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