KVM: arm64: kcov: Add kcov support in EL2 object

Change-Id: Ib1556c1194a0bae23438746bd3175ac780fae727

Author: tperami

arch/arm64/include/asm/kvm_asm.h

@@ -79,6 +79,13 @@ enum __kvm_host_smccc_func {
 	__KVM_HOST_SMCCC_FUNC___pkvm_init_vm,
 	__KVM_HOST_SMCCC_FUNC___pkvm_init_vcpu,
 	__KVM_HOST_SMCCC_FUNC___pkvm_teardown_vm,
+
+	/* Hypercalls available if CONFIG_NVHE_KCOV is set */
+	__KVM_HOST_SMCCC_FUNC___pkvm_kcov_init_buffer,
+	__KVM_HOST_SMCCC_FUNC___pkvm_kcov_buffer_add_page,
+	__KVM_HOST_SMCCC_FUNC___pkvm_kcov_teardown_buffer,
+	__KVM_HOST_SMCCC_FUNC___pkvm_kcov_enable,
+	__KVM_HOST_SMCCC_FUNC___pkvm_kcov_disable,
 };
 
 #define DECLARE_KVM_VHE_SYM(sym)	extern char sym[]

arch/arm64/include/asm/kvm_host.h

@@ -424,6 +424,19 @@ extern s64 kvm_nvhe_sym(hyp_physvirt_offset);
 extern u64 kvm_nvhe_sym(hyp_cpu_logical_map)[NR_CPUS];
 #define hyp_cpu_logical_map CHOOSE_NVHE_SYM(hyp_cpu_logical_map)
 
+#ifdef CONFIG_NVHE_KCOV
+extern u64 kvm_nvhe_sym(hyp_kimage_voffset);
+#define hyp_kimage_voffset CHOOSE_NVHE_SYM(hyp_kimage_voffset)
+
+extern u64 kvm_nvhe_sym(hyp_kimage_vaddr);
+#define hyp_kimage_vaddr CHOOSE_NVHE_SYM(hyp_kimage_vaddr)
+
+/* This function will fill in the previous two variable at setup time */
+void init_hyp_kcov_layout(void);
+#else
+static inline void init_hyp_kcov_layout(void){}
+#endif
+
 struct vcpu_reset_state {
 	unsigned long	pc;
 	unsigned long	r0;

arch/arm64/kvm/Kconfig

@@ -71,4 +71,23 @@ config PROTECTED_NVHE_STACKTRACE
 
 	  If unsure, or not using protected nVHE (pKVM), say N.
 
+config NVHE_KCOV
+	bool "Enable KCOV on the EL2 object"
+	depends on NVHE_EL2_DEBUG && KCOV
+	select PID_IN_CONTEXTIDR
+	select ARCH_HAS_HYPERVISOR_KCOV
+	default y
+	help
+	  Provide KCOV support at EL2. Enables support for the KCOV_ENABLE_HYP
+	  option (for buffers initialized with KCOV_INIT_HYP_TRACE)
+
+config NVHE_KCOV_NUM_BUFFERS
+	int "Number of KCOV buffers in the EL2 object"
+	depends on NVHE_KCOV
+	default 10
+	help
+	  The maximum number of buffers simultaneous initialized at EL2. Those
+	  are KCOV buffers intialized with KCOV_INIT_HYP_TRACE instead of
+	  KCOV_INIT_TRACE.
+
 endif # VIRTUALIZATION

arch/arm64/kvm/Makefile

@@ -23,6 +23,7 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \
 	 vgic/vgic-its.o vgic/vgic-debug.o
 
 kvm-$(CONFIG_HW_PERF_EVENTS)  += pmu-emul.o pmu.o
+kvm-$(CONFIG_NVHE_KCOV) += nvhe_kcov.o
 
 always-y := hyp_constants.h hyp-constants.s
 

arch/arm64/kvm/hyp/include/nvhe/kcov.h

@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 Google LLC
+ * Author: Thibaut Pérami <[email protected]>
+ */
+
+#ifndef __ARM64_KVM_NVHE_KCOV_H__
+#define __ARM64_KVM_NVHE_KCOV_H__
+
+#include <nvhe/pkvm.h>
+
+
+#ifdef CONFIG_NVHE_KCOV
+
+/** Initialize a kcov buffer and returns an index. Negative values for errors. */
+u64 __pkvm_kcov_init_buffer(uint size);
+
+/** Map the next page in a kcov buffer */
+u64 __pkvm_kcov_buffer_add_page(u64 idx, u64 pfn);
+
+/** Tear down a kcov buffer by index */
+int __pkvm_kcov_teardown_buffer(u64 idx);
+
+/** Enable tracing for the current user thread, on the buffer at that index */
+int __pkvm_kcov_enable(u64 idx);
+
+/** Disable tracing for the current user thread. One cannot disable tracing
+ * enabled by another thread */
+int __pkvm_kcov_disable(void);
+
+/** Call it on each EL2 entry point from host that require tracing, e.g. not
+ * asynchronous exceptions */
+void pkvm_kcov_enter_from_host(void);
+
+/** Call it on each EL2 exit to the host */
+void pkvm_kcov_exit_to_host(void);
+
+#else
+
+static inline u64 __pkvm_kcov_init_buffer(uint){
+	return -ENOSYS;
+}
+static inline u64 __pkvm_kcov_buffer_add_page(u64 idx, u64 pfn){
+	return -ENOSYS;
+}
+static inline u64 __pkvm_kcov_teardown_buffer(u64)
+{
+	return -ENOSYS;
+}
+static inline u64 __pkvm_kcov_enable(u64)
+{
+	return -ENOSYS;
+}
+static inline u64 __pkvm_kcov_disable(void)
+{
+	return -ENOSYS;
+}
+
+static inline void pkvm_kcov_enter_from_host(void) {}
+static inline void pkvm_kcov_exit_to_host(void) {}
+
+#endif /* CONFIG_NVHE_KCOV */
+
+#endif /* __ARM64_KVM_NVHE_KCOV_H__ */

arch/arm64/kvm/hyp/include/nvhe/memory.h

@@ -29,6 +29,7 @@ static inline phys_addr_t hyp_virt_to_phys(void *addr)
 
 #define hyp_phys_to_pfn(phys)	((phys) >> PAGE_SHIFT)
 #define hyp_pfn_to_phys(pfn)	((phys_addr_t)((pfn) << PAGE_SHIFT))
+#define hyp_pfn_to_virt(pfn)	(__hyp_va(hyp_pfn_to_phys(pfn)))
 #define hyp_phys_to_page(phys)	(&hyp_vmemmap[hyp_phys_to_pfn(phys)])
 #define hyp_virt_to_page(virt)	hyp_phys_to_page(__hyp_pa(virt))
 #define hyp_virt_to_pfn(virt)	hyp_phys_to_pfn(__hyp_pa(virt))

arch/arm64/kvm/hyp/nvhe/Makefile

@@ -23,6 +23,7 @@ lib-objs := $(addprefix ../../../lib/, $(lib-objs))
 hyp-obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
 	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o page_alloc.o \
 	 cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o stacktrace.o
+hyp-obj-$(CONFIG_NVHE_KCOV) += kcov.o
 hyp-obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
 	 ../fpsimd.o ../hyp-entry.o ../exception.o ../pgtable.o
 hyp-obj-$(CONFIG_DEBUG_LIST) += list_debug.o
@@ -105,7 +106,10 @@ GCOV_PROFILE	:= n
 KASAN_SANITIZE	:= n
 KCSAN_SANITIZE	:= n
 UBSAN_SANITIZE	:= n
-KCOV_INSTRUMENT	:= n
+KCOV_INSTRUMENT	:= $(if $(CONFIG_NVHE_KCOV),y,n)
+
+# Don't self instrument the kcov file
+KCOV_INSTRUMENT_kcov.nvhe.o := n
 
 # Skip objtool checking for this directory because nVHE code is compiled with
 # non-standard build rules.

arch/arm64/kvm/hyp/nvhe/hyp-main.c

@@ -17,6 +17,7 @@
 #include <nvhe/mm.h>
 #include <nvhe/pkvm.h>
 #include <nvhe/trap_handler.h>
+#include <nvhe/kcov.h>
 
 DEFINE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
 
@@ -294,6 +295,40 @@ static void handle___pkvm_teardown_vm(struct kvm_cpu_context *host_ctxt)
 	cpu_reg(host_ctxt, 1) = __pkvm_teardown_vm(handle);
 }
 
+static void handle___pkvm_kcov_init_buffer(struct kvm_cpu_context *host_ctxt)
+{
+	DECLARE_REG(uint, size, host_ctxt, 1);
+
+	cpu_reg(host_ctxt, 1) = __pkvm_kcov_init_buffer(size);
+}
+
+static void handle___pkvm_kcov_buffer_add_page(struct kvm_cpu_context *host_ctxt)
+{
+	DECLARE_REG(u64, index, host_ctxt, 1);
+	DECLARE_REG(u64, pfn, host_ctxt, 2);
+
+	cpu_reg(host_ctxt, 1) = __pkvm_kcov_buffer_add_page(index, pfn);
+}
+
+static void handle___pkvm_kcov_teardown_buffer(struct kvm_cpu_context *host_ctxt)
+{
+	DECLARE_REG(u64, index, host_ctxt, 1);
+
+	cpu_reg(host_ctxt, 1) = __pkvm_kcov_teardown_buffer(index);
+}
+
+static void handle___pkvm_kcov_enable(struct kvm_cpu_context *host_ctxt)
+{
+	DECLARE_REG(u64, index, host_ctxt, 1);
+
+	cpu_reg(host_ctxt, 1) = __pkvm_kcov_enable(index);
+}
+
+static void handle___pkvm_kcov_disable(struct kvm_cpu_context *host_ctxt)
+{
+	cpu_reg(host_ctxt, 1) = __pkvm_kcov_disable();
+}
+
 typedef void (*hcall_t)(struct kvm_cpu_context *);
 
 #define HANDLE_FUNC(x)	[__KVM_HOST_SMCCC_FUNC_##x] = (hcall_t)handle_##x
@@ -326,6 +361,12 @@ static const hcall_t host_hcall[] = {
 	HANDLE_FUNC(__pkvm_init_vm),
 	HANDLE_FUNC(__pkvm_init_vcpu),
 	HANDLE_FUNC(__pkvm_teardown_vm),
+
+	HANDLE_FUNC(__pkvm_kcov_init_buffer),
+	HANDLE_FUNC(__pkvm_kcov_buffer_add_page),
+	HANDLE_FUNC(__pkvm_kcov_teardown_buffer),
+	HANDLE_FUNC(__pkvm_kcov_enable),
+	HANDLE_FUNC(__pkvm_kcov_disable),
 };
 
 static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
@@ -384,6 +425,8 @@ void handle_trap(struct kvm_cpu_context *host_ctxt)
 {
 	u64 esr = read_sysreg_el2(SYS_ESR);
 
+        pkvm_kcov_enter_from_host();
+
 	switch (ESR_ELx_EC(esr)) {
 	case ESR_ELx_EC_HVC64:
 		handle_host_hcall(host_ctxt);
@@ -403,4 +446,5 @@ void handle_trap(struct kvm_cpu_context *host_ctxt)
 	default:
 		BUG();
 	}
+        pkvm_kcov_exit_to_host();
 }