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 += 60;
  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         /* Assumes @tsk is sleeping so unwinds from __switch_to */
 241         arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
 242 }
 243
 244 void save_stack_trace(struct stack_trace *trace)
 245 {
 246         /* Pass NULL for task so it unwinds the current call frame */
 247         arc_unwind_core(NULL, NULL, __collect_all, trace);
 248 }
 249 EXPORT_SYMBOL_GPL(save_stack_trace);
 250 #endif