[PATCH V3 06/22] vl: add helper to request re-exec

[Steve Sistare <steven.sistare@oracle.com>]

Add a qemu_exec_requested() hook that causes the main loop to exit and
re-exec qemu using the same initial arguments.  If /usr/bin/qemu-exec
exists, exec that instead.  This is an optional site-specific trampoline
that may alter the environment before exec'ing the qemu binary.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 include/sysemu/runstate.h |  1 +
 include/sysemu/sysemu.h   |  1 +
 softmmu/globals.c         |  1 +
 softmmu/runstate.c        | 28 ++++++++++++++++++++++++++++
 softmmu/vl.c              |  1 +
 5 files changed, 32 insertions(+)

diff --git a/include/sysemu/runstate.h b/include/sysemu/runstate.h
index a535691..50c84af 100644
--- a/include/sysemu/runstate.h
+++ b/include/sysemu/runstate.h
@@ -56,6 +56,7 @@ void qemu_system_wakeup_enable(WakeupReason reason, bool enabled);
 void qemu_register_wakeup_notifier(Notifier *notifier);
 void qemu_register_wakeup_support(void);
 void qemu_system_shutdown_request(ShutdownCause reason);
+void qemu_system_exec_request(void);
 void qemu_system_powerdown_request(void);
 void qemu_register_powerdown_notifier(Notifier *notifier);
 void qemu_register_shutdown_notifier(Notifier *notifier);
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 8fae667..f56058e 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -9,6 +9,7 @@
 /* vl.c */
 
 extern int only_migratable;
+extern char **argv_main;
 extern const char *qemu_name;
 extern QemuUUID qemu_uuid;
 extern bool qemu_uuid_set;
diff --git a/softmmu/globals.c b/softmmu/globals.c
index 7d0fc81..2bb630d 100644
--- a/softmmu/globals.c
+++ b/softmmu/globals.c
@@ -60,6 +60,7 @@ bool boot_strict;
 uint8_t *boot_splash_filedata;
 int only_migratable; /* turn it off unless user states otherwise */
 int icount_align_option;
+char **argv_main;
 
 /* The bytes in qemu_uuid are in the order specified by RFC4122, _not_ in the
  * little-endian "wire format" described in the SMBIOS 2.6 specification.
diff --git a/softmmu/runstate.c b/softmmu/runstate.c
index ce8977c..bea7513 100644
--- a/softmmu/runstate.c
+++ b/softmmu/runstate.c
@@ -338,6 +338,7 @@ static ShutdownCause reset_requested;
 static ShutdownCause shutdown_requested;
 static int shutdown_signal;
 static pid_t shutdown_pid;
+static int exec_requested;
 static int powerdown_requested;
 static int debug_requested;
 static int suspend_requested;
@@ -367,6 +368,11 @@ static int qemu_shutdown_requested(void)
     return qatomic_xchg(&shutdown_requested, SHUTDOWN_CAUSE_NONE);
 }
 
+static int qemu_exec_requested(void)
+{
+    return qatomic_xchg(&exec_requested, 0);
+}
+
 static void qemu_kill_report(void)
 {
     if (!qtest_driver() && shutdown_signal) {
@@ -625,6 +631,13 @@ void qemu_system_shutdown_request(ShutdownCause reason)
     qemu_notify_event();
 }
 
+void qemu_system_exec_request(void)
+{
+    shutdown_requested = 1;
+    exec_requested = 1;
+    qemu_notify_event();
+}
+
 static void qemu_system_powerdown(void)
 {
     qapi_event_send_powerdown();
@@ -660,6 +673,16 @@ void qemu_system_debug_request(void)
     qemu_notify_event();
 }
 
+static void qemu_exec(void)
+{
+    const char *helper = "/usr/bin/qemu-exec";
+    const char *bin = !access(helper, X_OK) ? helper : argv_main[0];
+
+    execvp(bin, argv_main);
+    error_report("execvp failed, errno %d.", errno);
+    exit(1);
+}
+
 static bool main_loop_should_exit(void)
 {
     RunState r;
@@ -673,6 +696,11 @@ static bool main_loop_should_exit(void)
     }
     request = qemu_shutdown_requested();
     if (request) {
+
+        if (qemu_exec_requested()) {
+            qemu_exec();
+            /* not reached */
+        }
         qemu_kill_report();
         qemu_system_shutdown(request);
         if (shutdown_action == SHUTDOWN_ACTION_PAUSE) {
diff --git a/softmmu/vl.c b/softmmu/vl.c
index aadb526..04ab752 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2662,6 +2662,7 @@ void qemu_init(int argc, char **argv, char **envp)
 
     error_init(argv[0]);
     qemu_init_exec_dir(argv[0]);
+    argv_main = argv;
 
     qemu_init_subsystems();
 
-- 
1.8.3.1