Re: [Crash-utility] [PATCH v2] Fix for "bt" command prints a bogus warning

Currently, the "bt" command may print a bogus exception frame and the remaining frame will be truncated on x86 64 when using the "virsh send-key <kvm guest> KEY_LEFTALT KEY_SYSRQ KEY_C" command to trigger a panic from the KVM host. For example: crash> bt PID: 0 TASK: ffff9e7a47e32f00 CPU: 3 COMMAND: "swapper/3" #0 [ffffba7900118bb8] machine_kexec at ffffffff87e5c2c7 #1 [ffffba7900118c08] __crash_kexec at ffffffff87f9500d #2 [ffffba7900118cd0] panic at ffffffff87edfff9 #3 [ffffba7900118d50] sysrq_handle_crash at ffffffff883ce2c1 #4 [ffffba7900118d58] __handle_sysrq.cold.15 at ffffffff883ceb56 #5 [ffffba7900118d88] sysrq_filter at ffffffff883ce9a2 #6 [ffffba7900118dc0] input_to_handler at ffffffff884fb0bf #7 [ffffba7900118df8] input_pass_values at ffffffff884fc1b7 #8 [ffffba7900118e20] input_handle_event at ffffffff884fe278 #9 [ffffba7900118e50] input_event at ffffffff884fe74b #10 [ffffba7900118e88] atkbd_interrupt at ffffffff88504e2f #11 [ffffba7900118ee0] serio_interrupt at ffffffff884f7516 #12 [ffffba7900118f10] i8042_interrupt at ffffffff884f8b04 #13 [ffffba7900118f50] __handle_irq_event_percpu at ffffffff87f51430 #14 [ffffba7900118f90] handle_irq_event_percpu at ffffffff87f51590 #15 [ffffba7900118fb8] handle_irq_event at ffffffff87f51616 #16 [ffffba7900118fd8] handle_edge_irq at ffffffff87f559f2 #17 [ffffba7900118ff0] asm_call_on_stack at ffffffff88800fa2 --- <IRQ stack> --- #18 [ffffba790008bda0] asm_call_on_stack at ffffffff88800fa2 RIP: ffffffffffffffff RSP: 0000000000000124 RFLAGS: 00000003 RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000 RDX: ffffffff88800c1e RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000001 R8: 0000000000000000 R9: 0000000000000000 R10: 0000000000000000 R11: ffffffff88760555 R12: ffffba790008be08 R13: ffffffff87f18002 R14: ffff9e7a47e32f00 R15: ffff9e7bb6198e00 ORIG_RAX: 0000000000000000 CS: 0003 SS: 0000 bt: WARNING: possibly bogus exception frame crash> The following related kernel commits cause the current issue, crash needs to adjust the value of irq eframe. Related kernel commits: [1] v5.8: 931b94145981 ("x86/entry: Provide helpers for executing on the irqstack") [2] v5.8: fa5e5c409213 ("x86/entry: Use idtentry for interrupts") [3] v5.12: 52d743f3b712 ("x86/softirq: Remove indirection in do_softirq_own_stack()") Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com&gt; Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; --- x86_64.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/x86_64.c b/x86_64.c index 7a5d6f050c89..5b671bd97775 100644 --- a/x86_64.c +++ b/x86_64.c @@ -3938,6 +3938,11 @@ in_exception_stack: if (irq_eframe) { bt->flags |= BT_EXCEPTION_FRAME; i = (irq_eframe - bt->stackbase)/sizeof(ulong); + if (symbol_exists("asm_common_interrupt")) { + i -= 1; + up = (ulong *)(&bt->stackbuf[i*sizeof(ulong)]); + bt->instptr = *up; + } x86_64_print_stack_entry(bt, ofp, level, i, bt->instptr); bt->flags &= ~(ulonglong)BT_EXCEPTION_FRAME; cs = x86_64_exception_frame(EFRAME_PRINT|EFRAME_CS, 0, @@ -6521,6 +6526,14 @@ x86_64_irq_eframe_link_init(void) else return; + if (symbol_exists("asm_common_interrupt")) { + if (symbol_exists("asm_call_on_stack")) + machdep->machspec->irq_eframe_link = -64; + else + machdep->machspec->irq_eframe_link = -32; + return; + } + if (THIS_KERNEL_VERSION < LINUX(2,6,9)) return;