Re: [PATCH v3 5/9] powerpc/traps: Print signal name for unhandled signals

[Joe Perches]

On Wed, 2018-08-01 at 08:37 +0200, Christophe LEROY wrote:
> Le 31/07/2018 à 16:50, Murilo Opsfelder Araujo a écrit :
> > This adds a human-readable name in the unhandled signal message.
> > Before this patch, a page fault looked like:
> >    pandafault[6303]: unhandled signal 11 at 100007d0 nip 1000061c lr 
> > 7fff93c55100 code 2 in pandafault[10000000+10000]
> > After this patch, a page fault looks like:
> >    pandafault[6352]: segfault (11) at 13a2a09f8 nip 13a2a086c lr 
> > 7fffb63e5100 code 2 in pandafault[13a2a0000+10000]
]]
> > diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
[]
> > @@ -96,6 +96,41 @@ EXPORT_SYMBOL(__debugger_fault_handler);
> >   #define TM_DEBUG(x...) do { } while(0)
> >   #endif
> >   
> > +static const char *signames[SIGRTMIN + 1] = {
> > +   "UNKNOWN",
> > +   "SIGHUP",                       // 1
> > +   "SIGINT",                       // 2
[]
> I don't think is is worth having that full table when we only use a few 
> of them. (As discussed in v1 https://patchwork.ozlabs.org/patch/948802/)
> 
> I would suggest to instead use a function like this:
> 
> static const char *signame(int signr)
> {
>       if (signr == SIGBUS)
>               return "bus error";
>       if (signr == SIGFPE)
>               return "floating point exception";
>       if (signr == SIGILL)
>               return "illegal instruction";
>       if (signr == SIGILL)
>               return "segfault";
>       if (signr == SIGTRAP)
>               return "unhandled trap";
>       return "unknown signal";
> }

trivia:

Unless the if tests are ordered most to least likely,
perhaps it would be better to use a switch/case and
let the compiler decide.

        switch (signr) {
        case SIGBUS:    return "bus error";
        case SIGFPE:    return "floating point exception";
        case SIGILL:    return "illegal instruction";
        case SIGSEGV:   return "segfault";
        case SIGTRAP:   return "unhandled trap";
        }
        return "unknown signal";
}