ARC: stacktracing APIs based on dw2 unwinder

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

2 files changed, 217 insertions, 2 deletions

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 0979d8e6fc16..84b23fae661c 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -60,6 +60,10 @@ config GENERIC_HWEIGHT
 config BINFMT_ELF
         def_bool y
 
+config STACKTRACE_SUPPORT
+        def_bool y
+        select STACKTRACE
+
 config HAVE_LATENCYTOP_SUPPORT
         def_bool y
 
diff --git a/arch/arc/kernel/stacktrace.c b/arch/arc/kernel/stacktrace.c
index b9d1646d1220..a63ff842564b 100644
--- a/arch/arc/kernel/stacktrace.c
+++ b/arch/arc/kernel/stacktrace.c
@@ -1,13 +1,206 @@
 /*
+ *      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)
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
+ *
+ *  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 <asm/arcregs.h>
+#include <asm/unwind.h>
+#include <asm/switch_to.h>
+
+/*-------------------------------------------------------------------------
+ *              Unwinder Iterator
+ *-------------------------------------------------------------------------
+ */
+
+#ifdef CONFIG_ARC_DW2_UNWIND
+
+static void seed_unwind_frame_info(struct task_struct *tsk,
+                                   struct pt_regs *regs,
+                                   struct unwind_frame_info *frame_info)
+{
+        if (tsk == NULL && regs == NULL) {
+                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 if (regs == NULL) {
+
+                frame_info->task = tsk;
+
+                frame_info->regs.r27 = KSTK_FP(tsk);
+                frame_info->regs.r28 = KSTK_ESP(tsk);
+                frame_info->regs.r31 = KSTK_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 += 64;
+                frame_info->call_frame = 0;
+
+        } else {
+                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;
+        }
+}
+
+#endif
+
+static 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;
+        unsigned int address;
+        struct unwind_frame_info frame_info;
+
+        seed_unwind_frame_info(tsk, regs, &frame_info);
+
+        while (1) {
+                address = UNW_PC(&frame_info);
+
+                if (address && __kernel_text_address(address)) {
+                        if (consumer_fn(address, arg) == -1)
+                                break;
+                }
+
+                ret = arc_unwind(&frame_info);
+
+                if (ret == 0) {
+                        frame_info.regs.r63 = frame_info.regs.r31;
+                        continue;
+                } else {
+                        break;
+                }
+        }
+
+        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("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 *unused)
+{
+        __print_symbol("  %s\n", 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
@@ -16,7 +209,8 @@
 
 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs)
 {
-        pr_info("\nStack Trace: NOT Available\n");
+        pr_info("\nStack Trace:\n");
+        arc_unwind_core(tsk, regs, __print_sym, NULL);
 }
 EXPORT_SYMBOL(show_stacktrace);
 
@@ -39,5 +233,22 @@ EXPORT_SYMBOL(dump_stack);
  */
 unsigned int get_wchan(struct task_struct *tsk)
 {
-        return 0;
+        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)
+{
+        arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
+}
+
+void save_stack_trace(struct stack_trace *trace)
+{
+        arc_unwind_core(current, NULL, __collect_all, trace);
 }
+#endif