dump_stack: consolidate dump_stack() implementations and unify their behaviors
[linux-3.10.git] / arch / arc / kernel / stacktrace.c
1 /*
2  *      stacktrace.c : stacktracing APIs needed by rest of kernel
3  *                      (wrappers over ARC dwarf based unwinder)
4  *
5  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  *
11  *  vineetg: aug 2009
12  *  -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( )
13  *   for displaying task's kernel mode call stack in /proc/<pid>/stack
14  *  -Iterator based approach to have single copy of unwinding core and APIs
15  *   needing unwinding, implement the logic in iterator regarding:
16  *      = which frame onwards to start capture
17  *      = which frame to stop capturing (wchan)
18  *      = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
19  *
20  *  vineetg: March 2009
21  *  -Implemented correct versions of thread_saved_pc() and get_wchan()
22  *
23  *  rajeshwarr: 2008
24  *  -Initial implementation
25  */
26
27 #include <linux/ptrace.h>
28 #include <linux/export.h>
29 #include <linux/stacktrace.h>
30 #include <linux/kallsyms.h>
31 #include <asm/arcregs.h>
32 #include <asm/unwind.h>
33 #include <asm/switch_to.h>
34
35 /*-------------------------------------------------------------------------
36  *              Unwinder Iterator
37  *-------------------------------------------------------------------------
38  */
39
40 #ifdef CONFIG_ARC_DW2_UNWIND
41
42 static void seed_unwind_frame_info(struct task_struct *tsk,
43                                    struct pt_regs *regs,
44                                    struct unwind_frame_info *frame_info)
45 {
46         if (tsk == NULL && regs == NULL) {
47                 unsigned long fp, sp, blink, ret;
48                 frame_info->task = current;
49
50                 __asm__ __volatile__(
51                         "mov %0,r27\n\t"
52                         "mov %1,r28\n\t"
53                         "mov %2,r31\n\t"
54                         "mov %3,r63\n\t"
55                         : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
56                 );
57
58                 frame_info->regs.r27 = fp;
59                 frame_info->regs.r28 = sp;
60                 frame_info->regs.r31 = blink;
61                 frame_info->regs.r63 = ret;
62                 frame_info->call_frame = 0;
63         } else if (regs == NULL) {
64
65                 frame_info->task = tsk;
66
67                 frame_info->regs.r27 = KSTK_FP(tsk);
68                 frame_info->regs.r28 = KSTK_ESP(tsk);
69                 frame_info->regs.r31 = KSTK_BLINK(tsk);
70                 frame_info->regs.r63 = (unsigned int)__switch_to;
71
72                 /* In the prologue of __switch_to, first FP is saved on stack
73                  * and then SP is copied to FP. Dwarf assumes cfa as FP based
74                  * but we didn't save FP. The value retrieved above is FP's
75                  * state in previous frame.
76                  * As a work around for this, we unwind from __switch_to start
77                  * and adjust SP accordingly. The other limitation is that
78                  * __switch_to macro is dwarf rules are not generated for inline
79                  * assembly code
80                  */
81                 frame_info->regs.r27 = 0;
82                 frame_info->regs.r28 += 64;
83                 frame_info->call_frame = 0;
84
85         } else {
86                 frame_info->task = tsk;
87
88                 frame_info->regs.r27 = regs->fp;
89                 frame_info->regs.r28 = regs->sp;
90                 frame_info->regs.r31 = regs->blink;
91                 frame_info->regs.r63 = regs->ret;
92                 frame_info->call_frame = 0;
93         }
94 }
95
96 #endif
97
98 static noinline unsigned int
99 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
100                 int (*consumer_fn) (unsigned int, void *), void *arg)
101 {
102 #ifdef CONFIG_ARC_DW2_UNWIND
103         int ret = 0;
104         unsigned int address;
105         struct unwind_frame_info frame_info;
106
107         seed_unwind_frame_info(tsk, regs, &frame_info);
108
109         while (1) {
110                 address = UNW_PC(&frame_info);
111
112                 if (address && __kernel_text_address(address)) {
113                         if (consumer_fn(address, arg) == -1)
114                                 break;
115                 }
116
117                 ret = arc_unwind(&frame_info);
118
119                 if (ret == 0) {
120                         frame_info.regs.r63 = frame_info.regs.r31;
121                         continue;
122                 } else {
123                         break;
124                 }
125         }
126
127         return address;         /* return the last address it saw */
128 #else
129         /* On ARC, only Dward based unwinder works. fp based backtracing is
130          * not possible (-fno-omit-frame-pointer) because of the way function
131          * prelogue is setup (callee regs saved and then fp set and not other
132          * way around
133          */
134         pr_warn("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
135         return 0;
136
137 #endif
138 }
139
140 /*-------------------------------------------------------------------------
141  * callbacks called by unwinder iterator to implement kernel APIs
142  *
143  * The callback can return -1 to force the iterator to stop, which by default
144  * keeps going till the bottom-most frame.
145  *-------------------------------------------------------------------------
146  */
147
148 /* Call-back which plugs into unwinding core to dump the stack in
149  * case of panic/OOPs/BUG etc
150  */
151 static int __print_sym(unsigned int address, void *unused)
152 {
153         __print_symbol("  %s\n", address);
154         return 0;
155 }
156
157 #ifdef CONFIG_STACKTRACE
158
159 /* Call-back which plugs into unwinding core to capture the
160  * traces needed by kernel on /proc/<pid>/stack
161  */
162 static int __collect_all(unsigned int address, void *arg)
163 {
164         struct stack_trace *trace = arg;
165
166         if (trace->skip > 0)
167                 trace->skip--;
168         else
169                 trace->entries[trace->nr_entries++] = address;
170
171         if (trace->nr_entries >= trace->max_entries)
172                 return -1;
173
174         return 0;
175 }
176
177 static int __collect_all_but_sched(unsigned int address, void *arg)
178 {
179         struct stack_trace *trace = arg;
180
181         if (in_sched_functions(address))
182                 return 0;
183
184         if (trace->skip > 0)
185                 trace->skip--;
186         else
187                 trace->entries[trace->nr_entries++] = address;
188
189         if (trace->nr_entries >= trace->max_entries)
190                 return -1;
191
192         return 0;
193 }
194
195 #endif
196
197 static int __get_first_nonsched(unsigned int address, void *unused)
198 {
199         if (in_sched_functions(address))
200                 return 0;
201
202         return -1;
203 }
204
205 /*-------------------------------------------------------------------------
206  *              APIs expected by various kernel sub-systems
207  *-------------------------------------------------------------------------
208  */
209
210 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs)
211 {
212         pr_info("\nStack Trace:\n");
213         arc_unwind_core(tsk, regs, __print_sym, NULL);
214 }
215 EXPORT_SYMBOL(show_stacktrace);
216
217 /* Expected by sched Code */
218 void show_stack(struct task_struct *tsk, unsigned long *sp)
219 {
220         show_stacktrace(tsk, NULL);
221 }
222
223 /* Another API expected by schedular, shows up in "ps" as Wait Channel
224  * Ofcourse just returning schedule( ) would be pointless so unwind until
225  * the function is not in schedular code
226  */
227 unsigned int get_wchan(struct task_struct *tsk)
228 {
229         return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
230 }
231
232 #ifdef CONFIG_STACKTRACE
233
234 /*
235  * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
236  * A typical use is when /proc/<pid>/stack is queried by userland
237  */
238 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
239 {
240         arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
241 }
242
243 void save_stack_trace(struct stack_trace *trace)
244 {
245         arc_unwind_core(current, NULL, __collect_all, trace);
246 }
247 #endif