[PATCH v4] kexec: implemented XEN KEXEC STATUS to determine if an image is loaded

Discussion:

Eric DeVolder

2017-01-25 15:31:15 UTC

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 <***@oracle.com>
Signed-off-by: Eric DeVolder <***@oracle.com>
---
CC: ***@lists.infradead.org
CC: xen-***@lists.xenproject.org
CC: Daniel Kiper <***@oracle.com>

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, posted on kexec mailing list
v4: Incorporated feedback from kexec mailing list
---
configure.ac | 8 +++-
kexec/kexec-xen.c | 26 +++++++++++++
kexec/kexec.8 | 6 +++
kexec/kexec.c | 114 ++++++++++++++++++++++++++++++++++++++----------------
kexec/kexec.h | 5 ++-
5 files changed, 123 insertions(+), 36 deletions(-)

diff --git a/configure.ac b/configure.ac
index 3044185..53fffc3 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..ec16247 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];
+ int result;
+ long native_arch;
+
+ /* set the arch */
+ native_arch = physical_arch();
+ if (native_arch < 0) {
+ return -1;
+ }
+ kexec_flags |= native_arch;

- /* 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;
-
- /* No digits were found */
- if (p == line)
- return -1;
-
- return (int)ret;
+ 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 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

Daniel Kiper

2017-01-25 23:02:48 UTC

Permalink

On Wed, Jan 25, 2017 at 09:31:15AM -0600, Eric DeVolder wrote:

[...]

Post by Eric DeVolder
diff --git a/kexec/kexec.c b/kexec/kexec.c
index 500e5a9..ec16247 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];
+ int result;
+ long native_arch;
+
+ /* set the arch */
+ native_arch = physical_arch();
+ if (native_arch < 0) {
+ return -1;
+ }
+ kexec_flags |= native_arch;
- /* 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;
-
- /* No digits were found */
- if (p == line)
- return -1;
-
- return (int)ret;
+ 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;
}

Ohhh... This is awful. Have you tried --patience option for "git format-patch"?
Does it help? If yes please repost. If it does not let's wait for maintainers
opinion about that. Maybe we should leave forward declaration in first patch
as is and then move kexec_loaded() in second (as a cleanup).

Though otherwise LGTM.

Daniel

Simon Horman

2017-01-26 10:22:19 UTC

Permalink

Post by Daniel Kiper
[...]

It did not seem to help when I tried.

I'm happy with things the way they are and I will apply this patch.

Daniel Kiper

2017-01-26 12:28:51 UTC

Permalink

Post by Simon Horman

Post by Daniel Kiper
[...]

It did not seem to help when I tried.
I'm happy with things the way they are and I will apply this patch.

Great! Thanks.

Daniel