I am working with an embedded board which supports u-boot.
I am trying to write and read the emmc device connected to the board,
After read, i need to have a look at the contents and compare it with the data that I have written to it.
Is there a way I can log the output of the a u-boot command, when I read a block from eMMC and store it in an address and try to view the contents of
it using:
mmc read 0x10700000 133120 1
mm.l 0x10700000
into a file and then can store the file in an emmc partition or a tftp server ?
Thank you for your time,
Nishad
The save command can be used to write memory to a file.
save file to a filesystem
save <interface> <dev[:part]> <addr> <filename> bytes [pos]
- Save binary file 'filename' to partition 'part' on device
type 'interface' instance 'dev' from addr 'addr' in memory.
'bytes' gives the size to save in bytes and is mandatory.
'pos' gives the file byte position to start writing to.
If 'pos' is 0 or omitted, the file is written from the start.
Of cause this requires the file system to be writable. For FAT this implies building with CONFIG_FAT_WRITE=y.
Related
I know we can use NFS, but I just don't want to use it.
(don't want to keep network connection to NFS server all the time).
I know we can use tftp in u-boot to load kernel and device-tree!
But can we use tftp in u-boot to download root-filesystem, put it in the right partition of SD card, and boot?
If yes, how to do it? (I googled, but found no answers)
Thanks,
Jerry
I use TFTP in uboot to flash my rootfs (for debug purposes) on my internal eMMC. It's nearly the same case as you.
First download in you RAM the filesystem:
tftpboot ${rootfs_addr} ${tftppath}/${rootfs_file}
rootfs_addr will be the RAM address, I use 0x10800000.
tftppath is the TFTP path (depends on your configuration)
rootfs_file is the ext4 or ext3 file
Then update the mmc device (you can run mmc listto show SD u-boot number)
mmc dev 2
Here I set the device to the number 2, you need to set it corresponding to the mmc list command.
Then write the content of the RAM to the SD:
setexpr rootfsblksz ${filesize} / 200
setexpr rootfsblksz ${rootfsblksz} + 1
mmc write ${rootfs_addr} 6000 ${rootfsblksz}
Description:
I create a rootfsblksz variable, it converts the number of bytes downloaded to a number of blocks. filesizeis set automatically when we use TFTP, it represents the size of the last downloaded file (in Bytes).
Here my block is 512Bytes (0x200)
I add +1 to the blocksize (to be shure to have all the data)
I write it on the eMMC (or SD) at the address 0x6000 (in blocks) -> 24 576 blocks -> 12 582 912 (in Bytes) -> 12MB because my ext partition is at 12MB offset
Hope it helps!
I test whether a file is empty in Shell.
test -s /sys/fs/cgroup/systemd/docker/d4e311735706485e748513bad611070e223cba76fdf4c72a1102d14b653da750/tasks
It returns false, and I found its size is 0 when I use ls -lh, but when I use cat, I can get 4071 in this file, this means the file is not empty. I think maybe this file is too small, I create a file in my home directory, and echo 4071 to it, I find its size is not 0. Is the file in /sys/fs/cgroup special?
The file that you are dealing with is a special file which is a part of the cgroup file system.
To understand why this happens, let's see what happens when you do test -e $filename.
We will be using strace command which prints the system calls a command does.
If you do strace test -e $filename, you will find this line in the results:
stat("$filename", {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
In this case it returns st_size = 0 which is the size of the file.
But the questions is what actually happens on the other side, inside the kernel:
When you try to deal with a file, you do a system call which goes to an intermediate layer in the kernel called the virtual file system which in turn calls the part responsible for the information needed. A stat system call will try to get the status out of the inode corresponding with file. The file system can create and manipulate the inode as it wants.
Cgroup is a special file system, when it adds a file (using the cgroup_add_file function defined in kernel/cgroup.c) it always passes size 0 to __kernfs_create_file so that is why any file inside /sys/fs/cgroups (created by cgroup fs) will always has a zero size regardless of the actual contents of the file.
For the other part, when cat the file. If you do strace cat $filename, that is what you will get:
open("$filename", O_RDONLY) = 3
read(3, "...", 131072) = ###
The read system call will go through the virtual file system to the kernel file system and using the file operations associated with the file, it will get you the needed data.
Cgroup fs has functions to generate the data in its files. This is how tasks file is defined in kernel/cgroup.c
{
.name = "tasks",
.seq_start = cgroup_pidlist_start,
.seq_next = cgroup_pidlist_next,
.seq_stop = cgroup_pidlist_stop,
.seq_show = cgroup_pidlist_show,
.private = CGROUP_FILE_TASKS,
.write = cgroup_tasks_write,
},
So seq_start, seq_next, seq_stop and seq_show are the functions responsible for generating the information needed for the file. You can easily go to kernel/cgroups.c and check for what they do.
Please note that if you are trying to know if the cgroup still has tasks, an easier way is to use notify on release.
from Documentation/cgroup-v1/cgroups.txt
If the notify_on_release flag is enabled (1) in a cgroup, then whenever the last task in the cgroup leaves (exits or attaches to some other cgroup) and the last child cgroup of that cgroup is removed, then the kernel runs the command specified by the contents of the "release_agent" file in that hierarchy's root directory, supplying the pathname (relative to the mount point of the cgroup file system) of the abandoned cgroup. This enables automatic removal of abandoned cgroups. The default value of notify_on_release in the root cgroup at system boot is disabled (0). The default value of other cgroups at creation is the current value of their parents' notify_on_release settings. The default value of a cgroup hierarchy's release_agent path is empty.
DD is a tool for linux which can Write partial data from MBR.bin to a sector in USB (instead of writing a whole sector). Now I need to do such thing in windows. There is a DD for windows, but it seems it will write a whole sector!
I need to write first 440 bytes of a mbr file to a usb stick. the code in linux is:
dd if=mbr.bin of=/dev/sd<X> bs=440 count=1
and in windows it will be:
dd bs=440 count=1 if=mbr.bin of=\\.\<x>:
where x is the volume letter. But in windows it will cause USB to be corrupted and usb need to be formatted. It seems it writes the whole data. How can I solve this problem?
Copy a complete block!
e.g. for a 512 byte blocksize (512-440=72)
copy mbr.bin mbr.full
dd bs=1 if=\\.\<x>: skip=440 seek=440 of=mbr.full count=72
dd bs=512 if=mbr.full of=\\.\<x>: count=1
Are you sure you pass the parameters correctly? Maybe the win version expects it to be /bs=440. Just a guess. Can't you anyway just truncate the file to 440 bytes?
I am trying to understand why lseek() is used in this image creator. Why 5 bytes away from start of file? If I changed that number, the OS won't boot.
The image creator creates a .img file with the bootloader.bin inside.
/* modify the sector count */
total_sector_number = file_size / 512
lseek(disk_image_fd, 5, SEEK_SET);
write(disk_image_fd, &total_sector_number, 2);
write(disk_image_fd, &kernel_32_sector_number, 2);
//printf("%d\n", lawl);
printf("TOTAL_SECTOR_NUMBER : %d\n", total_sector_number);
printf("KERNEL_32_SECTOR_NUMBER : %d\n", kernel_32_sector_number);
The source code (image maker):
http://pastebin.com/raw.php?i=MuDpYP3Y
Bootloader:
http://pastebin.com/raw.php?i=kzw2ZaU1
The hexdump with lseek() and writing umber of sectors to byte at offset 5:
Without lseek() OS does not boot correctly.
I only figured this out because of your previous post Bootloader memory location which contained different source code for the bootloader.
You mentioned the two unknown variables TOTALSECTORCOUNT and KERNEL32SECTORCOUNT. These variables were near the beginning of the file, and I guess when assembled they sit 5 bytes into the binary. Calling lseek with the SEEK_SET parameter moves the file pointer to 5 bytes after the beginning of the file. It then writes the two values which will overwrite the ones in the bootloader code.
When you remove the lseek it will instead append the two values to the end of the file. If you changed the offset parameter of lseek to zero it would overwrite the jmp command of the bootloader instead.
Notice in your hexdump.
00000000 00eb b8fa 02c0 0000 c000 e08e e88e 00b8
^ ^- kernel_32_sector_number is never initialized.
|-total_sector_number which was calculated in code before the write.
I'm attempting to create a fs within a file.
under linux it's very simple:
create a blank file size 8 gb
dd of=fsFile bs=1 count=0 seek=8G
"format" the drive:
mkfs.ext2 fsFile
works great.
however under cygwin running from /usr/sbin ./mkfs.ext2
has all kinds of weird errors (i assume because of some abstraction)
But with cygwin i get:
mkfs.ext2: Device size reported to be zero. Invalid partition specified, or
partition table wasn't reread after running fdisk, due to
a modified partition being busy and in use. You may need to reboot
to re-read your partition table.
or even worse (if i try to access a file through /cygdrive/...
mkfs.ext2: Bad file descriptor while trying to determine filesystem size
:(
please help,
Thanks
Well it seems that the way to solve it is to not use any path on the file you wish to modify.
doing that seems to have solved it.
also it seems that my 8 gig file does have a file size that's simply to big, it seems like it resets the size var i.e.
$ /usr/sbin/fsck.ext2 -f testFile8GiG
e2fsck 1.41.12 (17-May-2010)
The filesystem size (according to the superblock) is 2097152 blocks
The physical size of the device is 0 blocks
Either the superblock or the partition table is likely to be corrupt!
Abort? no
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
testFile8GiG: 122/524288 files (61.5% non-contiguous), 253313/2097152 blocks
Thanks anyway