx.com/support/documentation/user_guides/ug360.pdf
+	 */
+
+	/* First, turn PROGRAM_B low */
+	pio_set(PIO_CODR, PROGRAMB);
+
+	/* Then, wait little and then check init_b must go low */
+	for (i = 0; i < 50; i++) {
+		ud(10);
+		if (!pio_get(INITB))
+			break;
+	}
+
+	/* check status: initb must be low and done must be low */
+	if (pio_get(INITB)) {
+		fprintf(stderr, "%s: INIT_B is still high after PROGRAM_B\n",
+			argv[0]);
+		//exit(1);
+	}
+
+	if (!pio_get(DONE)) {
+		fprintf(stderr, "%s: DONE is already high after PROGRAM_B\n",
+			argv[0]);
+		//exit(1);
+	}
+
+	/* raise program_b, and initb must go high, too */
+	pio_set(PIO_SODR, PROGRAMB);
+	for (i = 0; i < 50; i++) {
+		ud(10);
+		if (pio_get(INITB))
+			break;
+	}
+	if (pio_get(INITB)) {
+		fprintf(stderr, "%s: INIT_B is not going back high\n",
+			argv[0]);
+		//exit(1);
+	}
+
+
+	/* Then write one byte at a time */
+	for (i = 0; i < bs_size; i++) {
+		int byte = bstream[i];
+		int bit;
+
+		if (!(i & 1023)) {
+				putchar('.'); fflush(stdout);
+		}
+		/* msb first */
+		for (bit = 0x80; bit > 0; bit >>= 1) {
+			/* data on rising edge of clock, which starts low */
+			if (byte & bit)
+				pio_set(PIO_SODR, TD0);
+			else
+				pio_set(PIO_CODR, TD0);
+
+			/* so, rising edge, after it's stable */
+			asm volatile("nop\n nop\n nop\n nop");
+			pio_set(PIO_SODR, TK0);
+			pio_set(PIO_CODR, TK0);
+		}
+		if (0 && /* don't do this check */ !pio_get(DONE)) {
+			fprintf(stderr, "%s: DONE is already high after "
+				"%i bytes (missing %i)\n", argv[0],
+				i, bs_size - i);
+			exit(1);
+		}
+	}
+	putchar('\n');
+
+	/* Then, wait a little and then check done must go high */
+	for (i = 0; i < 500; i++) {
+		ud(100);
+		if (!pio_get(DONE))
+			break;
+	}
+	if (pio_get(DONE)) {
+		fprintf(stderr, "%s: DONE is not going high after %i bytes\n",
+			argv[0], bs_size);
+		exit(1);
+	}
+
+	/* PA5 must go low then high */
+	pio_set(PIO_CODR, FPGA_RESET);
+	ud(10);
+	pio_set(PIO_SODR, FPGA_RESET);
+
+	exit(0);
+}

tools/mapper.c

+/*
+ * mapper.c -- simple file that mmap()s a file region and prints it
+ * Alessandro Rubini 1997-2008
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <errno.h>
+
+int main(int argc, char **argv)
+{
+    char *fname;
+    FILE *f;
+    int pagesize = getpagesize();
+    unsigned int pos, pos_pg, pos_off;
+    unsigned int len, len_pg, len_off;
+    void *address;
+    char *rest;
+
+    if (argc !=4
+       || sscanf(argv[2],"%i", &pos) != 1
+       || sscanf(argv[3],"%i", &len) != 1) {
+        fprintf(stderr, "%s: Usage \"%s <file> <offset> <len>\"\n", argv[0],
+                argv[0]);
+        exit(1);
+    }
+    /* note: pos may be more than 2G, so use strtoul */
+    pos = strtoul(argv[2], &rest, 0);
+    if (rest && *rest) {
+        fprintf(stderr, "%s: Usage \"%s <file> <offset> <len>\"\n", argv[0],
+                argv[0]);
+        exit(1);
+    }
+
+    fname=argv[1];
+    if (!(f=fopen(fname,"r"))) {
+        fprintf(stderr, "%s: %s: %s\n", argv[0], fname, strerror(errno));
+        exit(1);
+    }
+
+    /* page-align our numbers, as we depend on the MMU */
+    pos_pg  = pos & ~(pagesize-1);
+    pos_off = pos &  (pagesize-1);
+    len_pg  = (len + pos_off + pagesize-1) & ~(pagesize-1);
+    len_off = (len + pos_off) &  (pagesize-1);
+
+    address=mmap(0, len_pg,
+		 PROT_READ, MAP_FILE | MAP_PRIVATE, fileno(f), pos_pg);
+
+    if (address == (void *)-1) {
+        fprintf(stderr,"%s: mmap(): %s\n",argv[0],strerror(errno));
+        exit(1);
+    }
+    fclose(f);
+    fprintf(stderr, "mapped \"%s\" from %i to %i (0x%x to 0x%x) \n",
+            fname, pos, pos+len, pos_pg, pos_pg+len_pg);
+
+    if (fwrite(address+pos_off, 1, len, stdout) != len) {
+	fprintf(stderr, "%s: write(): %s\n", argv[0], strerror(errno));
+	exit(1);
+    }
+    return 0;
+}
+        

tools/spi-pll.c

+/*
+ * Trivial pll programmer using an spi controoler.
+ * PLL is AD9516, SPI is opencores
+ * Tomasz Wlostowski, Alessandro Rubini, 2011, for CERN.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <string.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <time.h>
+#include <sys/time.h>
+#include <sys/mman.h>
+
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(a) (sizeof(a)/sizeof(a[0]))
+#endif
+
+#define WRS3_SPI_BASE 0x10000000 /* FIXME */
+
+static void ud(int usecs) /* horrible udelay thing without scheduling */
+{
+	struct timeval tv1, tv2;
+	gettimeofday(&tv1, NULL);
+	do
+		gettimeofday(&tv2, NULL);
+	while ((tv2.tv_sec - tv1.tv_sec) * 1000*1000
+	       + tv2.tv_usec - tv1.tv_usec < usecs);
+}
+
+/*
+ * SPI stuff, used by later code
+ */
+
+#define SPI_REG_RX0	0
+#define SPI_REG_TX0	0
+#define SPI_REG_RX1	4
+#define SPI_REG_TX1	4
+#define SPI_REG_RX2	8
+#define SPI_REG_TX2	8
+#define SPI_REG_RX3	12
+#define SPI_REG_TX3	12
+
+#define SPI_REG_CTRL	16
+#define SPI_REG_DIVIDER	20
+#define SPI_REG_SS	24
+
+#define SPI_CTRL_ASS		(1<<13)
+#define SPI_CTRL_IE		(1<<12)
+#define SPI_CTRL_LSB		(1<<11)
+#define SPI_CTRL_TXNEG		(1<<10)
+#define SPI_CTRL_RXNEG		(1<<9)
+#define SPI_CTRL_GO_BSY		(1<<8)
+#define SPI_CTRL_CHAR_LEN(x)	((x) & 0x7f)
+
+static int oc_spi_base;
+
+static inline void ocspi_write(int addr, uint32_t val)
+{
+	if (!oc_spi_base)
+		return;
+	*(uint32_t *)(oc_spi_base + addr) = val;
+	printf("%08x := %08x\n", oc_spi_base + addr, val);
+}
+
+static inline uint32_t ocspi_read(int addr)
+{
+	uint32_t val;
+	if (!oc_spi_base)
+		return -1;
+	val =*(uint32_t *)(oc_spi_base + addr);
+	printf("%08x  = %08x\n", oc_spi_base + addr, val);
+	return val;
+}
+
+int oc_spi_init(char *prgname, uint32_t base_addr)
+{
+	int pagesize = getpagesize(); /* can't fail */
+	int fdmem;
+	void *addr;
+
+	/* /dev/mem for mmap of both gpio and spi1 */
+	if ((fdmem = open("/dev/mem", O_RDWR | O_SYNC)) < 0) {
+		fprintf(stderr, "%s: /dev/mem: %s\n",
+			prgname, strerror(errno));
+		return -1;
+	}
+
+	/* map a whole page (4kB, but we called getpagesize to know it) */
+	addr = mmap(0, pagesize, PROT_READ | PROT_WRITE,
+		       MAP_SHARED, fdmem,
+		       base_addr & (~(pagesize-1)));
+	if (addr == MAP_FAILED) {
+		fprintf(stderr, "%s: mmap(/dev/mem): %s\n",
+			prgname, strerror(errno));
+		return -1;
+	}
+	close(fdmem);
+	oc_spi_base = (int)addr + (base_addr & (pagesize-1));
+	ocspi_write(SPI_REG_DIVIDER, 1000);
+	return 0;
+}
+
+int oc_spi_txrx(int ss, int nbits, uint32_t in, uint32_t *out)
+{
+	uint32_t rval;
+
+	if (!out)
+		out = &rval;
+
+	ocspi_write( SPI_REG_CTRL,
+		     SPI_CTRL_ASS | SPI_CTRL_CHAR_LEN(nbits)
+		     | SPI_CTRL_TXNEG);
+	ocspi_write( SPI_REG_TX0, in);
+	ocspi_write( SPI_REG_SS, (1 << ss));
+	ocspi_write( SPI_REG_CTRL,
+		     SPI_CTRL_ASS | SPI_CTRL_CHAR_LEN(nbits)
+		     | SPI_CTRL_TXNEG | SPI_CTRL_GO_BSY);
+
+	while(ocspi_read(SPI_REG_CTRL) & SPI_CTRL_GO_BSY)
+		;
+
+	*out = ocspi_read(SPI_REG_RX0);
+	return 0;
+}
+
+#define CS_PLL	0 /* AD9516 on SPI CS0 */
+
+/*
+ * AD9516 stuff, using SPI, used by later code.
+ * "reg" is 12 bits, "val" is 8 bits, but both are better used as int
+ */
+
+static void ad9516_write_reg(int reg, int val)
+{
+	oc_spi_txrx(CS_PLL, 24, (reg << 8) | val, NULL);
+}
+
+static int ad9516_read_reg(int reg)
+{
+	uint32_t rval;
+	oc_spi_txrx(CS_PLL, 24, (reg << 8) | (1 << 23), &rval);
+	return rval & 0xff;
+}
+
+/* FIXME: table of registers .... */
+struct adregval {
+	int reg;
+	int val;
+};
+
+static struct adregval ad9516_regs[0];
+
+
+static int ad9516_init(FILE *fout)
+{
+	int i;
+
+	if (fout)
+		fprintf(fout, "Initializing AD9516 PLL...\n");
+
+	ad9516_write_reg(0x000, 0x99);
+	ad9516_write_reg(0x232, 0x01);
+
+	if (ad9516_read_reg(0x3) != 0xc3) {
+		fprintf(stderr,"Error: AD9516 PLL not responding.\n");
+		return -1;
+	}
+
+	for (i=0; i < ARRAY_SIZE(ad9516_regs); i++)
+		ad9516_write_reg (ad9516_regs[i].reg, ad9516_regs[i].val);
+
+	while ((ad9516_read_reg(0x1f) & 1) == 0)
+		ud(100);
+
+	// sync channels
+	ad9516_write_reg(0x230, 1);
+	ad9516_write_reg(0x232, 1);
+	ad9516_write_reg(0x230, 0);
+	ad9516_write_reg(0x232, 1);
+
+	if (fout)
+		fprintf(fout, "AD9516 locked.\n");
+
+	return 0;
+}
+
+/*
+ * That's it. Here's our main function
+ */
+
+int main(int argc, char **argv)
+{
+	if (oc_spi_init(argv[0], WRS3_SPI_BASE) < 0)
+		exit(1);
+
+	if (ad9516_init(stdout) < 0)
+		exit(1);
+
+	/* Wow! Nothing to do! */
+	exit(0);
+}

tools/wmapper.c

+/*
+ * wmapper.c -- simple file that mmap()s a file region and writes to it
+ * Alessandro Rubini 1997-2008
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <errno.h>
+
+int main(int argc, char **argv)
+{
+    char *fname;
+    FILE *f;
+    int pagesize = getpagesize();
+    unsigned int pos, pos_pg, pos_off;
+    unsigned int len, len_pg, len_off;
+    void *address;
+    char *rest;
+
+    if (argc !=4
+       || sscanf(argv[2],"%i", &pos) != 1
+       || sscanf(argv[3],"%i", &len) != 1) {
+        fprintf(stderr, "%s: Usage \"%s <file> <offset> <len>\"\n", argv[0],
+                argv[0]);
+        exit(1);
+    }
+    /* note: pos may be more than 2G, so use strtoul */
+    pos = strtoul(argv[2], &rest, 0);
+    if (rest && *rest) {
+        fprintf(stderr, "%s: Usage \"%s <file> <offset> <len>\"\n", argv[0],
+                argv[0]);
+        exit(1);
+    }
+
+    fname=argv[1];
+    if (!(f=fopen(fname,"r+"))) {
+        fprintf(stderr, "%s: %s: %s\n", argv[0], fname, strerror(errno));
+        exit(1);
+    }
+
+    /* page-align our numbers, as we depend on the MMU */
+    pos_pg  = pos & ~(pagesize-1);
+    pos_off = pos &  (pagesize-1);
+    len_pg  = (len + pos_off + pagesize-1) & ~(pagesize-1);
+    len_off = (len + pos_off) &  (pagesize-1);
+
+    address=mmap(0, len_pg, PROT_READ | PROT_WRITE,
+		 MAP_FILE | MAP_SHARED, fileno(f), pos_pg);
+
+    if (address == (void *)-1) {
+        fprintf(stderr,"%s: mmap(): %s\n",argv[0],strerror(errno));
+        exit(1);
+    }
+    fclose(f);
+    fprintf(stderr, "mapped \"%s\" from %i to %i (0x%x to 0x%x) \n",
+            fname, pos, pos+len, pos_pg, pos_pg+len_pg);
+
+    if (fread(address + pos_off, 1, len, stdin) != len) {
+	fprintf(stderr, "%s: short read\n", argv[0]);
+	exit(1);
+    }
+    return 0;
+}
+