printk: Add a short description string to kmsg_dump()

kmsg_dump doesn't forward the panic reason string to the kmsg_dumper
callback.
This patch adds a new struct kmsg_dump_detail, that will hold the

printk: Add a short description string to kmsg_dump()

kmsg_dump doesn't forward the panic reason string to the kmsg_dumper
callback.
This patch adds a new struct kmsg_dump_detail, that will hold the
reason and description, and pass it to the dump() callback.

To avoid updating all kmsg_dump() call, it adds a kmsg_dump_desc()
function and a macro for backward compatibility.

I've written this for drm_panic, but it can be useful for other
kmsg_dumper.
It allows to see the panic reason, like "sysrq triggered crash"
or "VFS: Unable to mount root fs on xxxx" on the drm panic screen.

v2:
* Use a struct kmsg_dump_detail to hold the reason and description
pointer, for more flexibility if we want to add other parameters.
(Kees Cook)
* Fix powerpc/nvram_64 build, as I didn't update the forward
declaration of oops_to_nvram()

Signed-off-by: Jocelyn Falempe <[email protected]>
Acked-by: Petr Mladek <[email protected]>
Acked-by: Michael Ellerman <[email protected]> (powerpc)
Acked-by: Kees Cook <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

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printk: kmsg_dump: remove _nolock() variants

kmsg_dump_rewind() and kmsg_dump_get_line() are lockless, so there is
no need for _nolock() variants. Remove these functions and switch all
callers of th

printk: kmsg_dump: remove _nolock() variants

kmsg_dump_rewind() and kmsg_dump_get_line() are lockless, so there is
no need for _nolock() variants. Remove these functions and switch all
callers of the _nolock() variants.

The functions without _nolock() were chosen because they are already
exported to kernel modules.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Signed-off-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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printk: introduce a kmsg_dump iterator

Rather than storing the iterator information in the registered
kmsg_dumper structure, create a separate iterator structure. The
kmsg_dump_iter structure can re

printk: introduce a kmsg_dump iterator

Rather than storing the iterator information in the registered
kmsg_dumper structure, create a separate iterator structure. The
kmsg_dump_iter structure can reside on the stack of the caller, thus
allowing lockless use of the kmsg_dump functions.

Update code that accesses the kernel logs using the kmsg_dumper
structure to use the new kmsg_dump_iter structure. For kmsg_dumpers,
this also means adding a call to kmsg_dump_rewind() to initialize
the iterator.

All this is in preparation for removal of @logbuf_lock.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Kees Cook <[email protected]> # pstore
Reviewed-by: Petr Mladek <[email protected]>
Signed-off-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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printk: kmsg_dumper: remove @active field

All 6 kmsg_dumpers do not benefit from the @active flag:

(provide their own synchronization)
- arch/powerpc/kernel/nvram_64.c
- arch/um/kernel/kmsg_d

printk: kmsg_dumper: remove @active field

All 6 kmsg_dumpers do not benefit from the @active flag:

(provide their own synchronization)
- arch/powerpc/kernel/nvram_64.c
- arch/um/kernel/kmsg_dump.c
- drivers/mtd/mtdoops.c
- fs/pstore/platform.c

(only dump on KMSG_DUMP_PANIC, which does not require
synchronization)
- arch/powerpc/platforms/powernv/opal-kmsg.c
- drivers/hv/vmbus_drv.c

The other 2 kmsg_dump users also do not rely on @active:

(hard-code @active to always be true)
- arch/powerpc/xmon/xmon.c
- kernel/debug/kdb/kdb_main.c

Therefore, @active can be removed.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Signed-off-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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printk: refactor kmsg_dump_get_buffer()

kmsg_dump_get_buffer() requires nearly the same logic as
syslog_print_all(), but uses different variable names and
does not make use of the ringbuffer loop ma

printk: refactor kmsg_dump_get_buffer()

kmsg_dump_get_buffer() requires nearly the same logic as
syslog_print_all(), but uses different variable names and
does not make use of the ringbuffer loop macros. Modify
kmsg_dump_get_buffer() so that the implementation is as similar
to syslog_print_all() as possible.

A follow-up commit will move this common logic into a
separate helper function.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Signed-off-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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printk: kmsg_dump: remove unused fields

struct kmsg_dumper still contains some fields that were used to
iterate the old ringbuffer. They are no longer used. Remove them
and update the struct documen

printk: kmsg_dump: remove unused fields

struct kmsg_dumper still contains some fields that were used to
iterate the old ringbuffer. They are no longer used. Remove them
and update the struct documentation.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Signed-off-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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printk: Introduce kmsg_dump_reason_str()

The pstore subsystem already had a private version of this function.
With the coming addition of the pstore/zone driver, this needs to be
shared. As it reall

printk: Introduce kmsg_dump_reason_str()

The pstore subsystem already had a private version of this function.
With the coming addition of the pstore/zone driver, this needs to be
shared. As it really should live with printk, move it there instead.

Link: https://lore.kernel.org/lkml/[email protected]/
Acked-by: Petr Mladek <[email protected]>
Acked-by: Sergey Senozhatsky <[email protected]>
Reviewed-by: Pavel Tatashin <[email protected]>
Signed-off-by: Kees Cook <[email protected]>

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printk: honor the max_reason field in kmsg_dumper

kmsg_dump() allows to dump kmesg buffer for various system events: oops,
panic, reboot, etc. It provides an interface to register a callback
call fo

printk: honor the max_reason field in kmsg_dumper

kmsg_dump() allows to dump kmesg buffer for various system events: oops,
panic, reboot, etc. It provides an interface to register a callback
call for clients, and in that callback interface there is a field
"max_reason", but it was getting ignored when set to any "reason"
higher than KMSG_DUMP_OOPS unless "always_kmsg_dump" was passed as
kernel parameter.

Allow clients to actually control their "max_reason", and keep the
current behavior when "max_reason" is not set.

Signed-off-by: Pavel Tatashin <[email protected]>
Link: https://lore.kernel.org/lkml/[email protected]/
Reviewed-by: Petr Mladek <[email protected]>
Signed-off-by: Kees Cook <[email protected]>

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printk: Collapse shutdown types into a single dump reason

To turn the KMSG_DUMP_* reasons into a more ordered list, collapse
the redundant KMSG_DUMP_(RESTART|HALT|POWEROFF) reasons into
KMSG_DUMP_SH

printk: Collapse shutdown types into a single dump reason

To turn the KMSG_DUMP_* reasons into a more ordered list, collapse
the redundant KMSG_DUMP_(RESTART|HALT|POWEROFF) reasons into
KMSG_DUMP_SHUTDOWN. The current users already don't meaningfully
distinguish between them, so there's no need to, as discussed here:
https://lore.kernel.org/lkml/CA+CK2bAPv5u1ih5y9t5FUnTyximtFCtDYXJCpuyjOyHNOkRdqw@mail.gmail.com/

Link: https://lore.kernel.org/lkml/[email protected]/
Reviewed-by: Pavel Tatashin <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Acked-by: Michael Ellerman <[email protected]> (powerpc)
Signed-off-by: Kees Cook <[email protected]>

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printk: Implement some unlocked kmsg_dump functions

If used from KDB, the locked variants are prone to deadlocks (suppose we
got to the debugger w/ the logbuf lock held).

So, we have to implement a

printk: Implement some unlocked kmsg_dump functions

If used from KDB, the locked variants are prone to deadlocks (suppose we
got to the debugger w/ the logbuf lock held).

So, we have to implement a few routines that grab no logbuf lock.

Yet we don't need these functions in modules, so we don't export them.

Signed-off-by: Anton Vorontsov <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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kmsg - kmsg_dump() fix CONFIG_PRINTK=n compilation

Signed-off-by: Kay Sievers <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Reported-by: Randy Dunlap <[email protected]>
Reported-by:

kmsg - kmsg_dump() fix CONFIG_PRINTK=n compilation

Signed-off-by: Kay Sievers <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Reported-by: Randy Dunlap <[email protected]>
Reported-by: Fengguang Wu <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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kmsg - kmsg_dump() use iterator to receive log buffer content

Provide an iterator to receive the log buffer content, and convert all
kmsg_dump() users to it.

The structured data in the kmsg buffer

kmsg - kmsg_dump() use iterator to receive log buffer content

Provide an iterator to receive the log buffer content, and convert all
kmsg_dump() users to it.

The structured data in the kmsg buffer now contains binary data, which
should no longer be copied verbatim to the kmsg_dump() users.

The iterator should provide reliable access to the buffer data, and also
supports proper log line-aware chunking of data while iterating.

Signed-off-by: Kay Sievers <[email protected]>
Tested-by: Tony Luck <[email protected]>
Reported-by: Anton Vorontsov <[email protected]>
Tested-by: Anton Vorontsov <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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kmsg_dump: don't run on non-error paths by default

Since commit 04c6862c055f ("kmsg_dump: add kmsg_dump() calls to the
reboot, halt, poweroff and emergency_restart paths"), kmsg_dump() gets
run on n

kmsg_dump: don't run on non-error paths by default

Since commit 04c6862c055f ("kmsg_dump: add kmsg_dump() calls to the
reboot, halt, poweroff and emergency_restart paths"), kmsg_dump() gets
run on normal paths including poweroff and reboot.

This is less than ideal given pstore implementations that can only
represent single backtraces, since a reboot may overwrite a stored oops
before it's been picked up by userspace. In addition, some pstore
backends may have low performance and provide a significant delay in
reboot as a result.

This patch adds a printk.always_kmsg_dump kernel parameter (which can also
be changed from userspace). Without it, the code will only be run on
failure paths rather than on normal paths. The option can be enabled in
environments where there's a desire to attempt to audit whether or not a
reboot was cleanly requested or not.

Signed-off-by: Matthew Garrett <[email protected]>
Acked-by: Seiji Aguchi <[email protected]>
Cc: Seiji Aguchi <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Marco Stornelli <[email protected]>
Cc: Artem Bityutskiy <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: Don Zickus <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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kexec: remove KMSG_DUMP_KEXEC

KMSG_DUMP_KEXEC is useless because we already save kernel messages inside
/proc/vmcore, and it is unsafe to allow modules to do other stuffs in a
crash dump scenario.

kexec: remove KMSG_DUMP_KEXEC

KMSG_DUMP_KEXEC is useless because we already save kernel messages inside
/proc/vmcore, and it is unsafe to allow modules to do other stuffs in a
crash dump scenario.

[[email protected]: fix powerpc build]
Signed-off-by: WANG Cong <[email protected]>
Reported-by: Vivek Goyal <[email protected]>
Acked-by: Vivek Goyal <[email protected]>
Acked-by: Jarod Wilson <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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kmsg_dump.h: fix build when CONFIG_PRINTK is disabled

Fix <linux/kmsg_dump.h> when CONFIG_PRINTK is not enabled:

include/linux/kmsg_dump.h:56: error: 'EINVAL' undeclared (first use in this functi

kmsg_dump.h: fix build when CONFIG_PRINTK is disabled

Fix <linux/kmsg_dump.h> when CONFIG_PRINTK is not enabled:

include/linux/kmsg_dump.h:56: error: 'EINVAL' undeclared (first use in this function)
include/linux/kmsg_dump.h:61: error: 'EINVAL' undeclared (first use in this function)

Looks like commit 595dd3d8bf95 ("kmsg_dump: fix build for
CONFIG_PRINTK=n") uses EINVAL without having the needed header file(s),
but I'm sure that I build tested that patch also. oh well.

Signed-off-by: Randy Dunlap <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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kmsg_dump: add kmsg_dump() calls to the reboot, halt, poweroff and emergency_restart paths

We need to know the reason why system rebooted in support service.
However, we can't inform our customers o

kmsg_dump: add kmsg_dump() calls to the reboot, halt, poweroff and emergency_restart paths

We need to know the reason why system rebooted in support service.
However, we can't inform our customers of the reason because final
messages are lost on current Linux kernel.

This patch improves the situation above because the final messages are
saved by adding kmsg_dump() to reboot, halt, poweroff and
emergency_restart path.

Signed-off-by: Seiji Aguchi <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Marco Stornelli <[email protected]>
Reviewed-by: Artem Bityutskiy <[email protected]>
Reviewed-by: KOSAKI Motohiro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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kmsg_dump: Dump on crash_kexec as well

crash_kexec gets called before kmsg_dump(KMSG_DUMP_OOPS) if
panic_on_oops is set, so the kernel log buffer is not stored
for this case.

This patch adds a KMSG

kmsg_dump: Dump on crash_kexec as well

crash_kexec gets called before kmsg_dump(KMSG_DUMP_OOPS) if
panic_on_oops is set, so the kernel log buffer is not stored
for this case.

This patch adds a KMSG_DUMP_KEXEC dump type which gets called
when crash_kexec() is invoked. To avoid getting double dumps,
the old KMSG_DUMP_PANIC is moved below crash_kexec(). The
mtdoops driver is modified to handle KMSG_DUMP_KEXEC in the
same way as a panic.

Signed-off-by: KOSAKI Motohiro <[email protected]>
Acked-by: Simon Kagstrom <[email protected]>
Signed-off-by: David Woodhouse <[email protected]>

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kmsg_dump: fix build for CONFIG_PRINTK=n

kmsg_dump() fails to build when CONFIG_PRINTK=n; provide stubs
for the kmsg_dump*() functions when CONFIG_PRINTK=n.

kernel/printk.c: In function 'kmsg_dump'

kmsg_dump: fix build for CONFIG_PRINTK=n

kmsg_dump() fails to build when CONFIG_PRINTK=n; provide stubs
for the kmsg_dump*() functions when CONFIG_PRINTK=n.

kernel/printk.c: In function 'kmsg_dump':
kernel/printk.c:1501: error: 'log_buf_len' undeclared (first use in this function)
kernel/printk.c:1502: error: 'logged_chars' undeclared (first use in this function)
kernel/printk.c:1506: error: 'log_buf' undeclared (first use in this function)

Signed-off-by: Randy Dunlap <[email protected]>
Acked-by: Simon Kagstrom <[email protected]>
Signed-off-by: David Woodhouse <[email protected]>

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core: Add kernel message dumper to call on oopses and panics

The core functionality is implemented as per Linus suggestion from

http://lists.infradead.org/pipermail/linux-mtd/2009-October/027620.

core: Add kernel message dumper to call on oopses and panics

The core functionality is implemented as per Linus suggestion from

http://lists.infradead.org/pipermail/linux-mtd/2009-October/027620.html

(with the kmsg_dump implementation by Linus). A struct kmsg_dumper has
been added which contains a callback to dump the kernel log buffers on
crashes. The kmsg_dump function gets called from oops_exit() and panic()
and invokes this callbacks with the crash reason.

[dwmw2: Fix log_end handling]
Signed-off-by: Simon Kagstrom <[email protected]>
Reviewed-by: Anders Grafstrom <[email protected]>
Reviewed-by: Linus Torvalds <[email protected]>
Acked-by: Ingo Molnar <[email protected]>
Signed-off-by: Artem Bityutskiy <[email protected]>
Signed-off-by: David Woodhouse <[email protected]>

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