Joakim Tjernlund <joakim.tjernl...@infinera.com> writes:
> Embedded PPC CPU should send SIGBUS to user space when applicable.
Yeah, but it's not clear that it's applicable in all cases.
At least I need some reasoning for why it's safe in all cases below to
just send a SIGBUS and take no other action.
Is there a particular CPU you're working on? Can we start with that and
look at all the machine check causes and which can be safely handled.
Some comments below ...
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index 0381242920d9..12715d24141c 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -621,6 +621,11 @@ int machine_check_e500mc(struct pt_regs *regs)
At the beginning of the function we have:
printk("Machine check in kernel mode.\n");
Which should be updated.
> reason & MCSR_MEA ? "Effective" : "Physical", addr);
> }
>
> + if ((user_mode(regs))) {
> + _exception(SIGBUS, regs, reason, regs->nip);
> + recoverable = 1;
> + }
For most of the error causes we take no action and set recoverable = 0.
Then you just declare that it is recoverable because it hit in
userspace. Depending on the cause that might be OK, but it's not
obviously correct in all cases.
> +
> silent_out:
> mtspr(SPRN_MCSR, mcsr);
> return mfspr(SPRN_MCSR) == 0 && recoverable;
> @@ -665,6 +670,10 @@ int machine_check_e500(struct pt_regs *regs)
Same comment about the printk().
> if (reason & MCSR_BUS_RPERR)
> printk("Bus - Read Parity Error\n");
>
> + if ((user_mode(regs))) {
> + _exception(SIGBUS, regs, reason, regs->nip);
> + return 1;
> + }
And same comment more or less.
Other than the MCSR_BUS_RBERR cases that are explicitly checked, the
function does nothing to clear the cause of the machine check.
> return 0;
> }
>
> @@ -695,6 +704,10 @@ int machine_check_e200(struct pt_regs *regs)
> if (reason & MCSR_BUS_WRERR)
> printk("Bus - Write Bus Error on buffered store or cache line
> push\n");
>
> + if ((user_mode(regs))) {
> + _exception(SIGBUS, regs, reason, regs->nip);
> + return 1;
> + }
Same.
> return 0;
> }
> #elif defined(CONFIG_PPC32)
> @@ -731,6 +744,10 @@ int machine_check_generic(struct pt_regs *regs)
> default:
> printk("Unknown values in msr\n");
> }
> + if ((user_mode(regs))) {
> + _exception(SIGBUS, regs, reason, regs->nip);
> + return 1;
> + }
Same.
> return 0;
> }
> #endif /* everything else */
> --
> 2.26.2
cheers
