armhf (fails to kexec to the crash kernel, anyway, for doc purposes) ----- vm sudo modprobe nbd sudo qemu-nbd -c /dev/nbd0 noble-server-cloudimg-armhf.img mkdir mnt sudo mount /dev/nbd0p16 mnt sudo cp mnt/vmlinuz-*-generic mnt/initrd.img-*-generic . sudo chown $USER vmlinuz-*-generic initrd.img-*-generic sudo umount mnt sudo qemu-nbd -d /dev/nbd0 sudo modprobe -r nbd qemu-system-arm \ -machine virt -cpu cortex-a15 \ \ -kernel vmlinuz-*-generic \ -initrd initrd.img-*-generic \ -append 'root=LABEL=cloudimg-rootfs crashkernel=512M' \ \ -smp cpus=2 -m 2048 \ -nodefaults -no-user-config \ -nographic -serial stdio \ \ -drive file=$DISK,if=none,id=drive0 \ -device virtio-blk,drive=drive0 \ \ -drive file=test-cidata.iso,media=cdrom \ \ -netdev user,hostfwd=::22225-:22,id=net0 \ -device virtio-net,netdev=net0 $ ssh ubuntu@127.0.0.1 -p 22225 $ lsb_release -cs No LSB modules are available. noble $ uname -m armv7l $ uname -rv 6.5.0-9-generic #9-Ubuntu SMP Fri Oct 6 23:14:49 UTC 2023 kdump-tools sudo apt update && sudo apt install -y linux-crashdump # No, Yes # kernel cmdline parameter crashkernel=512M already in qemu cmdline sudo reboot $ sudo dmesg | grep 'crashkernel' [ 0.000000] crashkernel reservation failed - No suitable area found. $ sudo cat /proc/iomem ... 40000000-bfffffff : System RAM 40308000-41dfffff : Kernel code 42000000-4230ff8f : Kernel data $ echo $(( 0x40000000 / 1024**2)) 1024 $ echo $(( (0xbfffffff + 1) / 1024 ** 2 )) 3072 Try at 2G address, i.e., crashkernel=512M@2G $ sudo dmesg | grep crashkernel [ 0.000000] Reserving 512MB of memory at 2048MB for crashkernel (System RAM: 768MB) [ 0.000000] Kernel command line: root=LABEL=cloudimg-rootfs crashkernel=512M@2G $ sudo kdump-config status current state : ready to kdump crashdump The VM never comes back from the kexec to the crashkernel; apparently it fails/oops and the panic kernel/crashkernel hits a kernel panic too! :) $ echo c | sudo tee /proc/sysrq-trigger [ 535.253829] sysrq: Trigger a crash [ 535.254672] Kernel panic - not syncing: sysrq triggered crash [ 535.255473] CPU: 0 PID: 1044 Comm: tee Kdump: loaded Not tainted 6.5.0-9-generic #9-Ubuntu [ 535.255995] Hardware name: Generic DT based system [ 535.256568] Backtrace: [ 535.257928] dump_backtrace from show_stack+0x20/0x38 [ 535.259183] r7:00000000 r6:00000000 r5:600d0093 r4:c1ab26a0 [ 535.259711] show_stack from dump_stack_lvl+0x48/0x68 [ 535.260137] dump_stack_lvl from dump_stack+0x18/0x28 [ 535.260422] r5:c2278a39 r4:c2278a24 [ 535.260801] dump_stack from panic+0x140/0x394 [ 535.261081] panic from sysrq_reset_seq_param_set+0x0/0xac [ 535.261374] r3:c0df9ec4 r2:00000000 r1:00000000 r0:c1b774c8 [ 535.261607] r7:00000000 [ 535.261741] sysrq_handle_crash from __handle_sysrq+0xc0/0x274 [ 535.262006] __handle_sysrq from write_sysrq_trigger+0x38/0x64 [ 535.262311] r10:f0c9df68 r9:00000002 r8:bed97404 r7:c4b81cc0 r6:00000000 r5:c0dfb488 [ 535.262633] r4:00000002 [ 535.262764] write_sysrq_trigger from proc_reg_write+0xcc/0x104 [ 535.263033] r5:c0dfb488 r4:c2dcfb80 [ 535.263192] proc_reg_write from vfs_write+0xc4/0x3ec [ 535.263549] r10:c428c800 r9:c0891b30 r8:c040031c r7:f0c9df68 r6:c4d7d800 r5:c4b81cc0 [ 535.264038] r4:00000002 r3:f0c9df68 [ 535.264334] vfs_write from ksys_write+0x80/0x114 [ 535.264812] r10:00000004 r9:c4d7d800 r8:c040031c r7:00000000 r6:00000000 r5:c4b81cc0 [ 535.265475] r4:c4b81cc0 [ 535.265847] ksys_write from sys_write+0x18/0x2c [ 535.266474] r7:00000004 r6:01754a00 r5:bed97404 r4:00000002 [ 535.266740] sys_write from ret_fast_syscall+0x0/0x4c [ 535.267185] Exception stack(0xf0c9dfa8 to 0xf0c9dff0) [ 535.267578] dfa0: 00000002 bed97404 00000003 bed97404 00000002 00000001 [ 535.267911] dfc0: 00000002 bed97404 01754a00 00000004 00000002 00000002 bed97404 017554b0 [ 535.268267] dfe0: 00000004 bed97350 b6ef7ca3 b6e689c6 [ 535.271397] CPU 1 will stop doing anything useful since another CPU has crashed [ 535.278326] Loading crashdump kernel... [ 535.283379] 8<--- cut here --- [ 535.285957] Unable to handle kernel NULL pointer dereference at virtual address 00000000 when write [ 535.287033] [00000000] *pgd=44b4c003, *pmd=00000000 [ 535.288477] Internal error: Oops: a06 [#1] SMP ARM [ 535.289161] Modules linked in: redboot cfi_cmdset_0001 cfi_probe cfi_util gen_probe physmap cfg80211 isofs binfmt_misc nls_iso8859_1 uio_pdrv_genirq uio drm efi_pstore dm_multipath ip_tables x_tables autofs4 btrfs blake2b_neon blake2b_generic raid10 raid456 async_raid6_recov async _memcpy async_pq async_xor async_tx xor xor_neon raid6_pq libcrc32c raid1 raid0 multipath linear gpio_keys aes_arm_bs crypto_simd cryptd [ 535.292392] CPU: 0 PID: 1044 Comm: tee Kdump: loaded Not tainted 6.5.0-9-generic #9-Ubuntu [ 535.292819] Hardware name: Generic DT based system [ 535.293136] PC is at mmiocpy+0x50/0x330 [ 535.293409] LR is at 0xa000001 [ 535.294188] pc : [] lr : [<0a000001>] psr: 800d0093 [ 535.294596] sp : f0c9dd4c ip : e3130001 fp : f0c9dd94 [ 535.294915] r10: 00000080 r9 : e4903004 r8 : 0a000014 [ 535.295226] r7 : 00000000 r6 : e3500000 r5 : e5971000 r4 : e5970004 [ 535.295590] r3 : e28f7078 r2 : ffffffe0 r1 : c0417220 r0 : 00000000 [ 535.296004] Flags: Nzcv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user [ 535.299273] Control: 30c5387d Table: 4977ca00 DAC: fffffffd [ 535.300024] Register r0 information: NULL pointer [ 535.301707] Register r1 information: non-slab/vmalloc memory [ 535.302993] Register r2 information: non-paged memory [ 535.303739] Register r3 information: non-slab/vmalloc memory [ 535.304200] Register r4 information: non-slab/vmalloc memory [ 535.304640] Register r5 information: non-slab/vmalloc memory [ 535.304968] Register r6 information: non-slab/vmalloc memory [ 535.305300] Register r7 information: NULL pointer [ 535.305618] Register r8 information: non-paged memory [ 535.305976] Register r9 information: non-slab/vmalloc memory [ 535.306304] Register r10 information: non-paged memory [ 535.306616] Register r11 information: 2-page vmalloc region starting at 0xf0c9c000 allocated at dup_task_struct+0x60/0x1b0 [ 535.307441] Register r12 information: non-slab/vmalloc memory [ 535.307786] Process tee (pid: 1044, stack limit = 0xc6f6de95) [ 535.309117] Stack: (0xf0c9dd4c to 0xf0c9e000) [ 535.309496] dd40: 00000000 00000000 00000080 c9862e00 00000000 [ 535.309888] dd60: 00000000 c0417120 00000000 c229eef0 00000000 00000000 00000000 00000063 [ 535.310345] dd80: 00000000 c174c290 f0c9ddfc f0c9dd98 c05659bc c04170b0 c1ab26a0 f0c9dd9c [ 535.310780] dda0: 00000000 ffffffc8 f0c9dd9c c229eef0 00000000 00000000 00000000 00000063 [ 535.311371] ddc0: 00000000 c174c290 f0c9dd94 f0c9dd98 f0c9dd88 c05659a8 c0563bc4 600d0093 [ 535.311851] dde0: 00000000 20d00a12 c2278a24 c2278a39 f0c9de24 f0c9de00 c1575af8 c0565930 [ 535.312193] de00: 00000000 00000000 f0c9de2c 20d00a12 f0c9de34 00000000 f0c9de44 f0c9de38 [ 535.315135] de20: c0df9ee4 c15759ac c1b774c8 00000000 00000000 c0df9ec4 f0c9de84 f0c9de48 [ 535.315727] de40: c0dfab94 c0df9ed0 c4d7d800 00000001 c4d7d800 00000004 f0c9de9c 00000002 [ 535.316266] de60: c0dfb488 00000000 c4b81cc0 bed97404 00000002 f0c9df68 f0c9de9c f0c9de88 [ 535.317159] de80: c0dfb4c0 c0dfaae0 c2dcfb80 c0dfb488 f0c9decc f0c9dea0 c0891bfc c0dfb494 [ 535.317670] dea0: f0c9df68 00000002 c4b81cc0 c4d7d800 f0c9df68 c040031c c0891b30 c428c800 [ 535.318081] dec0: f0c9df64 f0c9ded0 c07d8dfc c0891b3c 00000000 c44b2000 c44b2000 00004004 [ 535.318508] dee0: 00000000 bed97404 01000005 00000001 00000002 bed97404 00000000 00000000 [ 535.318947] df00: 00000001 00000000 c4b819c0 00000000 00000000 00000000 00000000 c08055e8 [ 535.319575] df20: c4d7d800 00000002 bed97404 bed97404 00000002 20d00a12 c4d7d800 c4b81cc0 [ 535.320082] df40: c4b81cc0 00000000 00000000 c040031c c4d7d800 00000004 f0c9df94 f0c9df68 [ 535.320523] df60: c07d93cc c07d8d44 00000000 00000000 00020241 20d00a12 00000002 bed97404 [ 535.320976] df80: 01754a00 00000004 f0c9dfa4 f0c9df98 c07d9478 c07d9358 00000000 f0c9dfa8 [ 535.321439] dfa0: c04000c0 c07d946c 00000002 bed97404 00000003 bed97404 00000002 00000001 [ 535.321904] dfc0: 00000002 bed97404 01754a00 00000004 00000002 00000002 bed97404 017554b0 [ 535.322349] dfe0: 00000004 bed97350 b6ef7ca3 b6e689c6 400d0030 00000003 00000000 00000000 [ 535.322870] Backtrace: [ 535.323110] machine_kexec from __crash_kexec+0x98/0xdc [ 535.323570] r10:c174c290 r9:00000000 r8:00000063 r7:00000000 r6:00000000 r5:00000000 [ 535.324025] r4:c229eef0 r3:00000000 [ 535.324253] __crash_kexec from panic+0x15c/0x394 [ 535.324570] r5:c2278a39 r4:c2278a24 [ 535.324798] panic from sysrq_reset_seq_param_set+0x0/0xac [ 535.325155] r3:c0df9ec4 r2:00000000 r1:00000000 r0:c1b774c8 [ 535.325505] r7:00000000 [ 535.325701] sysrq_handle_crash from __handle_sysrq+0xc0/0x274 [ 535.326062] __handle_sysrq from write_sysrq_trigger+0x38/0x64 [ 535.326457] r10:f0c9df68 r9:00000002 r8:bed97404 r7:c4b81cc0 r6:00000000 r5:c0dfb488 [ 535.326857] r4:00000002 [ 535.327042] write_sysrq_trigger from proc_reg_write+0xcc/0x104 [ 535.327400] r5:c0dfb488 r4:c2dcfb80 [ 535.327671] proc_reg_write from vfs_write+0xc4/0x3ec [ 535.328012] r10:c428c800 r9:c0891b30 r8:c040031c r7:f0c9df68 r6:c4d7d800 r5:c4b81cc0 [ 535.328447] r4:00000002 r3:f0c9df68 [ 535.328697] vfs_write from ksys_write+0x80/0x114 [ 535.329031] r10:00000004 r9:c4d7d800 r8:c040031c r7:00000000 r6:00000000 r5:c4b81cc0 [ 535.331142] r4:c4b81cc0 [ 535.331485] ksys_write from sys_write+0x18/0x2c [ 535.332102] r7:00000004 r6:01754a00 r5:bed97404 r4:00000002 [ 535.332529] sys_write from ret_fast_syscall+0x0/0x4c [ 535.332894] Exception stack(0xf0c9dfa8 to 0xf0c9dff0) [ 535.333194] dfa0: 00000002 bed97404 00000003 bed97404 00000002 00000001 [ 535.333665] dfc0: 00000002 bed97404 01754a00 00000004 00000002 00000002 bed97404 017554b0 [ 535.334132] dfe0: 00000004 bed97350 b6ef7ca3 b6e689c6 [ 535.334696] Code: f5d1f05c f5d1f07c e8b15378 e2522020 (e8a05378) [ 535.336237] ---[ end trace 0000000000000000 ]--- [ 535.336845] Kernel panic - not syncing: Fatal exception [ 535.338052] ---[ end Kernel panic - not syncing: Fatal exception ]--- ctrl-c qemu-system-arm: terminating on signal 2