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Subject[RFC PATCH 8/8] jump label v4 - add module support
Add support for 'jump label' for modules.

Signed-off-by: Jason Baron <jbaron@redhat.com>
---
arch/x86/kernel/ptrace.c | 1 +
include/linux/jump_label.h | 3 +-
include/linux/module.h | 5 +-
kernel/jump_label.c | 136 ++++++++++++++++++++++++++++++++++++++++++++
kernel/module.c | 7 ++
5 files changed, 150 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 017d937..94f5355 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -24,6 +24,7 @@
#include <linux/workqueue.h>
#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>
+#include <linux/module.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index 3d42e8c..fa81c0a 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -21,7 +21,8 @@ extern struct jump_entry __stop___jump_table[];

#define DEFINE_JUMP_LABEL(name) \
const char __jlstrtab_##name[] \
- __used __attribute__((section("__jump_strings"))) = #name;
+ __used __attribute__((section("__jump_strings"))) = #name; \
+ EXPORT_SYMBOL_GPL(__jlstrtab_##name);

extern void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type);
diff --git a/include/linux/module.h b/include/linux/module.h
index 6cb1a3c..df499cf 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -339,7 +339,10 @@ struct module
struct tracepoint *tracepoints;
unsigned int num_tracepoints;
#endif
-
+#ifdef __HAVE_ARCH_JUMP_LABEL
+ struct jump_entry *jump_entries;
+ unsigned int num_jump_entries;
+#endif
#ifdef CONFIG_TRACING
const char **trace_bprintk_fmt_start;
unsigned int num_trace_bprintk_fmt;
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 671fcbb..62b7467 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -30,6 +30,13 @@ struct jump_label_entry {
char name[0];
};

+struct jump_label_module_entry {
+ struct hlist_node hlist;
+ struct jump_entry *table;
+ int nr_entries;
+ struct module *mod;
+};
+
static void swap_jump_label_entries(struct jump_entry *previous, struct jump_entry *next)
{
struct jump_entry tmp;
@@ -145,6 +152,17 @@ int jump_label_update(const char *name, enum jump_label_type type)
arch_jump_label_transform(iter, type);
iter++;
}
+ /* eanble/disable jump labels in modules */
+ hlist_for_each_entry(e_module, module_node, &(entry->modules),
+ hlist) {
+ count = e_module->nr_entries;
+ iter = e_module->table;
+ while (count--) {
+ if (kernel_text_address(iter->code))
+ arch_jump_label_transform(iter, type);
+ iter++;
+ }
+ }
}
mutex_unlock(&jump_label_mutex);
return 0;
@@ -162,4 +180,122 @@ static int init_jump_label(void)
}
early_initcall(init_jump_label);

+#ifdef CONFIG_MODULES
+
+static struct jump_label_module_entry *add_jump_label_module_entry(struct jump_label_entry *entry, struct jump_entry *iter_begin, int count, struct module *mod)
+{
+ struct jump_label_module_entry *e;
+
+ e = kmalloc(sizeof(struct jump_label_module_entry), GFP_KERNEL);
+ if (!e)
+ return ERR_PTR(-ENOMEM);
+ e->mod = mod;
+ e->nr_entries = count;
+ e->table = iter_begin;
+ hlist_add_head(&e->hlist, &entry->modules);
+ return e;
+}
+
+static int add_jump_label_module(struct module *mod)
+{
+ struct jump_entry *iter, *iter_begin;
+ struct jump_label_entry *entry;
+ struct jump_label_module_entry *module_entry;
+ int count;
+
+ /* if the module doesn't have jump label entries, just return */
+ if (!mod->num_jump_entries)
+ return 0;
+
+ sort_jump_label_entries(mod->jump_entries,
+ mod->jump_entries + mod->num_jump_entries);
+ iter = mod->jump_entries;
+ while (iter < mod->jump_entries + mod->num_jump_entries) {
+ entry = get_jump_label_entry(iter->name);
+ iter_begin = iter;
+ count = 0;
+ while ((iter < mod->jump_entries + mod->num_jump_entries) &&
+ (strcmp(iter->name, iter_begin->name) == 0)) {
+ iter++;
+ count++;
+ }
+ if (!entry) {
+ entry = add_jump_label_entry(iter_begin->name, 0, NULL);
+ if (IS_ERR(entry))
+ return PTR_ERR(entry);
+ }
+ module_entry = add_jump_label_module_entry(entry, iter_begin,
+ count, mod);
+ if (IS_ERR(module_entry))
+ return PTR_ERR(module_entry);
+ }
+ return 0;
+}
+
+static void remove_jump_label_module(struct module *mod)
+{
+ struct hlist_head *head;
+ struct hlist_node *node, *node_next, *module_node, *module_node_next;
+ struct jump_label_entry *e;
+ struct jump_label_module_entry *e_module;
+ int i;
+
+ /* if the module doesn't have jump label entries, just return */
+ if (!mod->num_jump_entries)
+ return;
+
+ for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
+ head = &jump_label_table[i];
+ hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
+ hlist_for_each_entry_safe(e_module, module_node,
+ module_node_next,
+ &(e->modules), hlist) {
+ if (e_module->mod == mod) {
+ hlist_del(&e_module->hlist);
+ kfree(e_module);
+ }
+ }
+ if (hlist_empty(&e->modules) && (e->nr_entries == 0)) {
+ hlist_del(&e->hlist);
+ kfree(e);
+ }
+ }
+ }
+}
+
+static int jump_label_module_notify(struct notifier_block *self, unsigned long val, void *data)
+{
+ struct module *mod = data;
+ int ret = 0;
+
+ switch (val) {
+ case MODULE_STATE_COMING:
+ mutex_lock(&jump_label_mutex);
+ ret = add_jump_label_module(mod);
+ if (ret)
+ remove_jump_label_module(mod);
+ mutex_unlock(&jump_label_mutex);
+ break;
+ case MODULE_STATE_GOING:
+ mutex_lock(&jump_label_mutex);
+ remove_jump_label_module(mod);
+ mutex_unlock(&jump_label_mutex);
+ break;
+ }
+ return ret;
+}
+
+struct notifier_block jump_label_module_nb = {
+ .notifier_call = jump_label_module_notify,
+ .priority = 0,
+};
+
+static int init_jump_label_module(void)
+{
+ return register_module_notifier(&jump_label_module_nb);
+}
+__initcall(init_jump_label_module);
+
+#endif /* CONFIG_MODULES */
+
#endif
diff --git a/kernel/module.c b/kernel/module.c
index f82386b..4324bb1 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -55,6 +55,7 @@
#include <linux/async.h>
#include <linux/percpu.h>
#include <linux/kmemleak.h>
+#include <linux/jump_label.h>

#define CREATE_TRACE_POINTS
#include <trace/events/module.h>
@@ -2245,6 +2246,12 @@ static noinline struct module *load_module(void __user *umod,
sizeof(*mod->tracepoints),
&mod->num_tracepoints);
#endif
+#ifdef __HAVE_ARCH_JUMP_LABEL
+ mod->jump_entries = section_objs(hdr, sechdrs, secstrings,
+ "__jump_table",
+ sizeof(*mod->jump_entries),
+ &mod->num_jump_entries);
+#endif
#ifdef CONFIG_EVENT_TRACING
mod->trace_events = section_objs(hdr, sechdrs, secstrings,
"_ftrace_events",
--
1.6.5.1


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