How to convert the dumped firmware (from linksys-wrt54gl via JTAG port) in an understandable format

Question

Issuing some commands for the dumped firmware:

$ du -h fw.bin
4.0 M

$ file fw.bin
fw.bin: data

$ file -i fw.bin
fw.bin: application/octet-stream; charset=binary

$ binwalk fw.bin
-

$ enca -L none fw.bin
-

The way that I have dumped the firmware is by using the JTAG port:

And the pins on the linksys router are set according to the figure described in the datasheet (www.cse.buffalo.edu/~bina/amrita/cse524/wrt54gl.pdf):

And the corresponding pins from the BusPirate v3.6 is put on based on the reference (dangerousprototypes.com/docs/Bus_Pirate_I/O_Pin_Descriptions):

The OpenOCD command has been issued such as:

sudo openocd -f interface/buspirate.cfg -f board/linksys-wrt54gl.cfg -c "init"

The configurations for BusPirate interace/buspirate.cfg:

interface buspirate
buspirate_port /dev/ttyUSB0
buspirate_speed normal
reset_config srst_only

and the board/linksys-wrt54gl.cfg:

# Linksys WRT54GL v1.1
#
source [find target/bcm5352e.cfg]
set partition_list {
    CFE         { Bootloader                    0x1c000000 0x00040000 }
    firmware    { "Kernel+rootfs"               0x1c040000 0x003b0000 }
    nvram       { "Config space"                0x1c3f0000 0x00010000 }
}

# External 4MB NOR Flash (Intel TE28F320C3BD90 or similar)
set _FLASHNAME $_CHIPNAME.flash
flash bank $_FLASHNAME cfi 0x1c000000 0x00400000 2 2 $_TARGETNAME

and the source, target/bcm5352e.cfg , it refers to:

set _CHIPNAME bcm5352e
set _CPUID 0x0535217f

jtag newtap $_CHIPNAME cpu -irlen 8 -ircapture 0x1 -irmask 0x1f -expected-id $_CPUID

set _TARGETNAME $_CHIPNAME.cpu
target create $_TARGETNAME mips_m4k -endian little -chain-position $_TARGETNAME

gdb_memory_map disable
$_TARGETNAME configure -event gdb-attach {
   reset
   halt
}

I open a new terminal and telnet into the socket openocd has opened for communication and I dump the firmware as follows:

dump_image fw.bin 0x1c000000 0x00400000

The values are adapted from the linksys-wrt54gl.cfg file shown previously.

Any Ideas what might be wrong using/connecting the JTAG and dumping the firmware?

Info about the current Linksys-Wrt54gl:

Model: WRT54GL-EU

Firmware Version: v4.30.7, Jun.20, 2006

A copy of the "dumped" firmware can be obtained here: https://www.dropbox.com/s/kl02cnc5qqddx1x/fw.bin?dl=0

Answer 1

The firmware itself most likely is not a binary. Also usually when you run file it will tell you something like:
file busybox busybox: ELF 32-bit MSB executable, MIPS, MIPS32 version 1. My guess is that you haven't actually extracted any binaries yet. My advice would be to use something like binwalk to extract specific files and binaries from the firmware. Running objdump on an entire firmware will probably give you an object dump of every single binary in your firmware and that could be a lot.