linux.git/kernel/debug/debug_core.c, branch v6.6.132

kgdb: Flush console before entering kgdb on panic

2023-11-28T17:19:47+00:00

[ Upstream commit dd712d3d45807db9fcae28a522deee85c1f2fde6 ]

When entering kdb/kgdb on a kernel panic, it was be observed that the
console isn't flushed before the `kdb` prompt came up. Specifically,
when using the buddy lockup detector on arm64 and running:
  echo HARDLOCKUP > /sys/kernel/debug/provoke-crash/DIRECT

I could see:
  [   26.161099] lkdtm: Performing direct entry HARDLOCKUP
  [   32.499881] watchdog: Watchdog detected hard LOCKUP on cpu 6
  [   32.552865] Sending NMI from CPU 5 to CPUs 6:
  [   32.557359] NMI backtrace for cpu 6
  ... [backtrace for cpu 6] ...
  [   32.558353] NMI backtrace for cpu 5
  ... [backtrace for cpu 5] ...
  [   32.867471] Sending NMI from CPU 5 to CPUs 0-4,7:
  [   32.872321] NMI backtrace forP cpuANC: Hard LOCKUP

  Entering kdb (current=..., pid 0) on processor 5 due to Keyboard Entry
  [5]kdb>

As you can see, backtraces for the other CPUs start printing and get
interleaved with the kdb PANIC print.

Let's replicate the commands to flush the console in the kdb panic
entry point to avoid this.

Signed-off-by: Douglas Anderson 
Link: https://lore.kernel.org/r/20230822131945.1.I5b460ae8f954e4c4f628a373d6e74713c06dd26f@changeid
Signed-off-by: Daniel Thompson 
Signed-off-by: Sasha Levin

tty: sysrq: switch sysrq handlers from int to u8

2023-07-25T17:21:03+00:00

The passed parameter to sysrq handlers is a key (a character). So change
the type from 'int' to 'u8'. Let it specifically be 'u8' for two
reasons:
* unsigned: unsigned values come from the upper layers (devices) and the
  tty layer assumes unsigned on most places, and
* 8-bit: as that what's supposed to be one day in all the layers built
  on the top of tty. (Currently, we use mostly 'unsigned char' and
  somewhere still only 'char'. (But that also translates to the former
  thanks to -funsigned-char.))

Signed-off-by: Jiri Slaby (SUSE) 
Cc: Richard Henderson 
Cc: Ivan Kokshaysky 
Cc: Matt Turner 
Cc: Huacai Chen 
Cc: WANG Xuerui 
Cc: Thomas Bogendoerfer 
Cc: Michael Ellerman 
Cc: Nicholas Piggin 
Cc: Christophe Leroy 
Cc: "David S. Miller" 
Cc: Maarten Lankhorst 
Cc: Maxime Ripard 
Cc: Thomas Zimmermann 
Cc: David Airlie 
Cc: Daniel Vetter 
Cc: Jason Wessel 
Cc: Daniel Thompson 
Cc: Douglas Anderson 
Cc: "Rafael J. Wysocki" 
Cc: Len Brown 
Cc: Pavel Machek 
Cc: "Paul E. McKenney" 
Cc: Frederic Weisbecker 
Cc: Neeraj Upadhyay 
Cc: Joel Fernandes 
Cc: Josh Triplett 
Cc: Boqun Feng 
Cc: Steven Rostedt 
Cc: Mathieu Desnoyers 
Cc: Lai Jiangshan 
Cc: Zqiang 
Acked-by: Thomas Zimmermann  # DRM
Acked-by: WANG Xuerui  # loongarch
Acked-by: Paul E. McKenney 
Acked-by: Daniel Thompson 
Link: https://lore.kernel.org/r/20230712081811.29004-3-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman

mm: remove vmacache

2022-09-27T02:46:18+00:00

By using the maple tree and the maple tree state, the vmacache is no
longer beneficial and is complicating the VMA code.  Remove the vmacache
to reduce the work in keeping it up to date and code complexity.

Link: https://lkml.kernel.org/r/20220906194824.2110408-26-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett 
Acked-by: Vlastimil Babka 
Tested-by: Yu Zhao 
Cc: Catalin Marinas 
Cc: David Hildenbrand 
Cc: David Howells 
Cc: Davidlohr Bueso 
Cc: "Matthew Wilcox (Oracle)" 
Cc: SeongJae Park 
Cc: Sven Schnelle 
Cc: Will Deacon 
Signed-off-by: Andrew Morton

lockdown: also lock down previous kgdb use

2022-05-24T18:29:34+00:00

KGDB and KDB allow read and write access to kernel memory, and thus
should be restricted during lockdown.  An attacker with access to a
serial port (for example, via a hypervisor console, which some cloud
vendors provide over the network) could trigger the debugger so it is
important that the debugger respect the lockdown mode when/if it is
triggered.

Fix this by integrating lockdown into kdb's existing permissions
mechanism.  Unfortunately kgdb does not have any permissions mechanism
(although it certainly could be added later) so, for now, kgdb is simply
and brutally disabled by immediately exiting the gdb stub without taking
any action.

For lockdowns established early in the boot (e.g. the normal case) then
this should be fine but on systems where kgdb has set breakpoints before
the lockdown is enacted than "bad things" will happen.

CVE: CVE-2022-21499
Co-developed-by: Stephen Brennan 
Signed-off-by: Stephen Brennan 
Reviewed-by: Douglas Anderson 
Signed-off-by: Daniel Thompson 
Signed-off-by: Linus Torvalds

kernel: debug: Convert to SPDX identifier

2021-09-06T13:31:11+00:00

use SPDX-License-Identifier instead of a verbose license text

Signed-off-by: Cai Huoqing 
Link: https://lore.kernel.org/r/20210906112302.937-1-caihuoqing@baidu.com
Signed-off-by: Daniel Thompson

kgdb: Fix fall-through warning for Clang

2021-06-01T09:34:35+00:00

In preparation to enable -Wimplicit-fallthrough for Clang, fix a
fall-through warning by explicitly adding a goto statement instead
of letting the code fall through to the next case.

Link: https://github.com/KSPP/linux/issues/115
Signed-off-by: Gustavo A. R. Silva 
Link: https://lore.kernel.org/r/20210528200222.GA39201@embeddedor
Signed-off-by: Daniel Thompson

kgdb: Fix spelling mistakes

2021-06-01T09:29:21+00:00

Fix some spelling mistakes in comments:
initalization ==> initialization
detatch ==> detach
represntation ==> representation
hexidecimal ==> hexadecimal
delimeter ==> delimiter
architecure ==> architecture

Signed-off-by: Zhen Lei 
Link: https://lore.kernel.org/r/20210529110305.9446-3-thunder.leizhen@huawei.com
Signed-off-by: Daniel Thompson

kgdb: fix to kill breakpoints on initmem after boot

2021-02-26T17:41:05+00:00

Currently breakpoints in kernel .init.text section are not handled
correctly while allowing to remove them even after corresponding pages
have been freed.

Fix it via killing .init.text section breakpoints just prior to initmem
pages being freed.

Doug: "HW breakpoints aren't handled by this patch but it's probably
not such a big deal".

Link: https://lkml.kernel.org/r/20210224081652.587785-1-sumit.garg@linaro.org
Signed-off-by: Sumit Garg 
Suggested-by: Doug Anderson 
Acked-by: Doug Anderson 
Acked-by: Daniel Thompson 
Tested-by: Daniel Thompson 
Cc: Masami Hiramatsu 
Cc: Steven Rostedt (VMware) 
Cc: Jason Wessel 
Cc: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kgdb: Remove kgdb_schedule_breakpoint()

2021-02-11T10:51:56+00:00

To the very best of my knowledge there has never been any in-tree
code that calls this function. It exists largely to support an
out-of-tree driver that provides kgdb-over-ethernet using the
netpoll API.

kgdboe has been out-of-tree for more than 10 years and I don't
recall any serious attempt to upstream it at any point in the last
five. At this stage it looks better to stop carrying this code in
the kernel and integrate the code into the out-of-tree driver
instead.

The long term trajectory for the kernel looks likely to include
effort to remove or reduce the use of tasklets (something that has
also been true for the last 10 years). Thus the main real reason
for this patch is to make explicit that the in-tree kgdb features
do not require tasklets.

Signed-off-by: Daniel Thompson 
Link: https://lore.kernel.org/r/20210210142525.2876648-1-daniel.thompson@linaro.org
Reviewed-by: Douglas Anderson 
Acked-by: Davidlohr Bueso 
Acked-by: Jason Wessel

kgdb: rectify kernel-doc for kgdb_unregister_io_module()

2021-02-04T15:23:25+00:00

The command 'find ./kernel/debug/ | xargs ./scripts/kernel-doc -none'
reported a typo in the kernel-doc of kgdb_unregister_io_module().

Rectify the kernel-doc, such that no issues remain for ./kernel/debug/.

Signed-off-by: Lukas Bulwahn 
Link: https://lore.kernel.org/r/20210125144847.21896-1-lukas.bulwahn@gmail.com
Signed-off-by: Daniel Thompson