Subject: Re: [PATCH 6/7] powerpc/traps: Print signal name for unhandled signals

From: Murilo Opsfelder Araujo <[email-masked]>
Date: Wed, 25 Jul 2018 17:06:31 -0300

Hi, Christophe.

On Wed, Jul 25, 2018 at 05:49:27PM +0200, LEROY Christophe wrote:
> Murilo Opsfelder Araujo <[email-masked]> a écrit :
>
> > This adds a human-readable name in the unhandled signal message.
> >
> > Before this patch, a page fault looked like:
> >
> >     Jul 11 16:04:11 localhost kernel: pandafault[6303]: unhandled signal
> > 11 at 00000000100007d0 nip 000000001000061c lr 00007fff93c55100 code 2
> > in pandafault[10000000+10000]
> >
> > After this patch, a page fault looks like:
> >
> >     Jul 11 18:14:48 localhost kernel: pandafault[6352]: segfault (11) at
> > 000000013a2a09f8 nip 000000013a2a086c lr 00007fffb63e5100 code 2 in
> > pandafault[13a2a0000+10000]
> >
> > Signed-off-by: Murilo Opsfelder Araujo <[email-masked]>
> > ---
> >  arch/powerpc/kernel/traps.c | 43 +++++++++++++++++++++++++++++++++----
> >  1 file changed, 39 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> > index e6c43ef9fb50..e55ee639d010 100644
> > --- 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
> > +	"SIGQUIT",			// 3
> > +	"SIGILL",			// 4
> > +	"unhandled trap",		// 5 = SIGTRAP
> > +	"SIGABRT",			// 6 = SIGIOT
> > +	"bus error",			// 7 = SIGBUS
> > +	"floating point exception",	// 8 = SIGFPE
> > +	"illegal instruction",		// 9 = SIGILL
> > +	"SIGUSR1",			// 10
> > +	"segfault",			// 11 = SIGSEGV
> > +	"SIGUSR2",			// 12
> > +	"SIGPIPE",			// 13
> > +	"SIGALRM",			// 14
> > +	"SIGTERM",			// 15
> > +	"SIGSTKFLT",			// 16
> > +	"SIGCHLD",			// 17
> > +	"SIGCONT",			// 18
> > +	"SIGSTOP",			// 19
> > +	"SIGTSTP",			// 20
> > +	"SIGTTIN",			// 21
> > +	"SIGTTOU",			// 22
> > +	"SIGURG",			// 23
> > +	"SIGXCPU",			// 24
> > +	"SIGXFSZ",			// 25
> > +	"SIGVTALRM",			// 26
> > +	"SIGPROF",			// 27
> > +	"SIGWINCH",			// 28
> > +	"SIGIO",			// 29 = SIGPOLL = SIGLOST
> > +	"SIGPWR",			// 30
> > +	"SIGSYS",			// 31 = SIGUNUSED
> > +};
> > +
> >  /*
> >   * Trap & Exception support
> >   */
> > @@ -314,10 +349,10 @@ static void show_signal_msg(int signr, struct
> > pt_regs *regs, int code,
> >  	if (!unhandled_signal(current, signr))
> >  		return;
> >
> > -	pr_info("%s[%d]: unhandled signal %d at "REG_FMT \
> > -		" nip "REG_FMT" lr "REG_FMT" code %x",
> > -		current->comm, current->pid, signr, addr,
> > -		regs->nip, regs->link, code);
> > +	pr_info("%s[%d]: %s (%d) at "REG_FMT" nip "REG_FMT \
> > +		" lr "REG_FMT" code %x",
> > +		current->comm, current->pid, signames[signr],
> > +		signr, addr, regs->nip, regs->link, code);
>
> Are we sure that signr is always within the limits of the table ?

Looking at the code, we only pass the following signals:

    SIGBUS
    SIGFPE
    SIGILL
    SIGSEGV
    SIGTRAP

All of them are within the limits of the table.  We've added other
signals for completeness.

Cheers
Murilo