| Message ID | 20200618122537.9625-4-dbrazdil@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Split off nVHE hyp code | expand |
Hi David, On 2020-06-18 13:25, David Brazdil wrote: > 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 > }; I guess that one of the first use of this __KVM_NVHE_HYPERVISOR__ flag could be the has_vhe() predicate: if you're running the nVHE code, you are *guaranteed* not to use VHE at all. Something like: diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h index 5051b388c654..b2cb8fce43dd 100644 --- a/arch/arm64/include/asm/virt.h +++ b/arch/arm64/include/asm/virt.h @@ -85,10 +85,8 @@ static inline bool is_kernel_in_hyp_mode(void) static __always_inline bool has_vhe(void) { - if (cpus_have_final_cap(ARM64_HAS_VIRT_HOST_EXTN)) - return true; - - return false; + return (__is_defined(__KVM_NVHE_HYPERVISOR__) && + cpus_have_final_cap(ARM64_HAS_VIRT_HOST_EXTN)); } #endif /* __ASSEMBLY__ */ Thanks, M.
Hey Marc, > I guess that one of the first use of this __KVM_NVHE_HYPERVISOR__ > flag could be the has_vhe() predicate: if you're running the nVHE > code, you are *guaranteed* not to use VHE at all. Sure, I'll add that to the next respin. If I'm reading __is_defined correctly, it means I have to define the flag as =1. Easy. Thanks, -David
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 };
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