1 files changed, 274 insertions, 0 deletions
diff --git a/arch/arc/kernel/stacktrace.c b/arch/arc/kernel/stacktrace.c
new file mode 100644
index 000000000..f73da203b
--- /dev/null
+++ b/arch/arc/kernel/stacktrace.c
@@ -0,0 +1,274 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *	stacktrace.c : stacktracing APIs needed by rest of kernel
+ *			(wrappers over ARC dwarf based unwinder)
+ *
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ *  vineetg: aug 2009
+ *  -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( )
+ *   for displaying task's kernel mode call stack in /proc/<pid>/stack
+ *  -Iterator based approach to have single copy of unwinding core and APIs
+ *   needing unwinding, implement the logic in iterator regarding:
+ *      = which frame onwards to start capture
+ *      = which frame to stop capturing (wchan)
+ *      = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
+ *
+ *  vineetg: March 2009
+ *  -Implemented correct versions of thread_saved_pc() and get_wchan()
+ *
+ *  rajeshwarr: 2008
+ *  -Initial implementation
+ */
+
+#include <linux/ptrace.h>
+#include <linux/export.h>
+#include <linux/stacktrace.h>
+#include <linux/kallsyms.h>
+#include <linux/sched/debug.h>
+
+#include <asm/arcregs.h>
+#include <asm/unwind.h>
+#include <asm/switch_to.h>
+
+/*-------------------------------------------------------------------------
+ *              Unwinder Iterator
+ *-------------------------------------------------------------------------
+ */
+
+#ifdef CONFIG_ARC_DW2_UNWIND
+
+static int
+seed_unwind_frame_info(struct task_struct *tsk, struct pt_regs *regs,
+		       struct unwind_frame_info *frame_info)
+{
+	if (regs) {
+		/*
+		 * Asynchronous unwinding of intr/exception
+		 *  - Just uses the pt_regs passed
+		 */
+		frame_info->task = tsk;
+
+		frame_info->regs.r27 = regs->fp;
+		frame_info->regs.r28 = regs->sp;
+		frame_info->regs.r31 = regs->blink;
+		frame_info->regs.r63 = regs->ret;
+		frame_info->call_frame = 0;
+	} else if (tsk == NULL || tsk == current) {
+		/*
+		 * synchronous unwinding (e.g. dump_stack)
+		 *  - uses current values of SP and friends
+		 */
+		unsigned long fp, sp, blink, ret;
+		frame_info->task = current;
+
+		__asm__ __volatile__(
+			"mov %0,r27\n\t"
+			"mov %1,r28\n\t"
+			"mov %2,r31\n\t"
+			"mov %3,r63\n\t"
+			: "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
+		);
+
+		frame_info->regs.r27 = fp;
+		frame_info->regs.r28 = sp;
+		frame_info->regs.r31 = blink;
+		frame_info->regs.r63 = ret;
+		frame_info->call_frame = 0;
+	} else {
+		/*
+		 * Asynchronous unwinding of a likely sleeping task
+		 *  - first ensure it is actually sleeping
+		 *  - if so, it will be in __switch_to, kernel mode SP of task
+		 *    is safe-kept and BLINK at a well known location in there
+		 */
+
+		if (tsk->state == TASK_RUNNING)
+			return -1;
+
+		frame_info->task = tsk;
+
+		frame_info->regs.r27 = TSK_K_FP(tsk);
+		frame_info->regs.r28 = TSK_K_ESP(tsk);
+		frame_info->regs.r31 = TSK_K_BLINK(tsk);
+		frame_info->regs.r63 = (unsigned int)__switch_to;
+
+		/* In the prologue of __switch_to, first FP is saved on stack
+		 * and then SP is copied to FP. Dwarf assumes cfa as FP based
+		 * but we didn't save FP. The value retrieved above is FP's
+		 * state in previous frame.
+		 * As a work around for this, we unwind from __switch_to start
+		 * and adjust SP accordingly. The other limitation is that
+		 * __switch_to macro is dwarf rules are not generated for inline
+		 * assembly code
+		 */
+		frame_info->regs.r27 = 0;
+		frame_info->regs.r28 += 60;
+		frame_info->call_frame = 0;
+
+	}
+	return 0;
+}
+
+#endif
+
+notrace noinline unsigned int
+arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
+		int (*consumer_fn) (unsigned int, void *), void *arg)
+{
+#ifdef CONFIG_ARC_DW2_UNWIND
+	int ret = 0, cnt = 0;
+	unsigned int address;
+	struct unwind_frame_info frame_info;
+
+	if (seed_unwind_frame_info(tsk, regs, &frame_info))
+		return 0;
+
+	while (1) {
+		address = UNW_PC(&frame_info);
+
+		if (!address || !__kernel_text_address(address))
+			break;
+
+		if (consumer_fn(address, arg) == -1)
+			break;
+
+		ret = arc_unwind(&frame_info);
+		if (ret)
+			break;
+
+		frame_info.regs.r63 = frame_info.regs.r31;
+
+		if (cnt++ > 128) {
+			printk("unwinder looping too long, aborting !\n");
+			return 0;
+		}
+	}
+
+	return address;		/* return the last address it saw */
+#else
+	/* On ARC, only Dward based unwinder works. fp based backtracing is
+	 * not possible (-fno-omit-frame-pointer) because of the way function
+	 * prelogue is setup (callee regs saved and then fp set and not other
+	 * way around
+	 */
+	pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
+	return 0;
+
+#endif
+}
+
+/*-------------------------------------------------------------------------
+ * callbacks called by unwinder iterator to implement kernel APIs
+ *
+ * The callback can return -1 to force the iterator to stop, which by default
+ * keeps going till the bottom-most frame.
+ *-------------------------------------------------------------------------
+ */
+
+/* Call-back which plugs into unwinding core to dump the stack in
+ * case of panic/OOPs/BUG etc
+ */
+static int __print_sym(unsigned int address, void *arg)
+{
+	const char *loglvl = arg;
+
+	printk("%s  %pS\n", loglvl, (void *)address);
+	return 0;
+}
+
+#ifdef CONFIG_STACKTRACE
+
+/* Call-back which plugs into unwinding core to capture the
+ * traces needed by kernel on /proc/<pid>/stack
+ */
+static int __collect_all(unsigned int address, void *arg)
+{
+	struct stack_trace *trace = arg;
+
+	if (trace->skip > 0)
+		trace->skip--;
+	else
+		trace->entries[trace->nr_entries++] = address;
+
+	if (trace->nr_entries >= trace->max_entries)
+		return -1;
+
+	return 0;
+}
+
+static int __collect_all_but_sched(unsigned int address, void *arg)
+{
+	struct stack_trace *trace = arg;
+
+	if (in_sched_functions(address))
+		return 0;
+
+	if (trace->skip > 0)
+		trace->skip--;
+	else
+		trace->entries[trace->nr_entries++] = address;
+
+	if (trace->nr_entries >= trace->max_entries)
+		return -1;
+
+	return 0;
+}
+
+#endif
+
+static int __get_first_nonsched(unsigned int address, void *unused)
+{
+	if (in_sched_functions(address))
+		return 0;
+
+	return -1;
+}
+
+/*-------------------------------------------------------------------------
+ *              APIs expected by various kernel sub-systems
+ *-------------------------------------------------------------------------
+ */
+
+noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs,
+			      const char *loglvl)
+{
+	printk("%s\nStack Trace:\n", loglvl);
+	arc_unwind_core(tsk, regs, __print_sym, (void *)loglvl);
+}
+EXPORT_SYMBOL(show_stacktrace);
+
+/* Expected by sched Code */
+void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
+{
+	show_stacktrace(tsk, NULL, loglvl);
+}
+
+/* Another API expected by schedular, shows up in "ps" as Wait Channel
+ * Of course just returning schedule( ) would be pointless so unwind until
+ * the function is not in schedular code
+ */
+unsigned int get_wchan(struct task_struct *tsk)
+{
+	return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
+}
+
+#ifdef CONFIG_STACKTRACE
+
+/*
+ * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
+ * A typical use is when /proc/<pid>/stack is queried by userland
+ */
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+	/* Assumes @tsk is sleeping so unwinds from __switch_to */
+	arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
+}
+
+void save_stack_trace(struct stack_trace *trace)
+{
+	/* Pass NULL for task so it unwinds the current call frame */
+	arc_unwind_core(NULL, NULL, __collect_all, trace);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+#endif