uml: install panic notifier earlier

It turns out that if there's a panic early enough, UML will just sit there in
the LED-blinking loop because the panic notifier hadn't been installed yet.

This patch installs it earlier.

It also fixes the problem which exposed the hang, namely that if you give UML
a zero-sized initrd, it will ask alloc_bootmem for zero bytes, and that will
cause the panic.

While I was in initrd.c, I gave it a style makeover.

Prompted by checkpatch, I moved a couple extern declarations of uml_exitcode
to kern_util.h.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 40 insertions, 30 deletions

diff --git a/arch/um/kernel/initrd.c b/arch/um/kernel/initrd.c
index ae31c62f0323..fa015565001b 100644
--- a/arch/um/kernel/initrd.c
+++ b/arch/um/kernel/initrd.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2000, 2001, 2002 Jeff Dike (jdike@karaya.com)
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
 
@@ -20,18 +20,27 @@ static int __init read_initrd(void)
         long long size;
         int err;
 
-        if(initrd == NULL)
+        if (initrd == NULL)
                 return 0;
 
         err = os_file_size(initrd, &size);
-        if(err)
+        if (err)
                 return 0;
 
+        /*
+         * This is necessary because alloc_bootmem craps out if you
+         * ask for no memory.
+         */
+        if (size == 0) {
+                printk(KERN_ERR "\"%\" is a zero-size initrd\n");
+                return 0;
+        }
+
         area = alloc_bootmem(size);
-        if(area == NULL)
+        if (area == NULL)
                 return 0;
 
-        if(load_initrd(initrd, area, size) == -1)
+        if (load_initrd(initrd, area, size) == -1)
                 return 0;
 
         initrd_start = (unsigned long) area;
@@ -58,13 +67,15 @@ int load_initrd(char *filename, void *buf, int size)
         int fd, n;
 
         fd = os_open_file(filename, of_read(OPENFLAGS()), 0);
-        if(fd < 0){
-                printk("Opening '%s' failed - err = %d\n", filename, -fd);
+        if (fd < 0) {
+                printk(KERN_ERR "Opening '%s' failed - err = %d\n", filename,
+                       -fd);
                 return -1;
         }
         n = os_read_file(fd, buf, size);
-        if(n != size){
-                printk("Read of %d bytes from '%s' failed, err = %d\n", size,
+        if (n != size) {
+                printk(KERN_ERR "Read of %d bytes from '%s' failed, "
+                       "err = %d\n", size,
                        filename, -n);
                 return -1;
         }
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 9ba39ab5f4bd..cb7eef833bc8 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -223,6 +223,23 @@ static void __init uml_postsetup(void)
         return;
 }
 
+static int panic_exit(struct notifier_block *self, unsigned long unused1,
+                      void *unused2)
+{
+        bust_spinlocks(1);
+        show_regs(&(current->thread.regs));
+        bust_spinlocks(0);
+        uml_exitcode = 1;
+        os_dump_core();
+        return 0;
+}
+
+static struct notifier_block panic_exit_notifier = {
+        .notifier_call          = panic_exit,
+        .next                   = NULL,
+        .priority               = 0
+};
+
 /* Set during early boot */
 unsigned long brk_start;
 unsigned long end_iomem;
@@ -327,6 +344,9 @@ int __init linux_main(int argc, char **argv)
                 printf("Kernel virtual memory size shrunk to %lu bytes\n",
                        virtmem_size);
 
+        atomic_notifier_chain_register(&panic_notifier_list,
+                                       &panic_exit_notifier);
+
         uml_postsetup();
 
         stack_protections((unsigned long) &init_thread_info);
@@ -335,29 +355,8 @@ int __init linux_main(int argc, char **argv)
         return start_uml();
 }
 
-extern int uml_exitcode;
-
-static int panic_exit(struct notifier_block *self, unsigned long unused1,
-                      void *unused2)
-{
-        bust_spinlocks(1);
-        show_regs(&(current->thread.regs));
-        bust_spinlocks(0);
-        uml_exitcode = 1;
-        os_dump_core();
-        return 0;
-}
-
-static struct notifier_block panic_exit_notifier = {
-        .notifier_call          = panic_exit,
-        .next                   = NULL,
-        .priority               = 0
-};
-
 void __init setup_arch(char **cmdline_p)
 {
-        atomic_notifier_chain_register(&panic_notifier_list,
-                        &panic_exit_notifier);
         paging_init();
         strlcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
         *cmdline_p = command_line;