On Tue, Feb 13, 2018 at 11:06 AM, Gioh Kim <gurugio@xxxxxxxxx> wrote: > On Mon, Feb 12, 2018 at 7:56 AM, Bhupesh SHARMA <bhupesh.linux@xxxxxxxxx> wrote: >> Hello, >> >> On Fri, Feb 9, 2018 at 7:24 PM, Gioh Kim <gurugio@xxxxxxxxx> wrote: >>> Hello, >>> >>> "echo c > /proc/sysrq-trigger" generates the kernel dump but it >>> reboots the system. >>> I'd like to generate kernel dump without system reboot. >>> >>> I think it is possible to jump to the kdump kernel and generate kernel >>> dump, and come back to the operating kernel with kexec. >>> I know I can jump to the kdump kernel with "kexec -e" but I cannot >>> figure out how to come back to the operating kernel. >>> >>> For example, I tried following sequences after reading kexec manual page. >>> >>> 0. rebuild kernel with CONFIG_KEXEC_JUMP option >>> 1. kexec --load=/boot/vmlinuz --initrd=/boot/initrd --reuse-cmdline >> >> Instead you should be using something like: >> # kexec -l /boot/vmlinuz-`uname -r` --initrd=/boot/initramfs-`uname >> -r`.img --reuse-cmdline --load-preserve-context --mem-min=addr >> --mem-max=addr > > Hello Bhupesh, > > Thank you for your advice. > > I tried load-preserve-context as below but it failed with "Invalid > argument" error. > There is no reason in the error message. > But there is entry address that looks like the address "kexec -e" in > the kdump kernel will jump to. > Following is what I did. > > root@pserver:~# kexec -l /boot/vmlinuz-`uname -r` > --initrd=/boot/initrd.img-`uname -r` --reuse-cmdline > --load-preserve-context --mem-min=0x1000000 --mem-max=0xffffffff > kexec_load failed: Invalid argument > entry = 0xbffcb7f0 flags = 0x3e0002 > nr_segments = 7 > segment[0].buf = (nil) > segment[0].bufsz = 0x0 > segment[0].mem = 0x1000000 > segment[0].memsz = 0xba080000 > segment[1].buf = 0x7fe372eaa010 > segment[1].bufsz = 0x2f7fddc > segment[1].mem = 0xbb080000 > segment[1].memsz = 0x2f80000 > segment[2].buf = 0x7fe375e2e210 > segment[2].bufsz = 0x61c840 > segment[2].mem = 0xbe000000 > segment[2].memsz = 0x14e1000 > segment[3].buf = (nil) > segment[3].bufsz = 0x0 > segment[3].mem = 0xbf4e1000 > segment[3].memsz = 0xae5000 > segment[4].buf = 0x25eb920 > segment[4].bufsz = 0x42c6 > segment[4].mem = 0xbffc6000 > segment[4].memsz = 0x5000 > segment[5].buf = 0x25e27c0 > segment[5].bufsz = 0x9100 > segment[5].mem = 0xbffcb000 > segment[5].memsz = 0xb000 > segment[6].buf = 0x25e1e20 > segment[6].bufsz = 0x400 > segment[6].mem = 0xbffd6000 > segment[6].memsz = 0x4000 > root@pserver:~# > root@pserver:~# > root@pserver:~# kexec -e > Nothing has been loaded! > I'm sorry to bother you. I failed because I booted up wrong kernel without KEXEC_JUMP. I can jump to kdump kernel with booting a kernel with KEXEC_JUMP. And I can see "kexec_jump_back_entry=0x00000000000810d2" at kernel booting parameter. Now I can jump to kdump kernel and jump back to the original kernel. Can I ask just one more question? After jumping to kdump kernel, there is not /proc/vmcore file. I checked the kernel enabled CONFIG_PROC_VMCORE option. What kernel option should I enable to use /proc/vmcore? Or should I use another file instead /proc/vmcore? -- Best regards, Gioh Kim _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
