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AJvYcCWe8xfa0zW3QLnWappb7rzUjxXGKSOxD602VCuTuSZnE19RpeG372bm30/RVpe6i4iFdGBxoj8dSj3yi6JRwoMunto/ X-Gm-Message-State: AOJu0YxOENoRACAde+n3UTwMEZQ6vTCu6S1Cd3msoPB6PXzLlOakHAUt S7Ct4I9iGmThz2iBYs8cs7Oc6nhWhcDTQluy8CMpTFa233Z5BbGvKd6tHhStIr8zIHUmKdCDPA= = X-Google-Smtp-Source: AGHT+IGl14UbfzJFzP5FVcOdHdoo6VR8VgccIp2YuEQvM8uJdIjgJCFM5cwo5OdJoioDTQ1NLN2OfjF80w== X-Received: from ptosi.c.googlers.com ([fda3:e722:ac3:cc00:31:98fb:c0a8:11ec]) (user=ptosi job=sendgmr) by 2002:a05:6402:381b:b0:57c:803e:3a57 with SMTP id 4fb4d7f45d1cf-57c803e3c99mr3092a12.2.1718001200147; Sun, 09 Jun 2024 23:33:20 -0700 (PDT) Date: Mon, 10 Jun 2024 07:32:37 +0100 In-Reply-To: <20240610063244.2828978-1-ptosi@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240610063244.2828978-1-ptosi@google.com> X-Mailer: git-send-email 2.45.2.505.gda0bf45e8d-goog Message-ID: <20240610063244.2828978-9-ptosi@google.com> Subject: [PATCH v5 8/8] KVM: arm64: nVHE: Support CONFIG_CFI_CLANG at EL2 From: " =?utf-8?q?Pierre-Cl=C3=A9ment_Tosi?= " To: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org Cc: " =?utf-8?q?Pierre-Cl=C3=A9ment_Tosi?= " , Will Deacon , Marc Zyngier , Oliver Upton , Suzuki K Poulose , Vincent Donnefort The compiler implements kCFI by adding type information (u32) above every function that might be indirectly called and, whenever a function pointer is called, injects a read-and-compare of that u32 against the value corresponding to the expected type. In case of a mismatch, a BRK instruction gets executed. When the hypervisor triggers such an exception in nVHE, it panics and triggers and exception return to EL1. Therefore, teach nvhe_hyp_panic_handler() to detect kCFI errors from the ESR and report them. If necessary, remind the user that EL2 kCFI is not affected by CONFIG_CFI_PERMISSIVE. Pass $(CC_FLAGS_CFI) to the compiler when building the nVHE hyp code. Use SYM_TYPED_FUNC_START() for __pkvm_init_switch_pgd, as nVHE can't call it directly and must use a PA function pointer from C (because it is part of the idmap page), which would trigger a kCFI failure if the type ID wasn't present. Signed-off-by: Pierre-Clément Tosi Acked-by: Will Deacon --- arch/arm64/kvm/handle_exit.c | 10 ++++++++++ arch/arm64/kvm/hyp/nvhe/Makefile | 6 +++--- arch/arm64/kvm/hyp/nvhe/hyp-init.S | 6 +++++- 3 files changed, 18 insertions(+), 4 deletions(-) diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c index b3d6657a259d..69b08ac7322d 100644 --- a/arch/arm64/kvm/handle_exit.c +++ b/arch/arm64/kvm/handle_exit.c @@ -417,6 +417,14 @@ static void print_nvhe_hyp_panic(const char *name, u64 panic_addr) (void *)(panic_addr + kaslr_offset())); } +static void kvm_nvhe_report_cfi_failure(u64 panic_addr) +{ + print_nvhe_hyp_panic("CFI failure", panic_addr); + + if (IS_ENABLED(CONFIG_CFI_PERMISSIVE)) + kvm_err(" (CONFIG_CFI_PERMISSIVE ignored for hyp failures)\n"); +} + void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr, u64 elr_virt, u64 elr_phys, u64 par, uintptr_t vcpu, @@ -446,6 +454,8 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr, kvm_err("nVHE hyp BUG at: %s:%u!\n", file, line); else print_nvhe_hyp_panic("BUG", panic_addr); + } else if (IS_ENABLED(CONFIG_CFI_CLANG) && esr_is_cfi_brk(esr)) { + kvm_nvhe_report_cfi_failure(panic_addr); } else { print_nvhe_hyp_panic("panic", panic_addr); } diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile index 50fa0ffb6b7e..782b34b004be 100644 --- a/arch/arm64/kvm/hyp/nvhe/Makefile +++ b/arch/arm64/kvm/hyp/nvhe/Makefile @@ -89,9 +89,9 @@ quiet_cmd_hyprel = HYPREL $@ quiet_cmd_hypcopy = HYPCOPY $@ cmd_hypcopy = $(OBJCOPY) --prefix-symbols=__kvm_nvhe_ $< $@ -# Remove ftrace, Shadow Call Stack, and CFI CFLAGS. -# This is equivalent to the 'notrace', '__noscs', and '__nocfi' annotations. -KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) $(CC_FLAGS_CFI), $(KBUILD_CFLAGS)) +# Remove ftrace and Shadow Call Stack CFLAGS. +# This is equivalent to the 'notrace' and '__noscs' annotations. +KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS), $(KBUILD_CFLAGS)) # Starting from 13.0.0 llvm emits SHT_REL section '.llvm.call-graph-profile' # when profile optimization is applied. gen-hyprel does not support SHT_REL and # causes a build failure. Remove profile optimization flags. diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S index 3a2836a52e85..07120b37da35 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S +++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S @@ -5,6 +5,7 @@ */ #include +#include #include #include @@ -268,8 +269,11 @@ SYM_CODE_END(__kvm_handle_stub_hvc) /* * void __pkvm_init_switch_pgd(phys_addr_t pgd, unsigned long sp, * void (*fn)(void)); + * + * SYM_TYPED_FUNC_START() allows C to call this ID-mapped function indirectly + * using a physical pointer without triggering a kCFI failure. */ -SYM_FUNC_START(__pkvm_init_switch_pgd) +SYM_TYPED_FUNC_START(__pkvm_init_switch_pgd) /* Turn the MMU off */ pre_disable_mmu_workaround mrs x3, sctlr_el2