1 files changed, 118 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c
index d534ed901538..26a50603177c 100644
--- a/arch/powerpc/kernel/stacktrace.c
+++ b/arch/powerpc/kernel/stacktrace.c
@@ -2,7 +2,7 @@
  * Stack trace utility
  *
  * Copyright 2008 Christoph Hellwig, IBM Corp.
- *
+ * Copyright 2018 SUSE Linux GmbH
  *
  *      This program is free software; you can redistribute it and/or
  *      modify it under the terms of the GNU General Public License
@@ -11,11 +11,16 @@
  */
 
 #include <linux/export.h>
+#include <linux/kallsyms.h>
+#include <linux/module.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>
 
 /*
  * Save stack-backtrace addresses into a stack_trace buffer.
@@ -76,3 +81,115 @@ save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 	save_context_stack(trace, regs->gpr[1], current, 0);
 }
 EXPORT_SYMBOL_GPL(save_stack_trace_regs);
+
+#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
+int
+save_stack_trace_tsk_reliable(struct task_struct *tsk,
+				struct stack_trace *trace)
+{
+	unsigned long sp;
+	unsigned long stack_page = (unsigned long)task_stack_page(tsk);
+	unsigned long stack_end;
+	int graph_idx = 0;
+
+	/*
+	 * The last frame (unwinding first) may not yet have saved
+	 * its LR onto the stack.
+	 */
+	int firstframe = 1;
+
+	if (tsk == current)
+		sp = current_stack_pointer();
+	else
+		sp = tsk->thread.ksp;
+
+	stack_end = stack_page + THREAD_SIZE;
+	if (!is_idle_task(tsk)) {
+		/*
+		 * 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 (sp < stack_page + sizeof(struct thread_struct) ||
+	    sp > stack_end - STACK_FRAME_MIN_SIZE) {
+		return 1;
+	}
+
+	for (;;) {
+		unsigned long *stack = (unsigned long *) sp;
+		unsigned long newsp, ip;
+
+		/* sanity check: ABI requires SP to be aligned 16 bytes. */
+		if (sp & 0xF)
+			return 1;
+
+		/* Mark stacktraces with exception frames as unreliable. */
+		if (sp <= stack_end - STACK_INT_FRAME_SIZE &&
+		    stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
+			return 1;
+		}
+
+		newsp = stack[0];
+		/* Stack grows downwards; unwinder may only go up. */
+		if (newsp <= sp)
+			return 1;
+
+		if (newsp != stack_end &&
+		    newsp > stack_end - STACK_FRAME_MIN_SIZE) {
+			return 1; /* invalid backlink, too far up. */
+		}
+
+		/* Examine the saved LR: it must point into kernel code. */
+		ip = stack[STACK_FRAME_LR_SAVE];
+		if (!firstframe && !__kernel_text_address(ip))
+			return 1;
+		firstframe = 0;
+
+		/*
+		 * FIXME: IMHO these tests do not belong in
+		 * arch-dependent code, they are generic.
+		 */
+		ip = ftrace_graph_ret_addr(tsk, &graph_idx, ip, NULL);
+
+		/*
+		 * Mark stacktraces with kretprobed functions on them
+		 * as unreliable.
+		 */
+		if (ip == (unsigned long)kretprobe_trampoline)
+			return 1;
+
+		if (!trace->skip)
+			trace->entries[trace->nr_entries++] = ip;
+		else
+			trace->skip--;
+
+		if (newsp == stack_end)
+			break;
+
+		if (trace->nr_entries >= trace->max_entries)
+			return -E2BIG;
+
+		sp = newsp;
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(save_stack_trace_tsk_reliable);
+#endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */