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 /*
  10  * This disables KASAN checking when reading a value from another task's stack,
  11  * since the other task could be running on another CPU and could have poisoned
  12  * the stack in the meantime.
  13  */
  14 #define READ_ONCE_TASK_STACK(task, x)                   \
  15 ({                                                      \
  16         unsigned long val;                              \
  17         if (task == current)                            \
  18                 val = READ_ONCE(x);                     \
  19         else                                            \
  20                 val = READ_ONCE_NOCHECK(x);             \
  21         val;                                            \
  22 })
  23
  24 unsigned long unwind_get_return_address(struct unwind_state *state)
  25 {
  26         unsigned long addr;
  27         unsigned long *addr_p = unwind_get_return_address_ptr(state);
  28
  29         if (unwind_done(state))
  30                 return 0;
  31
  32         addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
  33         addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, addr,
  34                                      addr_p);
  35
  36         return __kernel_text_address(addr) ? addr : 0;
  37 }
  38 EXPORT_SYMBOL_GPL(unwind_get_return_address);
  39
  40 static bool update_stack_state(struct unwind_state *state, void *addr,
  41                                size_t len)
  42 {
  43         struct stack_info *info = &state->stack_info;
  44
  45         /*
  46          * If addr isn't on the current stack, switch to the next one.
  47          *
  48          * We may have to traverse multiple stacks to deal with the possibility
  49          * that 'info->next_sp' could point to an empty stack and 'addr' could
  50          * be on a subsequent stack.
  51          */
  52         while (!on_stack(info, addr, len))
  53                 if (get_stack_info(info->next_sp, state->task, info,
  54                                    &state->stack_mask))
  55                         return false;
  56
  57         return true;
  58 }
  59
  60 bool unwind_next_frame(struct unwind_state *state)
  61 {
  62         unsigned long *next_bp;
  63
  64         if (unwind_done(state))
  65                 return false;
  66
  67         next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task,*state->bp);
  68
  69         /* make sure the next frame's data is accessible */
  70         if (!update_stack_state(state, next_bp, FRAME_HEADER_SIZE))
  71                 return false;
  72
  73         /* move to the next frame */
  74         state->bp = next_bp;
  75         return true;
  76 }
  77 EXPORT_SYMBOL_GPL(unwind_next_frame);
  78
  79 void __unwind_start(struct unwind_state *state, struct task_struct *task,
  80                     struct pt_regs *regs, unsigned long *first_frame)
  81 {
  82         memset(state, 0, sizeof(*state));
  83         state->task = task;
  84
  85         /* don't even attempt to start from user mode regs */
  86         if (regs && user_mode(regs)) {
  87                 state->stack_info.type = STACK_TYPE_UNKNOWN;
  88                 return;
  89         }
  90
  91         /* set up the starting stack frame */
  92         state->bp = get_frame_pointer(task, regs);
  93
  94         /* initialize stack info and make sure the frame data is accessible */
  95         get_stack_info(state->bp, state->task, &state->stack_info,
  96                        &state->stack_mask);
  97         update_stack_state(state, state->bp, FRAME_HEADER_SIZE);
  98
  99         /*
 100          * The caller can provide the address of the first frame directly
 101          * (first_frame) or indirectly (regs->sp) to indicate which stack frame
 102          * to start unwinding at.  Skip ahead until we reach it.
 103          */
 104         while (!unwind_done(state) &&
 105                (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
 106                         state->bp < first_frame))
 107                 unwind_next_frame(state);
 108 }
 109 EXPORT_SYMBOL_GPL(__unwind_start);