KVM: arm64: Add build rules for separate VHE/nVHE object files

Add new folders arch/arm64/kvm/hyp/{vhe,nvhe} and Makefiles for building code
that runs in EL2 under VHE/nVHE KVM, repsectivelly. Add an include folder for
hyp-specific header files which will include code common to VHE/nVHE.

Build nVHE code with -D__KVM_NVHE_HYPERVISOR__, VHE code with
-D__KVM_VHE_HYPERVISOR__.

Under nVHE compile each source file into a `.hyp.tmp.o` object first, then
prefix all its symbols with "__kvm_nvhe_" using `objcopy` and produce
a `.hyp.o`. Suffixes were chosen so that it would be possible for VHE and nVHE
to share some source files, but compiled with different CFLAGS.

The nVHE ELF symbol prefix is added to kallsyms.c as ignored. EL2-only symbols
will never appear in EL1 stack traces.

Due to symbol prefixing, add a section in image-vars.h for aliases of symbols
that are defined in nVHE EL2 and accessed by kernel in EL1 or vice versa.

Signed-off-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200625131420.71444-4-dbrazdil@google.com

1 files changed, 14 insertions, 0 deletions

diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index be0a63ffed23..3dc27da47712 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -51,4 +51,18 @@ __efistub__ctype		= _ctype;
 
 #endif
 
+#ifdef CONFIG_KVM
+
+/*
+ * KVM nVHE code has its own symbol namespace prefixed with __kvm_nvhe_, to
+ * separate it from the kernel proper. The following symbols are legally
+ * accessed by it, therefore provide aliases to make them linkable.
+ * Do not include symbols which may not be safely accessed under hypervisor
+ * memory mappings.
+ */
+
+#define KVM_NVHE_ALIAS(sym) __kvm_nvhe_##sym = sym;
+
+#endif /* CONFIG_KVM */
+
 #endif /* __ARM64_KERNEL_IMAGE_VARS_H */