Hacking the Netgear wgt634u

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Abstract: This paper gives you some hints about how to compile click ( http://pdos.csail.mit.edu/click/ ) and madwifi.stripped driver (http://pdos.csail.mit.edu/~jbicket/madwifi.stripped/) using openwrt ( http://openwrt.org ) for the Netgear wgt634u router. General information about the router you can find at http://pdos.csail.mit.edu/roofnet/doku.php?id=wgt634u.

Credits: http://pdos.csail.mit.edu/roofnet/

OpenWRT setup

First of all you need to install the openwrt toolchain ( [1] ) on your build computer. 

 cvs -d:pserver:anonymous@openwrt.org:/openwrt login
 cvs -d:pserver:anonymous@openwrt.org:/openwrt co buildroot

The following tools/libs are required:

  • wget, tftp
  • cvs, subversion
  • gcc, gcc-c++, bison, flex
  • patch, gettext
  • autoconf, automake
  • zlib-devel

OpenWRT-Build-Prozess

Für die spätere Verwendung von Click wird ein C++-Compiler benötigt. Daher ist die folgende Änderung im $OPENWRT/buildroot/Makefile vorzunehmen: 

 INSTALL_LIBSTDCPP:=true

Sollten alle benötigten Bibliotheken vorliegen, so kann OpenWRT mit Hilfe von make gebaut werden: 

 linux:/home/wrt/buildroot/# make

Compiling click

To build click you have to copy the following Makefile (click.mk) to the $OPENWRT/buildroot/make directory: 

 #############################################################
 #
 # click
 #
 #############################################################
 CLICK_DIR:=$(BUILD_DIR)/click
 
 click-source: $(CLICK_DIR)/.unpacked
 
 
 $(CLICK_DIR)/.unpacked: $(DL_DIR)/$(CLICK_SOURCE)
       (cd $(BUILD_DIR); \
       svn co svn://merkur.sardmn.informatik.hu-berlin.de/click)
       touch $(CLICK_DIR)/.unpacked
 
 
 $(CLICK_DIR)/.configured: $(CLICK_DIR)/.unpacked
       (cd $(CLICK_DIR); rm -rf config.cache; \
               $(TARGET_CONFIGURE_OPTS) \
               CFLAGS="$(TARGET_CFLAGS)" \
               AR_CREATEFLAGS="cru" \
               CLFLAGS=-static \
               CXXFLAGS=-static \
               ./configure \
               --build=i686-pc-linux-gnu \
               --host=mipsel-linux \
               --disable-linuxmodule \
               --enable-brn \
               --disable-ip \
               --enable-wifi \
               --disable-ip \
               --enable-tools=mixed \
       );
       touch  $(CLICK_DIR)/.configured
 
 $(CLICK_DIR)/click: $(CLICK_DIR)/.configured
       $(MAKE) CC=$(TARGET_CC) -C $(CLICK_DIR)
 
 $(TARGET_DIR)/usr/bin/click: $(CLICK_DIR)/click
       install -c $(CLICK_DIR)/userlevel/click $(TARGET_DIR)/usr/bin/click
       $(STRIP) $(TARGET_DIR)/usr/bin/click > /dev/null 2>&1
 
 click: uclibc $(TARGET_DIR)/usr/bin/click 
 
 click-clean: 
       $(MAKE) -C $(CLICK_DIR) clean
       rm -rf $(TARGET_DIR)/usr/bin/click
 
 click-dirclean: 
       rm -rf $(CLICK_DIR)

That's all: run make click to build click. Currently, I only tested the userlevel click binary.

Compiling Madwifi.stripped

The madwifi.stripped driver lets Click directly read and write raw frames from the wireless card, and strips out the usual driver logic. To build the madwifi.stripped driver you have to copy the following Makefile (madwifi.mk) to the $OPENWRT/buildroot/make directory: 

 #############################################################
 #
 # madwifi.stripped
 #
 #############################################################
 MADWIFI_DIR:=$(BUILD_DIR)/madwifi
 
 
 $(DL_DIR)/$(MADWIFI_SOURCE):
       $(WGET) -P $(DL_DIR) $(MADWIFI_SITE)/$(MADWIFI_SOURCE)
 
 madwifi-source: $(DL_DIR)/$(MADWIFI_SOURCE)
 
 $(MADWIFI_DIR)/.unpacked: $(DL_DIR)/$(MADWIFI_SOURCE)
       (cd $(BUILD_DIR); \
       cvs -d :pserver:anoncvs@cvs.pdos.lcs.mit.edu:/cvs login)
       (cd $(BUILD_DIR); \
       cvs -z5 -d :pserver:anoncvs@cvs.pdos.lcs.mit.edu:/cvs co -d madwifi roofnet/release/stripped)
       touch $(MADWIFI_DIR)/.unpacked
 
 $(MADWIFI_DIR)/madwifi: $(MADWIFI_DIR)/.unpacked
       $(MAKE) CC=$(TARGET_CC) TARGET=mips-le-elf KERNELPATH=$(BUILD_DIR)/WRT54GS/release/src/linux/linux/ -C $(MADWIFI_DIR)
 
 $(TARGET_DIR)/usr/bin/madwifi: $(MADWIFI_DIR)/madwifi
       mkdir $(TARGET_DIR)/usr/bin/madwifi/
       cp $(MADWIFI_DIR)/madwifi/driver/ath_pci.o $(TARGET_DIR)/usr/bin/madwifi/
       cp $(MADWIFI_DIR)/madwifi/ath_hal/ath_hal.o $(TARGET_DIR)/usr/bin/madwifi/
       $(STRIP) $(TARGET_DIR)/usr/bin/madwifi/ath_pci.o > /dev/null 2>&1
       $(STRIP) $(TARGET_DIR)/usr/bin/madwifi/ath_hal.o > /dev/null 2>&1
 
 madwifi: uclibc $(TARGET_DIR)/usr/bin/madwifi/
 
 madwifi-clean: 
       $(MAKE) -C $(MADWIFI_DIR) clean
       rm -rf $(TARGET_DIR)/usr/bin/madwifi/
 
 madwifi-dirclean: 
       rm -rf $(MADWIFI_DIR)

That's all: run make madwifi to build the driver.

Compiling New Kernel

First, the stock kernel doesn’t link with gcc 3.3.3, so you’ll need to patch linux-2.4.x/arch/mips/brcm-boards/bcm947xx/cfe_flash_nvram.c. 

 @@ -927,6 +927,12 @@
       struct page *page, *end;
       unsigned int i;
 
 +       /* Register char device */
 +       if ((nvram_major = devfs_register_chrdev(252, "nvram", &nvram_fops)) < 0) {
 +               ret = nvram_major;
 +               return ret;
 +       }
 +
         /* Allocate and reserve memory to mmap() */
         while ((PAGE_SIZE << order) < NVRAM_SPACE)
                 order++;
 @@ -955,21 +961,11 @@
         /* Initialize hash table */
         nvram_rehash();
 
 -       /* Register char device */
 -       if ((nvram_major = devfs_register_chrdev(252, "nvram", &nvram_fops)) < 0) {
 -               ret = nvram_major;
 -               goto err;
 -       }
 -
         /* Create /dev/nvram handle */
         nvram_handle = devfs_register(NULL, "nvram", DEVFS_FL_NONE, nvram_major, 0,
                                       S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP, &nvram_fops, NULL);
         return 0;
 -
 - err:
 -       nvram_exit();
 -       return ret;
  }
 
  module_init(nvram_init);


Third, you’ll need to patch linux-2.4.x/Makefile. 

 27a28,29
 > MIPS_BASE     	= $(TOPDIR)/../../staging_dir/bin/
 > 
 29c31
 < LD		= $(CROSS_COMPILE)ld
 ---
 > LD		= $(MIPS_BASE)/$(CROSS_COMPILE)ld
 32,36c34,38
 < AR		= $(CROSS_COMPILE)ar
 < NM		= $(CROSS_COMPILE)nm
 < STRIP		= $(CROSS_COMPILE)strip
 < OBJCOPY		= $(CROSS_COMPILE)objcopy
 < OBJDUMP		= $(CROSS_COMPILE)objdump
 ---
 > AR		= $(MIPS_BASE)/$(CROSS_COMPILE)ar
 > NM		= $(MIPS_BASE)/$(CROSS_COMPILE)nm
 > STRIP		= $(MIPS_BASE)/$(CROSS_COMPILE)strip
 > OBJCOPY		= $(MIPS_BASE)/$(CROSS_COMPILE)objcopy
 > OBJDUMP		= $(MIPS_BASE)/$(CROSS_COMPILE)objdump


Fourth, you’ll need to patch linux-2.4.x/arch/mips/Makefile. 

 69c69
 < GCCFLAGS	+= -mcpu=r4600 -mips2 -Wa,--trap
 ---
 > GCCFLAGS	+= -mips2 -Wa,--trap
 72c72
 < GCCFLAGS	+= -mcpu=r4600 -mips2 -Wa,--trap
 ---
 > GCCFLAGS	+= -mips2 -Wa,--trap
 75c75
 < GCCFLAGS	+= -mcpu=r4600 -mips2 -Wa,--trap
 ---
 > GCCFLAGS	+= -mips2 -Wa,--trap
 78c78
 < GCCFLAGS	+= -mcpu=r4600 -mips2 -Wa,--trap
 ---
 > GCCFLAGS	+= -mips2 -Wa,--trap
 81c81
 < GCCFLAGS	+= -mcpu=r4600 -mips2 -Wa,--trap
 ---
 > GCCFLAGS	+= -mips2 -Wa,--trap

Fifth, you’ll need to patch linux-2.4.x/arch/mips/brcm-boards/bcm947xx/compressed/Makefile. 

 21d20
 < STRIP := $(CROSS_COMPILE)strip
 23c22,25
 < OBJCOPY		:= $(CROSS_COMPILE)objcopy -O binary -R .reginfo -R .note -R .comment -R .mdebug -S
 ---
 > MIPS_BASE	:= $(TOPDIR)/../../staging_dir/bin/
 > STRIP 		:= $(MIPS_BASE)/$(CROSS_COMPILE)strip
 > 
 > OBJCOPY		:= $(MIPS_BASE)/$(CROSS_COMPILE)objcopy -O binary -R .reginfo -R .note -R .comment -R .mdebug -S
 28c30
 < ASFLAGS		+= -G 0  -mno-abicalls -fno-pic -pipe -mcpu=r4600 -mips2 -Wa --trap -m4710a0kern
 ---
 > ASFLAGS		+= -G 0  -mno-abicalls -fno-pic -pipe -mips2


Last, if you’re planning to run userlevel click, edit the linux-2.4.x/.config file and change the CONFIG_ETHERTAP and CONFIG_TUN lines to y.

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