[Xen-devel] [PATCH v3] kexec: implemented XEN KEXEC STATUS to determine if an image is loaded

[Eric DeVolder <eric.devolder@xxxxxxxxxx>]

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@xxxxxxxxxx>
Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx>
---
Note: The corresponding Xen changes have been committed
to the Xen staging branch. Follow this thread:
https://lists.xenproject.org/archives/html/xen-devel/2017-01/msg01570.html

CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: kexec@xxxxxxxxxxxxxxxxxxx
CC: xen-devel@xxxxxxxxxxxxxxxxxxxx
CC: Daniel Kiper <daniel.kiper@xxxxxxxxxx>

v0: First version (internal product).
v1: Posted on kexec mailing list. Changed -s to -S
v2: Incorporated feedback from kexec mailing list, posted on kexec mailing list
v3: Incorporated feedback from kexec mailing list
---
 configure.ac      |  8 ++++++-
 kexec/kexec-xen.c | 26 +++++++++++++++++++++++
 kexec/kexec.8     |  6 ++++++
 kexec/kexec.c     | 62 ++++++++++++++++++++++++++++++++++++++++++++++++-------
 kexec/kexec.h     |  5 ++++-
 5 files changed, 98 insertions(+), 9 deletions(-)

diff --git a/configure.ac b/configure.ac
index 3044185..c6e864b 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 24a4191..2b448d3 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 4d0c1d1..f4b39a6 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 500e5a9..defbbe3 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;
@@ -58,6 +61,8 @@ static unsigned long kexec_flags = 0;
 static unsigned long kexec_file_flags = 0;
 int kexec_debug = 0;
 
+static int kexec_loaded(const char *file);
+
 void dbgprint_mem_range(const char *prefix, struct memory_range *mr, int nr_mr)
 {
        int i;
@@ -890,8 +895,6 @@ 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;
@@ -909,7 +912,7 @@ 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 +973,7 @@ 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++) {
@@ -981,7 +985,7 @@ void usage(void)
        printf("\n");
 }
 
-static int kexec_loaded(void)
+static int kexec_loaded(const char *file)
 {
        long ret = -1;
        FILE *fp;
@@ -992,7 +996,7 @@ static int kexec_loaded(void)
        if (xen_present())
                return 1;
 
-       fp = fopen("/sys/kernel/kexec_loaded", "r");
+       fp = fopen(file, "r");
        if (fp == NULL)
                return -1;
 
@@ -1015,6 +1019,30 @@ static int kexec_loaded(void)
        return (int)ret;
 }
 
+static int k_status(unsigned long kexec_flags)
+{
+       int result;
+       long native_arch;
+
+       /* set the arch */
+       native_arch = physical_arch();
+       if (native_arch < 0) {
+               return -1;
+       }
+       kexec_flags |= native_arch;
+
+       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 +1232,7 @@ 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 +1374,9 @@ 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 +1387,20 @@ 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 +1438,9 @@ 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 +1456,7 @@ 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 9194f1c..2b06f59 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 */
-- 
2.7.4


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