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 added as elf notes to /proc/vmcore, which is copied by user space scripts for post-analysis. The sequence of actions done by device drivers to append their device specific hardware/firmware logs to /proc/vmcore are as follows: 1. During probe (before hardware is initialized), device drivers register to the vmcore module (via vmcore_add_device_dump()), with callback function, along with buffer size and log name needed for firmware/hardware log collection. 2. vmcore module allocates the buffer with requested size. It adds an elf note 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 vmcore module. The device specific hardware/firmware logs can be seen as elf notes with note type 0x700, as shown below: # readelf -n /proc/vmcore Displaying notes found at file offset 0x00001000 with length 0x040032c0: Owner Data size Description LINUX 0x02000fec Unknown note type: (0x00000700) LINUX 0x02000fec Unknown note type: (0x00000700) CORE 0x00000150 NT_PRSTATUS (prstatus structure) CORE 0x00000150 NT_PRSTATUS (prstatus structure) CORE 0x00000150 NT_PRSTATUS (prstatus structure) CORE 0x00000150 NT_PRSTATUS (prstatus structure) CORE 0x00000150 NT_PRSTATUS (prstatus structure) CORE 0x00000150 NT_PRSTATUS (prstatus structure) CORE 0x00000150 NT_PRSTATUS (prstatus structure) CORE 0x00000150 NT_PRSTATUS (prstatus structure) VMCOREINFO 0x00000785 Unknown note type: (0x00000000) Patch 1 adds API to vmcore module to allow drivers to register callback to collect the device specific hardware/firmware logs. The logs will be added to /proc/vmcore as elf notes. Patch 2 updates read and mmap logic to append device specific hardware/ firmware logs as elf notes. Patch 3 shows a cxgb4 driver example using the API to collect hardware/firmware logs in crash recovery kernel, before hardware is initialized. Thanks, Rahul --- v7: - Removed "CHELSIO" vendor identifier in Elf Note name. Instead, writing "LINUX". - Moved vmcoredd_header to new file include/uapi/linux/vmcore.h - Reworked vmcoredd_header to include Elf Note as part of the header itself. - Removed vmcoredd_get_note_size(). - Renamed vmcoredd_write_note() to vmcoredd_write_header(). - Replaced all "unsigned long" with "unsigned int" for device dump size since max size of Elf Word is u32. v6: - Reworked device dump elf note name to contain vendor identifier. - Added vmcoredd_header that precedes actual dump in the Elf Note. - Device dump's name is moved inside vmcoredd_header. - Added "CHELSIO" string as vendor identifier in the Elf Note name for cxgb4 device dumps. v5: - Removed enabling CONFIG_PROC_VMCORE_DEVICE_DUMP by default and updated help message. v4: - Made __vmcore_add_device_dump() static. - Moved compile check to define vmcore_add_device_dump() to crash_dump.h to fix compilation when vmcore.c is not compiled in. - Convert ---help--- to help in Kconfig as indicated by checkpatch. - Rebased to tip. v3: - Dropped sysfs crashdd module. - Exported dumps as elf notes. Suggested by Eric Biederman <ebied...@xmission.com>. Added as patch 2 in this version. - Added CONFIG_PROC_VMCORE_DEVICE_DUMP to allow configuring device dump support. - Moved logic related to adding dumps from crashdd to vmcore module. - Rename all crashdd* to vmcoredd*. - Updated comments. v2: - Added ABI Documentation for crashdd. - Directly use octal permission instead of macro. Changes since rfc v2: - Moved exporting crashdd from procfs to sysfs. Suggested by Stephen Hemminger <step...@networkplumber.org> - 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 <ebied...@xmission.com>. - 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 (3): vmcore: add API to collect hardware dump in second kernel vmcore: append device dumps to vmcore as elf notes 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 | 10 + fs/proc/Kconfig | 15 + fs/proc/vmcore.c | 387 ++++++++++++++++++++++- include/linux/crash_dump.h | 18 ++ include/linux/kcore.h | 6 + include/uapi/linux/elf.h | 1 + include/uapi/linux/vmcore.h | 16 + 10 files changed, 472 insertions(+), 13 deletions(-) create mode 100644 include/uapi/linux/vmcore.h -- 2.14.1
