Santosh Sivaraj's on July 2, 2019 3:19 pm: > From: Reza Arbab <ar...@linux.ibm.com> > > Testing my memcpy_mcsafe() work in progress with an injected UE, I get > an error like this immediately after the function returns: > > BUG: Unable to handle kernel data access at 0x7fff84dec8f8 > Faulting instruction address: 0xc0080000009c00b0 > Oops: Kernel access of bad area, sig: 11 [#1] > LE PAGE_SIZE=64K MMU=Radix MMU=Hash SMP NR_CPUS=2048 NUMA PowerNV > Modules linked in: mce(O+) vmx_crypto crc32c_vpmsum > CPU: 0 PID: 1375 Comm: modprobe Tainted: G O 5.1.0-rc6 #267 > NIP: c0080000009c00b0 LR: c0080000009c00a8 CTR: c000000000095f90 > REGS: c0000000ee197790 TRAP: 0300 Tainted: G O (5.1.0-rc6) > MSR: 900000000280b033 <SF,HV,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 88002826 > XER: 00040000 > CFAR: c000000000095f8c DAR: 00007fff84dec8f8 DSISR: 40000000 IRQMASK: 0 > GPR00: 000000006c6c6568 c0000000ee197a20 c0080000009c8400 fffffffffffffff2 > GPR04: c0080000009c02e0 0000000000000006 0000000000000000 c000000003c834c8 > GPR08: 0080000000000000 776a6681b7fb5100 0000000000000000 c0080000009c01c8 > GPR12: c000000000095f90 00007fff84debc00 000000004d071440 0000000000000000 > GPR16: 0000000100000601 c0080000009e0000 c000000000c98dd8 c000000000c98d98 > GPR20: c000000003bba970 c0080000009c04d0 c0080000009c0618 c0000000001e5820 > GPR24: 0000000000000000 0000000000000100 0000000000000001 c000000003bba958 > GPR28: c0080000009c02e8 c0080000009c0318 c0080000009c02e0 0000000000000000 > NIP [c0080000009c00b0] cause_ue+0xa8/0xe8 [mce] > LR [c0080000009c00a8] cause_ue+0xa0/0xe8 [mce] > > To fix, ensure that r13 is properly restored after an MCE. > > This commit is needed for testing this series, this is a possible simulator > bug.
This introduces a bug, of course -- MCE occurring when r13 != PACA will corrupt r13. > --- > arch/powerpc/kernel/exceptions-64s.S | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/powerpc/kernel/exceptions-64s.S > b/arch/powerpc/kernel/exceptions-64s.S > index 311f1392a2ec..932d8d05892c 100644 > --- a/arch/powerpc/kernel/exceptions-64s.S > +++ b/arch/powerpc/kernel/exceptions-64s.S > @@ -265,6 +265,7 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_HVMODE) > EXC_REAL_END(machine_check, 0x200, 0x100) > EXC_VIRT_NONE(0x4200, 0x100) > TRAMP_REAL_BEGIN(machine_check_common_early) > + SET_SCRATCH0(r13) /* save r13 */ > EXCEPTION_PROLOG_1(PACA_EXMC, NOTEST, 0x200) > /* > * Register contents: > -- > 2.20.1 > >
