Re: smatch warnings in current upstream kernel

[Fengguang Wu <fengguang.wu@intel.com>]

On Tue, Sep 11, 2012 at 10:49:39PM +0800, Fengguang Wu wrote:
> On Tue, Sep 11, 2012 at 05:29:26PM +0300, Dan Carpenter wrote:
> > On Tue, Sep 11, 2012 at 07:06:40PM +0800, Fengguang Wu wrote:
> > > On Tue, Sep 11, 2012 at 01:51:27PM +0300, Dan Carpenter wrote:
> > >
> > > $SMATCH -p kernel "$@" > $SMATCH_OUT_ROOT/$PPID-$$-$RANDOM
> 
> FYI, the wrapper script is as simple as
> 
> SMATCH=/c/smatch/smatch
> $SMATCH -p kernel "$@" > $SMATCH_OUT_ROOT/$PPID-$$-$RANDOM
> 
> > Some of the warnings you are getting seem to mean that you're not
> > picking up the smatch_data/ directory.  For example some of the
> > buffer overflow errors:
> > 
> > drivers/mtd/ubi/wl.c:336 prot_queue_add() warn: buffer overflow 'ubi->pq' 10 <= 10
> > 
> > What is happening in that function is that Smatch sees the:
> > 	ubi_assert(pq_tail >= 0 && pq_tail < UBI_PROT_QUEUE_LEN);
> > 
> > and assumes that since there is a test for
> > "pq_tail < UBI_PROT_QUEUE_LEN" then it must be possible for
> > pq_tail = UBI_PROT_QUEUE_LEN.  There is a file called:
> > smatch_data/kernel.ignored_macros which has ubi_assert() and it
> > means to ignore everything that happens inside a ubi_assert().
> 
> Yes, I can see the data and function. Thank you very much for the tips!
> 
> > Normally Smatch looks for the data dir with the binary, but you can
> > also specify a directory with --data=/path/to/smatch_data/.  Then
> 
> The directory layout here is
> 
> /c/smatch/                      # git tree 
> /c/smatch/smatch                # binary
> /c/smatch/smatch_data/          # kernel.* data
> 
> > you can test that it's working by doing a:
> > 	kchecker drivers/mtd/ubi/wl.c
> > to verify that the warning goes away.
> 
> Both of these two tests run well w/o the above warning:
> 
> /c/smatch/smatch_scripts/kchecker drivers/mtd/ubi/wl.c
> 
> make C=1 CHECK=/c/kernel-tests/smatchcheck drivers/mtd/ubi/wl.o
> 
> This is interesting. I'll try adding --data=/c/smatch/smatch_data and
> check whether the end result becomes better.

It works now, after changing '-p kernel' to '--project=kernel'.

Next step would be to regenerate the smatch_data/ contents for each
new branch to make it work more reliably.

Thanks,
Fengguang