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jump label: Add jump_label_text_reserved() to reserve jump points

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Add a jump_label_text_reserved(void *start, void *end), so that other
pieces of code that want to modify kernel text, can first verify that
jump label has not reserved the instruction.

Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <06236663a3a7b1c1f13576bb9eccb6d9c17b7bfe.1284733808.git.jbaron@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Jason Baron
2010-09-17 11:09:08 -04:00
committed by Steven Rostedt
parent e0cf0cd496
commit 4c3ef6d793
4 changed files with 94 additions and 3 deletions
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83
kernel/jump_label.c
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@@ -177,6 +177,89 @@ void jump_label_update(unsigned long key, enum jump_label_type type)
mutex_unlock(&jump_label_mutex);
}
static int addr_conflict(struct jump_entry *entry, void *start, void *end)
{
if (entry->code <= (unsigned long)end &&
entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
return 1;
return 0;
}
#ifdef CONFIG_MODULES
static int module_conflict(void *start, void *end)
{
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;
struct jump_entry *iter;
int i, count;
int conflict = 0;
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) {
count = e_module->nr_entries;
iter = e_module->table;
while (count--) {
if (addr_conflict(iter, start, end)) {
conflict = 1;
goto out;
}
iter++;
}
}
}
}
out:
return conflict;
}
#endif
/***
* jump_label_text_reserved - check if addr range is reserved
* @start: start text addr
* @end: end text addr
*
* checks if the text addr located between @start and @end
* overlaps with any of the jump label patch addresses. Code
* that wants to modify kernel text should first verify that
* it does not overlap with any of the jump label addresses.
*
* returns 1 if there is an overlap, 0 otherwise
*/
int jump_label_text_reserved(void *start, void *end)
{
struct jump_entry *iter;
struct jump_entry *iter_start = __start___jump_table;
struct jump_entry *iter_stop = __start___jump_table;
int conflict = 0;
mutex_lock(&jump_label_mutex);
iter = iter_start;
while (iter < iter_stop) {
if (addr_conflict(iter, start, end)) {
conflict = 1;
goto out;
}
iter++;
}
/* now check modules */
#ifdef CONFIG_MODULES
conflict = module_conflict(start, end);
#endif
out:
mutex_unlock(&jump_label_mutex);
return conflict;
}
static __init int init_jump_label(void)
{
int ret;