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Linux/arch/arc/kernel/stacktrace.c

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  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 <linux/sched/debug.h>
 32 
 33 #include <asm/arcregs.h>
 34 #include <asm/unwind.h>
 35 #include <asm/switch_to.h>
 36 
 37 /*-------------------------------------------------------------------------
 38  *              Unwinder Iterator
 39  *-------------------------------------------------------------------------
 40  */
 41 
 42 #ifdef CONFIG_ARC_DW2_UNWIND
 43 
 44 static void seed_unwind_frame_info(struct task_struct *tsk,
 45                                    struct pt_regs *regs,
 46                                    struct unwind_frame_info *frame_info)
 47 {
 48         /*
 49          * synchronous unwinding (e.g. dump_stack)
 50          *  - uses current values of SP and friends
 51          */
 52         if (tsk == NULL && regs == NULL) {
 53                 unsigned long fp, sp, blink, ret;
 54                 frame_info->task = current;
 55 
 56                 __asm__ __volatile__(
 57                         "mov %0,r27\n\t"
 58                         "mov %1,r28\n\t"
 59                         "mov %2,r31\n\t"
 60                         "mov %3,r63\n\t"
 61                         : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
 62                 );
 63 
 64                 frame_info->regs.r27 = fp;
 65                 frame_info->regs.r28 = sp;
 66                 frame_info->regs.r31 = blink;
 67                 frame_info->regs.r63 = ret;
 68                 frame_info->call_frame = 0;
 69         } else if (regs == NULL) {
 70                 /*
 71                  * Asynchronous unwinding of sleeping task
 72                  *  - Gets SP etc from task's pt_regs (saved bottom of kernel
 73                  *    mode stack of task)
 74                  */
 75 
 76                 frame_info->task = tsk;
 77 
 78                 frame_info->regs.r27 = TSK_K_FP(tsk);
 79                 frame_info->regs.r28 = TSK_K_ESP(tsk);
 80                 frame_info->regs.r31 = TSK_K_BLINK(tsk);
 81                 frame_info->regs.r63 = (unsigned int)__switch_to;
 82 
 83                 /* In the prologue of __switch_to, first FP is saved on stack
 84                  * and then SP is copied to FP. Dwarf assumes cfa as FP based
 85                  * but we didn't save FP. The value retrieved above is FP's
 86                  * state in previous frame.
 87                  * As a work around for this, we unwind from __switch_to start
 88                  * and adjust SP accordingly. The other limitation is that
 89                  * __switch_to macro is dwarf rules are not generated for inline
 90                  * assembly code
 91                  */
 92                 frame_info->regs.r27 = 0;
 93                 frame_info->regs.r28 += 60;
 94                 frame_info->call_frame = 0;
 95 
 96         } else {
 97                 /*
 98                  * Asynchronous unwinding of intr/exception
 99                  *  - Just uses the pt_regs passed
100                  */
101                 frame_info->task = tsk;
102 
103                 frame_info->regs.r27 = regs->fp;
104                 frame_info->regs.r28 = regs->sp;
105                 frame_info->regs.r31 = regs->blink;
106                 frame_info->regs.r63 = regs->ret;
107                 frame_info->call_frame = 0;
108         }
109 }
110 
111 #endif
112 
113 notrace noinline unsigned int
114 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
115                 int (*consumer_fn) (unsigned int, void *), void *arg)
116 {
117 #ifdef CONFIG_ARC_DW2_UNWIND
118         int ret = 0;
119         unsigned int address;
120         struct unwind_frame_info frame_info;
121 
122         seed_unwind_frame_info(tsk, regs, &frame_info);
123 
124         while (1) {
125                 address = UNW_PC(&frame_info);
126 
127                 if (!address || !__kernel_text_address(address))
128                         break;
129 
130                 if (consumer_fn(address, arg) == -1)
131                         break;
132 
133                 ret = arc_unwind(&frame_info);
134                 if (ret)
135                         break;
136 
137                 frame_info.regs.r63 = frame_info.regs.r31;
138         }
139 
140         return address;         /* return the last address it saw */
141 #else
142         /* On ARC, only Dward based unwinder works. fp based backtracing is
143          * not possible (-fno-omit-frame-pointer) because of the way function
144          * prelogue is setup (callee regs saved and then fp set and not other
145          * way around
146          */
147         pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
148         return 0;
149 
150 #endif
151 }
152 
153 /*-------------------------------------------------------------------------
154  * callbacks called by unwinder iterator to implement kernel APIs
155  *
156  * The callback can return -1 to force the iterator to stop, which by default
157  * keeps going till the bottom-most frame.
158  *-------------------------------------------------------------------------
159  */
160 
161 /* Call-back which plugs into unwinding core to dump the stack in
162  * case of panic/OOPs/BUG etc
163  */
164 static int __print_sym(unsigned int address, void *unused)
165 {
166         printk("  %pS\n", (void *)address);
167         return 0;
168 }
169 
170 #ifdef CONFIG_STACKTRACE
171 
172 /* Call-back which plugs into unwinding core to capture the
173  * traces needed by kernel on /proc/<pid>/stack
174  */
175 static int __collect_all(unsigned int address, void *arg)
176 {
177         struct stack_trace *trace = arg;
178 
179         if (trace->skip > 0)
180                 trace->skip--;
181         else
182                 trace->entries[trace->nr_entries++] = address;
183 
184         if (trace->nr_entries >= trace->max_entries)
185                 return -1;
186 
187         return 0;
188 }
189 
190 static int __collect_all_but_sched(unsigned int address, void *arg)
191 {
192         struct stack_trace *trace = arg;
193 
194         if (in_sched_functions(address))
195                 return 0;
196 
197         if (trace->skip > 0)
198                 trace->skip--;
199         else
200                 trace->entries[trace->nr_entries++] = address;
201 
202         if (trace->nr_entries >= trace->max_entries)
203                 return -1;
204 
205         return 0;
206 }
207 
208 #endif
209 
210 static int __get_first_nonsched(unsigned int address, void *unused)
211 {
212         if (in_sched_functions(address))
213                 return 0;
214 
215         return -1;
216 }
217 
218 /*-------------------------------------------------------------------------
219  *              APIs expected by various kernel sub-systems
220  *-------------------------------------------------------------------------
221  */
222 
223 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs)
224 {
225         pr_info("\nStack Trace:\n");
226         arc_unwind_core(tsk, regs, __print_sym, NULL);
227 }
228 EXPORT_SYMBOL(show_stacktrace);
229 
230 /* Expected by sched Code */
231 void show_stack(struct task_struct *tsk, unsigned long *sp)
232 {
233         show_stacktrace(tsk, NULL);
234 }
235 
236 /* Another API expected by schedular, shows up in "ps" as Wait Channel
237  * Of course just returning schedule( ) would be pointless so unwind until
238  * the function is not in schedular code
239  */
240 unsigned int get_wchan(struct task_struct *tsk)
241 {
242         return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
243 }
244 
245 #ifdef CONFIG_STACKTRACE
246 
247 /*
248  * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
249  * A typical use is when /proc/<pid>/stack is queried by userland
250  */
251 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
252 {
253         /* Assumes @tsk is sleeping so unwinds from __switch_to */
254         arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
255 }
256 
257 void save_stack_trace(struct stack_trace *trace)
258 {
259         /* Pass NULL for task so it unwinds the current call frame */
260         arc_unwind_core(NULL, NULL, __collect_all, trace);
261 }
262 EXPORT_SYMBOL_GPL(save_stack_trace);
263 #endif
264 

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