arch/arc/kernel/stacktrace.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *      stacktrace.c : stacktracing APIs needed by rest of kernel
   4  *                      (wrappers over ARC dwarf based unwinder)
   5  *
   6  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   7  *
   8  *  vineetg: aug 2009
   9  *  -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( )
  10  *   for displaying task's kernel mode call stack in /proc/<pid>/stack
  11  *  -Iterator based approach to have single copy of unwinding core and APIs
  12  *   needing unwinding, implement the logic in iterator regarding:
  13  *      = which frame onwards to start capture
  14  *      = which frame to stop capturing (wchan)
  15  *      = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
  16  *
  17  *  vineetg: March 2009
  18  *  -Implemented correct versions of thread_saved_pc() and get_wchan()
  19  *
  20  *  rajeshwarr: 2008
  21  *  -Initial implementation
  22  */
  23
  24 #include <linux/ptrace.h>
  25 #include <linux/export.h>
  26 #include <linux/stacktrace.h>
  27 #include <linux/kallsyms.h>
  28 #include <linux/sched/debug.h>
  29
  30 #include <asm/arcregs.h>
  31 #include <asm/unwind.h>
  32 #include <asm/switch_to.h>
  33
  34 /*-------------------------------------------------------------------------
  35  *              Unwinder Iterator
  36  *-------------------------------------------------------------------------
  37  */
  38
  39 #ifdef CONFIG_ARC_DW2_UNWIND
  40
  41 static int
  42 seed_unwind_frame_info(struct task_struct *tsk, struct pt_regs *regs,
  43                        struct unwind_frame_info *frame_info)
  44 {
  45         if (regs) {
  46                 /*
  47                  * Asynchronous unwinding of intr/exception
  48                  *  - Just uses the pt_regs passed
  49                  */
  50                 frame_info->task = tsk;
  51
  52                 frame_info->regs.r27 = regs->fp;
  53                 frame_info->regs.r28 = regs->sp;
  54                 frame_info->regs.r31 = regs->blink;
  55                 frame_info->regs.r63 = regs->ret;
  56                 frame_info->call_frame = 0;
  57         } else if (tsk == NULL || tsk == current) {
  58                 /*
  59                  * synchronous unwinding (e.g. dump_stack)
  60                  *  - uses current values of SP and friends
  61                  */
  62                 unsigned long fp, sp, blink, ret;
  63                 frame_info->task = current;
  64
  65                 __asm__ __volatile__(
  66                         "mov %0,r27\n\t"
  67                         "mov %1,r28\n\t"
  68                         "mov %2,r31\n\t"
  69                         "mov %3,r63\n\t"
  70                         : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
  71                 );
  72
  73                 frame_info->regs.r27 = fp;
  74                 frame_info->regs.r28 = sp;
  75                 frame_info->regs.r31 = blink;
  76                 frame_info->regs.r63 = ret;
  77                 frame_info->call_frame = 0;
  78         } else {
  79                 /*
  80                  * Asynchronous unwinding of a likely sleeping task
  81                  *  - first ensure it is actually sleeping
  82                  *  - if so, it will be in __switch_to, kernel mode SP of task
  83                  *    is safe-kept and BLINK at a well known location in there
  84                  */
  85
  86                 if (task_is_running(tsk))
  87                         return -1;
  88
  89                 frame_info->task = tsk;
  90
  91                 frame_info->regs.r27 = TSK_K_FP(tsk);
  92                 frame_info->regs.r28 = TSK_K_ESP(tsk);
  93                 frame_info->regs.r31 = TSK_K_BLINK(tsk);
  94                 frame_info->regs.r63 = (unsigned int)__switch_to;
  95
  96                 /* In the prologue of __switch_to, first FP is saved on stack
  97                  * and then SP is copied to FP. Dwarf assumes cfa as FP based
  98                  * but we didn't save FP. The value retrieved above is FP's
  99                  * state in previous frame.
 100                  * As a work around for this, we unwind from __switch_to start
 101                  * and adjust SP accordingly. The other limitation is that
 102                  * __switch_to macro is dwarf rules are not generated for inline
 103                  * assembly code
 104                  */
 105                 frame_info->regs.r27 = 0;
 106                 frame_info->regs.r28 += 60;
 107                 frame_info->call_frame = 0;
 108
 109         }
 110         return 0;
 111 }
 112
 113 #endif
 114
 115 notrace noinline unsigned int
 116 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
 117                 int (*consumer_fn) (unsigned int, void *), void *arg)
 118 {
 119 #ifdef CONFIG_ARC_DW2_UNWIND
 120         int ret = 0, cnt = 0;
 121         unsigned int address;
 122         struct unwind_frame_info frame_info;
 123
 124         if (seed_unwind_frame_info(tsk, regs, &frame_info))
 125                 return 0;
 126
 127         while (1) {
 128                 address = UNW_PC(&frame_info);
 129
 130                 if (!address || !__kernel_text_address(address))
 131                         break;
 132
 133                 if (consumer_fn(address, arg) == -1)
 134                         break;
 135
 136                 ret = arc_unwind(&frame_info);
 137                 if (ret)
 138                         break;
 139
 140                 frame_info.regs.r63 = frame_info.regs.r31;
 141
 142                 if (cnt++ > 128) {
 143                         printk("unwinder looping too long, aborting !\n");
 144                         return 0;
 145                 }
 146         }
 147
 148         return address;         /* return the last address it saw */
 149 #else
 150         /* On ARC, only Dward based unwinder works. fp based backtracing is
 151          * not possible (-fno-omit-frame-pointer) because of the way function
 152          * prologue is setup (callee regs saved and then fp set and not other
 153          * way around
 154          */
 155         pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
 156         return 0;
 157
 158 #endif
 159 }
 160
 161 /*-------------------------------------------------------------------------
 162  * callbacks called by unwinder iterator to implement kernel APIs
 163  *
 164  * The callback can return -1 to force the iterator to stop, which by default
 165  * keeps going till the bottom-most frame.
 166  *-------------------------------------------------------------------------
 167  */
 168
 169 /* Call-back which plugs into unwinding core to dump the stack in
 170  * case of panic/OOPs/BUG etc
 171  */
 172 static int __print_sym(unsigned int address, void *arg)
 173 {
 174         const char *loglvl = arg;
 175
 176         printk("%s  %pS\n", loglvl, (void *)address);
 177         return 0;
 178 }
 179
 180 #ifdef CONFIG_STACKTRACE
 181
 182 /* Call-back which plugs into unwinding core to capture the
 183  * traces needed by kernel on /proc/<pid>/stack
 184  */
 185 static int __collect_all(unsigned int address, void *arg)
 186 {
 187         struct stack_trace *trace = arg;
 188
 189         if (trace->skip > 0)
 190                 trace->skip--;
 191         else
 192                 trace->entries[trace->nr_entries++] = address;
 193
 194         if (trace->nr_entries >= trace->max_entries)
 195                 return -1;
 196
 197         return 0;
 198 }
 199
 200 static int __collect_all_but_sched(unsigned int address, void *arg)
 201 {
 202         struct stack_trace *trace = arg;
 203
 204         if (in_sched_functions(address))
 205                 return 0;
 206
 207         if (trace->skip > 0)
 208                 trace->skip--;
 209         else
 210                 trace->entries[trace->nr_entries++] = address;
 211
 212         if (trace->nr_entries >= trace->max_entries)
 213                 return -1;
 214
 215         return 0;
 216 }
 217
 218 #endif
 219
 220 static int __get_first_nonsched(unsigned int address, void *unused)
 221 {
 222         if (in_sched_functions(address))
 223                 return 0;
 224
 225         return -1;
 226 }
 227
 228 /*-------------------------------------------------------------------------
 229  *              APIs expected by various kernel sub-systems
 230  *-------------------------------------------------------------------------
 231  */
 232
 233 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs,
 234                               const char *loglvl)
 235 {
 236         printk("%s\nStack Trace:\n", loglvl);
 237         arc_unwind_core(tsk, regs, __print_sym, (void *)loglvl);
 238 }
 239 EXPORT_SYMBOL(show_stacktrace);
 240
 241 /* Expected by sched Code */
 242 void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
 243 {
 244         show_stacktrace(tsk, NULL, loglvl);
 245 }
 246
 247 /* Another API expected by schedular, shows up in "ps" as Wait Channel
 248  * Of course just returning schedule( ) would be pointless so unwind until
 249  * the function is not in schedular code
 250  */
 251 unsigned int get_wchan(struct task_struct *tsk)
 252 {
 253         return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
 254 }
 255
 256 #ifdef CONFIG_STACKTRACE
 257
 258 /*
 259  * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
 260  * A typical use is when /proc/<pid>/stack is queried by userland
 261  */
 262 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 263 {
 264         /* Assumes @tsk is sleeping so unwinds from __switch_to */
 265         arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
 266 }
 267
 268 void save_stack_trace(struct stack_trace *trace)
 269 {
 270         /* Pass NULL for task so it unwinds the current call frame */
 271         arc_unwind_core(NULL, NULL, __collect_all, trace);
 272 }
 273 EXPORT_SYMBOL_GPL(save_stack_trace);
 274 #endif