arch/arm/kernel/stacktrace.c

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