arch/x86/kernel/stacktrace.c

   1 /*
   2  * Stack trace management functions
   3  *
   4  *  Copyright (C) 2006-2009 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
   5  */
   6 #include <linux/sched.h>
   7 #include <linux/sched/debug.h>
   8 #include <linux/sched/task_stack.h>
   9 #include <linux/stacktrace.h>
  10 #include <linux/export.h>
  11 #include <linux/uaccess.h>
  12 #include <asm/stacktrace.h>
  13 #include <asm/unwind.h>
  14
  15 void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
  16                      struct task_struct *task, struct pt_regs *regs)
  17 {
  18         struct unwind_state state;
  19         unsigned long addr;
  20
  21         if (regs && !consume_entry(cookie, regs->ip))
  22                 return;
  23
  24         for (unwind_start(&state, task, regs, NULL); !unwind_done(&state);
  25              unwind_next_frame(&state)) {
  26                 addr = unwind_get_return_address(&state);
  27                 if (!addr || !consume_entry(cookie, addr))
  28                         break;
  29         }
  30 }
  31
  32 /*
  33  * This function returns an error if it detects any unreliable features of the
  34  * stack.  Otherwise it guarantees that the stack trace is reliable.
  35  *
  36  * If the task is not 'current', the caller *must* ensure the task is inactive.
  37  */
  38 int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
  39                              void *cookie, struct task_struct *task)
  40 {
  41         struct unwind_state state;
  42         struct pt_regs *regs;
  43         unsigned long addr;
  44
  45         for (unwind_start(&state, task, NULL, NULL);
  46              !unwind_done(&state) && !unwind_error(&state);
  47              unwind_next_frame(&state)) {
  48
  49                 regs = unwind_get_entry_regs(&state, NULL);
  50                 if (regs) {
  51                         /* Success path for user tasks */
  52                         if (user_mode(regs))
  53                                 return 0;
  54
  55                         /*
  56                          * Kernel mode registers on the stack indicate an
  57                          * in-kernel interrupt or exception (e.g., preemption
  58                          * or a page fault), which can make frame pointers
  59                          * unreliable.
  60                          */
  61                         if (IS_ENABLED(CONFIG_FRAME_POINTER))
  62                                 return -EINVAL;
  63                 }
  64
  65                 addr = unwind_get_return_address(&state);
  66
  67                 /*
  68                  * A NULL or invalid return address probably means there's some
  69                  * generated code which __kernel_text_address() doesn't know
  70                  * about.
  71                  */
  72                 if (!addr)
  73                         return -EINVAL;
  74
  75                 if (!consume_entry(cookie, addr))
  76                         return -EINVAL;
  77         }
  78
  79         /* Check for stack corruption */
  80         if (unwind_error(&state))
  81                 return -EINVAL;
  82
  83         return 0;
  84 }
  85
  86 /* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */
  87
  88 struct stack_frame_user {
  89         const void __user       *next_fp;
  90         unsigned long           ret_addr;
  91 };
  92
  93 static int
  94 copy_stack_frame(const struct stack_frame_user __user *fp,
  95                  struct stack_frame_user *frame)
  96 {
  97         int ret;
  98
  99         if (__range_not_ok(fp, sizeof(*frame), TASK_SIZE))
 100                 return 0;
 101
 102         ret = 1;
 103         pagefault_disable();
 104         if (__get_user(frame->next_fp, &fp->next_fp) ||
 105             __get_user(frame->ret_addr, &fp->ret_addr))
 106                 ret = 0;
 107         pagefault_enable();
 108
 109         return ret;
 110 }
 111
 112 void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
 113                           const struct pt_regs *regs)
 114 {
 115         const void __user *fp = (const void __user *)regs->bp;
 116
 117         if (!consume_entry(cookie, regs->ip))
 118                 return;
 119
 120         while (1) {
 121                 struct stack_frame_user frame;
 122
 123                 frame.next_fp = NULL;
 124                 frame.ret_addr = 0;
 125                 if (!copy_stack_frame(fp, &frame))
 126                         break;
 127                 if ((unsigned long)fp < regs->sp)
 128                         break;
 129                 if (!frame.ret_addr)
 130                         break;
 131                 if (!consume_entry(cookie, frame.ret_addr))
 132                         break;
 133                 fp = frame.next_fp;
 134         }
 135 }
 136