lib/ukboot: Pass tmain to init context

Populate the init context with the thread that executes main().
When LIBUKBOOT_MAINTHREAD is selected, this allows libposix-process
to create INIT_PID from the main thread while excluding Unikraft's
init thread from the process.

Move the initialization of the main() thread before executing inittab.
With that change, update the parameters main_thread() function to pass
a pointer to ictx, so that it's possible for args to be updated by
inittab.

Signed-off-by: Michalis Pappas <michalis@unikraft.io>
Approved-by: Andrei Tatar <andrei@unikraft.io>
Approved-by: Sergiu Moga <sergiu@unikraft.io>
Reviewed-by: Andrei Tatar <andrei@unikraft.io>
Reviewed-by: Sergiu Moga <sergiu@unikraft.io>
GitHub-Closes: #1620

diff --git a/lib/ukboot/boot.c b/lib/ukboot/boot.c
index 65effd315bb7c84bf2bff4e742827b60560071cf..b0c14d8511e5bdd175d28f0c70d0eb99debda158 100644 (file)
--- a/lib/ukboot/boot.c
+++ b/lib/ukboot/boot.c
@@ -114,8 +114,9 @@ int main(int argc, char *argv[]) __weak;
 static inline int do_main(int argc, char *argv[]);
 
 #if CONFIG_LIBUKBOOT_MAINTHREAD
-static __noreturn void main_thread(void *, void *);
+static __noreturn void main_thread(void *);
 static void main_thread_dtor(struct uk_thread *m);
+struct uk_semaphore main_sema;
 #endif /* CONFIG_LIBUKBOOT_MAINTHREAD */
 
 #if defined(CONFIG_LIBUKBOOT_HEAP_BASE) && defined(CONFIG_LIBUKVMEM)
@@ -269,6 +270,8 @@ void uk_boot_entry(void)
        UK_ASSERT(boot_argc);
 
 #if CONFIG_LIBUKBOOT_MAINTHREAD
+       /* Initialize main thread semaphore */
+       uk_semaphore_init(&main_sema, 0);
        /* Initialize shutdown control structure */
        uk_boot_shutdown_ctl_init();
 #endif /* CONFIG_LIBUKBOOT_MAINTHREAD */
@@ -364,6 +367,21 @@ void uk_boot_entry(void)
        ictx.cmdline.argc = boot_argc;
        ictx.cmdline.argv = boot_argv;
 
+#if CONFIG_LIBUKBOOT_MAINTHREAD
+       /* Start main thread (will block on semaphore) */
+       m = uk_sched_thread_create_fn1(s, main_thread,
+                                      &ictx,
+                                      0x0 /* default stack size */,
+                                      0x0 /* default auxiliary stack size */,
+                                      false, false,
+                                      "main", NULL,
+                                      main_thread_dtor);
+       if (unlikely(!m || PTRISERR(m)))
+               UK_CRASH("Failed to launch application's main()\n");
+
+       ictx.tmain = m;
+#endif /* CONFIG_LIBUKBOOT_MAINTHREAD */
+
        /* Enable interrupts before starting the application */
        ukplat_lcpu_enable_irq();
 
@@ -400,18 +418,8 @@ void uk_boot_entry(void)
        tctx.target = UKPLAT_HALT;
 
 #else /* CONFIG_LIBUKBOOT_MAINTHREAD */
-       m = uk_sched_thread_create_fn2(s, main_thread,
-                                      (void *)((long)ictx.cmdline.argc),
-                                      (void *)ictx.cmdline.argv,
-                                      0x0 /* default stack size */,
-                                      0x0 /* default auxiliary stack size */,
-                                      false, false,
-                                      "main", NULL,
-                                      main_thread_dtor);
-       if (unlikely(!m || PTRISERR(m))) {
-               uk_pr_err("Failed to launch application's main()\n");
-               goto exit;
-       }
+       /* Unblock main thread (will execute main()) */
+       uk_semaphore_up(&main_sema);
 
        /* Block execution of "init" until we receive the first request */
        tctx.target = uk_boot_shutdown_barrier();
@@ -505,12 +513,17 @@ static inline int do_main(int argc, char *argv[])
 }
 
 #if CONFIG_LIBUKBOOT_MAINTHREAD
-static __noreturn void main_thread(void *a_argc, void *a_argv)
+/* Pass ictx so that inittab handlers can update args */
+static __noreturn void main_thread(void *ictx)
 {
-       int argc = (int)((__uptr)a_argc);
-       char **argv = (char **)a_argv;
+       UK_ASSERT(ictx);
+
+       /* block until we are allowed to execute main() */
+       uk_semaphore_down(&main_sema);
+
+       do_main(((struct uk_init_ctx *)ictx)->cmdline.argc,
+               ((struct uk_init_ctx *)ictx)->cmdline.argv);
 
-       do_main(argc, argv);
 #if !CONFIG_LIBUKBOOT_MAINTHREAD_NOHALT
        /* NOTE: The scheduler's garbage collector would also initiate a
         *       shutdown request via `main_thread_dtor()`.