projects / linux-2.6-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 7d4c738c | 1 | The s390 SCSI dump tool (zfcpdump) |
| 411ed322 MH |
2 | |
| 3 | System z machines (z900 or higher) provide hardware support for creating system | |
| 4 | dumps on SCSI disks. The dump process is initiated by booting a dump tool, which | |
| 5 | has to create a dump of the current (probably crashed) Linux image. In order to | |
| 6 | not overwrite memory of the crashed Linux with data of the dump tool, the | |
| 7d4c738c | 7 | hardware saves some memory plus the register sets of the boot CPU before the |
| 411ed322 MH |
8 | dump tool is loaded. There exists an SCLP hardware interface to obtain the saved |
| 9 | memory afterwards. Currently 32 MB are saved. | |
| 10 | ||
| 11 | This zfcpdump implementation consists of a Linux dump kernel together with | |
| 7d4c738c | 12 | a user space dump tool, which are loaded together into the saved memory region |
| 411ed322 MH |
13 | below 32 MB. zfcpdump is installed on a SCSI disk using zipl (as contained in |
| 14 | the s390-tools package) to make the device bootable. The operator of a Linux | |
| 15 | system can then trigger a SCSI dump by booting the SCSI disk, where zfcpdump | |
| 16 | resides on. | |
| 17 | ||
| ffa52d02 MS |
18 | The user space dump tool accesses the memory of the crashed system by means |
| 19 | of the /proc/vmcore interface. This interface exports the crashed system's | |
| 20 | memory and registers in ELF core dump format. To access the memory which has | |
| 21 | been saved by the hardware SCLP requests will be created at the time the data | |
| 22 | is needed by /proc/vmcore. The tail part of the crashed systems memory which | |
| 23 | has not been stashed by hardware can just be copied from real memory. | |
| 24 | ||
| 25 | To build a dump enabled kernel the kernel config option CONFIG_CRASH_DUMP | |
| 26 | has to be set. | |
| 411ed322 | 27 | |
| 7d4c738c | 28 | To get a valid zfcpdump kernel configuration use "make zfcpdump_defconfig". |
| 411ed322 | 29 | |
| 7d4c738c MH |
30 | The s390 zipl tool looks for the zfcpdump kernel and optional initrd/initramfs |
| 31 | under the following locations: | |
| 411ed322 | 32 | |
| 7d4c738c MH |
33 | * kernel: <zfcpdump directory>/zfcpdump.image |
| 34 | * ramdisk: <zfcpdump directory>/zfcpdump.rd | |
| 411ed322 | 35 | |
| 7d4c738c | 36 | The zfcpdump directory is defined in the s390-tools package. |
| 411ed322 | 37 | |
| 7d4c738c MH |
38 | The user space application of zfcpdump can reside in an intitramfs or an |
| 39 | initrd. It can also be included in a built-in kernel initramfs. The application | |
| 40 | reads from /proc/vmcore or zcore/mem and writes the system dump to a SCSI disk. | |
| 411ed322 | 41 | |
| 7d4c738c MH |
42 | The s390-tools package version 1.24.0 and above builds an external zfcpdump |
| 43 | initramfs with a user space application that writes the dump to a SCSI | |
| 44 | partition. | |
| 411ed322 MH |
45 | |
| 46 | For more information on how to use zfcpdump refer to the s390 'Using the Dump | |
| 47 | Tools book', which is available from | |
| 48 | http://www.ibm.com/developerworks/linux/linux390. |