[U-Boot-Users] Overwriting protected flash memory!!!

[Cliff Brake <cliff.brake@gmail.com>]

On Thu, 09 Dec 2004 20:22:10 +0100, Wolfgang Denk <wd@denx.de> wrote:

> No. Not even that. For most boards, the "protect" feature  in  U-Boot
> is  only  a  flag that prevents certain commands from working on such
> "protected" flash areas. Only very few flash chips,  and  even  fewer
> boards  using  these  chips,  actually  use  some  kind  of  hardware
> protection.In most cases,  just  using  a  couple  of  "mm"  or  "mw"
> commands  to  enter the erase or program seqence is all what's needed
> to erase / corrupt "protected" sectors.
> 
> The  "protect"  stuff  is  something  that  is  intended  to  prevent
> accidential data loss by a istyped command etc. It cannot protect you
> from doing stupid things.

Thanks for the information -- I had assumed the protect command set
the lock bits (for Intel flash).  Setting the CFG_FLASH_PROTECTION
option may cause the lock bits to be set in the flash (did not trace
through the code fully).  But it is still very possible to corrupt
flash as writes to a range of address will clear the lock bit (as
Wolfgang pointed out).

-- 
=======================
Cliff Brake
http://bec-systems.com