[PATCH v3 03/15] arm64: kvm: Add build rules for separate nVHE object files

David Brazdil
2020-06-18T12:27:54Z

Add new folder arch/arm64/kvm/hyp/nvhe and a Makefile for building code that
runs in EL2 under nVHE KVM.

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. nVHE build rules add
-D__KVM_NVHE_HYPERVISOR__.

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

Signed-off-by: David Brazdil <dbrazdil@google.com>
---
arch/arm64/kernel/image-vars.h | 12 +++++++++++
arch/arm64/kvm/hyp/Makefile | 2 +-
arch/arm64/kvm/hyp/nvhe/Makefile | 35 ++++++++++++++++++++++++++++++++
scripts/kallsyms.c | 1 +
4 files changed, 49 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/kvm/hyp/nvhe/Makefile

diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index be0a63ffed23..f32b406e90c0 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -51,4 +51,16 @@ __efistub__ctype = _ctype;

#endif

+#ifdef CONFIG_KVM
+
+/*
+ * KVM nVHE code has its own symbol namespace prefixed by __kvm_nvhe_, to
+ * isolate 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.
+ */
+
+#endif /* CONFIG_KVM */
+
#endif /* __ARM64_KERNEL_IMAGE_VARS_H */
diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
index 5d8357ddc234..5f4f217532e0 100644
--- a/arch/arm64/kvm/hyp/Makefile
+++ b/arch/arm64/kvm/hyp/Makefile
@@ -6,7 +6,7 @@
ccflags-y += -fno-stack-protector -DDISABLE_BRANCH_PROFILING \
$(DISABLE_STACKLEAK_PLUGIN)

-obj-$(CONFIG_KVM) += hyp.o
+obj-$(CONFIG_KVM) += hyp.o nvhe/
obj-$(CONFIG_KVM_INDIRECT_VECTORS) += smccc_wa.o

hyp-y := vgic-v3-sr.o timer-sr.o aarch32.o vgic-v2-cpuif-proxy.o sysreg-sr.o \
diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
new file mode 100644
index 000000000000..7d64235dba62
--- /dev/null
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -0,0 +1,35 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for Kernel-based Virtual Machine module, HYP/nVHE part
+#
+
+asflags-y := -D__KVM_NVHE_HYPERVISOR__
+ccflags-y := -D__KVM_NVHE_HYPERVISOR__ -fno-stack-protector \
+ -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK_PLUGIN)
+
+obj-y :=
+
+obj-y := $(patsubst %.o,%.hyp.o,$(obj-y))
+extra-y := $(patsubst %.hyp.o,%.hyp.tmp.o,$(obj-y))
+
+$(obj)/%.hyp.tmp.o: $(src)/%.c FORCE
+ $(call if_changed_rule,cc_o_c)
+$(obj)/%.hyp.tmp.o: $(src)/%.S FORCE
+ $(call if_changed_rule,as_o_S)
+$(obj)/%.hyp.o: $(obj)/%.hyp.tmp.o FORCE
+ $(call if_changed,hypcopy)
+
+quiet_cmd_hypcopy = HYPCOPY $@
+ cmd_hypcopy = $(OBJCOPY) --prefix-symbols=__kvm_nvhe_ $< $@
+
+# KVM nVHE code is run at a different exception code with a different map, so
+# compiler instrumentation that inserts callbacks or checks into the code may
+# cause crashes. Just disable it.
+GCOV_PROFILE := n
+KASAN_SANITIZE := n
+UBSAN_SANITIZE := n
+KCOV_INSTRUMENT := n
+
+# Skip objtool checking for this directory because nVHE code is compiled with
+# non-standard build rules.
+OBJECT_FILES_NON_STANDARD := y
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 6dc3078649fa..0096cd965332 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -109,6 +109,7 @@ static bool is_ignored_symbol(const char *name, char type)
".LASANPC", /* s390 kasan local symbols */
"__crc_", /* modversions */
"__efistub_", /* arm64 EFI stub namespace */
+ "__kvm_nvhe_", /* arm64 non-VHE KVM namespace */
NULL
};

--
2.27.0