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