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docs: kdump: convert docs to ReST and rename to *.rst
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Convert kdump documentation to ReST and add it to the
user faced manual, as the documents are mainly focused on
sysadmins that would be enabling kdump.

Note: the vmcoreinfo.rst has one very long title on one of its
sub-sections:

	PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision|PG_head_mask|PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy)|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline)

I opted to break this one, into two entries with the same content,
in order to make it easier to display after being parsed in html and PDF.

The conversion is actually:
  - add blank lines and identation in order to identify paragraphs;
  - fix tables markups;
  - add some lists markups;
  - mark literal blocks;
  - adjust title markups.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>
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mchehab authored and Jonathan Corbet committed Jun 14, 2019
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2 changes: 1 addition & 1 deletion Documentation/admin-guide/bug-hunting.rst
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Expand Up @@ -90,7 +90,7 @@ the disk is not available then you have three options:
run a null modem to a second machine and capture the output there
using your favourite communication program. Minicom works well.

(3) Use Kdump (see Documentation/kdump/kdump.txt),
(3) Use Kdump (see Documentation/kdump/kdump.rst),
extract the kernel ring buffer from old memory with using dmesg
gdbmacro in Documentation/kdump/gdbmacros.txt.

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6 changes: 3 additions & 3 deletions Documentation/admin-guide/kernel-parameters.txt
Original file line number Diff line number Diff line change
Expand Up @@ -708,14 +708,14 @@
[KNL, x86_64] select a region under 4G first, and
fall back to reserve region above 4G when '@offset'
hasn't been specified.
See Documentation/kdump/kdump.txt for further details.
See Documentation/kdump/kdump.rst for further details.

crashkernel=range1:size1[,range2:size2,...][@offset]
[KNL] Same as above, but depends on the memory
in the running system. The syntax of range is
start-[end] where start and end are both
a memory unit (amount[KMG]). See also
Documentation/kdump/kdump.txt for an example.
Documentation/kdump/kdump.rst for an example.

crashkernel=size[KMG],high
[KNL, x86_64] range could be above 4G. Allow kernel
Expand Down Expand Up @@ -1209,7 +1209,7 @@
Specifies physical address of start of kernel core
image elf header and optionally the size. Generally
kexec loader will pass this option to capture kernel.
See Documentation/kdump/kdump.txt for details.
See Documentation/kdump/kdump.rst for details.

enable_mtrr_cleanup [X86]
The kernel tries to adjust MTRR layout from continuous
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21 changes: 21 additions & 0 deletions Documentation/kdump/index.rst
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@@ -0,0 +1,21 @@
:orphan:

================================================================
Documentation for Kdump - The kexec-based Crash Dumping Solution
================================================================

This document includes overview, setup and installation, and analysis
information.

.. toctree::
:maxdepth: 1

kdump
vmcoreinfo

.. only:: subproject and html

Indices
=======

* :ref:`genindex`
131 changes: 78 additions & 53 deletions Documentation/kdump/kdump.txt → Documentation/kdump/kdump.rst
Original file line number Diff line number Diff line change
Expand Up @@ -71,35 +71,34 @@ This is a symlink to the latest version.

The latest kexec-tools git tree is available at:

git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
and
http://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
- git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
- http://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git

There is also a gitweb interface available at
http://www.kernel.org/git/?p=utils/kernel/kexec/kexec-tools.git

More information about kexec-tools can be found at
http://horms.net/projects/kexec/

3) Unpack the tarball with the tar command, as follows:
3) Unpack the tarball with the tar command, as follows::

tar xvpzf kexec-tools.tar.gz
tar xvpzf kexec-tools.tar.gz

4) Change to the kexec-tools directory, as follows:
4) Change to the kexec-tools directory, as follows::

cd kexec-tools-VERSION
cd kexec-tools-VERSION

5) Configure the package, as follows:
5) Configure the package, as follows::

./configure
./configure

6) Compile the package, as follows:
6) Compile the package, as follows::

make
make

7) Install the package, as follows:
7) Install the package, as follows::

make install
make install


Build the system and dump-capture kernels
Expand All @@ -126,25 +125,25 @@ dump-capture kernels for enabling kdump support.
System kernel config options
----------------------------

1) Enable "kexec system call" in "Processor type and features."
1) Enable "kexec system call" in "Processor type and features."::

CONFIG_KEXEC=y
CONFIG_KEXEC=y

2) Enable "sysfs file system support" in "Filesystem" -> "Pseudo
filesystems." This is usually enabled by default.
filesystems." This is usually enabled by default::

CONFIG_SYSFS=y
CONFIG_SYSFS=y

Note that "sysfs file system support" might not appear in the "Pseudo
filesystems" menu if "Configure standard kernel features (for small
systems)" is not enabled in "General Setup." In this case, check the
.config file itself to ensure that sysfs is turned on, as follows:
.config file itself to ensure that sysfs is turned on, as follows::

grep 'CONFIG_SYSFS' .config
grep 'CONFIG_SYSFS' .config

3) Enable "Compile the kernel with debug info" in "Kernel hacking."
3) Enable "Compile the kernel with debug info" in "Kernel hacking."::

CONFIG_DEBUG_INFO=Y
CONFIG_DEBUG_INFO=Y

This causes the kernel to be built with debug symbols. The dump
analysis tools require a vmlinux with debug symbols in order to read
Expand All @@ -154,39 +153,42 @@ Dump-capture kernel config options (Arch Independent)
-----------------------------------------------------

1) Enable "kernel crash dumps" support under "Processor type and
features":
features"::

CONFIG_CRASH_DUMP=y
CONFIG_CRASH_DUMP=y

2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems".
2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems"::

CONFIG_PROC_VMCORE=y

CONFIG_PROC_VMCORE=y
(CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)

Dump-capture kernel config options (Arch Dependent, i386 and x86_64)
--------------------------------------------------------------------

1) On i386, enable high memory support under "Processor type and
features":
features"::

CONFIG_HIGHMEM64G=y

or::

CONFIG_HIGHMEM64G=y
or
CONFIG_HIGHMEM4G
CONFIG_HIGHMEM4G

2) On i386 and x86_64, disable symmetric multi-processing support
under "Processor type and features":
under "Processor type and features"::

CONFIG_SMP=n
CONFIG_SMP=n

(If CONFIG_SMP=y, then specify maxcpus=1 on the kernel command line
when loading the dump-capture kernel, see section "Load the Dump-capture
Kernel".)

3) If one wants to build and use a relocatable kernel,
Enable "Build a relocatable kernel" support under "Processor type and
features"
features"::

CONFIG_RELOCATABLE=y
CONFIG_RELOCATABLE=y

4) Use a suitable value for "Physical address where the kernel is
loaded" (under "Processor type and features"). This only appears when
Expand All @@ -211,13 +213,13 @@ Dump-capture kernel config options (Arch Dependent, i386 and x86_64)
Dump-capture kernel config options (Arch Dependent, ppc64)
----------------------------------------------------------

1) Enable "Build a kdump crash kernel" support under "Kernel" options:
1) Enable "Build a kdump crash kernel" support under "Kernel" options::

CONFIG_CRASH_DUMP=y
CONFIG_CRASH_DUMP=y

2) Enable "Build a relocatable kernel" support
2) Enable "Build a relocatable kernel" support::

CONFIG_RELOCATABLE=y
CONFIG_RELOCATABLE=y

Make and install the kernel and its modules.

Expand All @@ -231,11 +233,13 @@ Dump-capture kernel config options (Arch Dependent, ia64)

The crashkernel region can be automatically placed by the system
kernel at run time. This is done by specifying the base address as 0,
or omitting it all together.
or omitting it all together::

crashkernel=256M@0
or
crashkernel=256M
crashkernel=256M@0

or::

crashkernel=256M

If the start address is specified, note that the start address of the
kernel will be aligned to 64Mb, so if the start address is not then
Expand All @@ -245,9 +249,9 @@ Dump-capture kernel config options (Arch Dependent, arm)
----------------------------------------------------------

- To use a relocatable kernel,
Enable "AUTO_ZRELADDR" support under "Boot" options:
Enable "AUTO_ZRELADDR" support under "Boot" options::

AUTO_ZRELADDR=y
AUTO_ZRELADDR=y

Dump-capture kernel config options (Arch Dependent, arm64)
----------------------------------------------------------
Expand All @@ -265,12 +269,12 @@ on the value of System RAM -- that's mostly for distributors that pre-setup
the kernel command line to avoid a unbootable system after some memory has
been removed from the machine.

The syntax is:
The syntax is::

crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
range=start-[end]

For example:
For example::

crashkernel=512M-2G:64M,2G-:128M

Expand Down Expand Up @@ -326,43 +330,54 @@ can choose to load the uncompressed vmlinux or compressed bzImage/vmlinuz
of dump-capture kernel. Following is the summary.

For i386 and x86_64:

- Use vmlinux if kernel is not relocatable.
- Use bzImage/vmlinuz if kernel is relocatable.

For ppc64:

- Use vmlinux

For ia64:

- Use vmlinux or vmlinuz.gz

For s390x:

- Use image or bzImage

For arm:

- Use zImage

For arm64:

- Use vmlinux or Image

If you are using an uncompressed vmlinux image then use following command
to load dump-capture kernel.
to load dump-capture kernel::

kexec -p <dump-capture-kernel-vmlinux-image> \
--initrd=<initrd-for-dump-capture-kernel> --args-linux \
--append="root=<root-dev> <arch-specific-options>"

If you are using a compressed bzImage/vmlinuz, then use following command
to load dump-capture kernel.
to load dump-capture kernel::

kexec -p <dump-capture-kernel-bzImage> \
--initrd=<initrd-for-dump-capture-kernel> \
--append="root=<root-dev> <arch-specific-options>"

If you are using a compressed zImage, then use following command
to load dump-capture kernel.
to load dump-capture kernel::

kexec --type zImage -p <dump-capture-kernel-bzImage> \
--initrd=<initrd-for-dump-capture-kernel> \
--dtb=<dtb-for-dump-capture-kernel> \
--append="root=<root-dev> <arch-specific-options>"

If you are using an uncompressed Image, then use following command
to load dump-capture kernel.
to load dump-capture kernel::

kexec -p <dump-capture-kernel-Image> \
--initrd=<initrd-for-dump-capture-kernel> \
Expand All @@ -376,18 +391,23 @@ Following are the arch specific command line options to be used while
loading dump-capture kernel.

For i386, x86_64 and ia64:

"1 irqpoll maxcpus=1 reset_devices"

For ppc64:

"1 maxcpus=1 noirqdistrib reset_devices"

For s390x:

"1 maxcpus=1 cgroup_disable=memory"

For arm:

"1 maxcpus=1 reset_devices"

For arm64:

"1 maxcpus=1 reset_devices"

Notes on loading the dump-capture kernel:
Expand Down Expand Up @@ -464,7 +484,7 @@ Write Out the Dump File
=======================

After the dump-capture kernel is booted, write out the dump file with
the following command:
the following command::

cp /proc/vmcore <dump-file>

Expand All @@ -476,7 +496,7 @@ Before analyzing the dump image, you should reboot into a stable kernel.

You can do limited analysis using GDB on the dump file copied out of
/proc/vmcore. Use the debug vmlinux built with -g and run the following
command:
command::

gdb vmlinux <dump-file>

Expand Down Expand Up @@ -504,6 +524,11 @@ to achieve the same behaviour.
Contact
=======

Vivek Goyal ([email protected])
Maneesh Soni ([email protected])
- Vivek Goyal ([email protected])
- Maneesh Soni ([email protected])

GDB macros
==========

.. include:: gdbmacros.txt
:literal:
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