[determine-reboot-cause] Support 'Kernel Panic' reboot cause (sonic-net#7153)

Signed-off-by: Yong Zhao yozhao@microsoft.com

Why I did it
If device reboot was caused by kernel panic, then we need retrieve and store the key information into the symbol file previous-reboot-cause.json. The CLI show reboot-cause will read this file to get the reason of previous reboot.

This PR is related to PR in sonic-utilities repo: sonic-net/sonic-utilities#1486

How I did it
The string variable previous_reboot_cause will be parsed to check whether it contains the keyword Kernel Panic. If it did, then store the keyword and time information into a dictionary.

How to verify it
I verified this change on a virtual testbed.

admin@vlab-01:/host/reboot-cause$ more previous-reboot-cause.json
{"gen_time": "2021_03_24_23_22_35", "cause": "Kernel Panic", "user": "N/A", "time": "Wed 24 Mar 2021 11:22:03 PM UTC", "comment": "N/A"}

admin@vlab-01:/host/reboot-cause$ show reboot-cause
Kernel Panic [Time: Wed 24 Mar 2021 11:22:03 PM UTC]

Author: yozhao101

src/sonic-host-services/scripts/determine-reboot-cause

@@ -127,7 +127,15 @@ def find_hardware_reboot_cause():
 
 
 def get_reboot_cause_dict(previous_reboot_cause, comment, gen_time):
-    # resultant dictionary
+    """Store the key infomation of device reboot into a dictionary by parsing the string in
+    previous_reboot_cause.
+
+    If user issused a command to reboot device, then user, command and time will be
+    stored into a dictionary.
+
+    If device was rebooted due to the kernel panic, then the string `Kernel Panic` 
+    and time will be stored into a dictionary.
+    """
     reboot_cause_dict = {}
     reboot_cause_dict['gen_time'] = gen_time
     reboot_cause_dict['cause'] = previous_reboot_cause
@@ -142,7 +150,12 @@ def get_reboot_cause_dict(previous_reboot_cause, comment, gen_time):
             reboot_cause_dict['cause'] = match.group(1)
             reboot_cause_dict['user'] = match.group(2)
             reboot_cause_dict['time'] = match.group(3)
-
+    elif re.search(r'Kernel Panic', previous_reboot_cause):
+        match = re.search(r'Kernel Panic \[Time: (.*)\]', previous_reboot_cause)
+        if match is not None:
+            reboot_cause_dict['cause'] = "Kernel Panic"
+            reboot_cause_dict['time'] = match.group(1)
+ 
     return reboot_cause_dict
 
 

src/sonic-host-services/tests/determine-reboot-cause_test.py

@@ -55,6 +55,9 @@
 GEN_TIME_WATCHDOG = "2020_10_22_03_15_08"
 REBOOT_CAUSE_USER = "User issued 'reboot' command [User: admin, Time: Thu Oct 22 03:11:08 UTC 2020]"
 GEN_TIME_USER = "2020_10_22_03_14_07"
+REBOOT_CAUSE_KERNEL_PANIC = "Kernel Panic [Time: Sun Mar 28 13:45:12 UTC 2021]"
+GEN_TIME_KERNEL_PANIC = "2021_3_28_13_48_49"
+
 
 EXPECTED_PARSE_WARMFAST_REBOOT_FROM_PROC_CMDLINE = "warm-reboot"
 EXPECTED_FIND_SOFTWARE_REBOOT_CAUSE_USER = "User issued 'warm-reboot' command [User: admin, Time: Mon Nov  2 22:37:45 UTC 2020]"
@@ -64,6 +67,7 @@
 
 EXPECTED_WATCHDOG_REBOOT_CAUSE_DICT = {'comment': '', 'gen_time': '2020_10_22_03_15_08', 'cause': 'Watchdog', 'user': 'N/A', 'time': 'N/A'}
 EXPECTED_USER_REBOOT_CAUSE_DICT = {'comment': '', 'gen_time': '2020_10_22_03_14_07', 'cause': 'reboot', 'user': 'admin', 'time': 'Thu Oct 22 03:11:08 UTC 2020'}
+EXPECTED_KERNEL_PANIC_REBOOT_CAUSE_DICT = {'comment': '', 'gen_time': '2021_3_28_13_48_49', 'cause': 'Kernel Panic', 'user': 'N/A', 'time': 'Sun Mar 28 13:45:12 UTC 2021'}
 
 
 class TestDetermineRebootCause(object):
@@ -114,3 +118,7 @@ def test_get_reboot_cause_dict_watchdog(self):
     def test_get_reboot_cause_dict_user(self):
         reboot_cause_dict = determine_reboot_cause.get_reboot_cause_dict(REBOOT_CAUSE_USER, "", GEN_TIME_USER)
         assert reboot_cause_dict == EXPECTED_USER_REBOOT_CAUSE_DICT
+
+    def test_get_reboot_cause_dict_kernel_panic(self):
+        reboot_cause_dict = determine_reboot_cause.get_reboot_cause_dict(REBOOT_CAUSE_KERNEL_PANIC, "", GEN_TIME_KERNEL_PANIC)
+        assert reboot_cause_dict == EXPECTED_KERNEL_PANIC_REBOOT_CAUSE_DICT