@@ -359,6 +359,9 @@ config HAVE_PERF_USER_STACK_DUMP
config HAVE_ARCH_JUMP_LABEL
bool
+config HAVE_ARCH_JUMP_LABEL_RELATIVE
+ bool
+
config HAVE_RCU_TABLE_FREE
bool
@@ -121,6 +121,32 @@ struct static_key {
#include <asm/jump_label.h>
#ifndef __ASSEMBLY__
+#ifdef CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE
+
+struct jump_entry {
+ s32 code;
+ s32 target;
+ long key; // key may be far away from the core kernel under KASLR
+};
+
+static inline unsigned long jump_entry_code(const struct jump_entry *entry)
+{
+ return (unsigned long)&entry->code + entry->code;
+}
+
+static inline unsigned long jump_entry_target(const struct jump_entry *entry)
+{
+ return (unsigned long)&entry->target + entry->target;
+}
+
+static inline struct static_key *jump_entry_key(const struct jump_entry *entry)
+{
+ long offset = entry->key & ~1L;
+
+ return (struct static_key *)((unsigned long)&entry->key + offset);
+}
+
+#else
static inline unsigned long jump_entry_code(const struct jump_entry *entry)
{
@@ -137,6 +163,8 @@ static inline struct static_key *jump_entry_key(const struct jump_entry *entry)
return (struct static_key *)((unsigned long)entry->key & ~1UL);
}
+#endif
+
static inline bool jump_entry_is_branch(const struct jump_entry *entry)
{
return (unsigned long)entry->key & 1UL;
@@ -47,14 +47,34 @@ static int jump_label_cmp(const void *a, const void *b)
return 0;
}
+static void jump_label_swap(void *a, void *b, int size)
+{
+ long delta = (unsigned long)a - (unsigned long)b;
+ struct jump_entry *jea = a;
+ struct jump_entry *jeb = b;
+ struct jump_entry tmp = *jea;
+
+ jea->code = jeb->code - delta;
+ jea->target = jeb->target - delta;
+ jea->key = jeb->key - delta;
+
+ jeb->code = tmp.code + delta;
+ jeb->target = tmp.target + delta;
+ jeb->key = tmp.key + delta;
+}
+
static void
jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
{
unsigned long size;
+ void *swapfn = NULL;
+
+ if (IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE))
+ swapfn = jump_label_swap;
size = (((unsigned long)stop - (unsigned long)start)
/ sizeof(struct jump_entry));
- sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
+ sort(start, size, sizeof(struct jump_entry), jump_label_cmp, swapfn);
}
static void jump_label_update(struct static_key *key);
To reduce the size taken up by absolute references in jump label entries themselves and the associated relocation records in the .init segment, add support for emitting them as relative references instead. Note that this requires some extra care in the sorting routine, given that the offsets change when entries are moved around in the jump_entry table. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/Kconfig | 3 +++ include/linux/jump_label.h | 28 ++++++++++++++++++++ kernel/jump_label.c | 22 ++++++++++++++- 3 files changed, 52 insertions(+), 1 deletion(-) -- 2.17.1