[PATCH 2/5] kernel/jump_label: implement generic support for relative references
From: peterz@infradead.org (Peter Zijlstra)
Date: 2018-06-28 08:50:17
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On Wed, Jun 27, 2018 at 06:06:01PM +0200, Ard Biesheuvel wrote:
quoted hunk ↗ jump to hunk
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; +};
I much prefer you use 'u32' there.
quoted hunk ↗ jump to hunk
+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); }
That will result in jump_label_swap being an unused symbol for some
compile options.
Would it not be much nicer to write that like:
static void jump_label_swap(void *a, void *b, int size)
{
struct jump_entry *jea = a, *jeb = b;
#ifdef CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE
long delta = a - b;
jea->code += delta;
jea->target += delta;
jea->key += delta;
jeb->code -= delta;
jeb->target -= delta;
jeb->key -= delta;
#else
swap(*jea, *jeb);
}
And then unconditionally use jump_label_swap().