linux-toradex.git/kernel/panic.c, branch v7.0-rc6

panic: add panic_force_cpu= parameter to redirect panic to a specific CPU

2026-02-03T16:21:26+00:00

Some platforms require panic handling to execute on a specific CPU for
crash dump to work reliably.  This can be due to firmware limitations,
interrupt routing constraints, or platform-specific requirements where
only a single CPU is able to safely enter the crash kernel.

Add the panic_force_cpu= kernel command-line parameter to redirect panic
execution to a designated CPU.  When the parameter is provided, the CPU
that initially triggers panic forwards the panic context to the target CPU
via IPI, which then proceeds with the normal panic and kexec flow.

The IPI delivery is implemented as a weak function
(panic_smp_redirect_cpu) so architectures with NMI support can override it
for more reliable delivery.

If the specified CPU is invalid, offline, or a panic is already in
progress on another CPU, the redirection is skipped and panic continues on
the current CPU.

[pnina.feder@mobileye.com: fix unused variable warning]
  Link: https://lkml.kernel.org/r/20260126122618.2967950-1-pnina.feder@mobileye.com
Link: https://lkml.kernel.org/r/20260122102457.1154599-1-pnina.feder@mobileye.com
Signed-off-by: Pnina Feder 
Reviewed-by: Petr Mladek 
Cc: Baoquan He 
Cc: Ingo Molnar 
Cc: Jonathan Corbet 
Cc: Mel Gorman 
Cc: Peter Zijlstra 
Cc: Sergey Senozhatsky 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton

panic: only warn about deprecated panic_print on write access

2026-01-19T20:30:01+00:00

The panic_print_deprecated() warning is being triggered on both read and
write operations to the panic_print parameter.

This causes spurious warnings when users run 'sysctl -a' to list all
sysctl values, since that command reads /proc/sys/kernel/panic_print and
triggers the deprecation notice.

Modify the handlers to only emit the deprecation warning when the
parameter is actually being set:

 - sysctl_panic_print_handler(): check 'write' flag before warning.
 - panic_print_get(): remove the deprecation call entirely.

This way, users are only warned when they actively try to use the
deprecated parameter, not when passively querying system state.

Link: https://lkml.kernel.org/r/20260106163321.83586-1-gal@nvidia.com
Fixes: ee13240cd78b ("panic: add note that panic_print sysctl interface is deprecated")
Fixes: 2683df6539cb ("panic: add note that 'panic_print' parameter is deprecated")
Signed-off-by: Gal Pressman 
Reviewed-by: Mark Bloch 
Reviewed-by: Nimrod Oren 
Cc: Feng Tang 
Cc: Joel Granados 
Cc: Petr Mladek 
Cc: 
Signed-off-by: Andrew Morton

Merge tag 'mm-nonmm-stable-2025-12-06-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-12-06T22:01:20+00:00

Pull non-MM updates from Andrew Morton:

 - "panic: sys_info: Refactor and fix a potential issue" (Andy Shevchenko)
   fixes a build issue and does some cleanup in ib/sys_info.c

 - "Implement mul_u64_u64_div_u64_roundup()" (David Laight)
   enhances the 64-bit math code on behalf of a PWM driver and beefs up
   the test module for these library functions

 - "scripts/gdb/symbols: make BPF debug info available to GDB" (Ilya Leoshkevich)
   makes BPF symbol names, sizes, and line numbers available to the GDB
   debugger

 - "Enable hung_task and lockup cases to dump system info on demand" (Feng Tang)
   adds a sysctl which can be used to cause additional info dumping when
   the hung-task and lockup detectors fire

 - "lib/base64: add generic encoder/decoder, migrate users" (Kuan-Wei Chiu)
   adds a general base64 encoder/decoder to lib/ and migrates several
   users away from their private implementations

 - "rbree: inline rb_first() and rb_last()" (Eric Dumazet)
   makes TCP a little faster

 - "liveupdate: Rework KHO for in-kernel users" (Pasha Tatashin)
   reworks the KEXEC Handover interfaces in preparation for Live Update
   Orchestrator (LUO), and possibly for other future clients

 - "kho: simplify state machine and enable dynamic updates" (Pasha Tatashin)
   increases the flexibility of KEXEC Handover. Also preparation for LUO

 - "Live Update Orchestrator" (Pasha Tatashin)
   is a major new feature targeted at cloud environments. Quoting the
   cover letter:

      This series introduces the Live Update Orchestrator, a kernel
      subsystem designed to facilitate live kernel updates using a
      kexec-based reboot. This capability is critical for cloud
      environments, allowing hypervisors to be updated with minimal
      downtime for running virtual machines. LUO achieves this by
      preserving the state of selected resources, such as memory,
      devices and their dependencies, across the kernel transition.

      As a key feature, this series includes support for preserving
      memfd file descriptors, which allows critical in-memory data, such
      as guest RAM or any other large memory region, to be maintained in
      RAM across the kexec reboot.

   Mike Rappaport merits a mention here, for his extensive review and
   testing work.

 - "kexec: reorganize kexec and kdump sysfs" (Sourabh Jain)
   moves the kexec and kdump sysfs entries from /sys/kernel/ to
   /sys/kernel/kexec/ and adds back-compatibility symlinks which can
   hopefully be removed one day

 - "kho: fixes for vmalloc restoration" (Mike Rapoport)
   fixes a BUG which was being hit during KHO restoration of vmalloc()
   regions

* tag 'mm-nonmm-stable-2025-12-06-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (139 commits)
  calibrate: update header inclusion
  Reinstate "resource: avoid unnecessary lookups in find_next_iomem_res()"
  vmcoreinfo: track and log recoverable hardware errors
  kho: fix restoring of contiguous ranges of order-0 pages
  kho: kho_restore_vmalloc: fix initialization of pages array
  MAINTAINERS: TPM DEVICE DRIVER: update the W-tag
  init: replace simple_strtoul with kstrtoul to improve lpj_setup
  KHO: fix boot failure due to kmemleak access to non-PRESENT pages
  Documentation/ABI: new kexec and kdump sysfs interface
  Documentation/ABI: mark old kexec sysfs deprecated
  kexec: move sysfs entries to /sys/kernel/kexec
  test_kho: always print restore status
  kho: free chunks using free_page() instead of kfree()
  selftests/liveupdate: add kexec test for multiple and empty sessions
  selftests/liveupdate: add simple kexec-based selftest for LUO
  selftests/liveupdate: add userspace API selftests
  docs: add documentation for memfd preservation via LUO
  mm: memfd_luo: allow preserving memfd
  liveupdate: luo_file: add private argument to store runtime state
  mm: shmem: export some functions to internal.h
  ...

Merge branch 'objtool/core'

2025-11-21T10:21:20+00:00

Bring in the UDB and objtool data annotations to avoid conflicts while further extending the bug exceptions.

Signed-off-by: Peter Zijlstra

panic: sys_info: align constant definition names with parameters

2025-11-20T22:03:40+00:00

Align constant definition names with parameters to make it easier to map. 
It's also better to maintain and extend the names while keeping their
uniqueness.

Link: https://lkml.kernel.org/r/20251030132007.3742368-3-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko 
Reviewed-by: Feng Tang 
Reviewed-by: Petr Mladek 
Signed-off-by: Andrew Morton

taint/module: remove unnecessary taint_flag.module field

2025-11-12T18:00:15+00:00

The TAINT_RANDSTRUCT and TAINT_FWCTL flags are mistakenly set in the
taint_flags table as per-module flags.  While this can be trivially
corrected, the issue can be avoided altogether by removing the
taint_flag.module field.

This is possible because, since commit 7fd8329ba502 ("taint/module: Clean
up global and module taint flags handling") in 2016, the handling of
module taint flags has been fully generic.  Specifically,
module_flags_taint() can print all flags, and the required output buffer
size is properly defined in terms of TAINT_FLAGS_COUNT.  The actual
per-module flags are always those added to module.taints by calls to
add_taint_module().

Link: https://lkml.kernel.org/r/20251022082938.26670-1-petr.pavlu@suse.com
Signed-off-by: Petr Pavlu 
Acked-by: Petr Mladek 
Reviewed-by: Randy Dunlap 
Cc: Aaron Tomlin 
Cc: Luis Chamberalin 
Cc: Petr Pavlu 
Cc: Sami Tolvanen 
Signed-off-by: Andrew Morton

taint: add reminder about updating docs and scripts

2025-11-12T18:00:15+00:00

Sometimes people update taint-related pieces of the kernel without
updating the supporting documentation or scripts.  Add a reminder to do
this.

Link: https://lkml.kernel.org/r/20251015221626.1126156-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap 
Suggested-by: Jason Gunthorpe 
Reviewed-by: Jason Gunthorpe 
Cc: David Gow 
Cc: Jonathan Corbet 
Signed-off-by: Andrew Morton

panic: remove CONFIG_PANIC_ON_OOPS_VALUE

2025-09-28T18:36:13+00:00

There's really no need for this since it's 0 or 1 when
CONFIG_PANIC_ON_OOPS is disabled/enabled, so just use IS_ENABLED()
instead.  The extra symbol goes back to the original code adding it in
commit 2a01bb3885c9 ("panic: Make panic_on_oops configurable").

Link: https://lkml.kernel.org/r/20250924094303.18521-2-johannes@sipsolutions.net
Signed-off-by: Johannes Berg 
Signed-off-by: Andrew Morton

panic: remove redundant panic-cpu backtrace

2025-09-14T00:32:54+00:00

Backtraces from all CPUs are printed during panic() when
SYS_INFO_ALL_CPU_BT is set.  It shows the backtrace for the panic-CPU even
when it has already been explicitly printed before.

Do not change the legacy code which prints the backtrace in various
contexts, for example, as part of Oops report, right after panic message. 
It will always be visible in the crash dump.

Instead, remember when the backtrace was printed, and skip it when dumping
the optional backtraces on all CPUs.

[akpm@linux-foundation.org: make panic_this_cpu_backtrace_printed static]
  Closes: https://lore.kernel.org/oe-kbuild-all/202509050048.FMpVvh1u-lkp@intel.com/
[pmladek@suse.com: Handle situations when the backtrace was not printed for the panic CPU]
Link: https://lkml.kernel.org/r/20250903100418.410026-1-pmladek@suse.com
Signed-off-by: Sergey Senozhatsky 
Link: https://lore.kernel.org/r/20250731030314.3818040-1-senozhatsky@chromium.org
Signed-off-by: Petr Mladek 
Tested-by: Feng Tang 
Reviewed-by: John Ogness 
Signed-off-by: Andrew Morton

panic/printk: replace this_cpu_in_panic() with panic_on_this_cpu()

2025-09-14T00:32:52+00:00

The helper this_cpu_in_panic() duplicated logic already provided by
panic_on_this_cpu().

Remove this_cpu_in_panic() and switch all users to panic_on_this_cpu().

This simplifies the code and avoids having two helpers for the same check.

Link: https://lkml.kernel.org/r/20250825022947.1596226-8-wangjinchao600@gmail.com
Signed-off-by: Jinchao Wang 
Cc: Anna Schumaker 
Cc: Baoquan He 
Cc: "Darrick J. Wong" 
Cc: Dave Young 
Cc: Doug Anderson 
Cc: "Guilherme G. Piccoli" 
Cc: Helge Deller 
Cc: Ingo Molnar 
Cc: Jason Gunthorpe 
Cc: Joanthan Cameron 
Cc: Joel Granados 
Cc: John Ogness 
Cc: Kees Cook 
Cc: Li Huafei 
Cc: "Luck, Tony" 
Cc: Luo Gengkun 
Cc: Max Kellermann 
Cc: Nam Cao 
Cc: oushixiong 
Cc: Petr Mladek 
Cc: Qianqiang Liu 
Cc: Sergey Senozhatsky 
Cc: Sohil Mehta 
Cc: Steven Rostedt 
Cc: Tejun Heo 
Cc: Thomas Gleinxer 
Cc: Thomas Zimemrmann 
Cc: Thorsten Blum 
Cc: Ville Syrjala 
Cc: Vivek Goyal 
Cc: Yicong Yang 
Cc: Yunhui Cui 
Cc: Yury Norov (NVIDIA) 
Signed-off-by: Andrew Morton