[PATCH 21/27] KVM: PPC: Introduce branch patching helper

[Alexander Graf]

We will need to patch several instruction streams over to a different
code path, so we need a way to patch a single instruction with a branch
somewhere else.

This patch adds a helper to facilitate this patching.

Signed-off-by: Alexander Graf <agraf at suse.de>

---

v2 -> v3:

  - add safety check for relocatable kernels
---
 arch/powerpc/kernel/kvm.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c
index 926f93f..239a70d 100644
--- a/arch/powerpc/kernel/kvm.c
+++ b/arch/powerpc/kernel/kvm.c
@@ -107,6 +107,20 @@ static void kvm_patch_ins_nop(u32 *inst)
 	kvm_patch_ins(inst, KVM_INST_NOP);
 }
 
+static void kvm_patch_ins_b(u32 *inst, int addr)
+{
+#ifdef CONFIG_RELOCATABLE
+	/* On relocatable kernels interrupts handlers and our code
+	   can be in different regions, so we don't patch them */
+
+	extern u32 __end_interrupts;
+	if ((ulong)inst < (ulong)&__end_interrupts)
+		return;
+#endif
+
+	kvm_patch_ins(inst, KVM_INST_B | (addr & KVM_INST_B_MASK));
+}
+
 static u32 *kvm_alloc(int len)
 {
 	u32 *p;
-- 
1.6.0.2