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-rw-r--r--arch/arm64/kvm/stacktrace.c245
1 files changed, 245 insertions, 0 deletions
diff --git a/arch/arm64/kvm/stacktrace.c b/arch/arm64/kvm/stacktrace.c
new file mode 100644
index 000000000..3ace5b758
--- /dev/null
+++ b/arch/arm64/kvm/stacktrace.c
@@ -0,0 +1,245 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * KVM nVHE hypervisor stack tracing support.
+ *
+ * The unwinder implementation depends on the nVHE mode:
+ *
+ * 1) Non-protected nVHE mode - the host can directly access the
+ * HYP stack pages and unwind the HYP stack in EL1. This saves having
+ * to allocate shared buffers for the host to read the unwinded
+ * stacktrace.
+ *
+ * 2) pKVM (protected nVHE) mode - the host cannot directly access
+ * the HYP memory. The stack is unwinded in EL2 and dumped to a shared
+ * buffer where the host can read and print the stacktrace.
+ *
+ * Copyright (C) 2022 Google LLC
+ */
+
+#include <linux/kvm.h>
+#include <linux/kvm_host.h>
+
+#include <asm/stacktrace/nvhe.h>
+
+static struct stack_info stackinfo_get_overflow(void)
+{
+ struct kvm_nvhe_stacktrace_info *stacktrace_info
+ = this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
+ unsigned long low = (unsigned long)stacktrace_info->overflow_stack_base;
+ unsigned long high = low + OVERFLOW_STACK_SIZE;
+
+ return (struct stack_info) {
+ .low = low,
+ .high = high,
+ };
+}
+
+static struct stack_info stackinfo_get_overflow_kern_va(void)
+{
+ unsigned long low = (unsigned long)this_cpu_ptr_nvhe_sym(overflow_stack);
+ unsigned long high = low + OVERFLOW_STACK_SIZE;
+
+ return (struct stack_info) {
+ .low = low,
+ .high = high,
+ };
+}
+
+static struct stack_info stackinfo_get_hyp(void)
+{
+ struct kvm_nvhe_stacktrace_info *stacktrace_info
+ = this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
+ unsigned long low = (unsigned long)stacktrace_info->stack_base;
+ unsigned long high = low + PAGE_SIZE;
+
+ return (struct stack_info) {
+ .low = low,
+ .high = high,
+ };
+}
+
+static struct stack_info stackinfo_get_hyp_kern_va(void)
+{
+ unsigned long low = (unsigned long)*this_cpu_ptr(&kvm_arm_hyp_stack_page);
+ unsigned long high = low + PAGE_SIZE;
+
+ return (struct stack_info) {
+ .low = low,
+ .high = high,
+ };
+}
+
+/*
+ * kvm_nvhe_stack_kern_va - Convert KVM nVHE HYP stack addresses to a kernel VAs
+ *
+ * The nVHE hypervisor stack is mapped in the flexible 'private' VA range, to
+ * allow for guard pages below the stack. Consequently, the fixed offset address
+ * translation macros won't work here.
+ *
+ * The kernel VA is calculated as an offset from the kernel VA of the hypervisor
+ * stack base.
+ *
+ * Returns true on success and updates @addr to its corresponding kernel VA;
+ * otherwise returns false.
+ */
+static bool kvm_nvhe_stack_kern_va(unsigned long *addr, unsigned long size)
+{
+ struct stack_info stack_hyp, stack_kern;
+
+ stack_hyp = stackinfo_get_hyp();
+ stack_kern = stackinfo_get_hyp_kern_va();
+ if (stackinfo_on_stack(&stack_hyp, *addr, size))
+ goto found;
+
+ stack_hyp = stackinfo_get_overflow();
+ stack_kern = stackinfo_get_overflow_kern_va();
+ if (stackinfo_on_stack(&stack_hyp, *addr, size))
+ goto found;
+
+ return false;
+
+found:
+ *addr = *addr - stack_hyp.low + stack_kern.low;
+ return true;
+}
+
+/*
+ * Convert a KVN nVHE HYP frame record address to a kernel VA
+ */
+static bool kvm_nvhe_stack_kern_record_va(unsigned long *addr)
+{
+ return kvm_nvhe_stack_kern_va(addr, 16);
+}
+
+static int unwind_next(struct unwind_state *state)
+{
+ /*
+ * The FP is in the hypervisor VA space. Convert it to the kernel VA
+ * space so it can be unwound by the regular unwind functions.
+ */
+ if (!kvm_nvhe_stack_kern_record_va(&state->fp))
+ return -EINVAL;
+
+ return unwind_next_frame_record(state);
+}
+
+static void 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;
+ }
+}
+
+/*
+ * kvm_nvhe_dump_backtrace_entry - Symbolize and print an nVHE backtrace entry
+ *
+ * @arg : the hypervisor offset, used for address translation
+ * @where : the program counter corresponding to the stack frame
+ */
+static bool kvm_nvhe_dump_backtrace_entry(void *arg, unsigned long where)
+{
+ unsigned long va_mask = GENMASK_ULL(vabits_actual - 1, 0);
+ unsigned long hyp_offset = (unsigned long)arg;
+
+ /* Mask tags and convert to kern addr */
+ where = (where & va_mask) + hyp_offset;
+ kvm_err(" [<%016lx>] %pB\n", where, (void *)(where + kaslr_offset()));
+
+ return true;
+}
+
+static void kvm_nvhe_dump_backtrace_start(void)
+{
+ kvm_err("nVHE call trace:\n");
+}
+
+static void kvm_nvhe_dump_backtrace_end(void)
+{
+ kvm_err("---[ end nVHE call trace ]---\n");
+}
+
+/*
+ * hyp_dump_backtrace - Dump the non-protected nVHE backtrace.
+ *
+ * @hyp_offset: hypervisor offset, used for address translation.
+ *
+ * The host can directly access HYP stack pages in non-protected
+ * mode, so the unwinding is done directly from EL1. This removes
+ * the need for shared buffers between host and hypervisor for
+ * the stacktrace.
+ */
+static void hyp_dump_backtrace(unsigned long hyp_offset)
+{
+ struct kvm_nvhe_stacktrace_info *stacktrace_info;
+ struct stack_info stacks[] = {
+ stackinfo_get_overflow_kern_va(),
+ stackinfo_get_hyp_kern_va(),
+ };
+ struct unwind_state state = {
+ .stacks = stacks,
+ .nr_stacks = ARRAY_SIZE(stacks),
+ };
+
+ stacktrace_info = this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
+
+ kvm_nvhe_unwind_init(&state, stacktrace_info->fp, stacktrace_info->pc);
+
+ kvm_nvhe_dump_backtrace_start();
+ unwind(&state, kvm_nvhe_dump_backtrace_entry, (void *)hyp_offset);
+ kvm_nvhe_dump_backtrace_end();
+}
+
+#ifdef CONFIG_PROTECTED_NVHE_STACKTRACE
+DECLARE_KVM_NVHE_PER_CPU(unsigned long [NVHE_STACKTRACE_SIZE/sizeof(long)],
+ pkvm_stacktrace);
+
+/*
+ * pkvm_dump_backtrace - Dump the protected nVHE HYP backtrace.
+ *
+ * @hyp_offset: hypervisor offset, used for address translation.
+ *
+ * Dumping of the pKVM HYP backtrace is done by reading the
+ * stack addresses from the shared stacktrace buffer, since the
+ * host cannot directly access hypervisor memory in protected
+ * mode.
+ */
+static void pkvm_dump_backtrace(unsigned long hyp_offset)
+{
+ unsigned long *stacktrace
+ = (unsigned long *) this_cpu_ptr_nvhe_sym(pkvm_stacktrace);
+ int i;
+
+ kvm_nvhe_dump_backtrace_start();
+ /* The saved stacktrace is terminated by a null entry */
+ for (i = 0;
+ i < ARRAY_SIZE(kvm_nvhe_sym(pkvm_stacktrace)) && stacktrace[i];
+ i++)
+ kvm_nvhe_dump_backtrace_entry((void *)hyp_offset, stacktrace[i]);
+ kvm_nvhe_dump_backtrace_end();
+}
+#else /* !CONFIG_PROTECTED_NVHE_STACKTRACE */
+static void pkvm_dump_backtrace(unsigned long hyp_offset)
+{
+ kvm_err("Cannot dump pKVM nVHE stacktrace: !CONFIG_PROTECTED_NVHE_STACKTRACE\n");
+}
+#endif /* CONFIG_PROTECTED_NVHE_STACKTRACE */
+
+/*
+ * kvm_nvhe_dump_backtrace - Dump KVM nVHE hypervisor backtrace.
+ *
+ * @hyp_offset: hypervisor offset, used for address translation.
+ */
+void kvm_nvhe_dump_backtrace(unsigned long hyp_offset)
+{
+ if (is_protected_kvm_enabled())
+ pkvm_dump_backtrace(hyp_offset);
+ else
+ hyp_dump_backtrace(hyp_offset);
+}