[PATCH V2 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/sysemu.h |  1 +
 softmmu/vl.c            | 30 ++++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 408eb56..2ab9f95 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -17,6 +17,7 @@ extern bool memfd_alloc;
 
 void qemu_add_data_dir(const char *path);
 
+void qemu_system_exec_request(void);
 void qemu_add_exit_notifier(Notifier *notify);
 void qemu_remove_exit_notifier(Notifier *notify);
 
diff --git a/softmmu/vl.c b/softmmu/vl.c
index 5668e2b..d395e80 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -165,6 +165,7 @@ uint8_t *boot_splash_filedata;
 int only_migratable; /* turn it off unless user states otherwise */
 bool wakeup_suspend_enabled;
 bool memfd_alloc;
+static char **argv_main;
 
 int icount_align_option;
 
@@ -1294,6 +1295,7 @@ 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;
@@ -1324,6 +1326,11 @@ static int qemu_shutdown_requested(void)
     return atomic_xchg(&shutdown_requested, SHUTDOWN_CAUSE_NONE);
 }
 
+static int qemu_exec_requested(void)
+{
+    return atomic_xchg(&exec_requested, 0);
+}
+
 static void qemu_kill_report(void)
 {
     if (!qtest_driver() && shutdown_signal) {
@@ -1570,6 +1577,13 @@ 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();
@@ -1605,6 +1619,16 @@ 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;
@@ -1625,6 +1649,11 @@ 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 (no_shutdown) {
@@ -2872,6 +2901,7 @@ void qemu_init(int argc, char **argv, char **envp)
 
     os_set_line_buffering();
 
+    argv_main = argv;
     error_init(argv[0]);
     module_call_init(MODULE_INIT_TRACE);
 
-- 
1.8.3.1