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 <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, cnt = 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                 if (cnt++ > 128) {
 140                         printk("unwinder looping too long, aborting !\n");
 141                         return 0;
 142                 }
 143         }
 144
 145         return address;         /* return the last address it saw */
 146 #else
 147         /* On ARC, only Dward based unwinder works. fp based backtracing is
 148          * not possible (-fno-omit-frame-pointer) because of the way function
 149          * prelogue is setup (callee regs saved and then fp set and not other
 150          * way around
 151          */
 152         pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
 153         return 0;
 154
 155 #endif
 156 }
 157
 158 /*-------------------------------------------------------------------------
 159  * callbacks called by unwinder iterator to implement kernel APIs
 160  *
 161  * The callback can return -1 to force the iterator to stop, which by default
 162  * keeps going till the bottom-most frame.
 163  *-------------------------------------------------------------------------
 164  */
 165
 166 /* Call-back which plugs into unwinding core to dump the stack in
 167  * case of panic/OOPs/BUG etc
 168  */
 169 static int __print_sym(unsigned int address, void *unused)
 170 {
 171         __print_symbol("  %s\n", address);
 172         return 0;
 173 }
 174
 175 #ifdef CONFIG_STACKTRACE
 176
 177 /* Call-back which plugs into unwinding core to capture the
 178  * traces needed by kernel on /proc/<pid>/stack
 179  */
 180 static int __collect_all(unsigned int address, void *arg)
 181 {
 182         struct stack_trace *trace = arg;
 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 static int __collect_all_but_sched(unsigned int address, void *arg)
 196 {
 197         struct stack_trace *trace = arg;
 198
 199         if (in_sched_functions(address))
 200                 return 0;
 201
 202         if (trace->skip > 0)
 203                 trace->skip--;
 204         else
 205                 trace->entries[trace->nr_entries++] = address;
 206
 207         if (trace->nr_entries >= trace->max_entries)
 208                 return -1;
 209
 210         return 0;
 211 }
 212
 213 #endif
 214
 215 static int __get_first_nonsched(unsigned int address, void *unused)
 216 {
 217         if (in_sched_functions(address))
 218                 return 0;
 219
 220         return -1;
 221 }
 222
 223 /*-------------------------------------------------------------------------
 224  *              APIs expected by various kernel sub-systems
 225  *-------------------------------------------------------------------------
 226  */
 227
 228 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs)
 229 {
 230         pr_info("\nStack Trace:\n");
 231         arc_unwind_core(tsk, regs, __print_sym, NULL);
 232 }
 233 EXPORT_SYMBOL(show_stacktrace);
 234
 235 /* Expected by sched Code */
 236 void show_stack(struct task_struct *tsk, unsigned long *sp)
 237 {
 238         show_stacktrace(tsk, NULL);
 239 }
 240
 241 /* Another API expected by schedular, shows up in "ps" as Wait Channel
 242  * Of course just returning schedule( ) would be pointless so unwind until
 243  * the function is not in schedular code
 244  */
 245 unsigned int get_wchan(struct task_struct *tsk)
 246 {
 247         return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
 248 }
 249
 250 #ifdef CONFIG_STACKTRACE
 251
 252 /*
 253  * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
 254  * A typical use is when /proc/<pid>/stack is queried by userland
 255  */
 256 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 257 {
 258         /* Assumes @tsk is sleeping so unwinds from __switch_to */
 259         arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
 260 }
 261
 262 void save_stack_trace(struct stack_trace *trace)
 263 {
 264         /* Pass NULL for task so it unwinds the current call frame */
 265         arc_unwind_core(NULL, NULL, __collect_all, trace);
 266 }
 267 EXPORT_SYMBOL_GPL(save_stack_trace);
 268 #endif