From: Fabio Aiuto <fabioaiuto83@gmail.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>,
Matthew Wilcox <willy@infradead.org>,
Julia Lawall <julia.lawall@inria.fr>,
outreachy-kernel@googlegroups.com,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [Outreachy kernel] [PATCH] :staging: rtl8723bs: Remove useless led_blink_hdl()
Date: Wed, 14 Apr 2021 09:40:36 +0200 [thread overview]
Message-ID: <20210414074035.GA1880@agape.jhs> (raw)
In-Reply-To: <20210414052150.GO6021@kadam>
On Wed, Apr 14, 2021 at 08:21:50AM +0300, Dan Carpenter wrote:
> On Tue, Apr 13, 2021 at 10:08:32PM +0200, Fabio M. De Francesco wrote:
> > On Tuesday, April 13, 2021 9:48:44 PM CEST Matthew Wilcox wrote:
> > > On Tue, Apr 13, 2021 at 09:45:03PM +0200, Fabio M. De Francesco wrote:
> > > > 1) The driver doesn't call that function from anywhere else than the
> > > > macro. 2) You have explained that the macro add its symbol to a slot
> > > > in an array that would shift all the subsequent elements down if that
> > > > macro is not used exactly in the line where it is.
> > > > 3) Dan Carpenter said that that array is full of null functions (or
> > > > empty slots?).
> > > >
> > > > Unless that function is called anonymously dereferencing its address
> > > > from the position it occupies in the array, I'm not able to see what
> > > > else means can any caller use.
> > > >
> > > > I know I have much less experience than you with C: what can go wrong?
> > >
> > > Here's where the driver calls that function:
> > >
> > > $ git grep wlancmds drivers/staging/rtl8723bs/
> > > drivers/staging/rtl8723bs/core/rtw_cmd.c:static struct cmd_hdl wlancmds[]
> > > = { drivers/staging/rtl8723bs/core/rtw_cmd.c: if
> > > (pcmd->cmdcode < ARRAY_SIZE(wlancmds)) {
> > > drivers/staging/rtl8723bs/core/rtw_cmd.c: cmd_hdl
> > > = wlancmds[pcmd->cmdcode].h2cfuns;
> > >
> > OK, I had imagined an anonymous call from its location in the array (as I
> > wrote in the last phrase of my message). However, I thought that it could
> > have been an improbable possibility, not a real one.
> >
> > Linux uses a lot of interesting ideas that newcomers like me should learn.
> > Things here are trickier than they appear at first sight.
>
> One trick would be to build the Smatch cross function database.
>
> https://www.spinics.net/lists/smatch/msg00568.html
>
> Then you could do:
>
> $ ~/path/to/smatch_data/db/smdb.py led_blink_hdl
> file | caller | function | type | parameter | key | value |
> drivers/staging/rtl8723bs/core/rtw_cmd.c | rtw_cmd_thread | rtw_cmd_thread ptr cmd_hdl | INTERNAL | -1 | | uchar(*)(struct adapter*, uchar*)
> drivers/staging/rtl8188eu/core/rtw_cmd.c | rtw_cmd_thread | rtw_cmd_thread ptr cmd_hdl | INTERNAL | -1 | | uchar(*)(struct adapter*, uchar*)
> drivers/staging/rtl8188eu/core/rtw_cmd.c | rtw_cmd_thread | rtw_cmd_thread ptr cmd_hdl | BUF_SIZE | 1 | pbuf | 1,4,6,8,12,14,16,19-20,23-24,48,740,884,892,900,960
>
>
> Which says that led_blink_hdl() is called as a function pointer called
> "cmd_hdl" from rtw_cmd_thread().
>
> Hm... It says it can be called from either rtw_cmd_thread() function
> (the rtl8723bs or rtl8188eu version) which is not ideal. But also
> basically harmless so whatever...
>
> regards,
> dan carpenter
>
very powerful tool.
I tried this:
fabio@agape:~/src/git/kernels/staging$ ~/src/git/smatch/smatch_data/db/smdb.py led_blink_hdl
Traceback (most recent call last):
File "/home/fabio/src/git/smatch/smatch_data/db/smdb.py", line 725, in <module>
print_caller_info("", func)
File "/home/fabio/src/git/smatch/smatch_data/db/smdb.py", line 366, in print_caller_info
ptrs = get_function_pointers(func)
File "/home/fabio/src/git/smatch/smatch_data/db/smdb.py", line 53, in get_function_pointers
get_function_pointers_helper(func)
File "/home/fabio/src/git/smatch/smatch_data/db/smdb.py", line 38, in get_function_pointers_helper
cur.execute("select distinct ptr from function_ptr where function = '%s';" %(func))
sqlite3.OperationalError: no such table: function_ptr
I run smatch version 1.71 on Debian Buster machine
what's happened?
thanks in advance,
fabio
next prev parent reply other threads:[~2021-04-14 7:40 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 15:59 [Outreachy kernel] [PATCH] :staging: rtl8723bs: Remove useless led_blink_hdl() Fabio M. De Francesco
2021-04-13 16:04 ` Julia Lawall
2021-04-13 16:19 ` Fabio M. De Francesco
2021-04-13 16:27 ` Julia Lawall
2021-04-13 16:47 ` Fabio M. De Francesco
2021-04-13 18:20 ` Dan Carpenter
2021-04-13 18:30 ` Fabio M. De Francesco
2021-04-13 18:57 ` Julia Lawall
2021-04-13 19:16 ` Fabio M. De Francesco
2021-04-13 19:25 ` Julia Lawall
2021-04-13 19:45 ` Fabio M. De Francesco
2021-04-13 19:48 ` Matthew Wilcox
2021-04-13 20:08 ` Fabio M. De Francesco
2021-04-14 5:21 ` Dan Carpenter
2021-04-14 6:33 ` Fabio M. De Francesco
2021-04-14 7:00 ` Dan Carpenter
2021-04-14 7:59 ` Fabio M. De Francesco
2021-04-14 8:06 ` Dan Carpenter
2021-04-14 7:40 ` Fabio Aiuto [this message]
2021-04-14 7:47 ` Dan Carpenter
2021-04-13 16:06 ` Greg Kroah-Hartman
-- strict thread matches above, loose matches on Subject: below --
2021-04-14 11:52 [Outreachy kernel] [PATCH] staging: " Fabio M. De Francesco
2021-04-14 12:00 ` Fabio Aiuto
2021-04-14 12:18 ` Greg Kroah-Hartman
2021-04-14 13:27 ` Fabio M. De Francesco
2021-04-14 13:24 ` Dan Carpenter
2021-04-14 15:36 ` Fabio M. De Francesco
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