Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 1537 insertions, 0 deletions

diff --git a/Documentation/admin-guide/kdump/gdbmacros.txt b/Documentation/admin-guide/kdump/gdbmacros.txt
new file mode 100644
index 000000000..030de95e3
--- /dev/null
+++ b/Documentation/admin-guide/kdump/gdbmacros.txt
@@ -0,0 +1,323 @@
+#
+# This file contains a few gdb macros (user defined commands) to extract
+# useful information from kernel crashdump (kdump) like stack traces of
+# all the processes or a particular process and trapinfo.
+#
+# These macros can be used by copying this file in .gdbinit (put in home
+# directory or current directory) or by invoking gdb command with
+# --command=<command-file-name> option
+#
+# Credits:
+# Alexander Nyberg <alexn@telia.com>
+# V Srivatsa <vatsa@in.ibm.com>
+# Maneesh Soni <maneesh@in.ibm.com>
+#
+
+define bttnobp
+	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+	set $init_t=&init_task
+	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+	set var $stacksize = sizeof(union thread_union)
+	while ($next_t != $init_t)
+		set $next_t=(struct task_struct *)$next_t
+		printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
+		printf "===================\n"
+		set var $stackp = $next_t.thread.sp
+		set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
+
+		while ($stackp < $stack_top)
+			if (*($stackp) > _stext && *($stackp) < _sinittext)
+				info symbol *($stackp)
+			end
+			set $stackp += 4
+		end
+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+		while ($next_th != $next_t)
+			set $next_th=(struct task_struct *)$next_th
+			printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
+			printf "===================\n"
+			set var $stackp = $next_t.thread.sp
+			set var $stack_top = ($stackp & ~($stacksize - 1)) + stacksize
+
+			while ($stackp < $stack_top)
+				if (*($stackp) > _stext && *($stackp) < _sinittext)
+					info symbol *($stackp)
+				end
+				set $stackp += 4
+			end
+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+		end
+		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+	end
+end
+document bttnobp
+	dump all thread stack traces on a kernel compiled with !CONFIG_FRAME_POINTER
+end
+
+define btthreadstack
+	set var $pid_task = $arg0
+
+	printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
+	printf "task struct: "
+	print $pid_task
+	printf "===================\n"
+	set var $stackp = $pid_task.thread.sp
+	set var $stacksize = sizeof(union thread_union)
+	set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
+	set var $stack_bot = ($stackp & ~($stacksize - 1))
+
+	set $stackp = *((unsigned long *) $stackp)
+	while (($stackp < $stack_top) && ($stackp > $stack_bot))
+		set var $addr = *(((unsigned long *) $stackp) + 1)
+		info symbol $addr
+		set $stackp = *((unsigned long *) $stackp)
+	end
+end
+document btthreadstack
+	 dump a thread stack using the given task structure pointer
+end
+
+
+define btt
+	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+	set $init_t=&init_task
+	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+	while ($next_t != $init_t)
+		set $next_t=(struct task_struct *)$next_t
+		btthreadstack $next_t
+
+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+		while ($next_th != $next_t)
+			set $next_th=(struct task_struct *)$next_th
+			btthreadstack $next_th
+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+		end
+		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+	end
+end
+document btt
+	dump all thread stack traces on a kernel compiled with CONFIG_FRAME_POINTER
+end
+
+define btpid
+	set var $pid = $arg0
+	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+	set $init_t=&init_task
+	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+	set var $pid_task = 0
+
+	while ($next_t != $init_t)
+		set $next_t=(struct task_struct *)$next_t
+
+		if ($next_t.pid == $pid)
+			set $pid_task = $next_t
+		end
+
+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+		while ($next_th != $next_t)
+			set $next_th=(struct task_struct *)$next_th
+			if ($next_th.pid == $pid)
+				set $pid_task = $next_th
+			end
+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+		end
+		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+	end
+
+	btthreadstack $pid_task
+end
+document btpid
+	backtrace of pid
+end
+
+
+define trapinfo
+	set var $pid = $arg0
+	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+	set $init_t=&init_task
+	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+	set var $pid_task = 0
+
+	while ($next_t != $init_t)
+		set $next_t=(struct task_struct *)$next_t
+
+		if ($next_t.pid == $pid)
+			set $pid_task = $next_t
+		end
+
+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+		while ($next_th != $next_t)
+			set $next_th=(struct task_struct *)$next_th
+			if ($next_th.pid == $pid)
+				set $pid_task = $next_th
+			end
+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+		end
+		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+	end
+
+	printf "Trapno %ld, cr2 0x%lx, error_code %ld\n", $pid_task.thread.trap_no, \
+				$pid_task.thread.cr2, $pid_task.thread.error_code
+
+end
+document trapinfo
+	Run info threads and lookup pid of thread #1
+	'trapinfo <pid>' will tell you by which trap & possibly
+	address the kernel panicked.
+end
+
+define dump_record
+	set var $desc = $arg0
+	set var $info = $arg1
+	if ($argc > 2)
+		set var $prev_flags = $arg2
+	else
+		set var $prev_flags = 0
+	end
+
+	set var $prefix = 1
+	set var $newline = 1
+
+	set var $begin = $desc->text_blk_lpos.begin % (1U << prb->text_data_ring.size_bits)
+	set var $next = $desc->text_blk_lpos.next % (1U << prb->text_data_ring.size_bits)
+
+	# handle data-less record
+	if ($begin & 1)
+		set var $text_len = 0
+		set var $log = ""
+	else
+		# handle wrapping data block
+		if ($begin > $next)
+			set var $begin = 0
+		end
+
+		# skip over descriptor id
+		set var $begin = $begin + sizeof(long)
+
+		# handle truncated message
+		if ($next - $begin < $info->text_len)
+			set var $text_len = $next - $begin
+		else
+			set var $text_len = $info->text_len
+		end
+
+		set var $log = &prb->text_data_ring.data[$begin]
+	end
+
+	# prev & LOG_CONT && !(info->flags & LOG_PREIX)
+	if (($prev_flags & 8) && !($info->flags & 4))
+		set var $prefix = 0
+	end
+
+	# info->flags & LOG_CONT
+	if ($info->flags & 8)
+		# (prev & LOG_CONT && !(prev & LOG_NEWLINE))
+		if (($prev_flags & 8) && !($prev_flags & 2))
+			set var $prefix = 0
+		end
+		# (!(info->flags & LOG_NEWLINE))
+		if (!($info->flags & 2))
+			set var $newline = 0
+		end
+	end
+
+	if ($prefix)
+		printf "[%5lu.%06lu] ", $info->ts_nsec / 1000000000, $info->ts_nsec % 1000000000
+	end
+	if ($text_len)
+		eval "printf \"%%%d.%ds\", $log", $text_len, $text_len
+	end
+	if ($newline)
+		printf "\n"
+	end
+
+	# handle dictionary data
+
+	set var $dict = &$info->dev_info.subsystem[0]
+	set var $dict_len = sizeof($info->dev_info.subsystem)
+	if ($dict[0] != '\0')
+		printf " SUBSYSTEM="
+		set var $idx = 0
+		while ($idx < $dict_len)
+			set var $c = $dict[$idx]
+			if ($c == '\0')
+				loop_break
+			else
+				if ($c < ' ' || $c >= 127 || $c == '\\')
+					printf "\\x%02x", $c
+				else
+					printf "%c", $c
+				end
+			end
+			set var $idx = $idx + 1
+		end
+		printf "\n"
+	end
+
+	set var $dict = &$info->dev_info.device[0]
+	set var $dict_len = sizeof($info->dev_info.device)
+	if ($dict[0] != '\0')
+		printf " DEVICE="
+		set var $idx = 0
+		while ($idx < $dict_len)
+			set var $c = $dict[$idx]
+			if ($c == '\0')
+				loop_break
+			else
+				if ($c < ' ' || $c >= 127 || $c == '\\')
+					printf "\\x%02x", $c
+				else
+					printf "%c", $c
+				end
+			end
+			set var $idx = $idx + 1
+		end
+		printf "\n"
+	end
+end
+document dump_record
+	Dump a single record. The first parameter is the descriptor,
+	the second parameter is the info, the third parameter is
+	optional and specifies the previous record's flags, used for
+	properly formatting continued lines.
+end
+
+define dmesg
+	# definitions from kernel/printk/printk_ringbuffer.h
+	set var $desc_committed = 1
+	set var $desc_finalized = 2
+	set var $desc_sv_bits = sizeof(long) * 8
+	set var $desc_flags_shift = $desc_sv_bits - 2
+	set var $desc_flags_mask = 3 << $desc_flags_shift
+	set var $id_mask = ~$desc_flags_mask
+
+	set var $desc_count = 1U << prb->desc_ring.count_bits
+	set var $prev_flags = 0
+
+	set var $id = prb->desc_ring.tail_id.counter
+	set var $end_id = prb->desc_ring.head_id.counter
+
+	while (1)
+		set var $desc = &prb->desc_ring.descs[$id % $desc_count]
+		set var $info = &prb->desc_ring.infos[$id % $desc_count]
+
+		# skip non-committed record
+		set var $state = 3 & ($desc->state_var.counter >> $desc_flags_shift)
+		if ($state == $desc_committed || $state == $desc_finalized)
+			dump_record $desc $info $prev_flags
+			set var $prev_flags = $info->flags
+		end
+
+		if ($id == $end_id)
+			loop_break
+		end
+		set var $id = ($id + 1) & $id_mask
+	end
+end
+document dmesg
+	print the kernel ring buffer
+end
diff --git a/Documentation/admin-guide/kdump/index.rst b/Documentation/admin-guide/kdump/index.rst
new file mode 100644
index 000000000..8e2ebd038
--- /dev/null
+++ b/Documentation/admin-guide/kdump/index.rst
@@ -0,0 +1,20 @@
+
+================================================================
+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`
diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
new file mode 100644
index 000000000..a748e7eb4
--- /dev/null
+++ b/Documentation/admin-guide/kdump/kdump.rst
@@ -0,0 +1,597 @@
+================================================================
+Documentation for Kdump - The kexec-based Crash Dumping Solution
+================================================================
+
+This document includes overview, setup, installation, and analysis
+information.
+
+Overview
+========
+
+Kdump uses kexec to quickly boot to a dump-capture kernel whenever a
+dump of the system kernel's memory needs to be taken (for example, when
+the system panics). The system kernel's memory image is preserved across
+the reboot and is accessible to the dump-capture kernel.
+
+You can use common commands, such as cp, scp or makedumpfile to copy
+the memory image to a dump file on the local disk, or across the network
+to a remote system.
+
+Kdump and kexec are currently supported on the x86, x86_64, ppc64, ia64,
+s390x, arm and arm64 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
+(DMA) from the system kernel does not corrupt the dump-capture kernel.
+The kexec -p command loads the dump-capture kernel into this reserved
+memory.
+
+On x86 machines, the first 640 KB of physical memory is needed for boot,
+regardless of where the kernel loads. For simpler handling, the whole
+low 1M is reserved to avoid any later kernel or device driver writing
+data into this area. Like this, the low 1M can be reused as system RAM
+by kdump kernel without extra handling.
+
+On PPC64 machines first 32KB of physical memory is needed for booting
+regardless of where the kernel is loaded and to support 64K page size
+kexec backs up the first 64KB memory.
+
+For s390x, when kdump is triggered, the crashkernel region is exchanged
+with the region [0, crashkernel region size] and then the kdump kernel
+runs in [0, crashkernel region size]. Therefore no relocatable kernel is
+needed for s390x.
+
+All of the necessary information about the system kernel's core image is
+encoded in the ELF format, and stored in a reserved area of memory
+before a crash. The physical address of the start of the ELF header is
+passed to the dump-capture kernel through the elfcorehdr= boot
+parameter. Optionally the size of the ELF header can also be passed
+when using the elfcorehdr=[size[KMG]@]offset[KMG] syntax.
+
+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. You can also use
+makedumpfile utility to analyze and write out filtered contents with
+options, e.g with '-d 31' it will only write out kernel data. 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
+======================
+
+Install kexec-tools
+-------------------
+
+1) Login as the root user.
+
+2) Download the kexec-tools user-space package from the following URL:
+
+http://kernel.org/pub/linux/utils/kernel/kexec/kexec-tools.tar.gz
+
+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
+- 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::
+
+	tar xvpzf kexec-tools.tar.gz
+
+4) Change to the kexec-tools directory, as follows::
+
+	cd kexec-tools-VERSION
+
+5) Configure the package, as follows::
+
+	./configure
+
+6) Compile the package, as follows::
+
+	make
+
+7) Install the package, as follows::
+
+	make install
+
+
+Build the system and dump-capture kernels
+-----------------------------------------
+There are two possible methods of using Kdump.
+
+1) Build a separate custom dump-capture kernel for capturing the
+   kernel core dump.
+
+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, ia64, arm and arm64 architectures support
+   relocatable kernel.
+
+Building a relocatable kernel is advantageous from the point of view that
+one does not have to build a second kernel for capturing the dump. But
+at the same time one might want to build a custom dump capture kernel
+suitable to his needs.
+
+Following are the configuration setting required for system and
+dump-capture kernels for enabling kdump support.
+
+System kernel config options
+----------------------------
+
+1) Enable "kexec system call" or "kexec file based system call" in
+   "Processor type and features."::
+
+	CONFIG_KEXEC=y or CONFIG_KEXEC_FILE=y
+
+   And both of them will select KEXEC_CORE::
+
+	CONFIG_KEXEC_CORE=y
+
+   Subsequently, CRASH_CORE is selected by KEXEC_CORE::
+
+	CONFIG_CRASH_CORE=y
+
+2) Enable "sysfs file system support" in "Filesystem" -> "Pseudo
+   filesystems." This is usually enabled by default::
+
+	CONFIG_SYSFS=y
+
+   Note that "sysfs file system support" might not appear in the "Pseudo
+   filesystems" menu if "Configure standard kernel features (expert users)"
+   is not enabled in "General Setup." In this case, check the .config file
+   itself to ensure that sysfs is turned on, as follows::
+
+	grep 'CONFIG_SYSFS' .config
+
+3) Enable "Compile the kernel with debug info" in "Kernel hacking."::
+
+	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
+   and analyze a dump file.
+
+Dump-capture kernel config options (Arch Independent)
+-----------------------------------------------------
+
+1) Enable "kernel crash dumps" support under "Processor type and
+   features"::
+
+	CONFIG_CRASH_DUMP=y
+
+2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems"::
+
+	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"::
+
+	CONFIG_HIGHMEM64G=y
+
+   or::
+
+	CONFIG_HIGHMEM4G
+
+2) With CONFIG_SMP=y, usually nr_cpus=1 need specified on the kernel
+   command line when loading the dump-capture kernel because one
+   CPU is enough for kdump kernel to dump vmcore on most of systems.
+
+   However, you can also specify nr_cpus=X to enable multiple processors
+   in kdump kernel. In this case, "disable_cpu_apicid=" is needed to
+   tell kdump kernel which cpu is 1st kernel's BSP. Please refer to
+   admin-guide/kernel-parameters.txt for more details.
+
+   With CONFIG_SMP=n, the above things are not related.
+
+3) A relocatable kernel is suggested to be built by default. If not yet,
+   enable "Build a relocatable kernel" support under "Processor type and
+   features"::
+
+	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
+   "kernel crash dumps" is enabled. A suitable value depends upon
+   whether kernel is relocatable or not.
+
+   If you are using a relocatable kernel use CONFIG_PHYSICAL_START=0x100000
+   This will compile the kernel for physical address 1MB, but given the fact
+   kernel is relocatable, it can be run from any physical address hence
+   kexec boot loader will load it in memory region reserved for dump-capture
+   kernel.
+
+   Otherwise it should be the start of memory region reserved for
+   second kernel using boot parameter "crashkernel=Y@X". Here X is
+   start of memory region reserved for dump-capture kernel.
+   Generally X is 16MB (0x1000000). So you can set
+   CONFIG_PHYSICAL_START=0x1000000
+
+5) Make and install the kernel and its modules. DO NOT add this kernel
+   to the boot loader configuration files.
+
+Dump-capture kernel config options (Arch Dependent, ppc64)
+----------------------------------------------------------
+
+1) Enable "Build a kdump crash kernel" support under "Kernel" options::
+
+	CONFIG_CRASH_DUMP=y
+
+2)   Enable "Build a relocatable kernel" support::
+
+	CONFIG_RELOCATABLE=y
+
+   Make and install the kernel and its modules.
+
+Dump-capture kernel config options (Arch Dependent, ia64)
+----------------------------------------------------------
+
+- No specific options are required to create a dump-capture kernel
+  for ia64, other than those specified in the arch independent section
+  above. This means that it is possible to use the system kernel
+  as a dump-capture kernel if desired.
+
+  The crashkernel region can be automatically placed by the system
+  kernel at runtime. This is done by specifying the base address as 0,
+  or omitting it all together::
+
+	crashkernel=256M@0
+
+  or::
+
+	crashkernel=256M
+
+Dump-capture kernel config options (Arch Dependent, arm)
+----------------------------------------------------------
+
+-   To use a relocatable kernel,
+    Enable "AUTO_ZRELADDR" support under "Boot" options::
+
+	AUTO_ZRELADDR=y
+
+Dump-capture kernel config options (Arch Dependent, arm64)
+----------------------------------------------------------
+
+- Please note that kvm of the dump-capture kernel will not be enabled
+  on non-VHE systems even if it is configured. This is because the CPU
+  will not be reset to EL2 on panic.
+
+crashkernel syntax
+===========================
+1) crashkernel=size@offset
+
+   Here 'size' specifies how much memory to reserve for the dump-capture kernel
+   and 'offset' specifies the beginning of this reserved memory. For example,
+   "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
+   starting at physical address 0x01000000 (16MB) for the dump-capture kernel.
+
+   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::
+
+         crashkernel=256M@0
+
+   or::
+
+         crashkernel=256M
+
+   If the start address is specified, note that the start address of the
+   kernel will be aligned to a value (which is Arch dependent), so if the
+   start address is not then any space below the alignment point will be
+   wasted.
+
+2) range1:size1[,range2:size2,...][@offset]
+
+   While the "crashkernel=size[@offset]" syntax is sufficient for most
+   configurations, sometimes it's handy to have the reserved memory dependent
+   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::
+
+       crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
+       range=start-[end]
+
+   For example::
+
+       crashkernel=512M-2G:64M,2G-:128M
+
+   This would mean:
+
+       1) if the RAM is smaller than 512M, then don't reserve anything
+          (this is the "rescue" case)
+       2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
+       3) if the RAM size is larger than 2G, then reserve 128M
+
+3) crashkernel=size,high and crashkernel=size,low
+
+   If memory above 4G is preferred, crashkernel=size,high can be used to
+   fulfill that. With it, physical memory is allowed to be allocated from top,
+   so could be above 4G if system has more than 4G RAM installed. Otherwise,
+   memory region will be allocated below 4G if available.
+
+   When crashkernel=X,high is passed, kernel could allocate physical memory
+   region above 4G, low memory under 4G is needed in this case. There are
+   three ways to get low memory:
+
+      1) Kernel will allocate at least 256M memory below 4G automatically
+         if crashkernel=Y,low is not specified.
+      2) Let user specify low memory size instead.
+      3) Specified value 0 will disable low memory allocation::
+
+            crashkernel=0,low
+
+Boot into System Kernel
+-----------------------
+1) Update the boot loader (such as grub, yaboot, or lilo) configuration
+   files as necessary.
+
+2) Boot the system kernel with the boot parameter "crashkernel=Y@X".
+
+   On x86 and x86_64, use "crashkernel=Y[@X]". Most of the time, the
+   start address 'X' is not necessary, kernel will search a suitable
+   area. Unless an explicit start address is expected.
+
+   On ppc64, use "crashkernel=128M@32M".
+
+   On ia64, 256M@256M is a generous value that typically works.
+   The region may be automatically placed on ia64, see the
+   dump-capture kernel config option notes above.
+   If use sparse memory, the size should be rounded to GRANULE boundaries.
+
+   On s390x, typically use "crashkernel=xxM". The value of xx is dependent
+   on the memory consumption of the kdump system. In general this is not
+   dependent on the memory size of the production system.
+
+   On arm, the use of "crashkernel=Y@X" is no longer necessary; the
+   kernel will automatically locate the crash kernel image within the
+   first 512MB of RAM if X is not given.
+
+   On arm64, use "crashkernel=Y[@X]".  Note that the start address of
+   the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).
+
+Load the Dump-capture Kernel
+============================
+
+After booting to the system kernel, dump-capture kernel needs to be
+loaded.
+
+Based on the architecture and type of image (relocatable or not), one
+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 bzImage/vmlinuz if kernel is relocatable.
+	- Use vmlinux if kernel is not 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::
+
+   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::
+
+   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::
+
+   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::
+
+   kexec -p <dump-capture-kernel-Image> \
+   --initrd=<initrd-for-dump-capture-kernel> \
+   --append="root=<root-dev> <arch-specific-options>"
+
+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
+
+Following are the arch specific command line options to be used while
+loading dump-capture kernel.
+
+For i386, x86_64 and ia64:
+
+	"1 irqpoll nr_cpus=1 reset_devices"
+
+For ppc64:
+
+	"1 maxcpus=1 noirqdistrib reset_devices"
+
+For s390x:
+
+	"1 nr_cpus=1 cgroup_disable=memory"
+
+For arm:
+
+	"1 maxcpus=1 reset_devices"
+
+For arm64:
+
+	"1 nr_cpus=1 reset_devices"
+
+Notes on loading the dump-capture kernel:
+
+* By default, the ELF headers are stored in ELF64 format to support
+  systems with more than 4GB memory. On i386, kexec automatically checks if
+  the physical RAM size exceeds the 4 GB limit and if not, uses ELF32.
+  So, on non-PAE systems, ELF32 is always used.
+
+  The --elf32-core-headers option can be used to force the generation of ELF32
+  headers. This is necessary because GDB currently cannot open vmcore files
+  with ELF64 headers on 32-bit systems.
+
+* The "irqpoll" boot parameter reduces driver initialization failures
+  due to shared interrupts in the dump-capture kernel.
+
+* You must specify <root-dev> in the format corresponding to the root
+  device name in the output of mount command.
+
+* Boot parameter "1" boots the dump-capture kernel into single-user
+  mode without networking. If you want networking, use "3".
+
+* We generally don't have to bring up a SMP kernel just to capture the
+  dump. Hence generally it is useful either to build a UP dump-capture
+  kernel or specify maxcpus=1 option while loading dump-capture kernel.
+  Note, though maxcpus always works, you had better replace it with
+  nr_cpus to save memory if supported by the current ARCH, such as x86.
+
+* You should enable multi-cpu support in dump-capture kernel if you intend
+  to use multi-thread programs with it, such as parallel dump feature of
+  makedumpfile. Otherwise, the multi-thread program may have a great
+  performance degradation. To enable multi-cpu support, you should bring up an
+  SMP dump-capture kernel and specify maxcpus/nr_cpus, disable_cpu_apicid=[X]
+  options while loading it.
+
+* For s390x there are two kdump modes: If a ELF header is specified with
+  the elfcorehdr= kernel parameter, it is used by the kdump kernel as it
+  is done on all other architectures. If no elfcorehdr= kernel parameter is
+  specified, the s390x kdump kernel dynamically creates the header. The
+  second mode has the advantage that for CPU and memory hotplug, kdump has
+  not to be reloaded with kexec_load().
+
+* For s390x systems with many attached devices the "cio_ignore" kernel
+  parameter should be used for the kdump kernel in order to prevent allocation
+  of kernel memory for devices that are not relevant for kdump. The same
+  applies to systems that use SCSI/FCP devices. In that case the
+  "allow_lun_scan" zfcp module parameter should be set to zero before
+  setting FCP devices online.
+
+Kernel Panic
+============
+
+After successfully loading the dump-capture kernel as previously
+described, the system will reboot into the dump-capture kernel if a
+system crash is triggered.  Trigger points are located in panic(),
+die(), die_nmi() and in the sysrq handler (ALT-SysRq-c).
+
+The following conditions will execute a crash trigger point:
+
+If a hard lockup is detected and "NMI watchdog" is configured, the system
+will boot into the dump-capture kernel ( die_nmi() ).
+
+If die() is called, and it happens to be a thread with pid 0 or 1, or die()
+is called inside interrupt context or die() is called and panic_on_oops is set,
+the system will boot into the dump-capture kernel.
+
+On powerpc systems when a soft-reset is generated, die() is called by all cpus
+and the system will boot into the dump-capture kernel.
+
+For testing purposes, you can trigger a crash by using "ALT-SysRq-c",
+"echo c > /proc/sysrq-trigger" or write a module to force the panic.
+
+Write Out the Dump File
+=======================
+
+After the dump-capture kernel is booted, write out the dump file with
+the following command::
+
+   cp /proc/vmcore <dump-file>
+
+or use scp to write out the dump file between hosts on a network, e.g::
+
+   scp /proc/vmcore remote_username@remote_ip:<dump-file>
+
+You can also use makedumpfile utility to write out the dump file
+with specified options to filter out unwanted contents, e.g::
+
+   makedumpfile -l --message-level 1 -d 31 /proc/vmcore <dump-file>
+
+Analysis
+========
+
+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::
+
+   gdb vmlinux <dump-file>
+
+Stack trace for the task on processor 0, register display, and memory
+display work fine.
+
+Note: GDB cannot analyze core files generated in ELF64 format for x86.
+On systems with a maximum of 4GB of memory, you can generate
+ELF32-format headers using the --elf32-core-headers kernel option on the
+dump kernel.
+
+You can also use the Crash utility to analyze dump files in Kdump
+format. Crash is available at the following URL:
+
+   https://github.com/crash-utility/crash
+
+Crash document can be found at:
+   https://crash-utility.github.io/
+
+Trigger Kdump on WARN()
+=======================
+
+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.
+
+Trigger Kdump on add_taint()
+============================
+
+The kernel parameter panic_on_taint facilitates a conditional call to panic()
+from within add_taint() whenever the value set in this bitmask matches with the
+bit flag being set by add_taint().
+This will cause a kdump to occur at the add_taint()->panic() call.
+
+Contact
+=======
+
+- kexec@lists.infradead.org
+
+GDB macros
+==========
+
+.. include:: gdbmacros.txt
+   :literal:
diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
new file mode 100644
index 000000000..6726f4399
--- /dev/null
+++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
@@ -0,0 +1,597 @@
+==========
+VMCOREINFO
+==========
+
+What is it?
+===========
+
+VMCOREINFO is a special ELF note section. It contains various
+information from the kernel like structure size, page size, symbol
+values, field offsets, etc. These data are packed into an ELF note
+section and used by user-space tools like crash and makedumpfile to
+analyze a kernel's memory layout.
+
+Common variables
+================
+
+init_uts_ns.name.release
+------------------------
+
+The version of the Linux kernel. Used to find the corresponding source
+code from which the kernel has been built. For example, crash uses it to
+find the corresponding vmlinux in order to process vmcore.
+
+PAGE_SIZE
+---------
+
+The size of a page. It is the smallest unit of data used by the memory
+management facilities. It is usually 4096 bytes of size and a page is
+aligned on 4096 bytes. Used for computing page addresses.
+
+init_uts_ns
+-----------
+
+The UTS namespace which is used to isolate two specific elements of the
+system that relate to the uname(2) system call. It is named after the
+data structure used to store information returned by the uname(2) system
+call.
+
+User-space tools can get the kernel name, host name, kernel release
+number, kernel version, architecture name and OS type from it.
+
+(uts_namespace, name)
+---------------------
+
+Offset of the name's member. Crash Utility and Makedumpfile get
+the start address of the init_uts_ns.name from this.
+
+node_online_map
+---------------
+
+An array node_states[N_ONLINE] which represents the set of online nodes
+in a system, one bit position per node number. Used to keep track of
+which nodes are in the system and online.
+
+swapper_pg_dir
+--------------
+
+The global page directory pointer of the kernel. Used to translate
+virtual to physical addresses.
+
+_stext
+------
+
+Defines the beginning of the text section. In general, _stext indicates
+the kernel start address. Used to convert a virtual address from the
+direct kernel map to a physical address.
+
+vmap_area_list
+--------------
+
+Stores the virtual area list. makedumpfile gets the vmalloc start value
+from this variable and its value is necessary for vmalloc translation.
+
+mem_map
+-------
+
+Physical addresses are translated to struct pages by treating them as
+an index into the mem_map array. Right-shifting a physical address
+PAGE_SHIFT bits converts it into a page frame number which is an index
+into that mem_map array.
+
+Used to map an address to the corresponding struct page.
+
+contig_page_data
+----------------
+
+Makedumpfile gets the pglist_data structure from this symbol, which is
+used to describe the memory layout.
+
+User-space tools use this to exclude free pages when dumping memory.
+
+mem_section|(mem_section, NR_SECTION_ROOTS)|(mem_section, section_mem_map)
+--------------------------------------------------------------------------
+
+The address of the mem_section array, its length, structure size, and
+the section_mem_map offset.
+
+It exists in the sparse memory mapping model, and it is also somewhat
+similar to the mem_map variable, both of them are used to translate an
+address.
+
+MAX_PHYSMEM_BITS
+----------------
+
+Defines the maximum supported physical address space memory.
+
+page
+----
+
+The size of a page structure. struct page is an important data structure
+and it is widely used to compute contiguous memory.
+
+pglist_data
+-----------
+
+The size of a pglist_data structure. This value is used to check if the
+pglist_data structure is valid. It is also used for checking the memory
+type.
+
+zone
+----
+
+The size of a zone structure. This value is used to check if the zone
+structure has been found. It is also used for excluding free pages.
+
+free_area
+---------
+
+The size of a free_area structure. It indicates whether the free_area
+structure is valid or not. Useful when excluding free pages.
+
+list_head
+---------
+
+The size of a list_head structure. Used when iterating lists in a
+post-mortem analysis session.
+
+nodemask_t
+----------
+
+The size of a nodemask_t type. Used to compute the number of online
+nodes.
+
+(page, flags|_refcount|mapping|lru|_mapcount|private|compound_dtor|compound_order|compound_head)
+-------------------------------------------------------------------------------------------------
+
+User-space tools compute their values based on the offset of these
+variables. The variables are used when excluding unnecessary pages.
+
+(pglist_data, node_zones|nr_zones|node_mem_map|node_start_pfn|node_spanned_pages|node_id)
+-----------------------------------------------------------------------------------------
+
+On NUMA machines, each NUMA node has a pg_data_t to describe its memory
+layout. On UMA machines there is a single pglist_data which describes the
+whole memory.
+
+These values are used to check the memory type and to compute the
+virtual address for memory map.
+
+(zone, free_area|vm_stat|spanned_pages)
+---------------------------------------
+
+Each node is divided into a number of blocks called zones which
+represent ranges within memory. A zone is described by a structure zone.
+
+User-space tools compute required values based on the offset of these
+variables.
+
+(free_area, free_list)
+----------------------
+
+Offset of the free_list's member. This value is used to compute the number
+of free pages.
+
+Each zone has a free_area structure array called free_area[MAX_ORDER].
+The free_list represents a linked list of free page blocks.
+
+(list_head, next|prev)
+----------------------
+
+Offsets of the list_head's members. list_head is used to define a
+circular linked list. User-space tools need these in order to traverse
+lists.
+
+(vmap_area, va_start|list)
+--------------------------
+
+Offsets of the vmap_area's members. They carry vmalloc-specific
+information. Makedumpfile gets the start address of the vmalloc region
+from this.
+
+(zone.free_area, MAX_ORDER)
+---------------------------
+
+Free areas descriptor. User-space tools use this value to iterate the
+free_area ranges. MAX_ORDER is used by the zone buddy allocator.
+
+prb
+---
+
+A pointer to the printk ringbuffer (struct printk_ringbuffer). This
+may be pointing to the static boot ringbuffer or the dynamically
+allocated ringbuffer, depending on when the core dump occurred.
+Used by user-space tools to read the active kernel log buffer.
+
+printk_rb_static
+----------------
+
+A pointer to the static boot printk ringbuffer. If @prb has a
+different value, this is useful for viewing the initial boot messages,
+which may have been overwritten in the dynamically allocated
+ringbuffer.
+
+clear_seq
+---------
+
+The sequence number of the printk() record after the last clear
+command. It indicates the first record after the last
+SYSLOG_ACTION_CLEAR, like issued by 'dmesg -c'. Used by user-space
+tools to dump a subset of the dmesg log.
+
+printk_ringbuffer
+-----------------
+
+The size of a printk_ringbuffer structure. This structure contains all
+information required for accessing the various components of the
+kernel log buffer.
+
+(printk_ringbuffer, desc_ring|text_data_ring|dict_data_ring|fail)
+-----------------------------------------------------------------
+
+Offsets for the various components of the printk ringbuffer. Used by
+user-space tools to view the kernel log buffer without requiring the
+declaration of the structure.
+
+prb_desc_ring
+-------------
+
+The size of the prb_desc_ring structure. This structure contains
+information about the set of record descriptors.
+
+(prb_desc_ring, count_bits|descs|head_id|tail_id)
+-------------------------------------------------
+
+Offsets for the fields describing the set of record descriptors. Used
+by user-space tools to be able to traverse the descriptors without
+requiring the declaration of the structure.
+
+prb_desc
+--------
+
+The size of the prb_desc structure. This structure contains
+information about a single record descriptor.
+
+(prb_desc, info|state_var|text_blk_lpos|dict_blk_lpos)
+------------------------------------------------------
+
+Offsets for the fields describing a record descriptors. Used by
+user-space tools to be able to read descriptors without requiring
+the declaration of the structure.
+
+prb_data_blk_lpos
+-----------------
+
+The size of the prb_data_blk_lpos structure. This structure contains
+information about where the text or dictionary data (data block) is
+located within the respective data ring.
+
+(prb_data_blk_lpos, begin|next)
+-------------------------------
+
+Offsets for the fields describing the location of a data block. Used
+by user-space tools to be able to locate data blocks without
+requiring the declaration of the structure.
+
+printk_info
+-----------
+
+The size of the printk_info structure. This structure contains all
+the meta-data for a record.
+
+(printk_info, seq|ts_nsec|text_len|dict_len|caller_id)
+------------------------------------------------------
+
+Offsets for the fields providing the meta-data for a record. Used by
+user-space tools to be able to read the information without requiring
+the declaration of the structure.
+
+prb_data_ring
+-------------
+
+The size of the prb_data_ring structure. This structure contains
+information about a set of data blocks.
+
+(prb_data_ring, size_bits|data|head_lpos|tail_lpos)
+---------------------------------------------------
+
+Offsets for the fields describing a set of data blocks. Used by
+user-space tools to be able to access the data blocks without
+requiring the declaration of the structure.
+
+atomic_long_t
+-------------
+
+The size of the atomic_long_t structure. Used by user-space tools to
+be able to copy the full structure, regardless of its
+architecture-specific implementation.
+
+(atomic_long_t, counter)
+------------------------
+
+Offset for the long value of an atomic_long_t variable. Used by
+user-space tools to access the long value without requiring the
+architecture-specific declaration.
+
+(free_area.free_list, MIGRATE_TYPES)
+------------------------------------
+
+The number of migrate types for pages. The free_list is described by the
+array. Used by tools to compute the number of free pages.
+
+NR_FREE_PAGES
+-------------
+
+On linux-2.6.21 or later, the number of free pages is in
+vm_stat[NR_FREE_PAGES]. Used to get the number of free pages.
+
+PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision|PG_head_mask
+------------------------------------------------------------------------------
+
+Page attributes. These flags are used to filter various unnecessary for
+dumping pages.
+
+PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy)|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline)
+-----------------------------------------------------------------------------
+
+More page attributes. These flags are used to filter various unnecessary for
+dumping pages.
+
+
+HUGETLB_PAGE_DTOR
+-----------------
+
+The HUGETLB_PAGE_DTOR flag denotes hugetlbfs pages. Makedumpfile
+excludes these pages.
+
+x86_64
+======
+
+phys_base
+---------
+
+Used to convert the virtual address of an exported kernel symbol to its
+corresponding physical address.
+
+init_top_pgt
+------------
+
+Used to walk through the whole page table and convert virtual addresses
+to physical addresses. The init_top_pgt is somewhat similar to
+swapper_pg_dir, but it is only used in x86_64.
+
+pgtable_l5_enabled
+------------------
+
+User-space tools need to know whether the crash kernel was in 5-level
+paging mode.
+
+node_data
+---------
+
+This is a struct pglist_data array and stores all NUMA nodes
+information. Makedumpfile gets the pglist_data structure from it.
+
+(node_data, MAX_NUMNODES)
+-------------------------
+
+The maximum number of nodes in system.
+
+KERNELOFFSET
+------------
+
+The kernel randomization offset. Used to compute the page offset. If
+KASLR is disabled, this value is zero.
+
+KERNEL_IMAGE_SIZE
+-----------------
+
+Currently unused by Makedumpfile. Used to compute the module virtual
+address by Crash.
+
+sme_mask
+--------
+
+AMD-specific with SME support: it indicates the secure memory encryption
+mask. Makedumpfile tools need to know whether the crash kernel was
+encrypted. If SME is enabled in the first kernel, the crash kernel's
+page table entries (pgd/pud/pmd/pte) contain the memory encryption
+mask. This is used to remove the SME mask and obtain the true physical
+address.
+
+Currently, sme_mask stores the value of the C-bit position. If needed,
+additional SME-relevant info can be placed in that variable.
+
+For example::
+
+  [ misc	        ][ enc bit  ][ other misc SME info       ]
+  0000_0000_0000_0000_1000_0000_0000_0000_0000_0000_..._0000
+  63   59   55   51   47   43   39   35   31   27   ... 3
+
+x86_32
+======
+
+X86_PAE
+-------
+
+Denotes whether physical address extensions are enabled. It has the cost
+of a higher page table lookup overhead, and also consumes more page
+table space per process. Used to check whether PAE was enabled in the
+crash kernel when converting virtual addresses to physical addresses.
+
+ia64
+====
+
+pgdat_list|(pgdat_list, MAX_NUMNODES)
+-------------------------------------
+
+pg_data_t array storing all NUMA nodes information. MAX_NUMNODES
+indicates the number of the nodes.
+
+node_memblk|(node_memblk, NR_NODE_MEMBLKS)
+------------------------------------------
+
+List of node memory chunks. Filled when parsing the SRAT table to obtain
+information about memory nodes. NR_NODE_MEMBLKS indicates the number of
+node memory chunks.
+
+These values are used to compute the number of nodes the crashed kernel used.
+
+node_memblk_s|(node_memblk_s, start_paddr)|(node_memblk_s, size)
+----------------------------------------------------------------
+
+The size of a struct node_memblk_s and the offsets of the
+node_memblk_s's members. Used to compute the number of nodes.
+
+PGTABLE_3|PGTABLE_4
+-------------------
+
+User-space tools need to know whether the crash kernel was in 3-level or
+4-level paging mode. Used to distinguish the page table.
+
+ARM64
+=====
+
+VA_BITS
+-------
+
+The maximum number of bits for virtual addresses. Used to compute the
+virtual memory ranges.
+
+kimage_voffset
+--------------
+
+The offset between the kernel virtual and physical mappings. Used to
+translate virtual to physical addresses.
+
+PHYS_OFFSET
+-----------
+
+Indicates the physical address of the start of memory. Similar to
+kimage_voffset, which is used to translate virtual to physical
+addresses.
+
+KERNELOFFSET
+------------
+
+The kernel randomization offset. Used to compute the page offset. If
+KASLR is disabled, this value is zero.
+
+KERNELPACMASK
+-------------
+
+The mask to extract the Pointer Authentication Code from a kernel virtual
+address.
+
+TCR_EL1.T1SZ
+------------
+
+Indicates the size offset of the memory region addressed by TTBR1_EL1.
+The region size is 2^(64-T1SZ) bytes.
+
+TTBR1_EL1 is the table base address register specified by ARMv8-A
+architecture which is used to lookup the page-tables for the Virtual
+addresses in the higher VA range (refer to ARMv8 ARM document for
+more details).
+
+MODULES_VADDR|MODULES_END|VMALLOC_START|VMALLOC_END|VMEMMAP_START|VMEMMAP_END
+-----------------------------------------------------------------------------
+
+Used to get the correct ranges:
+	MODULES_VADDR ~ MODULES_END-1 : Kernel module space.
+	VMALLOC_START ~ VMALLOC_END-1 : vmalloc() / ioremap() space.
+	VMEMMAP_START ~ VMEMMAP_END-1 : vmemmap region, used for struct page array.
+
+arm
+===
+
+ARM_LPAE
+--------
+
+It indicates whether the crash kernel supports large physical address
+extensions. Used to translate virtual to physical addresses.
+
+s390
+====
+
+lowcore_ptr
+-----------
+
+An array with a pointer to the lowcore of every CPU. Used to print the
+psw and all registers information.
+
+high_memory
+-----------
+
+Used to get the vmalloc_start address from the high_memory symbol.
+
+(lowcore_ptr, NR_CPUS)
+----------------------
+
+The maximum number of CPUs.
+
+powerpc
+=======
+
+
+node_data|(node_data, MAX_NUMNODES)
+-----------------------------------
+
+See above.
+
+contig_page_data
+----------------
+
+See above.
+
+vmemmap_list
+------------
+
+The vmemmap_list maintains the entire vmemmap physical mapping. Used
+to get vmemmap list count and populated vmemmap regions info. If the
+vmemmap address translation information is stored in the crash kernel,
+it is used to translate vmemmap kernel virtual addresses.
+
+mmu_vmemmap_psize
+-----------------
+
+The size of a page. Used to translate virtual to physical addresses.
+
+mmu_psize_defs
+--------------
+
+Page size definitions, i.e. 4k, 64k, or 16M.
+
+Used to make vtop translations.
+
+vmemmap_backing|(vmemmap_backing, list)|(vmemmap_backing, phys)|(vmemmap_backing, virt_addr)
+--------------------------------------------------------------------------------------------
+
+The vmemmap virtual address space management does not have a traditional
+page table to track which virtual struct pages are backed by a physical
+mapping. The virtual to physical mappings are tracked in a simple linked
+list format.
+
+User-space tools need to know the offset of list, phys and virt_addr
+when computing the count of vmemmap regions.
+
+mmu_psize_def|(mmu_psize_def, shift)
+------------------------------------
+
+The size of a struct mmu_psize_def and the offset of mmu_psize_def's
+member.
+
+Used in vtop translations.
+
+sh
+==
+
+node_data|(node_data, MAX_NUMNODES)
+-----------------------------------
+
+See above.
+
+X2TLB
+-----
+
+Indicates whether the crashed kernel enabled SH extended mode.