kexec: implemented XEN KEXEC STATUS to determine if an image is loaded

Instead of the scripts having to poke at various fields we can
provide that functionality via the -S parameter.

kexec_loaded/kexec_crash_loaded exposes Linux kernel kexec/crash
state. It does not say anything about Xen kexec/crash state. So,
we need a special approach to get the latter. Though for
compatibility we provide similar functionality in kexec-tools
for the former.

This change enables the --status or -S option to work either
with or without Xen.

Returns 0 if the payload is loaded. Can be used in combination
with -l or -p to get the state of the proper kexec image.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

5 files changed, 122 insertions, 35 deletions

diff --git a/configure.ac b/configure.ac
index 30441853..53fffc3a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -165,8 +165,14 @@ fi
 dnl find Xen control stack libraries
 if test "$with_xen" = yes ; then
 	AC_CHECK_HEADER(xenctrl.h,
-		[AC_CHECK_LIB(xenctrl, xc_kexec_load, ,
+		[AC_CHECK_LIB(xenctrl, xc_kexec_load, [ have_xenctrl_h=yes ],
 		AC_MSG_NOTICE([Xen support disabled]))])
+		if test "$have_xenctrl_h" = yes ; then
+			AC_CHECK_LIB(xenctrl, xc_kexec_status,
+				AC_DEFINE(HAVE_KEXEC_CMD_STATUS, 1,
+					[The kexec_status call is available]),
+				AC_MSG_NOTICE([The kexec_status call is not available]))
+		fi
 fi
 
 dnl ---Sanity checks
diff --git a/kexec/kexec-xen.c b/kexec/kexec-xen.c
index 24a41919..2b448d39 100644
--- a/kexec/kexec-xen.c
+++ b/kexec/kexec-xen.c
@@ -105,6 +105,27 @@ int xen_kexec_unload(uint64_t kexec_flags)
 	return ret;
 }
 
+int xen_kexec_status(uint64_t kexec_flags)
+{
+	xc_interface *xch;
+	uint8_t type;
+	int ret = -1;
+
+#ifdef HAVE_KEXEC_CMD_STATUS
+	xch = xc_interface_open(NULL, NULL, 0);
+	if (!xch)
+		return -1;
+
+	type = (kexec_flags & KEXEC_ON_CRASH) ? KEXEC_TYPE_CRASH : KEXEC_TYPE_DEFAULT;
+
+	ret = xc_kexec_status(xch, type);
+
+	xc_interface_close(xch);
+#endif
+
+	return ret;
+}
+
 void xen_kexec_exec(void)
 {
 	xc_interface *xch;
@@ -130,6 +151,11 @@ int xen_kexec_unload(uint64_t kexec_flags)
 	return -1;
 }
 
+int xen_kexec_status(uint64_t kexec_flags)
+{
+	return -1;
+}
+
 void xen_kexec_exec(void)
 {
 }
diff --git a/kexec/kexec.8 b/kexec/kexec.8
index 4d0c1d16..f4b39a65 100644
--- a/kexec/kexec.8
+++ b/kexec/kexec.8
@@ -107,6 +107,12 @@ command:
 .B \-d\ (\-\-debug)
 Enable debugging messages.
 .TP
+.B \-S\ (\-\-status)
+Return 0 if the type (by default crash) is loaded. Can be used in conjuction
+with -l or -p to toggle the type. Note this option supersedes other options
+and it will
+.BR not\ load\ or\ unload\ the\ kernel.
+.TP
 .B \-e\ (\-\-exec)
 Run the currently loaded kernel. Note that it will reboot into the loaded kernel without calling shutdown(8).
 .TP
diff --git a/kexec/kexec.c b/kexec/kexec.c
index 500e5a9e..ec16247a 100644
--- a/kexec/kexec.c
+++ b/kexec/kexec.c
@@ -51,6 +51,9 @@
 #include "kexec-lzma.h"
 #include <arch/options.h>
 
+#define KEXEC_LOADED_PATH "/sys/kernel/kexec_loaded"
+#define KEXEC_CRASH_LOADED_PATH "/sys/kernel/kexec_crash_loaded"
+
 unsigned long long mem_min = 0;
 unsigned long long mem_max = ULONG_MAX;
 static unsigned long kexec_flags = 0;
@@ -890,8 +893,6 @@ static int my_exec(void)
 	return -1;
 }
 
-static int kexec_loaded(void);
-
 static int load_jump_back_helper_image(unsigned long kexec_flags, void *entry)
 {
 	int result;
@@ -902,6 +903,40 @@ static int load_jump_back_helper_image(unsigned long kexec_flags, void *entry)
 	return result;
 }
 
+static int kexec_loaded(const char *file)
+{
+	long ret = -1;
+	FILE *fp;
+	char *p;
+	char line[3];
+
+	/* No way to tell if an image is loaded under Xen, assume it is. */
+	if (xen_present())
+		return 1;
+
+	fp = fopen(file, "r");
+	if (fp == NULL)
+		return -1;
+
+	p = fgets(line, sizeof(line), fp);
+	fclose(fp);
+
+	if (p == NULL)
+		return -1;
+
+	ret = strtol(line, &p, 10);
+
+	/* Too long */
+	if (ret > INT_MAX)
+		return -1;
+
+	/* No digits were found */
+	if (p == line)
+		return -1;
+
+	return (int)ret;
+}
+
 /*
  *	Jump back to the original kernel
  */
@@ -909,7 +944,7 @@ static int my_load_jump_back_helper(unsigned long kexec_flags, void *entry)
 {
 	int result;
 
-	if (kexec_loaded()) {
+	if (kexec_loaded(KEXEC_LOADED_PATH)) {
 		fprintf(stderr, "There is kexec kernel loaded, make sure "
 			"you are in kexeced kernel.\n");
 		return -1;
@@ -970,6 +1005,7 @@ void usage(void)
 	       "                      to original kernel.\n"
 	       " -s, --kexec-file-syscall Use file based syscall for kexec operation\n"
 	       " -d, --debug           Enable debugging to help spot a failure.\n"
+	       " -S, --status         Return 0 if the type (by default crash) is loaded.\n"
 	       "\n"
 	       "Supported kernel file types and options: \n");
 	for (i = 0; i < file_types; i++) {
@@ -981,40 +1017,30 @@ void usage(void)
 	printf("\n");
 }
 
-static int kexec_loaded(void)
+static int k_status(unsigned long kexec_flags)
 {
-	long ret = -1;
-	FILE *fp;
-	char *p;
-	char line[3];
-
-	/* No way to tell if an image is loaded under Xen, assume it is. */
-	if (xen_present())
-		return 1;
-
-	fp = fopen("/sys/kernel/kexec_loaded", "r");
-	if (fp == NULL)
-		return -1;
-
-	p = fgets(line, sizeof(line), fp);
-	fclose(fp);
-
-	if (p == NULL)
-		return -1;
-
-	ret = strtol(line, &p, 10);
-
-	/* Too long */
-	if (ret > INT_MAX)
-		return -1;
+	int result;
+	long native_arch;
 
-	/* No digits were found */
-	if (p == line)
+	/* set the arch */
+	native_arch = physical_arch();
+	if (native_arch < 0) {
 		return -1;
+	}
+	kexec_flags |= native_arch;
 
-	return (int)ret;
+	if (xen_present())
+		result = xen_kexec_status(kexec_flags);
+	else {
+		if (kexec_flags & KEXEC_ON_CRASH)
+			result = kexec_loaded(KEXEC_CRASH_LOADED_PATH);
+		else
+			result = kexec_loaded(KEXEC_LOADED_PATH);
+	}
+	return result;
 }
 
+
 /*
  * Remove parameter from a kernel command line. Helper function by get_command_line().
  */
@@ -1204,6 +1230,7 @@ int main(int argc, char *argv[])
 	int do_unload = 0;
 	int do_reuse_initrd = 0;
 	int do_kexec_file_syscall = 0;
+	int do_status = 0;
 	void *entry = 0;
 	char *type = 0;
 	char *endptr;
@@ -1345,6 +1372,9 @@ int main(int argc, char *argv[])
 		case OPT_KEXEC_FILE_SYSCALL:
 			/* We already parsed it. Nothing to do. */
 			break;
+		case OPT_STATUS:
+			do_status = 1;
+			break;
 		default:
 			break;
 		}
@@ -1355,6 +1385,20 @@ int main(int argc, char *argv[])
 	if (skip_sync)
 		do_sync = 0;
 
+	if (do_status) {
+		if (kexec_flags == 0)
+			kexec_flags = KEXEC_ON_CRASH;
+		do_load = 0;
+		do_reuse_initrd = 0;
+		do_unload = 0;
+		do_load = 0;
+		do_shutdown = 0;
+		do_sync = 0;
+		do_ifdown = 0;
+		do_exec = 0;
+		do_load_jump_back_helper = 0;
+	}
+
 	if (do_load && (kexec_flags & KEXEC_ON_CRASH) &&
 	    !is_crashkernel_mem_reserved()) {
 		die("Memory for crashkernel is not reserved\n"
@@ -1392,7 +1436,9 @@ int main(int argc, char *argv[])
 		check_reuse_initrd();
 		arch_reuse_initrd();
 	}
-
+	if (do_status) {
+		result = k_status(kexec_flags);
+	}
 	if (do_unload) {
 		if (do_kexec_file_syscall)
 			result = kexec_file_unload(kexec_file_flags);
@@ -1408,7 +1454,7 @@ int main(int argc, char *argv[])
 						kexec_flags, entry);
 	}
 	/* Don't shutdown unless there is something to reboot to! */
-	if ((result == 0) && (do_shutdown || do_exec) && !kexec_loaded()) {
+	if ((result == 0) && (do_shutdown || do_exec) && !kexec_loaded(KEXEC_LOADED_PATH)) {
 		die("Nothing has been loaded!\n");
 	}
 	if ((result == 0) && do_shutdown) {
diff --git a/kexec/kexec.h b/kexec/kexec.h
index 9194f1c8..2b06f590 100644
--- a/kexec/kexec.h
+++ b/kexec/kexec.h
@@ -219,6 +219,7 @@ extern int file_types;
 #define OPT_TYPE		't'
 #define OPT_PANIC		'p'
 #define OPT_KEXEC_FILE_SYSCALL	's'
+#define OPT_STATUS		'S'
 #define OPT_MEM_MIN             256
 #define OPT_MEM_MAX             257
 #define OPT_REUSE_INITRD	258
@@ -245,8 +246,9 @@ extern int file_types;
 	{ "reuseinitrd",	0, 0, OPT_REUSE_INITRD }, \
 	{ "kexec-file-syscall",	0, 0, OPT_KEXEC_FILE_SYSCALL }, \
 	{ "debug",		0, 0, OPT_DEBUG }, \
+	{ "status",		0, 0, OPT_STATUS }, \
 
-#define KEXEC_OPT_STR "h?vdfxyluet:ps"
+#define KEXEC_OPT_STR "h?vdfxyluet:psS"
 
 extern void dbgprint_mem_range(const char *prefix, struct memory_range *mr, int nr_mr);
 extern void die(const char *fmt, ...)
@@ -311,5 +313,6 @@ int xen_present(void);
 int xen_kexec_load(struct kexec_info *info);
 int xen_kexec_unload(uint64_t kexec_flags);
 void xen_kexec_exec(void);
+int xen_kexec_status(uint64_t kexec_flags);
 
 #endif /* KEXEC_H */