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powerpc: Improve ppc_save_regs()
authorNicholas Piggin <npiggin@gmail.com>
Fri, 3 Apr 2020 13:10:05 +0000 (23:10 +1000)
committerMichael Ellerman <mpe@ellerman.id.au>
Sat, 4 Apr 2020 10:40:57 +0000 (21:40 +1100)
Make ppc_save_regs() a bit more useful:
  - Set NIP to our caller rather rather than the caller's
    caller (which is what we save to LR in the stack frame).
  - Set SOFTE to the current irq soft-mask state rather than
    uninitialised.
  - Zero CFAR rather than leave it uninitialised.

In qemu, injecting a nmi to an idle CPU gives a nicer stack
trace (note NIP, IRQMASK, CFAR).

  Oops: System Reset, sig: 6 [#1]
  LE PAGE_SIZE=64K MMU=Hash PREEMPT SMP NR_CPUS=2048 NUMA PowerNV
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0-rc2-00429-ga76e38fd80bf #1277
  NIP:  c0000000000b6e5c LR: c0000000000b6e5c CTR: c000000000b06270
  REGS: c00000000173fb08 TRAP: 0100   Not tainted
  MSR:  9000000000001033 <SF,HV,ME,IR,DR,RI,LE>  CR: 28000224  XER: 00000000
  CFAR: c0000000016a2128 IRQMASK: c00000000173fc80
  GPR00: c0000000000b6e5c c00000000173fc80 c000000001743400 c00000000173fb08
  GPR04: 0000000000000000 0000000000000000 0000000000000008 0000000000000001
  GPR08: 00000001fea80000 0000000000000000 0000000000000000 ffffffffffffffff
  GPR12: c000000000b06270 c000000001930000 00000000300026c0 0000000000000000
  GPR16: 0000000000000000 0000000000000000 0000000000000003 c0000000016a2128
  GPR20: c0000001ffc97148 0000000000000001 c000000000f289a8 0000000000080000
  GPR24: c0000000016e1480 000000011dc870ba 0000000000000000 0000000000000003
  GPR28: c0000000016a2128 c0000001ffc97148 c0000000016a2260 0000000000000003
  NIP [c0000000000b6e5c] power9_idle_type+0x5c/0x70
  LR [c0000000000b6e5c] power9_idle_type+0x5c/0x70
  Call Trace:
  [c00000000173fc80] [c0000000000b6e5c] power9_idle_type+0x5c/0x70 (unreliable)
  [c00000000173fcb0] [c000000000b062b0] stop_loop+0x40/0x60
  [c00000000173fce0] [c000000000b022d8] cpuidle_enter_state+0xa8/0x660
  [c00000000173fd60] [c000000000b0292c] cpuidle_enter+0x4c/0x70
  [c00000000173fda0] [c00000000017624c] call_cpuidle+0x4c/0x90
  [c00000000173fdc0] [c000000000176768] do_idle+0x338/0x460
  [c00000000173fe60] [c000000000176b3c] cpu_startup_entry+0x3c/0x40
  [c00000000173fe90] [c0000000000126b4] rest_init+0x124/0x140
  [c00000000173fed0] [c0000000010948d4] start_kernel+0x938/0x988
  [c00000000173ff90] [c00000000000cdcc] start_here_common+0x1c/0x20

  Oops: System Reset, sig: 6 [#1]
  LE PAGE_SIZE=64K MMU=Hash PREEMPT SMP NR_CPUS=2048 NUMA PowerNV
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0-rc2-00430-gddce91b8712f #1278
  NIP:  c00000000001d150 LR: c0000000000b6e5c CTR: c000000000b06270
  REGS: c00000000173fb08 TRAP: 0100   Not tainted
  MSR:  9000000000001033 <SF,HV,ME,IR,DR,RI,LE>  CR: 28000224  XER: 00000000
  CFAR: 0000000000000000 IRQMASK: 1
  GPR00: c0000000000b6e5c c00000000173fc80 c000000001743400 c00000000173fb08
  GPR04: 0000000000000000 0000000000000000 0000000000000008 0000000000000001
  GPR08: 00000001fea80000 0000000000000000 0000000000000000 ffffffffffffffff
  GPR12: c000000000b06270 c000000001930000 00000000300026c0 0000000000000000
  GPR16: 0000000000000000 0000000000000000 0000000000000003 c0000000016a2128
  GPR20: c0000001ffc97148 0000000000000001 c000000000f289a8 0000000000080000
  GPR24: c0000000016e1480 00000000b68db8ce 0000000000000000 0000000000000003
  GPR28: c0000000016a2128 c0000001ffc97148 c0000000016a2260 0000000000000003
  NIP [c00000000001d150] replay_system_reset+0x30/0xa0
  LR [c0000000000b6e5c] power9_idle_type+0x5c/0x70
  Call Trace:
  [c00000000173fc80] [c0000000000b6e5c] power9_idle_type+0x5c/0x70 (unreliable)
  [c00000000173fcb0] [c000000000b062b0] stop_loop+0x40/0x60
  [c00000000173fce0] [c000000000b022d8] cpuidle_enter_state+0xa8/0x660
  [c00000000173fd60] [c000000000b0292c] cpuidle_enter+0x4c/0x70
  [c00000000173fda0] [c00000000017624c] call_cpuidle+0x4c/0x90
  [c00000000173fdc0] [c000000000176768] do_idle+0x338/0x460
  [c00000000173fe60] [c000000000176b38] cpu_startup_entry+0x38/0x40
  [c00000000173fe90] [c0000000000126b4] rest_init+0x124/0x140
  [c00000000173fed0] [c0000000010948d4] start_kernel+0x938/0x988
  [c00000000173ff90] [c00000000000cdcc] start_here_common+0x1c/0x20

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200403131006.123243-1-npiggin@gmail.com
arch/powerpc/kernel/ppc_save_regs.S patch | blob | blame | history

diff --git a/arch/powerpc/kernel/ppc_save_regs.S b/arch/powerpc/kernel/ppc_save_regs.S
index f3bd0bbf2ae808748c14d77b8283993ed5d075ec..2d4d21bb46a97e78605d1645e0b2da8e6a5080fe 100644 (file)
--- a/arch/powerpc/kernel/ppc_save_regs.S
+++ b/arch/powerpc/kernel/ppc_save_regs.S
@@ -55,14 +55,17 @@ _GLOBAL(ppc_save_regs)
        PPC_STL r29,29*SZL(r3)
        PPC_STL r30,30*SZL(r3)
        PPC_STL r31,31*SZL(r3)
+       lbz     r0,PACAIRQSOFTMASK(r13)
+       PPC_STL r0,SOFTE-STACK_FRAME_OVERHEAD(r3)
 #endif
        /* go up one stack frame for SP */
        PPC_LL  r4,0(r1)
        PPC_STL r4,1*SZL(r3)
        /* get caller's LR */
        PPC_LL  r0,LRSAVE(r4)
-       PPC_STL r0,_NIP-STACK_FRAME_OVERHEAD(r3)
        PPC_STL r0,_LINK-STACK_FRAME_OVERHEAD(r3)
+       mflr    r0
+       PPC_STL r0,_NIP-STACK_FRAME_OVERHEAD(r3)
        mfmsr   r0
        PPC_STL r0,_MSR-STACK_FRAME_OVERHEAD(r3)
        mfctr   r0
@@ -73,4 +76,5 @@ _GLOBAL(ppc_save_regs)
        PPC_STL r0,_CCR-STACK_FRAME_OVERHEAD(r3)
        li      r0,0
        PPC_STL r0,_TRAP-STACK_FRAME_OVERHEAD(r3)
+       PPC_STL r0,ORIG_GPR3-STACK_FRAME_OVERHEAD(r3)
        blr
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