[flashrom] [PATCH 2/3] add check_block_erasers which returns the number of well-defined erasers for a chip

Carl-Daniel Hailfinger c-d.hailfinger.devel.2006 at gmx.net
Fri Jul 1 00:19:30 CEST 2011


Am 30.06.2011 21:34 schrieb Stefan Tauner:
> On Thu, 30 Jun 2011 20:38:33 +0200
> Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net> wrote:
>
>   
>> Am 30.06.2011 20:07 schrieb Carl-Daniel Hailfinger:
>>     
>>> Am 30.06.2011 19:54 schrieb Carl-Daniel Hailfinger:  
>>> With the changes outlined above:
>>> Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net>
>>>   
>>>       
>> Ahem. I should have quoted the part where a new bug appears, and should
>> have requested a fix for that.
>>
>>     
>>>>> @@ -1814,13 +1824,13 @@ int chip_safety_check(struct flashchip
>>>>> *flash, int force, int read_it, int write } if (erase_it ||
>>>>> write_it) { /* Write needs erase. */ - if (flash->tested &
>>>>> TEST_BAD_ERASE) { + if (flash->tested & TEST_BAD_ERASE && 
>>>>>           
>> As discussed on IRC, this should be ||.
>>
>>
>>     
>>>>> + !check_block_erasers(flash, 0)) { msg_cerr("Erase is not working
>>>>> on this chip. "); if (!force) 
>>>>>           
>> And once you switch to || above, you may get a segfault if no block
>> erasers exist. Zero usable erase functions is a non-recoverable
>> condition, it can not be overridden with --force.
>>
>> We do perform that check for more than zero usable erase functions
>> elsewhere already. Either move that check here (with a separate if
>> statement, and add a comment in the original place that checking has
>> moved), or leave it where it is and keep the code here as is.
>>     
> i dont understand what you are talking about. the erasers are allocated
> no matter if they "exist" or not in a fix-sized array. a segfault
> could only happen if we try to dereference a block eraser function and
> jump there which we don't do here. what access(es) should segfault
> exactly?
>
> i have tried my current, reworked patch with:
> "./flashrom -p dummy:bus=spi,emulate="M25P10.RES" -V -c "M25P10.RES"
> -E" after deleting the block erasers for that chip i.e. .block_erasers = {};
> i get the expected output of "Erase is not working on this chip.
> Aborting."
>   

Did you also try specifying --force as well? That should get further
along until it tries to actually write/erase. We have precautions there
against empty erasers, so the segfault would not happen unless you axe
the now redundant check for usable_erasefunctions!=0 in
erase_and_write_flash(). Mh. There are even more safety checks in that
code, so we might be fine. I need to recheck this.

Regards,
Carl-Daniel

-- 
http://www.hailfinger.org/





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