--- zzzz-none-000/linux-3.10.107/Documentation/kdump/kdump.txt 2017-06-27 09:49:32.000000000 +0000 +++ scorpion-7490-727/linux-3.10.107/Documentation/kdump/kdump.txt 2021-02-04 17:41:59.000000000 +0000 @@ -18,7 +18,7 @@ a remote system. Kdump and kexec are currently supported on the x86, x86_64, ppc64, ia64, -and s390x architectures. +s390x and arm architectures. When the system kernel boots, it reserves a small section of memory for the dump-capture kernel. This ensures that ongoing Direct Memory Access @@ -47,19 +47,12 @@ when using the elfcorehdr=[size[KMG]@]offset[KMG] syntax. -With the dump-capture kernel, you can access the memory image, or "old -memory," in two ways: - -- Through a /dev/oldmem device interface. A capture utility can read the - device file and write out the memory in raw format. This is a raw dump - of memory. Analysis and capture tools must be intelligent enough to - determine where to look for the right information. - -- Through /proc/vmcore. This exports the dump as an ELF-format file that - you can write out using file copy commands such as cp or scp. Further, - you can use analysis tools such as the GNU Debugger (GDB) and the Crash - tool to debug the dump file. This method ensures that the dump pages are - correctly ordered. +With the dump-capture kernel, you can access the memory image through +/proc/vmcore. This exports the dump as an ELF-format file that you can +write out using file copy commands such as cp or scp. Further, you can +use analysis tools such as the GNU Debugger (GDB) and the Crash tool to +debug the dump file. This method ensures that the dump pages are correctly +ordered. Setup and Installation @@ -119,7 +112,7 @@ 2) Or use the system kernel binary itself as dump-capture kernel and there is no need to build a separate dump-capture kernel. This is possible only with the architectures which support a relocatable kernel. As - of today, i386, x86_64, ppc64 and ia64 architectures support relocatable + of today, i386, x86_64, ppc64, ia64 and arm architectures support relocatable kernel. Building a relocatable kernel is advantageous from the point of view that @@ -248,6 +241,13 @@ kernel will be aligned to 64Mb, so if the start address is not then any space below the alignment point will be wasted. +Dump-capture kernel config options (Arch Dependent, arm) +---------------------------------------------------------- + +- To use a relocatable kernel, + Enable "AUTO_ZRELADDR" support under "Boot" options: + + AUTO_ZRELADDR=y Extended crashkernel syntax =========================== @@ -263,6 +263,10 @@ crashkernel=:[,:,...][@offset] range=start-[end] +Please note, on arm, the offset is required. + crashkernel=:[,:,...]@offset + range=start-[end] + 'start' is inclusive and 'end' is exclusive. For example: @@ -303,6 +307,12 @@ on the memory consumption of the kdump system. In general this is not dependent on the memory size of the production system. + On arm, use "crashkernel=Y@X". Note that the start address of the kernel + will be aligned to 128MiB (0x08000000), so if the start address is not then + any space below the alignment point may be overwritten by the dump-capture kernel, + which means it is possible that the vmcore is not that precise as expected. + + Load the Dump-capture Kernel ============================ @@ -322,7 +332,8 @@ - Use vmlinux or vmlinuz.gz For s390x: - Use image or bzImage - +For arm: + - Use zImage If you are using a uncompressed vmlinux image then use following command to load dump-capture kernel. @@ -338,6 +349,15 @@ --initrd= \ --append="root= " +If you are using a compressed zImage, then use following command +to load dump-capture kernel. + + kexec --type zImage -p \ + --initrd= \ + --dtb= \ + --append="root= " + + Please note, that --args-linux does not need to be specified for ia64. It is planned to make this a no-op on that architecture, but for now it should be omitted @@ -354,6 +374,9 @@ For s390x: "1 maxcpus=1 cgroup_disable=memory" +For arm: + "1 maxcpus=1 reset_devices" + Notes on loading the dump-capture kernel: * By default, the ELF headers are stored in ELF64 format to support @@ -423,18 +446,6 @@ cp /proc/vmcore -You can also access dumped memory as a /dev/oldmem device for a linear -and raw view. To create the device, use the following command: - - mknod /dev/oldmem c 1 12 - -Use the dd command with suitable options for count, bs, and skip to -access specific portions of the dump. - -To see the entire memory, use the following command: - - dd if=/dev/oldmem of=oldmem.001 - Analysis ======== @@ -460,14 +471,13 @@ http://people.redhat.com/~anderson/ +Trigger Kdump on WARN() +======================= -To Do -===== - -1) Provide relocatable kernels for all architectures to help in maintaining - multiple kernels for crash_dump, and the same kernel as the system kernel - can be used to capture the dump. - +The kernel parameter, panic_on_warn, calls panic() in all WARN() paths. This +will cause a kdump to occur at the panic() call. In cases where a user wants +to specify this during runtime, /proc/sys/kernel/panic_on_warn can be set to 1 +to achieve the same behaviour. Contact =======