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

[Carl-Daniel Hailfinger]

Am 30.06.2011 21:34 schrieb Stefan Tauner:
> On Thu, 30 Jun 2011 20:38:33 +0200
> Carl-Daniel Hailfinger  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
> >
> > 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