KVM: arm64: Add kimg_hyp_va() helper

KVM/arm64 is so far unable to deal with function pointers, as the compiler
will generate the kernel's runtime VA, and not the linear mapping address,
meaning that kern_hyp_va() will give the wrong result.

We so far have been able to use PC-relative addressing, but that's not
always easy to use, and prevents the implementation of things like
the mapping of an index to a pointer.

To allow this, provide a new helper that computes the required
translation from the kernel image to the HYP VA space.

Signed-off-by: Marc Zyngier <maz@kernel.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 331394306cce..608c3a83e740 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -98,6 +98,24 @@ static __always_inline unsigned long __kern_hyp_va(unsigned long v)
 
 #define kern_hyp_va(v) 	((typeof(v))(__kern_hyp_va((unsigned long)(v))))
 
+static __always_inline unsigned long __kimg_hyp_va(unsigned long v)
+{
+	unsigned long offset;
+
+	asm volatile(ALTERNATIVE_CB("movz %0, #0\n"
+				    "movk %0, #0, lsl #16\n"
+				    "movk %0, #0, lsl #32\n"
+				    "movk %0, #0, lsl #48\n",
+				    kvm_update_kimg_phys_offset)
+		     : "=r" (offset));
+
+	return __kern_hyp_va((v - offset) | PAGE_OFFSET);
+}
+
+#define kimg_fn_hyp_va(v) 	((typeof(*v))(__kimg_hyp_va((unsigned long)(v))))
+
+#define kimg_fn_ptr(x)	(typeof(x) **)(x)
+
 /*
  * We currently support using a VM-specified IPA size. For backward
  * compatibility, the default IPA size is fixed to 40bits.