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