[U-Boot-Users] Protect Flash from tftpboot typos

Konstantin Kletschke lists at ku-gbr.de
Fri Jul 23 16:37:32 CEST 2004

Am 2004-07-23 15:46 +0200 schrieb Wolfgang Denk:

> i.  e.  if  you don't enable options like CFG_DIRECT_FLASH_TFTP which

I do not find CFG_DIRECT_FLASH_TFTP mentioned anywhere in our

Is it included by

#define CONFIG_COMMANDS         (CONFIG_CMD_DFL     \
                & ~CFG_CMD_LOADS    \
                & ~CFG_CMD_CONSOLE  \
                & ~CFG_CMD_AUTOSCRIPT   \
                | CFG_CMD_NET           \
                | CFG_CMD_PING          \
                | CFG_CMD_DHCP          \

Otherwise I don't know where else I could have this option enabled.

> "UNIX was not designed to stop you from doing stupid things,  because
> that would also stop you from doing clever things."       - Doug Gwyn

Yeah, thats right. I have to protect our customers to fry their boards, 
not me :)

> > I also do typos there and an 0x0 as 1st Argument destroys contents of
> > Flash though it is protected!
> Seems you have configured U-Boot like that. On systems for which I am
> responsible attempts to TFTP to flash will not do harm.

tftp to flash does no harm. It is the mapped Area which is not protected
by an default load adress when typos occur.

> This may be, but a TFTP download will write to increasing  addresses,
> while  the  programming sequence must be written to certain addresses
> which are (1) not contiguous and (2)  which  must  be  written  in  a
> special  sequence.  I  don't  think that TFTP (or a copy) to a memory
> region can accidentally trigger a flash programming sequence,  unless
> the  code  explicitely  attemts  to program the flash (like TFTP with
> CFG_DIRECT_FLASH_TFTP option aenabled, or the  "cp"  command  with  a
> target address in flash memory).

Reading this I agree to you unlocking, erasing is not possible on
increasing adresses. Otherwise IIRC I think the whole block can be
unlocked and erased on different access adresses inside the block!

Otherwise how is it possible typos fry the flash device?

I am using intel 28F128J3...

I think I will replace tftpboot an cp commands for customers by two
argument less firmware - linux kernel or rootfs - commands.


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