arch/x86/kernel/unwind_frame.c

   1 #include <linux/sched.h>
   2 #include <asm/ptrace.h>
   3 #include <asm/bitops.h>
   4 #include <asm/stacktrace.h>
   5 #include <asm/unwind.h>
   6
   7 #define FRAME_HEADER_SIZE (sizeof(long) * 2)
   8
   9 unsigned long unwind_get_return_address(struct unwind_state *state)
  10 {
  11         unsigned long addr;
  12         unsigned long *addr_p = unwind_get_return_address_ptr(state);
  13
  14         if (unwind_done(state))
  15                 return 0;
  16
  17         addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, *addr_p,
  18                                      addr_p);
  19
  20         return __kernel_text_address(addr) ? addr : 0;
  21 }
  22 EXPORT_SYMBOL_GPL(unwind_get_return_address);
  23
  24 static bool update_stack_state(struct unwind_state *state, void *addr,
  25                                size_t len)
  26 {
  27         struct stack_info *info = &state->stack_info;
  28
  29         /*
  30          * If addr isn't on the current stack, switch to the next one.
  31          *
  32          * We may have to traverse multiple stacks to deal with the possibility
  33          * that 'info->next_sp' could point to an empty stack and 'addr' could
  34          * be on a subsequent stack.
  35          */
  36         while (!on_stack(info, addr, len))
  37                 if (get_stack_info(info->next_sp, state->task, info,
  38                                    &state->stack_mask))
  39                         return false;
  40
  41         return true;
  42 }
  43
  44 bool unwind_next_frame(struct unwind_state *state)
  45 {
  46         unsigned long *next_bp;
  47
  48         if (unwind_done(state))
  49                 return false;
  50
  51         next_bp = (unsigned long *)*state->bp;
  52
  53         /* make sure the next frame's data is accessible */
  54         if (!update_stack_state(state, next_bp, FRAME_HEADER_SIZE))
  55                 return false;
  56
  57         /* move to the next frame */
  58         state->bp = next_bp;
  59         return true;
  60 }
  61 EXPORT_SYMBOL_GPL(unwind_next_frame);
  62
  63 void __unwind_start(struct unwind_state *state, struct task_struct *task,
  64                     struct pt_regs *regs, unsigned long *first_frame)
  65 {
  66         memset(state, 0, sizeof(*state));
  67         state->task = task;
  68
  69         /* don't even attempt to start from user mode regs */
  70         if (regs && user_mode(regs)) {
  71                 state->stack_info.type = STACK_TYPE_UNKNOWN;
  72                 return;
  73         }
  74
  75         /* set up the starting stack frame */
  76         state->bp = get_frame_pointer(task, regs);
  77
  78         /* initialize stack info and make sure the frame data is accessible */
  79         get_stack_info(state->bp, state->task, &state->stack_info,
  80                        &state->stack_mask);
  81         update_stack_state(state, state->bp, FRAME_HEADER_SIZE);
  82
  83         /*
  84          * The caller can provide the address of the first frame directly
  85          * (first_frame) or indirectly (regs->sp) to indicate which stack frame
  86          * to start unwinding at.  Skip ahead until we reach it.
  87          */
  88         while (!unwind_done(state) &&
  89                (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
  90                         state->bp < first_frame))
  91                 unwind_next_frame(state);
  92 }
  93 EXPORT_SYMBOL_GPL(__unwind_start);