On Mon, Oct 29, 2018 at 02:20:51PM +0000, Wiebe, Wladislav (Nokia - DE/Ulm) wrote: > When running into situations like: > "Unhandled fault: synchronous external abort (0x210) at 0xXXX" > or > "Unhandled prefetch abort: synchronous external abort (0x210) at 0xXXX" > it is useful to know the content of ADFSR (Auxiliary Data Fault Status > Register) to indicate an ECC double-bit error in L1 or L2 cache. > > Refer to: > Cortex-A15 Technical Reference Manual, Revision: r2p1 > [6.4.8. Error Correction Code] > > Signed-off-by: Wladislav Wiebe <[email protected]> > --- > arch/arm/mm/fault.c | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c > index 3232afb6fdc0..5e240deb6ed6 100644 > --- a/arch/arm/mm/fault.c > +++ b/arch/arm/mm/fault.c > @@ -547,6 +547,22 @@ hook_fault_code(int nr, int (*fn)(unsigned long, > unsigned int, struct pt_regs *) > fsr_info[nr].name = name; > } > > +/* > + * Check for ECC double-bit errors in Auxiliary Data Fault Status Register > + */ > +static void check_adfsr_for_ecc(void) > +{ > + u32 adfsr = 0; > + > + asm("mrc p15, 0, %0, c5, c1, 0" : "=r" (adfsr)); > + > + if (adfsr & (BIT(31) | BIT(23))) { > + pr_alert("ADFSR status 0x%x indicates that an L1 or L2 cache\n" > + "ECC double-bit error occurred at some time.\n", > + adfsr); > + } > +} > + > /* > * Dispatch a data abort to the relevant handler. > */ > @@ -559,6 +575,7 @@ do_DataAbort(unsigned long addr, unsigned int fsr, struct > pt_regs *regs) > if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs)) > return; > > + check_adfsr_for_ecc(); > pr_alert("Unhandled fault: %s (0x%03x) at 0x%08lx\n", > inf->name, fsr, addr); > show_pte(current->mm, addr); > @@ -593,6 +610,7 @@ do_PrefetchAbort(unsigned long addr, unsigned int ifsr, > struct pt_regs *regs) > if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs)) > return; > > + check_adfsr_for_ecc(); > pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n", > inf->name, ifsr, addr);
IIUC at this point the task is preemptible (and interruptible), so I believe this is too late to snapshot the ADFSR. The task could have been migrated to a different core, with an irrelavant ADFSR, or a fault could have occured within an interrupt handler, etc. Thanks, Mark.
