[PATCH v3 2/6] crashdump: introduce the hotplug command line options

[Eric DeVolder]

Introducing the --hotplug command line option, which is used to
indicate to the kernel that the kdump image is setup to permit
the kernel to directly modify the elfcorehdr in response to CPU
and memory hotplug and/or online/offline events.

This option is only meaningful for kexec_load() syscall. For the
kexec_file_load() syscall, this option is a no-op as the kernel
handles all aspects of loading the kdump image.

This is the command line processing and documentation.

Signed-off-by: Eric DeVolder <eric.devolder at oracle.com>
---
 kexec/kexec.8 | 6 ++++++
 kexec/kexec.c | 6 ++++++
 kexec/kexec.h | 7 ++++++-
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/kexec/kexec.8 b/kexec/kexec.8
index 3a344c5..4400baf 100644
--- a/kexec/kexec.8
+++ b/kexec/kexec.8
@@ -132,6 +132,12 @@ in one call.
 Open a help file for
 .BR kexec .
 .TP
+.B \-\-hotplug
+Setup for kernel modification of the elfcorehdr. This option performs
+the steps needed to support kernel updates to the elfcorehdr in the
+presence of hot un/plug and/or on/offline events. This option only
+useful for KEXEC_LOAD syscall.
+.TP
 .B \-i\ (\-\-no-checks)
 Fast reboot, no memory integrity checks.
 .TP
diff --git a/kexec/kexec.c b/kexec/kexec.c
index 1edbd34..d790748 100644
--- a/kexec/kexec.c
+++ b/kexec/kexec.c
@@ -58,6 +58,8 @@
 
 unsigned long long mem_min = 0;
 unsigned long long mem_max = ULONG_MAX;
+unsigned long elfcorehdrsz = 0;
+int do_hotplug = 0;
 static unsigned long kexec_flags = 0;
 /* Flags for kexec file (fd) based syscall */
 static unsigned long kexec_file_flags = 0;
@@ -1069,6 +1071,7 @@ void usage(void)
 	       "                      back to the compatibility syscall when file based\n"
 	       "                      syscall is not supported or the kernel did not\n"
 	       "                      understand the image (default)\n"
+	       " --hotplug            Setup for kernel modification of elfcorehdr.\n"
 	       " -d, --debug          Enable debugging to help spot a failure.\n"
 	       " -S, --status         Return 1 if the type (by default crash) is loaded,\n"
 	       "                      0 if not.\n"
@@ -1579,6 +1582,9 @@ int main(int argc, char *argv[])
 		case OPT_PRINT_CKR_SIZE:
 			print_crashkernel_region_size();
 			return 0;
+		case OPT_HOTPLUG:
+			do_hotplug = 1;
+			break;
 		default:
 			break;
 		}
diff --git a/kexec/kexec.h b/kexec/kexec.h
index 0933389..487f707 100644
--- a/kexec/kexec.h
+++ b/kexec/kexec.h
@@ -232,7 +232,8 @@ extern int file_types;
 #define OPT_PRINT_CKR_SIZE	262
 #define OPT_LOAD_LIVE_UPDATE	263
 #define OPT_EXEC_LIVE_UPDATE	264
-#define OPT_MAX			265
+#define OPT_HOTPLUG		        265
+#define OPT_MAX		266
 #define KEXEC_OPTIONS \
 	{ "help",		0, 0, OPT_HELP }, \
 	{ "version",		0, 0, OPT_VERSION }, \
@@ -259,6 +260,7 @@ extern int file_types;
 	{ "debug",		0, 0, OPT_DEBUG }, \
 	{ "status",		0, 0, OPT_STATUS }, \
 	{ "print-ckr-size",     0, 0, OPT_PRINT_CKR_SIZE }, \
+	{ "hotplug",		    0, 0, OPT_HOTPLUG }, \
 
 #define KEXEC_OPT_STR "h?vdfixyluet:pscaS"
 
@@ -297,6 +299,9 @@ extern int ifdown(void);
 extern char purgatory[];
 extern size_t purgatory_size;
 
+extern unsigned long elfcorehdrsz;
+extern int do_hotplug;
+
 #define BOOTLOADER "kexec"
 #define BOOTLOADER_VERSION PACKAGE_VERSION
 
-- 
2.39.3