module scanning in kgdb 2.x

["Amit S. Kale" <amitkale@emsyssoft.com>]

Hi,

Here is code to scan modules in kgdb for 2.6 kernels. It's been contributed by 
TimeSys Corporation. 

It does following things:
1. Adds MODULE_STATE_GONE to indicate that a module was removed. This is 
differnent from MODULE_STATE_GOING. gdb needs to be notified of a module 
event _after_ a module has been removed. Or else it'll still find the module 
during a module list scan and will not remove it from its core.

2. Defines a structure mod_section which stores module section names and 
offsets preserved during loading of a module.

3. Adds a couple of fields to struct module to keep module section 
information.

4. Adds a few notifications for gdb to know module related events.

5. Saves module section names and offsets in load_module.

-Amit

Index: linux-2.6.3-kgdb/include/linux/module.h
===================================================================
--- linux-2.6.3-kgdb.orig/include/linux/module.h	2004-02-24 10:44:47.000000000 
+0530
+++ linux-2.6.3-kgdb/include/linux/module.h	2004-03-04 18:58:47.116645760 
+0530
@@ -186,8 +186,17 @@
 	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
+
 struct module
 {
 	enum module_state state;
@@ -198,6 +207,13 @@
 	/* 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
+
 	/* Exported symbols */
 	const struct kernel_symbol *syms;
 	unsigned int num_syms;
Index: linux-2.6.3-kgdb/kernel/module.c
===================================================================
--- linux-2.6.3-kgdb.orig/kernel/module.c	2004-02-24 10:44:56.000000000 +0530
+++ linux-2.6.3-kgdb/kernel/module.c	2004-03-04 18:55:59.136182672 +0530
@@ -727,6 +727,11 @@
 	mod->state = MODULE_STATE_GOING;
 	restart_refcounts();
 
+	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);
@@ -734,6 +739,10 @@
 	/* Final destruction now noone is using it. */
 	mod->exit();
 	free_module(mod);
+	down(&notify_mutex);
+	notifier_call_chain(&module_notify_list, MODULE_STATE_GONE,
+				NULL);
+	up(&notify_mutex);
 
  out:
 	up(&module_mutex);
@@ -1087,6 +1096,11 @@
 	/* Arch-specific cleanup. */
 	module_arch_cleanup(mod);
 
+#ifdef CONFIG_KGDB
+	/* kgdb info */
+	vfree(mod->mod_sections);
+#endif
+
 	/* Module unload stuff */
 	module_unload_free(mod);
 
@@ -1302,6 +1316,30 @@
 	return NULL;
 }
 
+#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)
 {
@@ -1650,6 +1688,12 @@
 	percpu_modcopy(mod->percpu, (void *)sechdrs[pcpuindex].sh_addr,
 		       sechdrs[pcpuindex].sh_size);
 
+#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;
@@ -1688,6 +1732,11 @@
  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:
@@ -1758,7 +1807,12 @@
 	if (ret < 0) {
 		/* 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_kernel();
 		if (mod->unsafe)
 			printk(KERN_ERR "%s: module is now stuck!\n",