arm64: kvm: deal with kernel symbols outside of linear mapping

KVM on arm64 uses a fixed offset between the linear mapping at EL1 and
the HYP mapping at EL2. Before we can move the kernel virtual mapping
out of the linear mapping, we have to make sure that references to kernel
symbols that are accessed via the HYP mapping are translated to their
linear equivalent.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 52b777b7d407..31b56008f412 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -26,7 +26,24 @@
 #define KVM_ARM64_DEBUG_DIRTY_SHIFT	0
 #define KVM_ARM64_DEBUG_DIRTY		(1 << KVM_ARM64_DEBUG_DIRTY_SHIFT)
 
+#define kvm_ksym_ref(sym)		((void *)&sym + kvm_ksym_shift)
+
 #ifndef __ASSEMBLY__
+#if __GNUC__ > 4
+#define kvm_ksym_shift			(PAGE_OFFSET - KIMAGE_VADDR)
+#else
+/*
+ * GCC versions 4.9 and older will fold the constant below into the addend of
+ * the reference to 'sym' above if kvm_ksym_shift is declared static or if the
+ * constant is used directly. However, since we use the small code model for
+ * the core kernel, the reference to 'sym' will be emitted as a adrp/add pair,
+ * with a +/- 4 GB range, resulting in linker relocation errors if the shift
+ * is sufficiently large. So prevent the compiler from folding the shift into
+ * the addend, by making the shift a variable with external linkage.
+ */
+__weak u64 kvm_ksym_shift = PAGE_OFFSET - KIMAGE_VADDR;
+#endif
+
 struct kvm;
 struct kvm_vcpu;