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SubjectRe: [REVIEW][PATCH 08/22] signal/mips: Use force_sig_fault where appropriate
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.

Eric

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