From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org,
linux-arch@vger.kernel.org, linux-toolchains@vger.kernel.org,
Masahiro Yamada <masahiroy@kernel.org>,
Kees Cook <keescook@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v2] kbuild: treat char as always unsigned
Date: Mon, 24 Oct 2022 17:17:47 +0200 [thread overview]
Message-ID: <Y1asm2GnqgXirEIy@zx2c4.com> (raw)
In-Reply-To: <Y1ZZyP4ZRBIbv+Kg@kili>
On Mon, Oct 24, 2022 at 12:24:24PM +0300, Dan Carpenter wrote:
> On Wed, Oct 19, 2022 at 02:30:34PM -0600, Jason A. Donenfeld wrote:
> > Recently, some compile-time checking I added to the clamp_t family of
> > functions triggered a build error when a poorly written driver was
> > compiled on ARM, because the driver assumed that the naked `char` type
> > is signed, but ARM treats it as unsigned, and the C standard says it's
> > architecture-dependent.
> >
> > I doubt this particular driver is the only instance in which
> > unsuspecting authors make assumptions about `char` with no `signed` or
> > `unsigned` specifier. We were lucky enough this time that that driver
> > used `clamp_t(char, negative_value, positive_value)`, so the new
> > checking code found it, and I've sent a patch to fix it, but there are
> > likely other places lurking that won't be so easily unearthed.
> >
> > So let's just eliminate this particular variety of heisensign bugs
> > entirely. Set `-funsigned-char` globally, so that gcc makes the type
> > unsigned on all architectures.
> >
> > This will break things in some places and fix things in others, so this
> > will likely cause a bit of churn while reconciling the type misuse.
> >
>
> This is a very daring change and obviously is going to introduce bugs.
> It might be better to create a static checker rule that says "char"
> without explicit signedness can only be used for strings.
Indeed this would be great.
>
> arch/parisc/kernel/drivers.c:337 print_hwpath() warn: impossible condition '(path->bc[i] == -1) => (0-255 == (-1))'
> arch/parisc/kernel/drivers.c:410 setup_bus_id() warn: impossible condition '(path.bc[i] == -1) => (0-255 == (-1))'
> arch/parisc/kernel/drivers.c:486 create_parisc_device() warn: impossible condition '(modpath->bc[i] == -1) => (0-255 == (-1))'
> arch/parisc/kernel/drivers.c:759 hwpath_to_device() warn: impossible condition '(modpath->bc[i] == -1) => (0-255 == (-1))'
> drivers/media/dvb-frontends/stv0288.c:471 stv0288_set_frontend() warn: assigning (-9) to unsigned variable 'tm'
> drivers/media/dvb-frontends/stv0288.c:471 stv0288_set_frontend() warn: we never enter this loop
> drivers/misc/sgi-gru/grumain.c:711 gru_check_chiplet_assignment() warn: 'gts->ts_user_chiplet_id' is unsigned
> drivers/net/wireless/cisco/airo.c:5316 proc_wepkey_on_close() warn: assigning (-16) to unsigned variable 'key[i / 3]'
> drivers/net/wireless/ralink/rt2x00/rt2800lib.c:9415 rt2800_iq_search() warn: assigning (-32) to unsigned variable 'idx0'
> drivers/net/wireless/ralink/rt2x00/rt2800lib.c:9470 rt2800_iq_search() warn: assigning (-32) to unsigned variable 'perr'
> drivers/video/fbdev/sis/init301.c:3549 SiS_GetCRT2Data301() warn: 'SiS_Pr->SiS_EModeIDTable[ModeIdIndex]->ROMMODEIDX661' is unsigned
> sound/pci/au88x0/au88x0_core.c:2029 vortex_adb_checkinout() warn: signedness bug returning '(-22)'
> sound/pci/au88x0/au88x0_core.c:2046 vortex_adb_checkinout() warn: signedness bug returning '(-12)'
> sound/pci/au88x0/au88x0_core.c:2125 vortex_adb_allocroute() warn: 'vortex_adb_checkinout(vortex, (0), en, 0)' is unsigned
> sound/pci/au88x0/au88x0_core.c:2170 vortex_adb_allocroute() warn: 'vortex_adb_checkinout(vortex, stream->resources, en, 4)' is unsigned
> sound/pci/rme9652/hdsp.c:3953 hdsp_channel_buffer_location() warn: 'hdsp->channel_map[channel]' is unsigned
> sound/pci/rme9652/rme9652.c:1833 rme9652_channel_buffer_location() warn: 'rme9652->channel_map[channel]' is unsigned
Thanks. I'll fix these up.
Jason
next prev parent reply other threads:[~2022-10-24 16:33 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-19 16:26 [PATCH] kbuild: treat char as always signed Jason A. Donenfeld
2022-10-19 16:54 ` Segher Boessenkool
2022-10-19 17:14 ` Linus Torvalds
2022-10-19 17:26 ` Linus Torvalds
2022-10-19 18:10 ` Nick Desaulniers
2022-10-19 18:35 ` Linus Torvalds
2022-10-19 19:23 ` Andy Shevchenko
2022-10-19 19:36 ` Linus Torvalds
2022-10-19 17:43 ` Segher Boessenkool
2022-10-19 18:11 ` Linus Torvalds
2022-10-19 18:20 ` Nick Desaulniers
2022-10-19 18:56 ` Linus Torvalds
2022-10-19 19:11 ` Kees Cook
2022-10-19 19:30 ` Linus Torvalds
2022-10-19 20:35 ` Jason A. Donenfeld
2022-10-20 0:10 ` Linus Torvalds
2022-10-20 3:11 ` Jason A. Donenfeld
2022-10-19 20:15 ` Segher Boessenkool
2022-10-19 21:07 ` David Laight
2022-10-19 21:26 ` Segher Boessenkool
2022-10-20 10:41 ` Gabriel Paubert
2022-10-21 22:46 ` Linus Torvalds
2022-10-22 6:06 ` Gabriel Paubert
2022-10-22 18:16 ` Linus Torvalds
2022-10-23 20:23 ` Gabriel Paubert
2022-10-25 23:00 ` Kees Cook
2022-10-26 0:04 ` Jason A. Donenfeld
2022-10-26 15:41 ` Kees Cook
2022-10-19 19:54 ` Linus Torvalds
2022-10-19 20:23 ` Jason A. Donenfeld
2022-10-19 20:30 ` [PATCH v2] kbuild: treat char as always unsigned Jason A. Donenfeld
2022-10-19 23:56 ` Linus Torvalds
2022-10-20 0:02 ` Jason A. Donenfeld
2022-10-20 0:38 ` Linus Torvalds
2022-10-20 2:59 ` Jason A. Donenfeld
2022-10-20 18:41 ` Kees Cook
2022-10-21 1:01 ` Jason A. Donenfeld
2022-10-20 20:24 ` Segher Boessenkool
2022-10-24 9:24 ` Dan Carpenter
2022-10-24 9:30 ` Dan Carpenter
2022-10-24 16:33 ` Jason A. Donenfeld
2022-10-24 17:10 ` Linus Torvalds
2022-10-24 17:17 ` Jason A. Donenfeld
2022-10-25 19:22 ` Kalle Valo
2022-10-25 10:16 ` David Laight
2022-10-24 15:17 ` Jason A. Donenfeld [this message]
2022-12-21 14:53 ` Guenter Roeck
2022-12-21 15:05 ` Geert Uytterhoeven
2022-12-21 15:23 ` Guenter Roeck
2022-12-21 15:29 ` Rasmus Villemoes
2022-12-21 15:56 ` Guenter Roeck
2022-12-21 17:06 ` Linus Torvalds
2022-12-21 17:19 ` Guenter Roeck
2022-12-21 18:46 ` Linus Torvalds
2022-12-21 19:08 ` Linus Torvalds
2022-12-21 21:01 ` Guenter Roeck
2022-12-22 13:05 ` Geert Uytterhoeven
2022-12-22 10:41 ` David Laight
[not found] ` <f02e0ac7f2d805020a7ba66803aaff3e31b5eeff.camel@t-online.de>
2022-12-24 9:47 ` Geert Uytterhoeven
2022-12-30 11:39 ` David Laight
2022-12-30 13:13 ` David Laight
2023-01-02 8:29 ` Geert Uytterhoeven
2022-12-21 17:49 ` Andreas Schwab
2022-12-21 16:57 ` Geert Uytterhoeven
2022-10-19 20:58 ` [PATCH] kbuild: treat char as always signed David Laight
2022-10-26 0:10 ` make ctype ascii only? (was [PATCH] kbuild: treat char as always signed) Rasmus Villemoes
2022-10-26 18:10 ` Linus Torvalds
2022-10-27 7:59 ` Rasmus Villemoes
2022-10-27 18:28 ` Linus Torvalds
[not found] ` <202210201618.8XhEGsLd-lkp@intel.com>
2022-10-20 16:33 ` [PATCH] kbuild: treat char as always signed Jason A. Donenfeld
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