linux-toradex.git/kernel/panic.c, branch v5.6-rc6

locking/refcount: Remove unused 'refcount_error_report()' function

2019-11-25T08:15:42+00:00

'refcount_error_report()' has no callers. Remove it.

Signed-off-by: Will Deacon 
Reviewed-by: Ard Biesheuvel 
Acked-by: Kees Cook 
Tested-by: Hanjun Guo 
Cc: Ard Biesheuvel 
Cc: Elena Reshetova 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20191121115902.2551-10-will@kernel.org
Signed-off-by: Ingo Molnar

panic: ensure preemption is disabled during panic()

2019-10-07T22:47:19+00:00

Calling 'panic()' on a kernel with CONFIG_PREEMPT=y can leave the
calling CPU in an infinite loop, but with interrupts and preemption
enabled.  From this state, userspace can continue to be scheduled,
despite the system being "dead" as far as the kernel is concerned.

This is easily reproducible on arm64 when booting with "nosmp" on the
command line; a couple of shell scripts print out a periodic "Ping"
message whilst another triggers a crash by writing to
/proc/sysrq-trigger:

  | sysrq: Trigger a crash
  | Kernel panic - not syncing: sysrq triggered crash
  | CPU: 0 PID: 1 Comm: init Not tainted 5.2.15 #1
  | Hardware name: linux,dummy-virt (DT)
  | Call trace:
  |  dump_backtrace+0x0/0x148
  |  show_stack+0x14/0x20
  |  dump_stack+0xa0/0xc4
  |  panic+0x140/0x32c
  |  sysrq_handle_reboot+0x0/0x20
  |  __handle_sysrq+0x124/0x190
  |  write_sysrq_trigger+0x64/0x88
  |  proc_reg_write+0x60/0xa8
  |  __vfs_write+0x18/0x40
  |  vfs_write+0xa4/0x1b8
  |  ksys_write+0x64/0xf0
  |  __arm64_sys_write+0x14/0x20
  |  el0_svc_common.constprop.0+0xb0/0x168
  |  el0_svc_handler+0x28/0x78
  |  el0_svc+0x8/0xc
  | Kernel Offset: disabled
  | CPU features: 0x0002,24002004
  | Memory Limit: none
  | ---[ end Kernel panic - not syncing: sysrq triggered crash ]---
  |  Ping 2!
  |  Ping 1!
  |  Ping 1!
  |  Ping 2!

The issue can also be triggered on x86 kernels if CONFIG_SMP=n,
otherwise local interrupts are disabled in 'smp_send_stop()'.

Disable preemption in 'panic()' before re-enabling interrupts.

Link: http://lkml.kernel.org/r/20191002123538.22609-1-will@kernel.org
Link: https://lore.kernel.org/r/BX1W47JXPMR8.58IYW53H6M5N@dragonstone
Signed-off-by: Will Deacon 
Reported-by: Xogium 
Reviewed-by: Kees Cook 
Cc: Russell King 
Cc: Greg Kroah-Hartman 
Cc: Ingo Molnar 
Cc: Petr Mladek 
Cc: Feng Tang 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bug: consolidate __WARN_FLAGS usage

2019-09-26T00:51:41+00:00

Instead of having separate tests for __WARN_FLAGS, merge the two #ifdef
blocks and replace the synonym WANT_WARN_ON_SLOWPATH macro.

Link: http://lkml.kernel.org/r/20190819234111.9019-7-keescook@chromium.org
Signed-off-by: Kees Cook 
Cc: Arnd Bergmann 
Cc: Borislav Petkov 
Cc: Christophe Leroy 
Cc: Drew Davenport 
Cc: Feng Tang 
Cc: Mauro Carvalho Chehab 
Cc: Peter Zijlstra 
Cc: Petr Mladek 
Cc: "Steven Rostedt (VMware)" 
Cc: YueHaibing 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bug: lift "cut here" out of __warn()

2019-09-26T00:51:40+00:00

In preparation for cleaning up "cut here", move the "cut here" logic up
out of __warn() and into callers that pass non-NULL args.  For anyone
looking closely, there are two callers that pass NULL args: one already
explicitly prints "cut here".  The remaining case is covered by how a WARN
is built, which will be cleaned up in the next patch.

Link: http://lkml.kernel.org/r/20190819234111.9019-5-keescook@chromium.org
Signed-off-by: Kees Cook 
Cc: Arnd Bergmann 
Cc: Borislav Petkov 
Cc: Christophe Leroy 
Cc: Drew Davenport 
Cc: Feng Tang 
Cc: Mauro Carvalho Chehab 
Cc: Peter Zijlstra 
Cc: Petr Mladek 
Cc: "Steven Rostedt (VMware)" 
Cc: YueHaibing 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bug: consolidate warn_slowpath_fmt() usage

2019-09-26T00:51:40+00:00

Instead of having a separate helper for no printk output, just consolidate
the logic into warn_slowpath_fmt().

Link: http://lkml.kernel.org/r/20190819234111.9019-4-keescook@chromium.org
Signed-off-by: Kees Cook 
Cc: Arnd Bergmann 
Cc: Borislav Petkov 
Cc: Christophe Leroy 
Cc: Drew Davenport 
Cc: Feng Tang 
Cc: Mauro Carvalho Chehab 
Cc: Peter Zijlstra 
Cc: Petr Mladek 
Cc: "Steven Rostedt (VMware)" 
Cc: YueHaibing 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bug: refactor away warn_slowpath_fmt_taint()

2019-09-26T00:51:40+00:00

Patch series "Clean up WARN() "cut here" handling", v2.

Christophe Leroy noticed that the fix for missing "cut here" in the WARN()
case was adding explicit printk() calls instead of teaching the exception
handler to add it.  This refactors the bug/warn infrastructure to pass
this information as a new BUGFLAG.

Longer details repeated from the last patch in the series:

bug: move WARN_ON() "cut here" into exception handler

The original cleanup of "cut here" missed the WARN_ON() case (that does
not have a printk message), which was fixed recently by adding an explicit
printk of "cut here".  This had the downside of adding a printk() to every
WARN_ON() caller, which reduces the utility of using an instruction
exception to streamline the resulting code.  By making this a new BUGFLAG,
all of these can be removed and "cut here" can be handled by the exception
handler.

This was very pronounced on PowerPC, but the effect can be seen on x86 as
well.  The resulting text size of a defconfig build shows some small
savings from this patch:

   text    data     bss     dec     hex filename
19691167        5134320 1646664 26472151        193eed7 vmlinux.before
19676362        5134260 1663048 26473670        193f4c6 vmlinux.after

This change also opens the door for creating something like BUG_MSG(),
where a custom printk() before issuing BUG(), without confusing the "cut
here" line.

This patch (of 7):

There's no reason to have specialized helpers for passing the warn taint
down to __warn().  Consolidate and refactor helper macros, removing
__WARN_printf() and warn_slowpath_fmt_taint().

Link: http://lkml.kernel.org/r/20190819234111.9019-2-keescook@chromium.org
Signed-off-by: Kees Cook 
Cc: Christophe Leroy 
Cc: Peter Zijlstra 
Cc: Christophe Leroy 
Cc: Drew Davenport 
Cc: Arnd Bergmann 
Cc: "Steven Rostedt (VMware)" 
Cc: Feng Tang 
Cc: Petr Mladek 
Cc: Mauro Carvalho Chehab 
Cc: Borislav Petkov 
Cc: YueHaibing 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kgdb: don't use a notifier to enter kgdb at panic; call directly

2019-09-26T00:51:40+00:00

Right now kgdb/kdb hooks up to debug panics by registering for the panic
notifier.  This works OK except that it means that kgdb/kdb gets called
_after_ the CPUs in the system are taken offline.  That means that if
anything important was happening on those CPUs (like something that might
have contributed to the panic) you can't debug them.

Specifically I ran into a case where I got a panic because a task was
"blocked for more than 120 seconds" which was detected on CPU 2.  I nicely
got shown stack traces in the kernel log for all CPUs including CPU 0,
which was running 'PID: 111 Comm: kworker/0:1H' and was in the middle of
__mmc_switch().

I then ended up at the kdb prompt where switched over to kgdb to try to
look at local variables of the process on CPU 0.  I found that I couldn't.
Digging more, I found that I had no info on any tasks running on CPUs
other than CPU 2 and that asking kdb for help showed me "Error: no saved
data for this cpu".  This was because all the CPUs were offline.

Let's move the entry of kdb/kgdb to a direct call from panic() and stop
using the generic notifier.  Putting a direct call in allows us to order
things more properly and it also doesn't seem like we're breaking any
abstractions by calling into the debugger from the panic function.

Daniel said:

: This patch changes the way kdump and kgdb interact with each other.
: However it would seem rather odd to have both tools simultaneously armed
: and, even if they were, the user still has the option to use panic_timeout
: to force a kdump to happen.  Thus I think the change of order is
: acceptable.

Link: http://lkml.kernel.org/r/20190703170354.217312-1-dianders@chromium.org
Signed-off-by: Douglas Anderson 
Reviewed-by: Daniel Thompson 
Cc: Jason Wessel 
Cc: Kees Cook 
Cc: Borislav Petkov 
Cc: Thomas Gleixner 
Cc: Feng Tang 
Cc: YueHaibing 
Cc: Sergey Senozhatsky 
Cc: "Steven Rostedt (VMware)" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

docs: admin-guide: move sysctl directory to it

2019-07-15T14:03:01+00:00

The stuff under sysctl describes /sys interface from userspace
point of view. So, add it to the admin-guide and remove the
:orphan: from its index file.

Signed-off-by: Mauro Carvalho Chehab

docs: sysctl: convert to ReST

2019-07-15T12:20:26+00:00

Rename the /proc/sys/ documentation files to ReST, using the
README file as a template for an index.rst, adding the other
files there via TOC markup.

Despite being written on different times with different
styles, try to make them somewhat coherent with a similar
look and feel, ensuring that they'll look nice as both
raw text file and as via the html output produced by the
Sphinx build system.

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

treewide: Add SPDX license identifier for missed files

2019-05-21T08:50:45+00:00

Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have EXPORT_.*_SYMBOL_GPL inside which was used in the
   initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman