Messages in this thread Patch in this message | | | From | Ard Biesheuvel <> | Subject | [PATCH 2/5] kernel/jump_label: implement generic support for relative references | Date | Wed, 27 Jun 2018 18:06:01 +0200 |
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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 32-bit 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 | 20 +++++++++++++- 3 files changed, 50 insertions(+), 1 deletion(-)
diff --git a/arch/Kconfig b/arch/Kconfig index 2b8b70820002..22fa3792626e 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -348,6 +348,9 @@ 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 diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h index 86ec0652d3b1..aa203dffe72c 100644 --- a/include/linux/jump_label.h +++ b/include/linux/jump_label.h @@ -121,6 +121,32 @@ struct static_key { #include <asm/jump_label.h> #ifndef __ASSEMBLY__ +#ifdef CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE + +struct jump_entry { + int code; + int target; + int key; +}; + +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) +{ + unsigned long key = (unsigned long)&entry->key + entry->key; + + return (struct static_key *)(key & ~1UL); +} + +#else struct jump_entry; /* defined by the architecture */ @@ -139,6 +165,8 @@ 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; diff --git a/kernel/jump_label.c b/kernel/jump_label.c index c3524c9b3004..285eff13ecd1 100644 --- a/kernel/jump_label.c +++ b/kernel/jump_label.c @@ -49,6 +49,22 @@ 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) { @@ -56,7 +72,9 @@ jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop) 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, + IS_ENABLED(CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE) ? jump_label_swap + : NULL); } static void jump_label_update(struct static_key *key); -- 2.11.0
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