device coredump: add new device coredump class

Many devices run firmware and/or complex hardware, and most of that
can have bugs. When it misbehaves, however, it is often much harder
to debug than software running on the host.

Introduce a "device coredump" mechanism to allow dumping internal
device/firmware state through a generalized mechanism. As devices
are different and information needed can vary accordingly, this
doesn't prescribe a file format - it just provides mechanism to
get data to be able to capture it in a generalized way (e.g. in
distributions.)

The dumped data will be readable in sysfs in the virtual device's
data file under /sys/class/devcoredump/devcd*/. Writing to it will
free the data and remove the device, as does a 5-minute timeout.

Note that generalized capturing of such data may result in privacy
issues, so users generally need to be involved. In order to allow
certain users/system integrators/... to disable the feature at all,
introduce a Kconfig option to override the drivers that would like
to have the feature.

For now, this provides two ways of dumping data:
 1) with a vmalloc'ed area, that is then given to the subsystem
    and freed after retrieval or timeout
 2) with a generalized reader/free function method

We could/should add more options, e.g. a list of pages, since the
vmalloc area is very limited on some architectures.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 4e7f0ff83ae7..134f763d90fd 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -165,6 +165,27 @@ config FW_LOADER_USER_HELPER_FALLBACK
 
           If you are unsure about this, say N here.
 
+config WANT_DEV_COREDUMP
+        bool
+        help
+          Drivers should "select" this option if they desire to use the
+          device coredump mechanism.
+
+config DISABLE_DEV_COREDUMP
+        bool "Disable device coredump" if EXPERT
+        help
+          Disable the device coredump mechanism despite drivers wanting to
+          use it; this allows for more sensitive systems or systems that
+          don't want to ever access the information to not have the code,
+          nor keep any data.
+
+          If unsure, say N.
+
+config DEV_COREDUMP
+        bool
+        default y if WANT_DEV_COREDUMP
+        depends on !DISABLE_DEV_COREDUMP
+
 config DEBUG_DRIVER
         bool "Driver Core verbose debug messages"
         depends on DEBUG_KERNEL