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authorMarc Zyngier <maz@kernel.org>2022-07-27 20:33:27 +0300
committerMarc Zyngier <maz@kernel.org>2022-07-27 20:33:27 +0300
commit0982c8d859f8f7022b9fd44d421c7ec721bb41f9 (patch)
treef6f9cb6622374da505eb728ab88e7a5f91c93583 /arch/arm64/kvm/hyp
parentae98a4a989935bb8e1431565e2eb86d7a19c2309 (diff)
parenta4c750e2328a117dc9b19a2a61db0d4347902029 (diff)
downloadlinux-0982c8d859f8f7022b9fd44d421c7ec721bb41f9.tar.xz
Merge branch kvm-arm64/nvhe-stacktrace into kvmarm-master/next
* kvm-arm64/nvhe-stacktrace: (27 commits) : . : Add an overflow stack to the nVHE EL2 code, allowing : the implementation of an unwinder, courtesy of : Kalesh Singh. From the cover letter (slightly edited): : : "nVHE has two modes of operation: protected (pKVM) and unprotected : (conventional nVHE). Depending on the mode, a slightly different approach : is used to dump the hypervisor stacktrace but the core unwinding logic : remains the same. : : * Protected nVHE (pKVM) stacktraces: : : In protected nVHE mode, the host cannot directly access hypervisor memory. : : The hypervisor stack unwinding happens in EL2 and is made accessible to : the host via a shared buffer. Symbolizing and printing the stacktrace : addresses is delegated to the host and happens in EL1. : : * Non-protected (Conventional) nVHE stacktraces: : : In non-protected mode, the host is able to directly access the hypervisor : stack pages. : : The hypervisor stack unwinding and dumping of the stacktrace is performed : by the host in EL1, as this avoids the memory overhead of setting up : shared buffers between the host and hypervisor." : : Additional patches from Oliver Upton and Marc Zyngier, tidying up : the initial series. : . arm64: Update 'unwinder howto' KVM: arm64: Don't open code ARRAY_SIZE() KVM: arm64: Move nVHE-only helpers into kvm/stacktrace.c KVM: arm64: Make unwind()/on_accessible_stack() per-unwinder functions KVM: arm64: Move nVHE stacktrace unwinding into its own compilation unit KVM: arm64: Move PROTECTED_NVHE_STACKTRACE around KVM: arm64: Introduce pkvm_dump_backtrace() KVM: arm64: Implement protected nVHE hyp stack unwinder KVM: arm64: Save protected-nVHE (pKVM) hyp stacktrace KVM: arm64: Stub implementation of pKVM HYP stack unwinder KVM: arm64: Allocate shared pKVM hyp stacktrace buffers KVM: arm64: Add PROTECTED_NVHE_STACKTRACE Kconfig KVM: arm64: Introduce hyp_dump_backtrace() KVM: arm64: Implement non-protected nVHE hyp stack unwinder KVM: arm64: Prepare non-protected nVHE hypervisor stacktrace KVM: arm64: Stub implementation of non-protected nVHE HYP stack unwinder KVM: arm64: On stack overflow switch to hyp overflow_stack arm64: stacktrace: Add description of stacktrace/common.h arm64: stacktrace: Factor out common unwind() arm64: stacktrace: Handle frame pointer from different address spaces ... Signed-off-by: Marc Zyngier <maz@kernel.org>
Diffstat (limited to 'arch/arm64/kvm/hyp')
-rw-r--r--arch/arm64/kvm/hyp/nvhe/Makefile2
-rw-r--r--arch/arm64/kvm/hyp/nvhe/host.S9
-rw-r--r--arch/arm64/kvm/hyp/nvhe/stacktrace.c160
-rw-r--r--arch/arm64/kvm/hyp/nvhe/switch.c6
4 files changed, 169 insertions, 8 deletions
diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index a2b0d043dddf..ed5d222e2826 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -14,7 +14,7 @@ lib-objs := $(addprefix ../../../lib/, $(lib-objs))
hyp-obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
hyp-main.o hyp-smp.o psci-relay.o early_alloc.o page_alloc.o \
- cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o
+ cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o stacktrace.o
hyp-obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
../fpsimd.o ../hyp-entry.o ../exception.o ../pgtable.o
hyp-obj-$(CONFIG_DEBUG_LIST) += list_debug.o
diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index ea6a397b64a6..b6c0188c4b35 100644
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -177,13 +177,8 @@ SYM_FUNC_END(__host_hvc)
b hyp_panic
.L__hyp_sp_overflow\@:
- /*
- * Reset SP to the top of the stack, to allow handling the hyp_panic.
- * This corrupts the stack but is ok, since we won't be attempting
- * any unwinding here.
- */
- ldr_this_cpu x0, kvm_init_params + NVHE_INIT_STACK_HYP_VA, x1
- mov sp, x0
+ /* Switch to the overflow stack */
+ adr_this_cpu sp, overflow_stack + OVERFLOW_STACK_SIZE, x0
b hyp_panic_bad_stack
ASM_BUG()
diff --git a/arch/arm64/kvm/hyp/nvhe/stacktrace.c b/arch/arm64/kvm/hyp/nvhe/stacktrace.c
new file mode 100644
index 000000000000..58f645ad66bc
--- /dev/null
+++ b/arch/arm64/kvm/hyp/nvhe/stacktrace.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KVM nVHE hypervisor stack tracing support.
+ *
+ * Copyright (C) 2022 Google LLC
+ */
+#include <asm/kvm_asm.h>
+#include <asm/kvm_hyp.h>
+#include <asm/memory.h>
+#include <asm/percpu.h>
+
+DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack)
+ __aligned(16);
+
+DEFINE_PER_CPU(struct kvm_nvhe_stacktrace_info, kvm_stacktrace_info);
+
+/*
+ * hyp_prepare_backtrace - Prepare non-protected nVHE backtrace.
+ *
+ * @fp : frame pointer at which to start the unwinding.
+ * @pc : program counter at which to start the unwinding.
+ *
+ * Save the information needed by the host to unwind the non-protected
+ * nVHE hypervisor stack in EL1.
+ */
+static void hyp_prepare_backtrace(unsigned long fp, unsigned long pc)
+{
+ struct kvm_nvhe_stacktrace_info *stacktrace_info = this_cpu_ptr(&kvm_stacktrace_info);
+ struct kvm_nvhe_init_params *params = this_cpu_ptr(&kvm_init_params);
+
+ stacktrace_info->stack_base = (unsigned long)(params->stack_hyp_va - PAGE_SIZE);
+ stacktrace_info->overflow_stack_base = (unsigned long)this_cpu_ptr(overflow_stack);
+ stacktrace_info->fp = fp;
+ stacktrace_info->pc = pc;
+}
+
+#ifdef CONFIG_PROTECTED_NVHE_STACKTRACE
+#include <asm/stacktrace/nvhe.h>
+
+DEFINE_PER_CPU(unsigned long [NVHE_STACKTRACE_SIZE/sizeof(long)], pkvm_stacktrace);
+
+static bool on_overflow_stack(unsigned long sp, unsigned long size,
+ struct stack_info *info)
+{
+ unsigned long low = (unsigned long)this_cpu_ptr(overflow_stack);
+ unsigned long high = low + OVERFLOW_STACK_SIZE;
+
+ return on_stack(sp, size, low, high, STACK_TYPE_OVERFLOW, info);
+}
+
+static bool on_hyp_stack(unsigned long sp, unsigned long size,
+ struct stack_info *info)
+{
+ struct kvm_nvhe_init_params *params = this_cpu_ptr(&kvm_init_params);
+ unsigned long high = params->stack_hyp_va;
+ unsigned long low = high - PAGE_SIZE;
+
+ return on_stack(sp, size, low, high, STACK_TYPE_HYP, info);
+}
+
+static bool on_accessible_stack(const struct task_struct *tsk,
+ unsigned long sp, unsigned long size,
+ struct stack_info *info)
+{
+ if (info)
+ info->type = STACK_TYPE_UNKNOWN;
+
+ return (on_overflow_stack(sp, size, info) ||
+ on_hyp_stack(sp, size, info));
+}
+
+static int unwind_next(struct unwind_state *state)
+{
+ struct stack_info info;
+
+ return unwind_next_common(state, &info, on_accessible_stack, NULL);
+}
+
+static void notrace unwind(struct unwind_state *state,
+ stack_trace_consume_fn consume_entry,
+ void *cookie)
+{
+ while (1) {
+ int ret;
+
+ if (!consume_entry(cookie, state->pc))
+ break;
+ ret = unwind_next(state);
+ if (ret < 0)
+ break;
+ }
+}
+
+/*
+ * pkvm_save_backtrace_entry - Saves a protected nVHE HYP stacktrace entry
+ *
+ * @arg : index of the entry in the stacktrace buffer
+ * @where : the program counter corresponding to the stack frame
+ *
+ * Save the return address of a stack frame to the shared stacktrace buffer.
+ * The host can access this shared buffer from EL1 to dump the backtrace.
+ */
+static bool pkvm_save_backtrace_entry(void *arg, unsigned long where)
+{
+ unsigned long *stacktrace = this_cpu_ptr(pkvm_stacktrace);
+ int *idx = (int *)arg;
+
+ /*
+ * Need 2 free slots: 1 for current entry and 1 for the
+ * delimiter.
+ */
+ if (*idx > ARRAY_SIZE(pkvm_stacktrace) - 2)
+ return false;
+
+ stacktrace[*idx] = where;
+ stacktrace[++*idx] = 0UL;
+
+ return true;
+}
+
+/*
+ * pkvm_save_backtrace - Saves the protected nVHE HYP stacktrace
+ *
+ * @fp : frame pointer at which to start the unwinding.
+ * @pc : program counter at which to start the unwinding.
+ *
+ * Save the unwinded stack addresses to the shared stacktrace buffer.
+ * The host can access this shared buffer from EL1 to dump the backtrace.
+ */
+static void pkvm_save_backtrace(unsigned long fp, unsigned long pc)
+{
+ struct unwind_state state;
+ int idx = 0;
+
+ kvm_nvhe_unwind_init(&state, fp, pc);
+
+ unwind(&state, pkvm_save_backtrace_entry, &idx);
+}
+#else /* !CONFIG_PROTECTED_NVHE_STACKTRACE */
+static void pkvm_save_backtrace(unsigned long fp, unsigned long pc)
+{
+}
+#endif /* CONFIG_PROTECTED_NVHE_STACKTRACE */
+
+/*
+ * kvm_nvhe_prepare_backtrace - prepare to dump the nVHE backtrace
+ *
+ * @fp : frame pointer at which to start the unwinding.
+ * @pc : program counter at which to start the unwinding.
+ *
+ * Saves the information needed by the host to dump the nVHE hypervisor
+ * backtrace.
+ */
+void kvm_nvhe_prepare_backtrace(unsigned long fp, unsigned long pc)
+{
+ if (is_protected_kvm_enabled())
+ pkvm_save_backtrace(fp, pc);
+ else
+ hyp_prepare_backtrace(fp, pc);
+}
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index ab0e19117dfe..9f6385702061 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -34,6 +34,8 @@ DEFINE_PER_CPU(struct kvm_host_data, kvm_host_data);
DEFINE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
DEFINE_PER_CPU(unsigned long, kvm_hyp_vector);
+extern void kvm_nvhe_prepare_backtrace(unsigned long fp, unsigned long pc);
+
static void __activate_traps(struct kvm_vcpu *vcpu)
{
u64 val;
@@ -375,6 +377,10 @@ asmlinkage void __noreturn hyp_panic(void)
__sysreg_restore_state_nvhe(host_ctxt);
}
+ /* Prepare to dump kvm nvhe hyp stacktrace */
+ kvm_nvhe_prepare_backtrace((unsigned long)__builtin_frame_address(0),
+ _THIS_IP_);
+
__hyp_do_panic(host_ctxt, spsr, elr, par);
unreachable();
}