From: christophe leroy <christophe.leroy@c-s.fr>
To: Mathieu Malaterre <malat@debian.org>,
Segher Boessenkool <segher@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
LKML <linux-kernel@vger.kernel.org>,
Paul Mackerras <paulus@samba.org>, Jiri Slaby <jslaby@suse.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH 06/21] powerpc: Avoid comparison of unsigned long >= 0 in __access_ok
Date: Mon, 26 Feb 2018 21:00:09 +0100 [thread overview]
Message-ID: <4ddba8bc-b1e5-24a0-602e-672e7b51b203@c-s.fr> (raw)
In-Reply-To: <CA+7wUsx047shRJ92PJ+cvg24HNhMnYzM0t5zUdEOaSE00sXkSg@mail.gmail.com>
Le 26/02/2018 à 18:50, Mathieu Malaterre a écrit :
> On Mon, Feb 26, 2018 at 8:44 AM, Mathieu Malaterre <malat@debian.org> wrote:
>> On Mon, Feb 26, 2018 at 7:50 AM, Christophe LEROY
>> <christophe.leroy@c-s.fr> wrote:
>>>
>>>
>>> Le 26/02/2018 à 07:34, Christophe LEROY a écrit :
>>>>
>>>>
>>>>
>>>> Le 25/02/2018 à 18:22, Mathieu Malaterre a écrit :
>>>>>
>>>>> Rewrite check size - 1 <= Y as size < Y since `size` is unsigned value.
>>>>> Fix warning (treated as error in W=1):
>>>>>
>>>>> CC arch/powerpc/kernel/signal_32.o
>>>>> In file included from ./include/linux/uaccess.h:14:0,
>>>>> from ./include/asm-generic/termios-base.h:8,
>>>>> from ./arch/powerpc/include/asm/termios.h:20,
>>>>> from ./include/uapi/linux/termios.h:6,
>>>>> from ./include/linux/tty.h:7,
>>>>> from arch/powerpc/kernel/signal_32.c:36:
>>>>> ./include/asm-generic/termios-base.h: In function
>>>>> ‘user_termio_to_kernel_termios’:
>>>>> ./arch/powerpc/include/asm/uaccess.h:52:35: error: comparison of unsigned
>>>>> expression >= 0 is always true [-Werror=type-limits]
>>>>> (((size) == 0) || (((size) - 1) <= ((segment).seg - (addr)))))
>>>>> ^
>>>>> ./arch/powerpc/include/asm/uaccess.h:58:3: note: in expansion of macro
>>>>> ‘__access_ok’
>>>>> __access_ok((__force unsigned long)(addr), (size), get_fs()))
>>>>> ^~~~~~~~~~~
>>>>> ./arch/powerpc/include/asm/uaccess.h:262:6: note: in expansion of macro
>>>>> ‘access_ok’
>>>>> if (access_ok(VERIFY_READ, __gu_addr, (size))) \
>>>>> ^~~~~~~~~
>>>>> ./arch/powerpc/include/asm/uaccess.h:80:2: note: in expansion of macro
>>>>> ‘__get_user_check’
>>>>> __get_user_check((x), (ptr), sizeof(*(ptr)))
>>>>> ^~~~~~~~~~~~~~~~
>>>>> ./include/asm-generic/termios-base.h:36:6: note: in expansion of macro
>>>>> ‘get_user’
>>>>> if (get_user(termios->c_line, &termio->c_line) < 0)
>>>>> ^~~~~~~~
>>>>> [...]
>>>>> cc1: all warnings being treated as errors
>>>>>
>>>>> Signed-off-by: Mathieu Malaterre <malat@debian.org>
>>>>> ---
>>>>> arch/powerpc/include/asm/uaccess.h | 2 +-
>>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/arch/powerpc/include/asm/uaccess.h
>>>>> b/arch/powerpc/include/asm/uaccess.h
>>>>> index 51bfeb8777f0..fadc406bd39d 100644
>>>>> --- a/arch/powerpc/include/asm/uaccess.h
>>>>> +++ b/arch/powerpc/include/asm/uaccess.h
>>>>> @@ -49,7 +49,7 @@
>>>>> #define __access_ok(addr, size, segment) \
>>>>> (((addr) <= (segment).seg) && \
>>>>> - (((size) == 0) || (((size) - 1) <= ((segment).seg - (addr)))))
>>>>> + (((size) == 0) || ((size) < ((segment).seg - (addr)))))
>>>>
>>>>
>>>> IIUC, ((2 - 1) <= 1) is the same as (2 < 1) ?????
>>>
>>
>> The whole series was pretty mediocre, but this one was actually pretty
>> destructive. Thanks for catching this.
>>
>>>
>>> Note that I already try to submit a fix for this warning 3 years ago
>>> (https://patchwork.ozlabs.org/patch/418075/) and it was rejected with the
>>> following comment:
>
> Tested again today with gcc 6.3.0 and gcc is still producing the
> original warning (treated as error).
That's right, it seems that recent versions of gcc are not happy anymore
with that change.
Maybe Segher has a suggestion for that one ?
>
>>> Again, I don't think Linux enables this warning. What did you do to
>>> produce this? In any case, it's a bad warning that doesn't take macros
>>> into account, and the answer is not to make the code less clear by hiding
>>> the fact that zero is a special case.
>>
>> Right. I'll try to see how to make W=1 run without error with an
>> alternate solution.
>
> So the other alternative is to update a bunch of ppc32 defconfig(s)
> with: CONFIG_PPC_DISABLE_WERROR=y.
>
> Would that be preferable ?
No I don't think it is the solution. PPC is built with WERROR in order
to catch warnings on real problems.
You could disable it selectively when you want to run 'make W=1' and see
all possible warnings, then select by yourself which warnings are worth
fixing up.
Christophe
>
>>> Christophe
>>>
>>>
>>>>
>>>> Christophe
>>>>
>>>>> #endif
>>>>>
>>>
---
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next prev parent reply other threads:[~2018-02-26 20:00 UTC|newest]
Thread overview: 83+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-25 17:22 [PATCH 00/21] powerpc/gamecube: make W=1 compilation errors free Mathieu Malaterre
2018-02-25 17:22 ` [PATCH 01/21] powerpc: Remove warning on array size when empty Mathieu Malaterre
2018-02-25 18:53 ` Segher Boessenkool
2018-02-26 14:44 ` Andy Shevchenko
2018-02-26 14:45 ` Andy Shevchenko
2018-02-27 7:25 ` Mathieu Malaterre
2018-02-27 7:33 ` Christophe LEROY
2018-02-27 7:44 ` Mathieu Malaterre
2018-02-27 15:52 ` Andy Shevchenko
2018-02-27 17:25 ` Mathieu Malaterre
2018-02-27 20:42 ` Segher Boessenkool
2018-02-28 15:50 ` Andy Shevchenko
2018-03-01 2:55 ` Michael Ellerman
2018-03-01 7:01 ` Mathieu Malaterre
2018-03-01 9:33 ` Michael Ellerman
2018-03-02 19:49 ` [PATCH v2 " Mathieu Malaterre
2018-03-14 9:28 ` [v2,01/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 02/21] powerpc: Move the inline keyword at the beginning of function declaration Mathieu Malaterre
2018-03-14 9:27 ` [02/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 03/21] powerpc: Mark the variable earlycon_acpi_spcr_enable maybe_unused Mathieu Malaterre
2018-03-04 10:54 ` Michael Ellerman
2018-03-10 18:08 ` Mathieu Malaterre
2018-02-25 17:22 ` [PATCH 04/21] powerpc: Mark both tmp variables as unused Mathieu Malaterre
2018-03-14 9:27 ` [04/21] " Michael Ellerman
2018-03-14 10:38 ` [PATCH 04/21] " Christophe LEROY
2018-03-16 14:08 ` Michael Ellerman
2018-02-25 17:22 ` [PATCH 05/21] powerpc: Avoid comparison of unsigned long >= 0 in pfn_valid Mathieu Malaterre
2018-02-26 6:32 ` Christophe LEROY
2018-02-26 7:49 ` Mathieu Malaterre
2018-02-26 8:46 ` Segher Boessenkool
2018-03-02 19:54 ` Mathieu Malaterre
2018-03-03 7:45 ` christophe leroy
2018-03-04 10:55 ` Michael Ellerman
2018-03-04 19:46 ` christophe leroy
2018-03-07 20:34 ` [PATCH v2 " Mathieu Malaterre
2018-03-14 9:28 ` [v2, " Michael Ellerman
2018-02-25 17:22 ` [PATCH 06/21] powerpc: Avoid comparison of unsigned long >= 0 in __access_ok Mathieu Malaterre
2018-02-26 6:34 ` Christophe LEROY
2018-02-26 6:50 ` Christophe LEROY
2018-02-26 7:44 ` Mathieu Malaterre
2018-02-26 17:50 ` Mathieu Malaterre
2018-02-26 20:00 ` christophe leroy [this message]
2018-02-26 22:17 ` Segher Boessenkool
2018-03-02 19:50 ` [PATCH v2 " Mathieu Malaterre
2018-03-03 7:44 ` christophe leroy
2018-03-14 9:28 ` [v2, " Michael Ellerman
2018-02-25 17:22 ` [PATCH 07/21] powerpc: Make functions flipper_pic_init & ug_udbg_putc static Mathieu Malaterre
2018-03-14 9:27 ` [07/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 08/21] powerpc: Make function __giveup_fpu static Mathieu Malaterre
2018-03-14 9:28 ` [08/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 09/21] powerpc: Make function save_all static Mathieu Malaterre
2018-02-25 17:22 ` [PATCH 10/21] powerpc: Add missing prototype for slb_miss_bad_addr Mathieu Malaterre
2018-03-14 9:27 ` [10/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 11/21] powerpc: Add missing prototype for hdec_interrupt Mathieu Malaterre
2018-03-14 9:27 ` [11/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 12/21] powerpc: Add missing prototype for time_init Mathieu Malaterre
2018-03-14 9:27 ` [12/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 13/21] powerpc: Add missing prototype for arch_dup_task_struct Mathieu Malaterre
2018-03-14 9:27 ` [13/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 14/21] powerpc: Add missing prototype for arch_irq_work_raise Mathieu Malaterre
2018-03-14 9:27 ` [14/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 15/21] powerpc: Add missing prototype for MMU_setup Mathieu Malaterre
2018-03-04 10:54 ` Michael Ellerman
2018-03-07 20:32 ` [PATCH v2 15/21] powerpc: Make function MMU_setup static Mathieu Malaterre
2018-03-14 9:28 ` [v2,15/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 16/21] powerpc: Add missing prototype for init_IRQ Mathieu Malaterre
2018-03-14 9:28 ` [16/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 17/21] powerpc: Add missing prototype for sys_debug_setcontext Mathieu Malaterre
2018-03-04 10:54 ` Michael Ellerman
2018-03-07 20:37 ` Mathieu Malaterre
2018-03-08 10:36 ` Michael Ellerman
2018-03-26 18:56 ` Mathieu Malaterre
2018-03-27 8:50 ` Michael Ellerman
2018-03-14 9:28 ` [17/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 18/21] powerpc: Add missing prototypes for sys_sigreturn & sys_rt_sigreturn Mathieu Malaterre
2018-03-14 9:28 ` [18/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 19/21] powerpc: Add missing prototypes for hw_breakpoint_handler & arch_unregister_hw_breakpoint Mathieu Malaterre
2018-03-14 9:28 ` [19/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 20/21] powerpc: Add missing prototypes for ppc_select & ppc_fadvise64_64 Mathieu Malaterre
2018-03-14 9:28 ` [20/21] " Michael Ellerman
2018-02-25 17:22 ` [PATCH 21/21] powerpc: Add missing prototypes in setup_32.c Mathieu Malaterre
2018-03-08 11:44 ` Michael Ellerman
2018-03-14 9:28 ` [21/21] " Michael Ellerman
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