arch/arm/kernel/stacktrace.c

   1 #include <linux/export.h>
   2 #include <linux/sched.h>
   3 #include <linux/stacktrace.h>
   4
   5 #include <asm/stacktrace.h>
   6 #include <asm/traps.h>
   7
   8 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
   9 /*
  10  * Unwind the current stack frame and store the new register values in the
  11  * structure passed as argument. Unwinding is equivalent to a function return,
  12  * hence the new PC value rather than LR should be used for backtrace.
  13  *
  14  * With framepointer enabled, a simple function prologue looks like this:
  15  *      mov     ip, sp
  16  *      stmdb   sp!, {fp, ip, lr, pc}
  17  *      sub     fp, ip, #4
  18  *
  19  * A simple function epilogue looks like this:
  20  *      ldm     sp, {fp, sp, pc}
  21  *
  22  * Note that with framepointer enabled, even the leaf functions have the same
  23  * prologue and epilogue, therefore we can ignore the LR value in this case.
  24  */
  25 int notrace unwind_frame(struct stackframe *frame)
  26 {
  27         unsigned long high, low;
  28         unsigned long fp = frame->fp;
  29
  30         /* only go to a higher address on the stack */
  31         low = frame->sp;
  32         high = ALIGN(low, THREAD_SIZE);
  33
  34         /* check current frame pointer is within bounds */
  35         if (fp < low + 12 || fp > high - 4)
  36                 return -EINVAL;
  37
  38         /* restore the registers from the stack frame */
  39         frame->fp = *(unsigned long *)(fp - 12);
  40         frame->sp = *(unsigned long *)(fp - 8);
  41         frame->pc = *(unsigned long *)(fp - 4);
  42
  43         return 0;
  44 }
  45 #endif
  46
  47 void notrace walk_stackframe(struct stackframe *frame,
  48                      int (*fn)(struct stackframe *, void *), void *data)
  49 {
  50         while (1) {
  51                 int ret;
  52
  53                 if (fn(frame, data))
  54                         break;
  55                 ret = unwind_frame(frame);
  56                 if (ret < 0)
  57                         break;
  58         }
  59 }
  60 EXPORT_SYMBOL(walk_stackframe);
  61
  62 #ifdef CONFIG_STACKTRACE
  63 struct stack_trace_data {
  64         struct stack_trace *trace;
  65         unsigned long last_pc;
  66         unsigned int no_sched_functions;
  67         unsigned int skip;
  68 };
  69
  70 static int save_trace(struct stackframe *frame, void *d)
  71 {
  72         struct stack_trace_data *data = d;
  73         struct stack_trace *trace = data->trace;
  74         struct pt_regs *regs;
  75         unsigned long addr = frame->pc;
  76
  77         if (data->no_sched_functions && in_sched_functions(addr))
  78                 return 0;
  79         if (data->skip) {
  80                 data->skip--;
  81                 return 0;
  82         }
  83
  84         trace->entries[trace->nr_entries++] = addr;
  85
  86         if (trace->nr_entries >= trace->max_entries)
  87                 return 1;
  88
  89         /*
  90          * in_exception_text() is designed to test if the PC is one of
  91          * the functions which has an exception stack above it, but
  92          * unfortunately what is in frame->pc is the return LR value,
  93          * not the saved PC value.  So, we need to track the previous
  94          * frame PC value when doing this.
  95          */
  96         addr = data->last_pc;
  97         data->last_pc = frame->pc;
  98         if (!in_exception_text(addr))
  99                 return 0;
 100
 101         regs = (struct pt_regs *)frame->sp;
 102
 103         trace->entries[trace->nr_entries++] = regs->ARM_pc;
 104
 105         return trace->nr_entries >= trace->max_entries;
 106 }
 107
 108 /* This must be noinline to so that our skip calculation works correctly */
 109 static noinline void __save_stack_trace(struct task_struct *tsk,
 110         struct stack_trace *trace, unsigned int nosched)
 111 {
 112         struct stack_trace_data data;
 113         struct stackframe frame;
 114
 115         data.trace = trace;
 116         data.last_pc = ULONG_MAX;
 117         data.skip = trace->skip;
 118         data.no_sched_functions = nosched;
 119
 120         if (tsk != current) {
 121 #ifdef CONFIG_SMP
 122                 /*
 123                  * What guarantees do we have here that 'tsk' is not
 124                  * running on another CPU?  For now, ignore it as we
 125                  * can't guarantee we won't explode.
 126                  */
 127                 if (trace->nr_entries < trace->max_entries)
 128                         trace->entries[trace->nr_entries++] = ULONG_MAX;
 129                 return;
 130 #else
 131                 frame.fp = thread_saved_fp(tsk);
 132                 frame.sp = thread_saved_sp(tsk);
 133                 frame.lr = 0;           /* recovered from the stack */
 134                 frame.pc = thread_saved_pc(tsk);
 135 #endif
 136         } else {
 137                 register unsigned long current_sp asm ("sp");
 138
 139                 /* We don't want this function nor the caller */
 140                 data.skip += 2;
 141                 frame.fp = (unsigned long)__builtin_frame_address(0);
 142                 frame.sp = current_sp;
 143                 frame.lr = (unsigned long)__builtin_return_address(0);
 144                 frame.pc = (unsigned long)__save_stack_trace;
 145         }
 146
 147         walk_stackframe(&frame, save_trace, &data);
 148         if (trace->nr_entries < trace->max_entries)
 149                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 150 }
 151
 152 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 153 {
 154         struct stack_trace_data data;
 155         struct stackframe frame;
 156
 157         data.trace = trace;
 158         data.skip = trace->skip;
 159         data.no_sched_functions = 0;
 160
 161         frame.fp = regs->ARM_fp;
 162         frame.sp = regs->ARM_sp;
 163         frame.lr = regs->ARM_lr;
 164         frame.pc = regs->ARM_pc;
 165
 166         walk_stackframe(&frame, save_trace, &data);
 167         if (trace->nr_entries < trace->max_entries)
 168                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 169 }
 170
 171 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 172 {
 173         __save_stack_trace(tsk, trace, 1);
 174 }
 175
 176 void save_stack_trace(struct stack_trace *trace)
 177 {
 178         __save_stack_trace(current, trace, 0);
 179 }
 180 EXPORT_SYMBOL_GPL(save_stack_trace);
 181 #endif