[PATCH,RFC 2.6.14 15/15] KGDB: Better support for loaded modules

[Tom Rini <trini@kernel.crashing.org>]

This allows for KGDB to better deal with autoloaded modules.  The way this
works, requires a patch to GDB.  This patch can be found at
ftp://source.mvista.com/pub/kgdb/gdb-6.3-kgdb-module-notification.patch

The way this works is that the solib-search-path must contain the location of
any module to be debugged, and then when a module is loaded GDB acts like a
shared library has been loaded now, and can be used that way.

 include/linux/module.h |   16 ++++++++++++++
 kernel/module.c        |   56 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+)

Index: linux-2.6.14/include/linux/module.h
===================================================================
--- linux-2.6.14.orig/include/linux/module.h
+++ linux-2.6.14/include/linux/module.h
@@ -210,8 +210,17 @@ enum module_state
 	MODULE_STATE_LIVE,
 	MODULE_STATE_COMING,
 	MODULE_STATE_GOING,
+ 	MODULE_STATE_GONE,
 };
 
+#ifdef CONFIG_KGDB
+#define MAX_SECTNAME 31
+struct mod_section {
+       void *address;
+       char name[MAX_SECTNAME + 1];
+};
+#endif
+
 /* Similar stuff for section attributes. */
 #define MODULE_SECT_NAME_LEN 32
 struct module_sect_attr
@@ -239,6 +248,13 @@ struct module
 	/* Unique handle for this module */
 	char name[MODULE_NAME_LEN];
 
+#ifdef CONFIG_KGDB
+	/* keep kgdb info at the begining so that gdb doesn't have a chance to
+	 * miss out any fields */
+	unsigned long num_sections;
+	struct mod_section *mod_sections;
+#endif
+
 	/* Sysfs stuff. */
 	struct module_kobject mkobj;
 	struct module_param_attrs *param_attrs;
Index: linux-2.6.14/kernel/module.c
===================================================================
--- linux-2.6.14.orig/kernel/module.c
+++ linux-2.6.14/kernel/module.c
@@ -624,6 +624,12 @@ sys_delete_module(const char __user *nam
 	if (ret != 0)
 		goto out;
 
+	down(&notify_mutex);
+	notifier_call_chain(&module_notify_list, MODULE_STATE_GOING,
+        			mod);
+	up(&notify_mutex);
+
+
 	/* Never wait if forced. */
 	if (!forced && module_refcount(mod) != 0)
 		wait_for_zero_refcount(mod);
@@ -636,6 +642,11 @@ sys_delete_module(const char __user *nam
 	}
 	free_module(mod);
 
+	down(&notify_mutex);
+	notifier_call_chain(&module_notify_list, MODULE_STATE_GONE,
+			NULL);
+	up(&notify_mutex);
+
  out:
 	up(&module_mutex);
 	return ret;
@@ -1174,6 +1185,11 @@ static void free_module(struct module *m
 	/* Arch-specific cleanup. */
 	module_arch_cleanup(mod);
 
+#ifdef CONFIG_KGDB
+	/* kgdb info */
+	vfree(mod->mod_sections);
+#endif
+
 	/* Module unload stuff */
 	module_unload_free(mod);
 
@@ -1408,6 +1424,31 @@ static void setup_modinfo(struct module 
 }
 #endif
 
+#ifdef CONFIG_KGDB
+int add_modsects (struct module *mod, Elf_Ehdr *hdr, Elf_Shdr *sechdrs, const
+                char *secstrings)
+{
+        int i;
+
+        mod->num_sections = hdr->e_shnum - 1;
+        mod->mod_sections = vmalloc((hdr->e_shnum - 1)*
+		sizeof (struct mod_section));
+
+        if (mod->mod_sections == NULL) {
+                return -ENOMEM;
+        }
+
+        for (i = 1; i < hdr->e_shnum; i++) {
+                mod->mod_sections[i - 1].address = (void *)sechdrs[i].sh_addr;
+                strncpy(mod->mod_sections[i - 1].name, secstrings +
+                                sechdrs[i].sh_name, MAX_SECTNAME);
+                mod->mod_sections[i - 1].name[MAX_SECTNAME] = '\0';
+	}
+
+	return 0;
+}
+#endif
+
 #ifdef CONFIG_KALLSYMS
 int is_exported(const char *name, const struct module *mod)
 {
@@ -1777,6 +1818,12 @@ static struct module *load_module(void _
 
 	add_kallsyms(mod, sechdrs, symindex, strindex, secstrings);
 
+#ifdef CONFIG_KGDB
+        if ((err = add_modsects(mod, hdr, sechdrs, secstrings)) < 0) {
+                goto nomodsectinfo;
+        }
+#endif
+
 	err = module_finalize(hdr, sechdrs, mod);
 	if (err < 0)
 		goto cleanup;
@@ -1842,6 +1889,11 @@ static struct module *load_module(void _
  arch_cleanup:
 	module_arch_cleanup(mod);
  cleanup:
+
+#ifdef CONFIG_KGDB
+nomodsectinfo:
+       vfree(mod->mod_sections);
+#endif
 	module_unload_free(mod);
 	module_free(mod, mod->module_init);
  free_core:
@@ -1915,6 +1967,10 @@ sys_init_module(void __user *umod,
 		/* Init routine failed: abort.  Try to protect us from
                    buggy refcounters. */
 		mod->state = MODULE_STATE_GOING;
+		down(&notify_mutex);
+		notifier_call_chain(&module_notify_list, MODULE_STATE_GOING,
+				mod);
+		up(&notify_mutex);
 		synchronize_sched();
 		if (mod->unsafe)
 			printk(KERN_ERR "%s: module is now stuck!\n",

-- 
Tom