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From: ebiederm@xmission.com (Eric W. Biederman)
To: Matt Redfearn <matt.redfearn@mips.com>
Cc: <linux-arch@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	Ralf Baechle <ralf@linux-mips.org>,
	James Hogan <jhogan@kernel.org>, <linux-mips@linux-mips.org>
Subject: Re: [REVIEW][PATCH 08/22] signal/mips: Use force_sig_fault where appropriate
Date: Thu, 10 May 2018 21:31:06 -0500	[thread overview]
Message-ID: <87603uordh.fsf@xmission.com> (raw)
In-Reply-To: <6811e06d-ac0d-35a6-7d86-57838d5d7f8e@mips.com> (Matt Redfearn's message of "Thu, 10 May 2018 08:59:26 +0100")

Matt Redfearn <matt.redfearn@mips.com> writes:

> Hi Eric,
>
> On 10/05/18 03:39, Eric W. Biederman wrote:
>> Matt Redfearn <matt.redfearn@mips.com> writes:
>>
>>> Hi Eric,
>>>
>>> On 20/04/18 15:37, Eric W. Biederman wrote:
>>>> Filling in struct siginfo before calling force_sig_info a tedious and
>>>> error prone process, where once in a great while the wrong fields
>>>> are filled out, and siginfo has been inconsistently cleared.
>>>>
>>>> Simplify this process by using the helper force_sig_fault.  Which
>>>> takes as a parameters all of the information it needs, ensures
>>>> all of the fiddly bits of filling in struct siginfo are done properly
>>>> and then calls force_sig_info.
>>>>
>>>> In short about a 5 line reduction in code for every time force_sig_info
>>>> is called, which makes the calling function clearer.
>>>>
>>>> Cc: Ralf Baechle <ralf@linux-mips.org>
>>>> Cc: James Hogan <jhogan@kernel.org>
>>>> Cc: linux-mips@linux-mips.org
>>>> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
>>>> ---
>>>>    arch/mips/kernel/traps.c | 65 ++++++++++++++----------------------------------
>>>>    arch/mips/mm/fault.c     | 19 ++++----------
>>>>    2 files changed, 23 insertions(+), 61 deletions(-)
>>>>
>>>> diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
>>>> index 967e9e4e795e..66ec4b0b484d 100644
>>>> --- a/arch/mips/kernel/traps.c
>>>> +++ b/arch/mips/kernel/traps.c
>>>> @@ -699,17 +699,11 @@ static int simulate_sync(struct pt_regs *regs, unsigned int opcode)
>>>>    asmlinkage void do_ov(struct pt_regs *regs)
>>>>    {
>>>>    	enum ctx_state prev_state;
>>>> -	siginfo_t info;
>>>> -
>>>> -	clear_siginfo(&info);
>>>> -	info.si_signo = SIGFPE;
>>>> -	info.si_code = FPE_INTOVF;
>>>> -	info.si_addr = (void __user *)regs->cp0_epc;
>>>>      	prev_state = exception_enter();
>>>>    	die_if_kernel("Integer overflow", regs);
>>>>    -	force_sig_info(SIGFPE, &info, current);
>>>> +	force_sig_fault(SIGFPE, FPE_INTOVF, (void __user *)regs->cp0_epc, current);
>>>>    	exception_exit(prev_state);
>>>>    }
>>>>    @@ -722,32 +716,27 @@ asmlinkage void do_ov(struct pt_regs *regs)
>>>>    void force_fcr31_sig(unsigned long fcr31, void __user *fault_addr,
>>>>    		     struct task_struct *tsk)
>>>>    {
>>>> -	struct siginfo si;
>>>> -
>>>> -	clear_siginfo(&si);
>>>> -	si.si_addr = fault_addr;
>>>> -	si.si_signo = SIGFPE;
>>>> +	int si_code;
>>>
>>> This is giving build errors in Linux next
>>> (https://storage.kernelci.org/next/master/next-20180509/mips/defconfig+kselftest/build.log)
>>>
>>> si_code would have ended up as 0 before from the clear_siginfo(), but perhaps
>>
>> And si_code 0 is not a valid si_code to use with a floating point
>> siginfo layout.
>>
>>> int si_code = FPE_FLTUNK;
>>>
>>> Would make a more sensible default?
>>
>> FPE_FLTUNK would make a more sensible default.
>>
>> I seem to remember someone telling me that case can never happen in
>> practice so I have simply not worried about it.  Perhaps I am
>> misremembering this.
>
> It probably can't happen in practise - but the issue is that the
> kernel doesn't even compile because -Werror=maybe-uninitialized
> results in a build error since the compiler can't know that one of the
> branches will definitely be taken to set si_code.

My cross compile work.  So I don't know where that
-Werror=maybe-unitialized comes from.

I agree it is an issue.   I agree that FPE_FLTUNK is one of the good
solutions.  Another is to add a final else where you return without
doing anything.

Right now this looks like mips people issue that I have unearthed.
I could appreciate some guidance on which way mips folks would like to
handle this.

If you can point me to where the fatal error is coming from I will
definitely do something in my tree so that this is not a harmful issue.

Eric

  reply	other threads:[~2018-05-11  2:31 UTC|newest]

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-20  1:01 [REVIEW][PATCH 00/17] siginfo bugfixes and cleanups Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 01/17] signal/alpha: Document a conflict with SI_USER for SIGFPE Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 02/17] sparc: fix compat siginfo ABI regression Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 03/17] signal/sh: Use force_sig_fault in hw_breakpoint_handler Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 04/17] signal/nds32: Use force_sig in unhandled_interruption and unhandled_exceptions Eric W. Biederman
2018-04-25 12:14   ` Vincent Chen
2018-04-20  1:03 ` [REVIEW][PATCH 05/17] signal/nds32: Use force_sig(SIGILL) in do_revisn Eric W. Biederman
2018-04-25 12:10   ` Vincent Chen
2018-04-25 16:13     ` [PATCH] signal/nds32: More information in do_revinsn Eric W. Biederman
2018-04-26  3:02       ` Vincent Chen
2018-04-20  1:03 ` [REVIEW][PATCH 06/17] signal: Ensure every siginfo we send has all bits initialized Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 07/17] signal: Reduce copy_siginfo_to_user to just copy_to_user Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 08/17] signal: Stop special casing TRAP_FIXME and FPE_FIXME in siginfo_layout Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 09/17] signal: Remove SEGV_BNDERR ifdefs Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 10/17] signal: Remove ifdefs for BUS_MCEERR_AR and BUS_MCEERR_AO Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 11/17] signal/alpha: Replace FPE_FIXME with FPE_FLTUNK Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 12/17] signal/ia64: " Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 13/17] signal/powerpc: " Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 14/17] signal/unicore32: Use FPE_FLTUNK instead of 0 in ucf64_raise_sigfpe Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 15/17] signal: Add TRAP_UNK si_code for undiagnosted trap exceptions Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 16/17] signal/alpha: Replace TRAP_FIXME with TRAP_UNK Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 17/17] signal/powerpc: " Eric W. Biederman
2018-04-20 14:35 ` [REVIEW][PATCH 00/22] Simplifying siginfo users Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 01/22] signal/alpha: Use send_sig_fault where appropriate Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 02/22] signal/alpha: Use force_sig_fault " Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 03/22] signal/c6x: " Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 04/22] signal/hexagon: Use force_sig_fault as appropriate Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 05/22] signal/m68k: Use force_sig_fault where appropriate Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 06/22] signal/microblaze: Remove the commented out force_sig_info in do_page_fault Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 07/22] signal/microblaze: Use force_sig_fault where appropriate Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 08/22] signal/mips: " Eric W. Biederman
2018-05-09 15:14     ` Matt Redfearn
2018-05-10  2:39       ` Eric W. Biederman
2018-05-10  7:59         ` Matt Redfearn
2018-05-11  2:31           ` Eric W. Biederman [this message]
2018-04-20 14:37   ` [REVIEW][PATCH 09/22] signal/nds32: " Eric W. Biederman
2018-04-25 11:29     ` Vincent Chen
2018-04-25 15:57       ` Eric W. Biederman
2018-04-26  1:24         ` Greentime Hu
2018-04-20 14:37   ` [REVIEW][PATCH 10/22] signal/nios2: " Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 11/22] signal/openrisc: " Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 12/22] signal/parisc: Use force_sig_mceerr " Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 13/22] signal/parisc: Use force_sig_fault " Eric W. Biederman
2018-04-21 17:24     ` Helge Deller
2018-04-20 14:38   ` [REVIEW][PATCH 14/22] signal/riscv: " Eric W. Biederman
2018-04-21  7:25     ` Christoph Hellwig
2018-04-24 15:31       ` [REVIEW][PATCH 23/22] signal/riscv: Replace do_trap_siginfo with force_sig_fault Eric W. Biederman
2018-04-23 19:11     ` [REVIEW][PATCH 14/22] signal/riscv: Use force_sig_fault where appropriate Palmer Dabbelt
2018-04-24 15:28       ` Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 15/22] signal/s390: " Eric W. Biederman
2018-04-23  5:44     ` Martin Schwidefsky
2018-04-20 14:38   ` [REVIEW][PATCH 16/22] signal/sh: " Eric W. Biederman
2018-04-20 14:55     ` Rich Felker
2018-05-28  9:19       ` Geert Uytterhoeven
2018-05-29 15:00         ` [PATCH] signal/sh: Stop gcc warning about an impossible case in do_divide_error Eric W. Biederman
2018-05-30  7:54           ` Sergei Shtylyov
2018-04-20 14:38   ` [REVIEW][PATCH 17/22] signal/sparc: Use send_sig_fault where appropriate Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 18/22] signal/sparc: Use force_sig_fault " Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 19/22] signal/um: Use force_sig_fault in relay_signal Eric W. Biederman
2018-04-20 16:06     ` [uml-devel] " Anton Ivanov
2018-04-24  8:32       ` Richard Weinberger
2018-04-24  8:44         ` Anton Ivanov
2018-04-24 15:59           ` Eric W. Biederman
     [not found]             ` <CAMD8JhwgcWCp6c=O4-spNW1VdY5M-eAjr7M5PieeAfeTSe_4yw@mail.gmail.com>
2018-04-24 22:03               ` Martin Pärtel
2018-04-24 22:24                 ` Eric W. Biederman
2018-04-25 23:05                   ` Martin Pärtel
2018-04-28 14:02                     ` [REVIEW][PATCH 0/5] Improving siginfo_layout and fixing uml's relay_signal Eric W. Biederman
2018-04-28 14:06                       ` [REVIEW][PATCH 1/5] signal/signalfd: Remove __put_user from signalfd_copyinfo Eric W. Biederman
2018-04-28 14:06                       ` [REVIEW][PATCH 2/5] signal/signalfd: Add support for SIGSYS Eric W. Biederman
2018-04-28 14:07                       ` [REVIEW][PATCH 3/5] signal: Remove unncessary #ifdef SEGV_PKUERR in 32bit compat code Eric W. Biederman
2018-04-28 14:07                       ` [REVIEW][PATCH 4/5] signal: Extend siginfo_layout with SIL_FAULT_{MCEERR|BNDERR|PKUERR} Eric W. Biederman
2018-04-28 14:07                       ` [REVIEW][PATCH 5/5] signal/um: More carefully relay signals in relay_signal Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 20/22] signal/um: Use force_sig_fault where appropriate Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 21/22] signal/xtensa: Consistenly use SIGBUS in do_unaligned_user Eric W. Biederman
2018-04-20 16:06     ` Max Filippov
2018-04-20 14:38   ` [REVIEW][PATCH 22/22] signal/xtensa: Use force_sig_fault where appropriate Eric W. Biederman
2018-04-20 16:27     ` Max Filippov

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