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1st kernel will build up the kernel command parameter dmcryptkeys as
similar to elfcorehdr to pass the memory address of the stored info of dm
crypt key to kdump kernel.
Link: https://lkml.kernel.org/r/20250502011246.99238-8-coxu@redhat.com
Signed-off-by: Coiby Xu <coxu@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: "Daniel P. Berrange" <berrange@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Jan Pazdziora <jpazdziora@redhat.com>
Cc: Liu Pingfan <kernelfans@gmail.com>
Cc: Milan Broz <gmazyland@gmail.com>
Cc: Ondrej Kozina <okozina@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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When there are CPU and memory hot un/plugs, the dm crypt keys may need to
be reloaded again depending on the solution for crash hotplug support.
Currently, there are two solutions. One is to utilizes udev to instruct
user space to reload the kdump kernel image and initrd, elfcorehdr and etc
again. The other is to only update the elfcorehdr segment introduced in
commit 247262756121 ("crash: add generic infrastructure for crash hotplug
support").
For the 1st solution, the dm crypt keys need to be reloaded again. The
user space can write true to /sys/kernel/config/crash_dm_crypt_key/reuse
so the stored keys can be re-used.
For the 2nd solution, the dm crypt keys don't need to be reloaded.
Currently, only x86 supports the 2nd solution. If the 2nd solution gets
extended to all arches, this patch can be dropped.
Link: https://lkml.kernel.org/r/20250502011246.99238-5-coxu@redhat.com
Signed-off-by: Coiby Xu <coxu@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: "Daniel P. Berrange" <berrange@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Jan Pazdziora <jpazdziora@redhat.com>
Cc: Liu Pingfan <kernelfans@gmail.com>
Cc: Milan Broz <gmazyland@gmail.com>
Cc: Ondrej Kozina <okozina@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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A configfs /sys/kernel/config/crash_dm_crypt_keys is provided for user
space to make the dm crypt keys persist for the kdump kernel. Take the
case of dumping to a LUKS-encrypted target as an example, here is the life
cycle of the kdump copies of LUKS volume keys,
1. After the 1st kernel loads the initramfs during boot, systemd uses
an user-input passphrase to de-crypt the LUKS volume keys or simply
TPM-sealed volume keys and then save the volume keys to specified
keyring (using the --link-vk-to-keyring API) and the keys will expire
within specified time.
2. A user space tool (kdump initramfs loader like kdump-utils) create
key items inside /sys/kernel/config/crash_dm_crypt_keys to inform
the 1st kernel which keys are needed.
3. When the kdump initramfs is loaded by the kexec_file_load
syscall, the 1st kernel will iterate created key items, save the
keys to kdump reserved memory.
4. When the 1st kernel crashes and the kdump initramfs is booted, the
kdump initramfs asks the kdump kernel to create a user key using the
key stored in kdump reserved memory by writing yes to
/sys/kernel/crash_dm_crypt_keys/restore. Then the LUKS encrypted
device is unlocked with libcryptsetup's --volume-key-keyring API.
5. The system gets rebooted to the 1st kernel after dumping vmcore to
the LUKS encrypted device is finished
Eventually the keys have to stay in the kdump reserved memory for the
kdump kernel to unlock encrypted volumes. During this process, some
measures like letting the keys expire within specified time are desirable
to reduce security risk.
This patch assumes,
1) there are 128 LUKS devices at maximum to be unlocked thus
MAX_KEY_NUM=128.
2) a key description won't exceed 128 bytes thus KEY_DESC_MAX_LEN=128.
And here is a demo on how to interact with
/sys/kernel/config/crash_dm_crypt_keys,
# Add key #1
mkdir /sys/kernel/config/crash_dm_crypt_keys/7d26b7b4-e342-4d2d-b660-7426b0996720
# Add key #1's description
echo cryptsetup:7d26b7b4-e342-4d2d-b660-7426b0996720 > /sys/kernel/config/crash_dm_crypt_keys/description
# how many keys do we have now?
cat /sys/kernel/config/crash_dm_crypt_keys/count
1
# Add key# 2 in the same way
# how many keys do we have now?
cat /sys/kernel/config/crash_dm_crypt_keys/count
2
# the tree structure of /crash_dm_crypt_keys configfs
tree /sys/kernel/config/crash_dm_crypt_keys/
/sys/kernel/config/crash_dm_crypt_keys/
├── 7d26b7b4-e342-4d2d-b660-7426b0996720
│ └── description
├── count
├── fce2cd38-4d59-4317-8ce2-1fd24d52c46a
│ └── description
Link: https://lkml.kernel.org/r/20250502011246.99238-3-coxu@redhat.com
Signed-off-by: Coiby Xu <coxu@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: "Daniel P. Berrange" <berrange@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Jan Pazdziora <jpazdziora@redhat.com>
Cc: Liu Pingfan <kernelfans@gmail.com>
Cc: Milan Broz <gmazyland@gmail.com>
Cc: Ondrej Kozina <okozina@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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HIGHMEM64G support was added in linux-2.3.25 to support (then)
high-end Pentium Pro and Pentium III Xeon servers with more than 4GB of
addressing, NUMA and PCI-X slots started appearing.
I have found no evidence of this ever being used in regular dual-socket
servers or consumer devices, all the users seem obsolete these days,
even by i386 standards:
- Support for NUMA servers (NUMA-Q, IBM x440, unisys) was already
removed ten years ago.
- 4+ socket non-NUMA servers based on Intel 450GX/450NX, HP F8 and
ServerWorks ServerSet/GrandChampion could theoretically still work
with 8GB, but these were exceptionally rare even 20 years ago and
would have usually been equipped with than the maximum amount of
RAM.
- Some SKUs of the Celeron D from 2004 had 64-bit mode fused off but
could still work in a Socket 775 mainboard designed for the later
Core 2 Duo and 8GB. Apparently most BIOSes at the time only allowed
64-bit CPUs.
- The rare Xeon LV "Sossaman" came on a few motherboards with
registered DDR2 memory support up to 16GB.
- In the early days of x86-64 hardware, there was sometimes the need
to run a 32-bit kernel to work around bugs in the hardware drivers,
or in the syscall emulation for 32-bit userspace. This likely still
works but there should never be a need for this any more.
PAE mode is still required to get access to the 'NX' bit on Atom
'Pentium M' and 'Core Duo' CPUs.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250226213714.4040853-6-arnd@kernel.org
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After commit 443cbaf9e2fd ("crash: split vmcoreinfo exporting code out
from crash_core.c"), Kconfig item CRASH_CORE has gone away in kernel.
Items VMCORE_INFO and CRASH_RESERVE are used instead.
So clean up the outdated description about CRASH_CORE and update it
accordingly.
Link: https://lkml.kernel.org/r/20240329132825.1102459-3-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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When a kdump kernel is started from a crashing CPU then there is no
guarantee that this CPU is the real boot CPU (BSP). If the kdump kernel
tries to online the BSP then the INIT sequence will reset the machine.
There is a command line option to prevent this, but in case of nested kdump
kernels this is wrong.
But that command line option is not required at all because the real
BSP is enumerated as the first CPU by firmware. Support for the only
known system which was different (Voyager) got removed long ago.
Detect whether the boot CPU APIC ID is the first APIC ID enumerated by
the firmware. If the first APIC ID enumerated is not matching the boot
CPU APIC ID then skip registering it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.348542071@linutronix.de
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Drop or update mentions of IA64, as appropriate.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Except cp and makedumpfile, add scp example to write out the dump file.
Link: https://lkml.kernel.org/r/1644324666-15947-3-git-send-email-yangtiezhu@loongson.cn
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marco Elver <elver@google.com>
Cc: Xuefeng Li <lixuefeng@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Patch series "Update doc and fix some issues about kdump", v2.
This patch (of 5):
After commit 6a108a14fa35 ("kconfig: rename CONFIG_EMBEDDED to
CONFIG_EXPERT"), "Configure standard kernel features (for small
systems)" is not exist, we should use "Configure standard kernel
features (expert users)" now.
Link: https://lkml.kernel.org/r/1644324666-15947-1-git-send-email-yangtiezhu@loongson.cn
Link: https://lkml.kernel.org/r/1644324666-15947-2-git-send-email-yangtiezhu@loongson.cn
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marco Elver <elver@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Xuefeng Li <lixuefeng@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Some parts of the guide are aged, hence need be updated.
1) The backup area of the 1st 640K on X86_64 has been removed
by below commits, update the description accordingly.
commit 7c321eb2b843 ("x86/kdump: Remove the backup region handling")
commit 6f599d84231f ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified")
2) Sort out the descripiton of "crashkernel syntax" part.
3) And some other minor cleanups.
Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
Link: https://lore.kernel.org/r/20210609083218.GB591017@MiWiFi-R3L-srv
[jc: added blank line to fix added build warning]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Since crash utility has been moved to github, the original URL is no
longer available. Let's update it accordingly.
Suggested-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
Link: https://lore.kernel.org/r/a088bff5-1174-25fa-ac26-6e46795f4085@redhat.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Analogously to the introduction of panic_on_warn, this patch introduces
a kernel option named panic_on_taint in order to provide a simple and
generic way to stop execution and catch a coredump when the kernel gets
tainted by any given flag.
This is useful for debugging sessions as it avoids having to rebuild the
kernel to explicitly add calls to panic() into the code sites that
introduce the taint flags of interest.
For instance, if one is interested in proceeding with a post-mortem
analysis at the point a given code path is hitting a bad page (i.e.
unaccount_page_cache_page(), or slab_bug()), a coredump can be collected
by rebooting the kernel with 'panic_on_taint=0x20' amended to the
command line.
Another, perhaps less frequent, use for this option would be as a means
for assuring a security policy case where only a subset of taints, or no
single taint (in paranoid mode), is allowed for the running system. The
optional switch 'nousertaint' is handy in this particular scenario, as
it will avoid userspace induced crashes by writes to sysctl interface
/proc/sys/kernel/tainted causing false positive hits for such policies.
[akpm@linux-foundation.org: tweak kernel-parameters.txt wording]
Suggested-by: Qian Cai <cai@lca.pw>
Signed-off-by: Rafael Aquini <aquini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Adrian Bunk <bunk@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Takashi Iwai <tiwai@suse.de>
Link: http://lkml.kernel.org/r/20200515175502.146720-1-aquini@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The Kdump documentation describes procedures with admins use
in order to solve issues on their systems.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
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