Support saving crash dumps on systems hosted in RAM

By default, Kdump reboots the system after the crash dump is saved.
While this works in most cases, it does not work for systems hosted in
RAM where the crash dump is lost once rebooted. To support this
scenario, a new option in the kdump.conf, save_core_to_ram, is
added and set to 0 by default. Setting this option to 1 will disable the
reboot and use the core_collector config option, if specified, to save a
compressed dump. This is necessary because there is no disk to save the
dump to, and there is not enough space in memory to copy the entirety of
the crashed kernel's memory space using the `cp` command. Instead, a
compressed ump must be saved to meet these space limitations.

Author: nangelastro

SPECS/kexec-tools/kdump.conf

@@ -162,6 +162,14 @@
 #             to send fence_kdump notifications to.
 #             (this option is mandatory to enable fence_kdump).
 #
+# save_core_to_ram <0 | 1>
+#           - Disables the default action to copy the entire vmcore and to reboot
+#             after the crash dump is saved. Instead, a compressed crash dump is
+#             saved and the system remains up afterwards. This is particularly useful
+#             when the operating system is running in RAM and reboots would otherwise remove
+#             the crash dump.
+#             Specify 1 to disable rebooting once the crash dump is saved.
+#
 
 #raw /dev/vg/lv_kdump
 #ext4 /dev/vg/lv_kdump
@@ -183,3 +191,4 @@ core_collector makedumpfile -l --message-level 1 -d 31
 #dracut_args --omit-drivers "cfg80211 snd" --add-drivers "ext2 ext3"
 #fence_kdump_args -p 7410 -f auto -c 0 -i 10
 #fence_kdump_nodes node1 node2
+#save_core_to_ram 0

SPECS/kexec-tools/kdumpctl

@@ -87,6 +87,20 @@ save_core()
 	fi
 }
 
+save_core_to_ram()
+{
+	coredir="/var/crash/`date +"%Y-%m-%d-%H:%M"`"
+	mkdir -p $coredir
+	CORE_COLLECTOR=`grep ^core_collector $KDUMP_CONFIG_FILE | cut -d\  -f2`
+
+	if [[ -n $CORE_COLLECTOR ]]; then
+		CORE_COLLECTOR=`type -P $CORE_COLLECTOR`
+		$CORE_COLLECTOR /proc/vmcore $coredir/vmcore
+	else
+		makedumpfile -l --message-level 1 -d 31 /proc/vmcore $coredir/vmcore
+	fi
+}
+
 rebuild_fadump_initrd()
 {
 	local target_initrd_tmp
@@ -243,7 +257,7 @@ check_config()
 		case "$config_opt" in
 		\#* | "")
 			;;
-		raw|ext2|ext3|ext4|minix|btrfs|xfs|nfs|ssh|sshkey|path|core_collector|kdump_post|kdump_pre|extra_bins|extra_modules|failure_action|default|final_action|force_rebuild|force_no_rebuild|dracut_args|fence_kdump_args|fence_kdump_nodes)
+		raw|ext2|ext3|ext4|minix|btrfs|xfs|nfs|ssh|sshkey|path|core_collector|kdump_post|kdump_pre|extra_bins|extra_modules|failure_action|default|final_action|force_rebuild|force_no_rebuild|dracut_args|fence_kdump_args|fence_kdump_nodes|save_core_to_ram)
 			# remove inline comments after the end of a directive.
 			[ -z "$config_val" ] && {
 				echo "Invalid kdump config value for option $config_opt."
@@ -1248,6 +1262,23 @@ main ()
 	case "$1" in
 	  start)
 		if [ -s /proc/vmcore ]; then
+			local _save_core_to_ram save_core_to_ram="0"
+			_save_core_to_ram=`grep ^save_core_to_ram $KDUMP_CONFIG_FILE 2>/dev/null`
+
+			if [ $? -eq 0 ]; then
+				save_core_to_ram=`echo $_save_core_to_ram | cut -d' '  -f2`
+
+				if [ "$save_core_to_ram" != "0" ] && [ "$save_core_to_ram" != "1" ]; then
+					echo "Error: save_core_to_ram value is invalid"
+					return 1
+				fi
+			fi
+
+			if [ "$save_core_to_ram" == "1" ]; then
+				save_core_to_ram
+				exit 0
+			fi
+
 			save_core
 			reboot
 		else

SPECS/kexec-tools/kexec-tools.signatures.json

@@ -20,14 +20,14 @@
   "kdump-lib-initramfs.sh": "ff4b63f99470ee796fd7e4a532dde241c4da02909306926a08a172457775a92a",
   "kdump-lib.sh": "3d50507626d4a92b8448c7d6604923f6f460c4cb5c8b18977381a7d5e516dfba",
   "kdump-udev-throttler": "125d538a59172f779b40ea32fea1e4eb50d849f25eb2537a48328d4401136679",
-  "kdump.conf": "c4cd6c4a2f00e7df10d939bc2f35f8b6b8a3edd71245aa3ba0d7fff53d9f42e8",
+  "kdump.conf": "ac3a8fa40431f3ff0c8d29f4168e9553acfe2efd6973fe64124e8b79dda1e211",
   "kdump.conf.5": "bab6c7b171f76e8c6df91bb7db852815caacbc3cd3d4309a1dc58d36950440e4",
   "kdump.service": "ed8d22fafa6cfafaddcfd9fec82e3fa7fa42aa0366f69676fafa97e200b0506a",
   "kdump.sysconfig": "d03a24659c08aa4ce5a8e54edbe64e149f8c572c76c4e338d84dbdfbeab8fb63",
   "kdump.sysconfig.aarch64": "a829f3a0f88d983ccec2782b048f12a2eafca71aac4dd42acac2eaea8f7dd8d9",
   "kdump.sysconfig.i386": "1175bcc11be49841d4b8c3f9612e68bb7b2e0e8f00067ffa782fd9dba04f821d",
   "kdump.sysconfig.x86_64": "850b3be780165d0721edb8d34b2ba28aafc60b29850ff627daf04190369e359c",
-  "kdumpctl": "34976fa2ca34a455f393d2ac212a628d73ba4113b44f0e819c3cb5b1195e504b",
+  "kdumpctl": "a16d67962e2e09a2318715f3e20098a739296ac5132e6cd1357bd56185d28cc3",
   "kdumpctl.8": "025a39d212eed0584da7c23c1bb50d6ab797a0fa3c686ac6b80391af875dbaec",
   "kexec-kdump-howto.txt": "e783390a9aa582a2b5e7981cd3277081385340b5873a3f0633c789811876eccb",
   "kexec-tools-2.0.27.tar.xz": "38d78bcfa33a88928324b57dc81f50c1dfc279eede45e80957ca18f4e84b8187",

SPECS/kexec-tools/kexec-tools.spec

@@ -6,7 +6,7 @@
 Summary:        The kexec/kdump userspace component
 Name:           kexec-tools
 Version:        2.0.27
-Release:        7%{?dist}
+Release:        8%{?dist}
 License:        GPLv2
 Vendor:         Microsoft Corporation
 Distribution:   Azure Linux
@@ -330,6 +330,9 @@ done
 /usr/share/makedumpfile/
 
 %changelog
+* Mon Sep 30 2024 Nicholas Angelastro <nangelastro@microsoft.com> - 2.0.27-8
+- Support saving crash dumps on systems hosted in RAM
+
 * Tue Jul 09 2024 Chris Co <chrco@microsoft.com> - 2.0.27-7
 - Remove requires on dhcp-client