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