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