^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) ================================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) Documentation for Kdump - The kexec-based Crash Dumping Solution
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) ================================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) This document includes overview, setup and installation, and analysis
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6) information.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) Overview
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) ========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) Kdump uses kexec to quickly boot to a dump-capture kernel whenever a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) dump of the system kernel's memory needs to be taken (for example, when
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) the system panics). The system kernel's memory image is preserved across
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) the reboot and is accessible to the dump-capture kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) You can use common commands, such as cp and scp, to copy the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) memory image to a dump file on the local disk, or across the network to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) a remote system.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) Kdump and kexec are currently supported on the x86, x86_64, ppc64, ia64,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) s390x, arm and arm64 architectures.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) When the system kernel boots, it reserves a small section of memory for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) the dump-capture kernel. This ensures that ongoing Direct Memory Access
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) (DMA) from the system kernel does not corrupt the dump-capture kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) The kexec -p command loads the dump-capture kernel into this reserved
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) memory.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) On x86 machines, the first 640 KB of physical memory is needed to boot,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) regardless of where the kernel loads. Therefore, kexec backs up this
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) region just before rebooting into the dump-capture kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) Similarly on PPC64 machines first 32KB of physical memory is needed for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) booting regardless of where the kernel is loaded and to support 64K page
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) size kexec backs up the first 64KB memory.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) For s390x, when kdump is triggered, the crashkernel region is exchanged
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) with the region [0, crashkernel region size] and then the kdump kernel
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) runs in [0, crashkernel region size]. Therefore no relocatable kernel is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) needed for s390x.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) All of the necessary information about the system kernel's core image is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) encoded in the ELF format, and stored in a reserved area of memory
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) before a crash. The physical address of the start of the ELF header is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) passed to the dump-capture kernel through the elfcorehdr= boot
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) parameter. Optionally the size of the ELF header can also be passed
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) when using the elfcorehdr=[size[KMG]@]offset[KMG] syntax.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) With the dump-capture kernel, you can access the memory image through
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) /proc/vmcore. This exports the dump as an ELF-format file that you can
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) write out using file copy commands such as cp or scp. Further, you can
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) use analysis tools such as the GNU Debugger (GDB) and the Crash tool to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) debug the dump file. This method ensures that the dump pages are correctly
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) ordered.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) Setup and Installation
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) ======================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) Install kexec-tools
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) -------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) 1) Login as the root user.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) 2) Download the kexec-tools user-space package from the following URL:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) http://kernel.org/pub/linux/utils/kernel/kexec/kexec-tools.tar.gz
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) This is a symlink to the latest version.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) The latest kexec-tools git tree is available at:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) - git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75) - http://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) There is also a gitweb interface available at
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) http://www.kernel.org/git/?p=utils/kernel/kexec/kexec-tools.git
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) More information about kexec-tools can be found at
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) http://horms.net/projects/kexec/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) 3) Unpack the tarball with the tar command, as follows::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) tar xvpzf kexec-tools.tar.gz
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) 4) Change to the kexec-tools directory, as follows::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) cd kexec-tools-VERSION
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) 5) Configure the package, as follows::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) ./configure
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) 6) Compile the package, as follows::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) make
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99) 7) Install the package, as follows::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) make install
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) Build the system and dump-capture kernels
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) -----------------------------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) There are two possible methods of using Kdump.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) 1) Build a separate custom dump-capture kernel for capturing the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) kernel core dump.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) 2) Or use the system kernel binary itself as dump-capture kernel and there is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) no need to build a separate dump-capture kernel. This is possible
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) only with the architectures which support a relocatable kernel. As
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) of today, i386, x86_64, ppc64, ia64, arm and arm64 architectures support
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) relocatable kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) Building a relocatable kernel is advantageous from the point of view that
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118) one does not have to build a second kernel for capturing the dump. But
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) at the same time one might want to build a custom dump capture kernel
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) suitable to his needs.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) Following are the configuration setting required for system and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) dump-capture kernels for enabling kdump support.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) System kernel config options
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126) ----------------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) 1) Enable "kexec system call" in "Processor type and features."::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) CONFIG_KEXEC=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132) 2) Enable "sysfs file system support" in "Filesystem" -> "Pseudo
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) filesystems." This is usually enabled by default::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) CONFIG_SYSFS=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) Note that "sysfs file system support" might not appear in the "Pseudo
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138) filesystems" menu if "Configure standard kernel features (for small
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) systems)" is not enabled in "General Setup." In this case, check the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140) .config file itself to ensure that sysfs is turned on, as follows::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142) grep 'CONFIG_SYSFS' .config
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144) 3) Enable "Compile the kernel with debug info" in "Kernel hacking."::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146) CONFIG_DEBUG_INFO=Y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148) This causes the kernel to be built with debug symbols. The dump
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149) analysis tools require a vmlinux with debug symbols in order to read
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) and analyze a dump file.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152) Dump-capture kernel config options (Arch Independent)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153) -----------------------------------------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) 1) Enable "kernel crash dumps" support under "Processor type and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156) features"::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158) CONFIG_CRASH_DUMP=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160) 2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems"::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162) CONFIG_PROC_VMCORE=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164) (CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166) Dump-capture kernel config options (Arch Dependent, i386 and x86_64)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167) --------------------------------------------------------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169) 1) On i386, enable high memory support under "Processor type and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170) features"::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172) CONFIG_HIGHMEM64G=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) or::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176) CONFIG_HIGHMEM4G
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178) 2) On i386 and x86_64, disable symmetric multi-processing support
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179) under "Processor type and features"::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181) CONFIG_SMP=n
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183) (If CONFIG_SMP=y, then specify maxcpus=1 on the kernel command line
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) when loading the dump-capture kernel, see section "Load the Dump-capture
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185) Kernel".)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 187) 3) If one wants to build and use a relocatable kernel,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 188) Enable "Build a relocatable kernel" support under "Processor type and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 189) features"::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 190)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 191) CONFIG_RELOCATABLE=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 192)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 193) 4) Use a suitable value for "Physical address where the kernel is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 194) loaded" (under "Processor type and features"). This only appears when
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 195) "kernel crash dumps" is enabled. A suitable value depends upon
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 196) whether kernel is relocatable or not.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 197)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 198) If you are using a relocatable kernel use CONFIG_PHYSICAL_START=0x100000
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 199) This will compile the kernel for physical address 1MB, but given the fact
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 200) kernel is relocatable, it can be run from any physical address hence
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 201) kexec boot loader will load it in memory region reserved for dump-capture
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 202) kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 203)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 204) Otherwise it should be the start of memory region reserved for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 205) second kernel using boot parameter "crashkernel=Y@X". Here X is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 206) start of memory region reserved for dump-capture kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 207) Generally X is 16MB (0x1000000). So you can set
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 208) CONFIG_PHYSICAL_START=0x1000000
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 209)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 210) 5) Make and install the kernel and its modules. DO NOT add this kernel
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 211) to the boot loader configuration files.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 212)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 213) Dump-capture kernel config options (Arch Dependent, ppc64)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 214) ----------------------------------------------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 215)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 216) 1) Enable "Build a kdump crash kernel" support under "Kernel" options::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 217)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 218) CONFIG_CRASH_DUMP=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 219)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 220) 2) Enable "Build a relocatable kernel" support::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 221)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 222) CONFIG_RELOCATABLE=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 223)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 224) Make and install the kernel and its modules.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 225)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 226) Dump-capture kernel config options (Arch Dependent, ia64)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 227) ----------------------------------------------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 228)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 229) - No specific options are required to create a dump-capture kernel
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 230) for ia64, other than those specified in the arch independent section
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 231) above. This means that it is possible to use the system kernel
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 232) as a dump-capture kernel if desired.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 233)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 234) The crashkernel region can be automatically placed by the system
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 235) kernel at run time. This is done by specifying the base address as 0,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 236) or omitting it all together::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 237)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 238) crashkernel=256M@0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 239)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 240) or::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 241)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 242) crashkernel=256M
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 243)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 244) If the start address is specified, note that the start address of the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 245) kernel will be aligned to 64Mb, so if the start address is not then
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 246) any space below the alignment point will be wasted.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 247)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 248) Dump-capture kernel config options (Arch Dependent, arm)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 249) ----------------------------------------------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 250)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 251) - To use a relocatable kernel,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 252) Enable "AUTO_ZRELADDR" support under "Boot" options::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 253)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 254) AUTO_ZRELADDR=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 255)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 256) Dump-capture kernel config options (Arch Dependent, arm64)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 257) ----------------------------------------------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 258)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 259) - Please note that kvm of the dump-capture kernel will not be enabled
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 260) on non-VHE systems even if it is configured. This is because the CPU
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 261) will not be reset to EL2 on panic.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 262)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 263) Extended crashkernel syntax
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 264) ===========================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 265)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 266) While the "crashkernel=size[@offset]" syntax is sufficient for most
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 267) configurations, sometimes it's handy to have the reserved memory dependent
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 268) on the value of System RAM -- that's mostly for distributors that pre-setup
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 269) the kernel command line to avoid a unbootable system after some memory has
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 270) been removed from the machine.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 271)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 272) The syntax is::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 273)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 274) crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 275) range=start-[end]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 276)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 277) For example::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 278)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 279) crashkernel=512M-2G:64M,2G-:128M
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 280)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 281) This would mean:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 282)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 283) 1) if the RAM is smaller than 512M, then don't reserve anything
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 284) (this is the "rescue" case)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 285) 2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 286) 3) if the RAM size is larger than 2G, then reserve 128M
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 287)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 288)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 289)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 290) Boot into System Kernel
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 291) =======================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 292)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 293) 1) Update the boot loader (such as grub, yaboot, or lilo) configuration
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 294) files as necessary.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 295)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 296) 2) Boot the system kernel with the boot parameter "crashkernel=Y@X",
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 297) where Y specifies how much memory to reserve for the dump-capture kernel
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 298) and X specifies the beginning of this reserved memory. For example,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 299) "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 300) starting at physical address 0x01000000 (16MB) for the dump-capture kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 301)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 302) On x86 and x86_64, use "crashkernel=64M@16M".
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 303)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 304) On ppc64, use "crashkernel=128M@32M".
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 305)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 306) On ia64, 256M@256M is a generous value that typically works.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 307) The region may be automatically placed on ia64, see the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 308) dump-capture kernel config option notes above.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 309) If use sparse memory, the size should be rounded to GRANULE boundaries.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 310)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 311) On s390x, typically use "crashkernel=xxM". The value of xx is dependent
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 312) on the memory consumption of the kdump system. In general this is not
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 313) dependent on the memory size of the production system.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 314)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 315) On arm, the use of "crashkernel=Y@X" is no longer necessary; the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 316) kernel will automatically locate the crash kernel image within the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 317) first 512MB of RAM if X is not given.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 318)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 319) On arm64, use "crashkernel=Y[@X]". Note that the start address of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 320) the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 321)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 322) Load the Dump-capture Kernel
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 323) ============================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 324)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 325) After booting to the system kernel, dump-capture kernel needs to be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 326) loaded.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 327)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 328) Based on the architecture and type of image (relocatable or not), one
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 329) can choose to load the uncompressed vmlinux or compressed bzImage/vmlinuz
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 330) of dump-capture kernel. Following is the summary.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 331)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 332) For i386 and x86_64:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 333)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 334) - Use vmlinux if kernel is not relocatable.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 335) - Use bzImage/vmlinuz if kernel is relocatable.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 336)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 337) For ppc64:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 338)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 339) - Use vmlinux
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 340)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 341) For ia64:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 342)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 343) - Use vmlinux or vmlinuz.gz
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 344)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 345) For s390x:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 346)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 347) - Use image or bzImage
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 348)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 349) For arm:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 350)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 351) - Use zImage
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 352)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 353) For arm64:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 354)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 355) - Use vmlinux or Image
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 356)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 357) If you are using an uncompressed vmlinux image then use following command
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 358) to load dump-capture kernel::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 359)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 360) kexec -p <dump-capture-kernel-vmlinux-image> \
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 361) --initrd=<initrd-for-dump-capture-kernel> --args-linux \
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 362) --append="root=<root-dev> <arch-specific-options>"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 363)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 364) If you are using a compressed bzImage/vmlinuz, then use following command
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 365) to load dump-capture kernel::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 366)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 367) kexec -p <dump-capture-kernel-bzImage> \
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 368) --initrd=<initrd-for-dump-capture-kernel> \
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 369) --append="root=<root-dev> <arch-specific-options>"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 370)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 371) If you are using a compressed zImage, then use following command
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 372) to load dump-capture kernel::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 373)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 374) kexec --type zImage -p <dump-capture-kernel-bzImage> \
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 375) --initrd=<initrd-for-dump-capture-kernel> \
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 376) --dtb=<dtb-for-dump-capture-kernel> \
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 377) --append="root=<root-dev> <arch-specific-options>"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 378)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 379) If you are using an uncompressed Image, then use following command
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 380) to load dump-capture kernel::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 381)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 382) kexec -p <dump-capture-kernel-Image> \
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 383) --initrd=<initrd-for-dump-capture-kernel> \
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 384) --append="root=<root-dev> <arch-specific-options>"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 385)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 386) Please note, that --args-linux does not need to be specified for ia64.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 387) It is planned to make this a no-op on that architecture, but for now
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 388) it should be omitted
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 389)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 390) Following are the arch specific command line options to be used while
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 391) loading dump-capture kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 392)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 393) For i386, x86_64 and ia64:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 394)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 395) "1 irqpoll maxcpus=1 reset_devices"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 396)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 397) For ppc64:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 398)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 399) "1 maxcpus=1 noirqdistrib reset_devices"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 400)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 401) For s390x:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 402)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 403) "1 maxcpus=1 cgroup_disable=memory"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 404)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 405) For arm:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 406)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 407) "1 maxcpus=1 reset_devices"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 408)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 409) For arm64:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 410)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 411) "1 maxcpus=1 reset_devices"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 412)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 413) Notes on loading the dump-capture kernel:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 414)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 415) * By default, the ELF headers are stored in ELF64 format to support
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 416) systems with more than 4GB memory. On i386, kexec automatically checks if
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 417) the physical RAM size exceeds the 4 GB limit and if not, uses ELF32.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 418) So, on non-PAE systems, ELF32 is always used.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 419)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 420) The --elf32-core-headers option can be used to force the generation of ELF32
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 421) headers. This is necessary because GDB currently cannot open vmcore files
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 422) with ELF64 headers on 32-bit systems.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 423)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 424) * The "irqpoll" boot parameter reduces driver initialization failures
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 425) due to shared interrupts in the dump-capture kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 426)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 427) * You must specify <root-dev> in the format corresponding to the root
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 428) device name in the output of mount command.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 429)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 430) * Boot parameter "1" boots the dump-capture kernel into single-user
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 431) mode without networking. If you want networking, use "3".
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 432)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 433) * We generally don't have to bring up a SMP kernel just to capture the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 434) dump. Hence generally it is useful either to build a UP dump-capture
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 435) kernel or specify maxcpus=1 option while loading dump-capture kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 436) Note, though maxcpus always works, you had better replace it with
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 437) nr_cpus to save memory if supported by the current ARCH, such as x86.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 438)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 439) * You should enable multi-cpu support in dump-capture kernel if you intend
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 440) to use multi-thread programs with it, such as parallel dump feature of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 441) makedumpfile. Otherwise, the multi-thread program may have a great
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 442) performance degradation. To enable multi-cpu support, you should bring up an
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 443) SMP dump-capture kernel and specify maxcpus/nr_cpus, disable_cpu_apicid=[X]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 444) options while loading it.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 445)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 446) * For s390x there are two kdump modes: If a ELF header is specified with
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 447) the elfcorehdr= kernel parameter, it is used by the kdump kernel as it
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 448) is done on all other architectures. If no elfcorehdr= kernel parameter is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 449) specified, the s390x kdump kernel dynamically creates the header. The
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 450) second mode has the advantage that for CPU and memory hotplug, kdump has
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 451) not to be reloaded with kexec_load().
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 452)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 453) * For s390x systems with many attached devices the "cio_ignore" kernel
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 454) parameter should be used for the kdump kernel in order to prevent allocation
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 455) of kernel memory for devices that are not relevant for kdump. The same
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 456) applies to systems that use SCSI/FCP devices. In that case the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 457) "allow_lun_scan" zfcp module parameter should be set to zero before
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 458) setting FCP devices online.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 459)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 460) Kernel Panic
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 461) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 462)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 463) After successfully loading the dump-capture kernel as previously
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 464) described, the system will reboot into the dump-capture kernel if a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 465) system crash is triggered. Trigger points are located in panic(),
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 466) die(), die_nmi() and in the sysrq handler (ALT-SysRq-c).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 467)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 468) The following conditions will execute a crash trigger point:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 469)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 470) If a hard lockup is detected and "NMI watchdog" is configured, the system
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 471) will boot into the dump-capture kernel ( die_nmi() ).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 472)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 473) If die() is called, and it happens to be a thread with pid 0 or 1, or die()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 474) is called inside interrupt context or die() is called and panic_on_oops is set,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 475) the system will boot into the dump-capture kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 476)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 477) On powerpc systems when a soft-reset is generated, die() is called by all cpus
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 478) and the system will boot into the dump-capture kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 479)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 480) For testing purposes, you can trigger a crash by using "ALT-SysRq-c",
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 481) "echo c > /proc/sysrq-trigger" or write a module to force the panic.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 482)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 483) Write Out the Dump File
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 484) =======================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 485)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 486) After the dump-capture kernel is booted, write out the dump file with
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 487) the following command::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 488)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 489) cp /proc/vmcore <dump-file>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 490)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 491)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 492) Analysis
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 493) ========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 494)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 495) Before analyzing the dump image, you should reboot into a stable kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 496)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 497) You can do limited analysis using GDB on the dump file copied out of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 498) /proc/vmcore. Use the debug vmlinux built with -g and run the following
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 499) command::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 500)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 501) gdb vmlinux <dump-file>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 502)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 503) Stack trace for the task on processor 0, register display, and memory
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 504) display work fine.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 505)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 506) Note: GDB cannot analyze core files generated in ELF64 format for x86.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 507) On systems with a maximum of 4GB of memory, you can generate
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 508) ELF32-format headers using the --elf32-core-headers kernel option on the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 509) dump kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 510)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 511) You can also use the Crash utility to analyze dump files in Kdump
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 512) format. Crash is available at the following URL:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 513)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 514) https://github.com/crash-utility/crash
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 515)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 516) Crash document can be found at:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 517) https://crash-utility.github.io/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 518)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 519) Trigger Kdump on WARN()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 520) =======================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 521)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 522) The kernel parameter, panic_on_warn, calls panic() in all WARN() paths. This
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 523) will cause a kdump to occur at the panic() call. In cases where a user wants
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 524) to specify this during runtime, /proc/sys/kernel/panic_on_warn can be set to 1
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 525) to achieve the same behaviour.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 526)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 527) Trigger Kdump on add_taint()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 528) ============================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 529)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 530) The kernel parameter panic_on_taint facilitates a conditional call to panic()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 531) from within add_taint() whenever the value set in this bitmask matches with the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 532) bit flag being set by add_taint().
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 533) This will cause a kdump to occur at the add_taint()->panic() call.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 534)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 535) Contact
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 536) =======
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 537)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 538) - Vivek Goyal (vgoyal@redhat.com)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 539) - Maneesh Soni (maneesh@in.ibm.com)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 540)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 541) GDB macros
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 542) ==========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 543)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 544) .. include:: gdbmacros.txt
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 545) :literal:
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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