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Help: U-boot

Environment

If you get Too many args error while trying to set an environment variable, try to do that from within Linux using fw_setenv instead of setenv in U-boot.

U-boot console:

hisilicon # setenv uk 'mw.b 0x82000000 ff 1000000; tftp 0x82000000 uImage.${soc}; sf probe 0; sf erase 0x50000 0x200000; sf write 0x82000000 0x50000 ${filesize}'
** Too many args (max. 16) **

OpenIPC Linux:

root@openipc-hi3518ev100:~# fw_setenv uk 'mw.b 0x82000000 ff 1000000; tftp 0x82000000 uImage.${soc}; sf probe 0; sf erase 0x50000 0x200000; sf write 0x82000000 0x50000 ${filesize}'
root@openipc-hi3518ev100:~#

Saving original firmware without using tftp.

In the terminal program you use connect to UART port with, enable saving a log file of the session. I like to use screen for that, and my command to connect to the UART adapter with logging of the active session into a file would look like this:

$ screen -L -Logfile fulldump.log /dev/ttyUSB0 115200

After connecting to the bootloader console, run a set of commands for reading whole amount of data from flash memory chip into RAM, and then dumping it as hexadecimal values into terminal window.

Use hexadecimal notation for addresses, where 0 is 0x0, 8 MB is 0x800000, and 16 MB is 0x1000000.

For reading whole 8 MB flash memory run

mw.b 0x82000000 ff 0x800000
sf probe 0
sf read 0x82000000 0x0 0x800000
md.b 0x82000000 0x800000

and for 16 MB flash memory run

mw.b 0x82000000 ff 0x1000000
sf probe 0
sf read 0x82000000 0x0 0x1000000
md.b 0x82000000 0x1000000

Since the process of reading is going to take a considerable amount of time (literally hours), you might want to disconnect from the terminal session to avoid accidental keystrokes contaminating the output. Press Ctrl-a followed by d to detach the session from active terminal. Run screen -r when you need to reconnect it later, after the size of the log file will stop growing. Reading of an 8 MB flash memory should result in a ~40 MB log file, and for a 16 MB chip the file should be twice that size.

Convert the hex dump into a binary firmware file and use it for further research or restoring camera to its pristine state.

cat fulldump.log | sed -E "s/^[0-9a-f]{8}\b: //i" | sed -E "s/ {4}.{16}\r?$//" > fulldump.hex
xxd -revert -plain fulldump.hex fulldump.bin

Use binwalk to unpack the binary file.

Saving firmware via SD card.

Sometimes your camera only has a wireless connection, which does not work directly from the bootloader. Very often such cameras have a microSD card slot. In this case you can try to save a copy of the original firmware using an SD card as an intermediary medium.

Since you’re going to save firmware in its binary form, the amount of data will be either 8 MB or 16 MB, depending on the size of camera’s flash memory chip. So any SD card will do, even the smallest one.

Insert the card into the card slot on the camera, connect the serial adapter to the UART port, supply power to the camera and stop the boot process to get into the bootloader console.

Initialize access to the card, and clear some space to save firmware on. Data is written onto card in blocks of 512 bytes. You need to erase 16384 blocks to clear 8 MB, 32768 blocks for 16 MB, which are 0x4000 and 0x8000 hexadecimal, respectively.

Note that we are going to write directly to the card registers, bypassing the partition table. To avoid conflicts when accessing card data later from your PC, offset 8 kilobytes from the beginning of the card (8 * 1024 = 8192 bytes or 16 blocks of 512 bytes, or 0x10 blocks in hexadecimal representation).

mmc dev 0
mmc erase 0x10 0x8000

Now you need to copy the contents of the firmware from the flash memory chip to the RAM of the camera. To do that, clear a section of RAM (0x800000 bytes for a 8MB chip or 0x1000000 bytes for a 16MB chip), read the flash memory and copy the entire contents to the prepared space in RAM. Then export the copied data from RAM to the card.

NB! In the example below we use the starting address 0x2000000, but it varies for different cameras. Please consult SoC data sheet, or seek help on our Telegram channel.

mw.b 0x2000000 ff 0x1000000
sf probe 0
sf read 0x2000000 0x0 0x1000000
mmc write 0x2000000 0x10 0x8000

Remove the card from the camera and insert it into a computer running Linux. Use dd command to copy data from the card to a binary file on the computer.

dd bs=512 skip=16 count=32768 if=/dev/sdc of=./fulldump.bin

Uploading binary image via serial connection.

There are cameras that only have wireless connection unavailable directly from bootloader. Most of such cameras also have SD card slot but some don’t, or it does not work for some reason, or you don’t have a card, or something. Anyway, you still can upload a binary image onto camera and either run it, or save it into the flash memory. Here’s how.

First of all, you’ll need to install lrzsz package on your desktop computer. I presume it runs Linux and preferrably of a Debian family, that’ll be easier on examples. So, run this command to satisfy prerequisites:

apt install lrzsz

Now you are ready.

Place the binary file you are going to upload into the same directory where you will be starting a screen session to your camera from. Start the session and boot into the bootloader console interrupting booting routine with a key combo.

Now you can run help and check what data transfer protocols are supported by your version of bootloader. If you see loady in the list of commands, then you can use ymodem protocol. Run loady on you camera, then press Ctrl-a followed by : (semi-colon). It will switch you into command line at the very bottom of the screen. Enter exec !! sz --ymodem filename.bin where filename.bin and see your file uploading via serial connection. At 115200 bps. Slow, very slow.

After the file is uploaded, you can do the usual magic. Either boot from the memory image right away using bootm, or write it into the flash memory.

Reading binary image from SD card.

If your camera supports SD card and you have fatload command in bootloader, then you can read firmware binary files from an SD card.

First, prepage the card: format it into FAT filesystem and place bootloader, kernel, and rootsf binary files there. Insert the card into camera and boot into bootloader console.

Check that you have access to the card.

mmc rescan

Then unlock access to flash memory and start writing content of the files from the card into the flash memory.

NB! Please note that load address and names of files used in this example not necessarily match those for your particular camera. Consult documentation, or seek help on our Telegram channel.

sf probe 0

mw.b 0x80600000 ff 1000000
sf erase 0x0 0x50000
fatload mmc 0:1 0x80600000 u-boot-with-spl.bin
sf write 0x80600000 0x0 ${filesize}

mw.b 0x80600000 ff 1000000
sf erase 0x50000 0x200000
fatload mmc 0:1 0x80600000 uimage.t31
sf write 0x80600000 0x50000 ${filesize}

mw.b 0x80600000 ff 1000000
sf erase 0x250000 0x500000
fatload mmc 0:1 0x80600000 rootfs.squashfs.t31
sf write 0x80600000 0x250000 ${filesize}

Bypassing password-protected bootloader.

Changing the bootloader is a risky operation. There’s a high probability of turning your camera into a paperweight if something goes wrong. So before you flash a new bootloader you have to weigh up all the risks and benefits. In most cases the original bootloader plus new kernel and new operating system should work just fine. But there are exceptions.

Downgrading stock firmware.

Today, we see more and more cameras where access to bootloader console is protected with a password. Thus, even if you connect to the camera’s UART port, all you will see after interrupting the standard boot cycle is a prompt for password. In that case, a relatively safe solution is to downgrade the firmware to a version where the password protection was not yet implemented. For example, for Xiongmai cameras the bootloader password protection started popping up somewhere around July 2021, hence you need a firmware for your camera from an earlier date. After you successfully downgrade your camera to a password-free bootloader, you could install the OpenIPC firmware in a regular way.

Side-loading unlocked bootloader.

Modern cameras utilize fastboot protocol that allows camera to sideload a bootloader into memory and then run it from there. Check if burn utility supports your SoC.

Modifying stock firmware.

One way to bypass the bootloader protection is to dump original firmware and replace bootloader there with an unlocked alternative. Or you could flash the entire OpenIPC firmware since you have the chip in the programmer, anyway.

DO NOT FORGET TO MAKE A BACKUP OF YOUR ORIGINAL FIRMWARE!