On production servers running variety of workloads over time, kernel panic can happen sporadically after days or even months. It is important to collect as much debug logs as possible to root cause and fix the problem, that may not be easy to reproduce. Snapshot of underlying hardware/firmware state (like register dump, firmware logs, adapter memory, etc.), at the time of kernel panic will be very helpful while debugging the culprit device driver. This series of patches add new generic framework that enable device drivers to collect device specific snapshot of the hardware/firmware state of the underlying device in the crash recovery kernel. In crash recovery kernel, the collected logs are exposed via /sys/kernel/crashdd/ directory, which is copied by user space scripts for post-analysis. A kernel module crashdd is newly added. In crash recovery kernel, crashdd exposes /sys/kernel/crashdd/ directory containing device specific hardware/firmware logs. The sequence of actions done by device drivers to append their device specific hardware/firmware logs to /sys/kernel/crashdd/ directory are as follows: 1. During probe (before hardware is initialized), device drivers register to the crashdd module (via crashdd_add_dump()), with callback function, along with buffer size and log name needed for firmware/hardware log collection. 2. Crashdd creates a driver's directory under /sys/kernel/crashdd/<driver>. Then, it allocates the buffer with requested size and invokes the device driver's registered callback function. 3. Device driver collects all hardware/firmware logs into the buffer and returns control back to crashdd. 4. Crashdd exposes the buffer as a file via /sys/kernel/crashdd/<driver>/<dump_file>. 5. User space script (/usr/lib/kdump/kdump-lib-initramfs.sh) copies the entire /sys/kernel/crashdd/ directory to /var/crash/ directory. Patch 1 adds crashdd module to allow drivers to register callback to collect the device specific hardware/firmware logs. The module also exports /sys/kernel/crashdd/ directory containing the hardware/firmware logs. Patch 2 shows a cxgb4 driver example using the API to collect hardware/firmware logs in crash recovery kernel, before hardware is initialized. The logs for the devices are made available under /sys/kernel/crashdd/cxgb4/ directory. Thanks, Rahul RFC v1: https://lkml.org/lkml/2018/3/2/542 RFC v2: https://lkml.org/lkml/2018/3/16/326 --- Changes since rfc v2: - Moved exporting crashdd from procfs to sysfs. Suggested by Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx> - Moved code from fs/proc/crashdd.c to fs/crashdd/ directory. - Replaced all proc API with sysfs API and updated comments. - Calling driver callback before creating the binary file under crashdd sysfs. - Changed binary dump file permission from S_IRUSR to S_IRUGO. - Changed module name from CRASH_DRIVER_DUMP to CRASH_DEVICE_DUMP. rfc v2: - Collecting logs in 2nd kernel instead of during kernel panic. Suggested by Eric Biederman <ebiederm@xxxxxxxxxxxx>. - Added new crashdd module that exports /proc/crashdd/ containing driver's registered hardware/firmware logs in patch 1. - Replaced the API to allow drivers to register their hardware/firmware log collect routine in crash recovery kernel in patch 1. - Updated patch 2 to use the new API in patch 1. Rahul Lakkireddy (2): fs/crashdd: add API to collect hardware dump in second kernel cxgb4: collect hardware dump in second kernel drivers/net/ethernet/chelsio/cxgb4/cxgb4.h | 4 + drivers/net/ethernet/chelsio/cxgb4/cxgb4_cudbg.c | 25 +++ drivers/net/ethernet/chelsio/cxgb4/cxgb4_cudbg.h | 3 + drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c | 12 ++ fs/Kconfig | 1 + fs/Makefile | 1 + fs/crashdd/Kconfig | 10 + fs/crashdd/Makefile | 3 + fs/crashdd/crashdd.c | 234 +++++++++++++++++++++++ fs/crashdd/crashdd_internal.h | 24 +++ include/linux/crashdd.h | 24 +++ 11 files changed, 341 insertions(+) create mode 100644 fs/crashdd/Kconfig create mode 100644 fs/crashdd/Makefile create mode 100644 fs/crashdd/crashdd.c create mode 100644 fs/crashdd/crashdd_internal.h create mode 100644 include/linux/crashdd.h -- 2.14.1
