From: James Clarke <[email protected]>
Date: Sat, 22 Oct 2016 10:51:28 +0100
> @@ -19,12 +19,20 @@ void arch_jump_label_transform(struct jump_entry *entry,
> if (type == JUMP_LABEL_JMP) {
> s32 off = (s32)entry->target - (s32)entry->code;
>
> + BUG_ON(off & 3);
> +
> #ifdef CONFIG_SPARC64
> - /* ba,pt %xcc, . + (off << 2) */
> - val = 0x10680000 | ((u32) off >> 2);
> + /* WDISP19 - target is . + (immed << 2) */
> + BUG_ON(off > 0xfffff);
> + BUG_ON(off < -0x100000);
> + /* ba,pt %xcc, . + off */
> + val = 0x10680000 | (((u32) off >> 2) & 0x7ffff);
> #else
> - /* ba . + (off << 2) */
> - val = 0x10800000 | ((u32) off >> 2);
> + /* WDISP22 - target is . + (immed << 2) */
> + BUG_ON(off > 0x7fffff);
> + BUG_ON(off < -0x800000);
> + /* ba . + off */
> + val = 0x10800000 | (((u32) off >> 2) & 0x3fffff);
> #endif
Since we can determine at run time whether we need to use a non-v9
branch or not, it makes no sense to fail when a v9 branch is out of
range.
We can simply downgrade to a pre-v9 one.
Something like this:
diff --git a/arch/sparc/kernel/jump_label.c b/arch/sparc/kernel/jump_label.c
index 59bbeff..689e557 100644
--- a/arch/sparc/kernel/jump_label.c
+++ b/arch/sparc/kernel/jump_label.c
@@ -13,19 +13,24 @@
void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type)
{
- u32 val;
u32 *insn = (u32 *) (unsigned long) entry->code;
+ u32 val;
if (type == JUMP_LABEL_JMP) {
s32 off = (s32)entry->target - (s32)entry->code;
+ bool use_v9_branch = false;
#ifdef CONFIG_SPARC64
- /* ba,pt %xcc, . + (off << 2) */
- val = 0x10680000 | ((u32) off >> 2);
-#else
- /* ba . + (off << 2) */
- val = 0x10800000 | ((u32) off >> 2);
+ if (off <= 0xfffff && off >= -0x100000)
+ use_v9_branch = true;
#endif
+ if (use_v9_branch) {
+ /* ba,pt %xcc, . + (off << 2) */
+ val = 0x10680000 | (((u32) off >> 2) & 0x7ffff);
+ } else {
+ /* ba . + (off << 2) */
+ val = 0x10800000 | (((u32) off >> 2) & 0x3fffff);
+ }
} else {
val = 0x01000000;
}
