Re: [PATCH V7 04/10] arm64: exception: handle Synchronous External Abort

["Baicar, Tyler" <tbaicar@xxxxxxxxxxxxxx>]

On 1/17/2017 3:23 AM, James Morse wrote:
> Hi Tyler,
>
> On 16/01/17 11:53, Will Deacon wrote:
> > On Thu, Jan 12, 2017 at 11:15:18AM -0700, Tyler Baicar wrote:
> > > SEA exceptions are often caused by an uncorrected hardware
> > > error, and are handled when data abort and instruction abort
> > > exception classes have specific values for their Fault Status
> > > Code.
> > > When SEA occurs, before killing the process, go through
> > > the handlers registered in the notification list.
> > > Update fault_info[] with specific SEA faults so that the
> > > new SEA handler is used.
> > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> > > index 05d2bd7..81039c7 100644
> > > --- a/arch/arm64/mm/fault.c
> > > +++ b/arch/arm64/mm/fault.c
> > > @@ -480,6 +496,28 @@ static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> > >   	return 1;
> > >   }
> > >   
> > > +/*
> > > + * This abort handler deals with Synchronous External Abort.
> > > + * It calls notifiers, and then returns "fault".
> > > + */
> > > +static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> > > +{
> > > +	struct siginfo info;
> > > +
> > > +	atomic_notifier_call_chain(&sea_handler_chain, 0, NULL);
> > > +
> > > +	pr_err("Synchronous External Abort: %s (0x%08x) at 0x%016lx\n",
> > > +		 fault_name(esr), esr, addr);
> > > +
> > > +	info.si_signo = SIGBUS;
> > > +	info.si_errno = 0;
> > > +	info.si_code  = 0;
> > > +	info.si_addr  = (void __user *)addr;
> > > +	arm64_notify_die("", regs, &info, esr);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >   static const struct fault_info {
> > >   	int	(*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs);
> > >   	int	sig;
> > > @@ -502,22 +540,22 @@ static const struct fault_info {
> > >   	{ do_page_fault,	SIGSEGV, SEGV_ACCERR,	"level 1 permission fault"	},
> > >   	{ do_page_fault,	SIGSEGV, SEGV_ACCERR,	"level 2 permission fault"	},
> > >   	{ do_page_fault,	SIGSEGV, SEGV_ACCERR,	"level 3 permission fault"	},
> > > -	{ do_bad,		SIGBUS,  0,		"synchronous external abort"	},
> > > +	{ do_sea,		SIGBUS,  0,		"synchronous external abort"	},
> > >   	{ do_bad,		SIGBUS,  0,		"unknown 17"			},
> > >   	{ do_bad,		SIGBUS,  0,		"unknown 18"			},
> > >   	{ do_bad,		SIGBUS,  0,		"unknown 19"			},
> > > -	{ do_bad,		SIGBUS,  0,		"synchronous abort (translation table walk)" },
> > > -	{ do_bad,		SIGBUS,  0,		"synchronous abort (translation table walk)" },
> > > -	{ do_bad,		SIGBUS,  0,		"synchronous abort (translation table walk)" },
> > > -	{ do_bad,		SIGBUS,  0,		"synchronous abort (translation table walk)" },
> > > -	{ do_bad,		SIGBUS,  0,		"synchronous parity error"	},
> > > +	{ do_sea,		SIGBUS,  0,		"level 0 SEA (translation table walk)"	},
> > > +	{ do_sea,		SIGBUS,  0,		"level 1 SEA (translation table walk)"	},
> > > +	{ do_sea,		SIGBUS,  0,		"level 2 SEA (translation table walk)"	},
> > > +	{ do_sea,		SIGBUS,  0,		"level 3 SEA (translation table walk)"	},
> > Perhaps I wasn't clear enough in my previous review, but please expand the
> > acronym for strings and comments.
>
> The 'SEA' in this user-string doesn't add anything. Now that these use do_sea()
> instead of do_bad(), when they are printed won't it be:
> > Synchronous External Abort: level 3 SEA (translation table walk) (...) at ....

Good point, yes they will:

+	pr_err("Synchronous External Abort: %s (0x%08x) at 0x%016lx\n",
+		 fault_name(esr), esr, addr);

I can just remove SEA here then.

Thanks,
Tyler


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