1 files changed, 228 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c
new file mode 100644
index 000000000..a2443d617
--- /dev/null
+++ b/arch/powerpc/kernel/stacktrace.c
@@ -0,0 +1,228 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Stack trace utility functions etc.
+ *
+ * Copyright 2008 Christoph Hellwig, IBM Corp.
+ * Copyright 2018 SUSE Linux GmbH
+ * Copyright 2018 Nick Piggin, Michael Ellerman, IBM Corp.
+ */
+
+#include <linux/delay.h>
+#include <linux/export.h>
+#include <linux/kallsyms.h>
+#include <linux/module.h>
+#include <linux/nmi.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/task_stack.h>
+#include <linux/stacktrace.h>
+#include <asm/ptrace.h>
+#include <asm/processor.h>
+#include <linux/ftrace.h>
+#include <asm/kprobes.h>
+
+#include <asm/paca.h>
+
+void __no_sanitize_address arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
+					   struct task_struct *task, struct pt_regs *regs)
+{
+	unsigned long sp;
+
+	if (regs && !consume_entry(cookie, regs->nip))
+		return;
+
+	if (regs)
+		sp = regs->gpr[1];
+	else if (task == current)
+		sp = current_stack_frame();
+	else
+		sp = task->thread.ksp;
+
+	for (;;) {
+		unsigned long *stack = (unsigned long *) sp;
+		unsigned long newsp, ip;
+
+		if (!validate_sp(sp, task, STACK_FRAME_OVERHEAD))
+			return;
+
+		newsp = stack[0];
+		ip = stack[STACK_FRAME_LR_SAVE];
+
+		if (!consume_entry(cookie, ip))
+			return;
+
+		sp = newsp;
+	}
+}
+
+/*
+ * This function returns an error if it detects any unreliable features of the
+ * stack.  Otherwise it guarantees that the stack trace is reliable.
+ *
+ * If the task is not 'current', the caller *must* ensure the task is inactive.
+ */
+int __no_sanitize_address arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
+						   void *cookie, struct task_struct *task)
+{
+	unsigned long sp;
+	unsigned long newsp;
+	unsigned long stack_page = (unsigned long)task_stack_page(task);
+	unsigned long stack_end;
+	int graph_idx = 0;
+	bool firstframe;
+
+	stack_end = stack_page + THREAD_SIZE;
+	if (!is_idle_task(task)) {
+		/*
+		 * For user tasks, this is the SP value loaded on
+		 * kernel entry, see "PACAKSAVE(r13)" in _switch() and
+		 * system_call_common()/EXCEPTION_PROLOG_COMMON().
+		 *
+		 * Likewise for non-swapper kernel threads,
+		 * this also happens to be the top of the stack
+		 * as setup by copy_thread().
+		 *
+		 * Note that stack backlinks are not properly setup by
+		 * copy_thread() and thus, a forked task() will have
+		 * an unreliable stack trace until it's been
+		 * _switch()'ed to for the first time.
+		 */
+		stack_end -= STACK_FRAME_OVERHEAD + sizeof(struct pt_regs);
+	} else {
+		/*
+		 * idle tasks have a custom stack layout,
+		 * c.f. cpu_idle_thread_init().
+		 */
+		stack_end -= STACK_FRAME_OVERHEAD;
+	}
+
+	if (task == current)
+		sp = current_stack_frame();
+	else
+		sp = task->thread.ksp;
+
+	if (sp < stack_page + sizeof(struct thread_struct) ||
+	    sp > stack_end - STACK_FRAME_MIN_SIZE) {
+		return -EINVAL;
+	}
+
+	for (firstframe = true; sp != stack_end;
+	     firstframe = false, sp = newsp) {
+		unsigned long *stack = (unsigned long *) sp;
+		unsigned long ip;
+
+		/* sanity check: ABI requires SP to be aligned 16 bytes. */
+		if (sp & 0xF)
+			return -EINVAL;
+
+		newsp = stack[0];
+		/* Stack grows downwards; unwinder may only go up. */
+		if (newsp <= sp)
+			return -EINVAL;
+
+		if (newsp != stack_end &&
+		    newsp > stack_end - STACK_FRAME_MIN_SIZE) {
+			return -EINVAL; /* invalid backlink, too far up. */
+		}
+
+		/*
+		 * We can only trust the bottom frame's backlink, the
+		 * rest of the frame may be uninitialized, continue to
+		 * the next.
+		 */
+		if (firstframe)
+			continue;
+
+		/* Mark stacktraces with exception frames as unreliable. */
+		if (sp <= stack_end - STACK_INT_FRAME_SIZE &&
+		    stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
+			return -EINVAL;
+		}
+
+		/* Examine the saved LR: it must point into kernel code. */
+		ip = stack[STACK_FRAME_LR_SAVE];
+		if (!__kernel_text_address(ip))
+			return -EINVAL;
+
+		/*
+		 * FIXME: IMHO these tests do not belong in
+		 * arch-dependent code, they are generic.
+		 */
+		ip = ftrace_graph_ret_addr(task, &graph_idx, ip, stack);
+#ifdef CONFIG_KPROBES
+		/*
+		 * Mark stacktraces with kretprobed functions on them
+		 * as unreliable.
+		 */
+		if (ip == (unsigned long)__kretprobe_trampoline)
+			return -EINVAL;
+#endif
+
+		if (!consume_entry(cookie, ip))
+			return -EINVAL;
+	}
+	return 0;
+}
+
+#if defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI)
+static void handle_backtrace_ipi(struct pt_regs *regs)
+{
+	nmi_cpu_backtrace(regs);
+}
+
+static void raise_backtrace_ipi(cpumask_t *mask)
+{
+	struct paca_struct *p;
+	unsigned int cpu;
+	u64 delay_us;
+
+	for_each_cpu(cpu, mask) {
+		if (cpu == smp_processor_id()) {
+			handle_backtrace_ipi(NULL);
+			continue;
+		}
+
+		delay_us = 5 * USEC_PER_SEC;
+
+		if (smp_send_safe_nmi_ipi(cpu, handle_backtrace_ipi, delay_us)) {
+			// Now wait up to 5s for the other CPU to do its backtrace
+			while (cpumask_test_cpu(cpu, mask) && delay_us) {
+				udelay(1);
+				delay_us--;
+			}
+
+			// Other CPU cleared itself from the mask
+			if (delay_us)
+				continue;
+		}
+
+		p = paca_ptrs[cpu];
+
+		cpumask_clear_cpu(cpu, mask);
+
+		pr_warn("CPU %d didn't respond to backtrace IPI, inspecting paca.\n", cpu);
+		if (!virt_addr_valid(p)) {
+			pr_warn("paca pointer appears corrupt? (%px)\n", p);
+			continue;
+		}
+
+		pr_warn("irq_soft_mask: 0x%02x in_mce: %d in_nmi: %d",
+			p->irq_soft_mask, p->in_mce, p->in_nmi);
+
+		if (virt_addr_valid(p->__current))
+			pr_cont(" current: %d (%s)\n", p->__current->pid,
+				p->__current->comm);
+		else
+			pr_cont(" current pointer corrupt? (%px)\n", p->__current);
+
+		pr_warn("Back trace of paca->saved_r1 (0x%016llx) (possibly stale):\n", p->saved_r1);
+		show_stack(p->__current, (unsigned long *)p->saved_r1, KERN_WARNING);
+	}
+}
+
+void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+{
+	nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
+}
+#endif /* defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) */