"Maciej W. Rozycki" <ma...@imgtec.com> writes: > On Tue, 18 Jul 2017, Eric W. Biederman wrote: > >> diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c >> index b68b4d0726d3..6c9cca9c5341 100644 >> --- a/arch/mips/kernel/traps.c >> +++ b/arch/mips/kernel/traps.c >> @@ -735,7 +735,7 @@ void force_fcr31_sig(unsigned long fcr31, void __user >> *fault_addr, >> else if (fcr31 & FPU_CSR_INE_X) >> si.si_code = FPE_FLTRES; >> else >> - si.si_code = __SI_FAULT; >> + si.si_code = FPE_FIXME; > > This is an "impossible" state to reach unless your hardware is on fire. > One or more of the FCSR Cause bits will have been set (in `fcr31') or the > FPE exception would not have happened. > > Of course there could be a simulator bug, or we could have breakage > somewhere causing `process_fpemu_return' to be called with SIGFPE and > inconsistent `fcr31'. So we need to handle it somehow. > > So what would be the right value of `si_code' to use here for such an > unexpected exception condition? I think `BUG()' would be too big a > hammer here. Or wouldn't it?
The possible solutions I can think of are: WARN_ON_ONCE with a comment. Add a new si_code to uapi/asm-generic/siginfo.h perhaps FPE_IMPOSSIBLE. Like syscall numbers si_codes are cheap. Call force_sig() instead of force_sig_info, using just a generic si_code. If this is truly impossible and the compiler doesn't complain just drop the code. Eric