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 static int save_stack_address(struct stack_trace *trace, unsigned long addr,
  16                               bool nosched)
  17 {
  18         if (nosched && in_sched_functions(addr))
  19                 return 0;
  20
  21         if (trace->skip > 0) {
  22                 trace->skip--;
  23                 return 0;
  24         }
  25
  26         if (trace->nr_entries >= trace->max_entries)
  27                 return -1;
  28
  29         trace->entries[trace->nr_entries++] = addr;
  30         return 0;
  31 }
  32
  33 static void noinline __save_stack_trace(struct stack_trace *trace,
  34                                struct task_struct *task, struct pt_regs *regs,
  35                                bool nosched)
  36 {
  37         struct unwind_state state;
  38         unsigned long addr;
  39
  40         if (regs)
  41                 save_stack_address(trace, regs->ip, nosched);
  42
  43         for (unwind_start(&state, task, regs, NULL); !unwind_done(&state);
  44              unwind_next_frame(&state)) {
  45                 addr = unwind_get_return_address(&state);
  46                 if (!addr || save_stack_address(trace, addr, nosched))
  47                         break;
  48         }
  49
  50         if (trace->nr_entries < trace->max_entries)
  51                 trace->entries[trace->nr_entries++] = ULONG_MAX;
  52 }
  53
  54 /*
  55  * Save stack-backtrace addresses into a stack_trace buffer.
  56  */
  57 void save_stack_trace(struct stack_trace *trace)
  58 {
  59         trace->skip++;
  60         __save_stack_trace(trace, current, NULL, false);
  61 }
  62 EXPORT_SYMBOL_GPL(save_stack_trace);
  63
  64 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
  65 {
  66         __save_stack_trace(trace, current, regs, false);
  67 }
  68
  69 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
  70 {
  71         if (!try_get_task_stack(tsk))
  72                 return;
  73
  74         if (tsk == current)
  75                 trace->skip++;
  76         __save_stack_trace(trace, tsk, NULL, true);
  77
  78         put_task_stack(tsk);
  79 }
  80 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
  81
  82 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
  83
  84 static int __always_inline
  85 __save_stack_trace_reliable(struct stack_trace *trace,
  86                             struct task_struct *task)
  87 {
  88         struct unwind_state state;
  89         struct pt_regs *regs;
  90         unsigned long addr;
  91
  92         for (unwind_start(&state, task, NULL, NULL);
  93              !unwind_done(&state) && !unwind_error(&state);
  94              unwind_next_frame(&state)) {
  95
  96                 regs = unwind_get_entry_regs(&state, NULL);
  97                 if (regs) {
  98                         /* Success path for user tasks */
  99                         if (user_mode(regs))
 100                                 goto success;
 101
 102                         /*
 103                          * Kernel mode registers on the stack indicate an
 104                          * in-kernel interrupt or exception (e.g., preemption
 105                          * or a page fault), which can make frame pointers
 106                          * unreliable.
 107                          */
 108
 109                         if (IS_ENABLED(CONFIG_FRAME_POINTER))
 110                                 return -EINVAL;
 111                 }
 112
 113                 addr = unwind_get_return_address(&state);
 114
 115                 /*
 116                  * A NULL or invalid return address probably means there's some
 117                  * generated code which __kernel_text_address() doesn't know
 118                  * about.
 119                  */
 120                 if (!addr)
 121                         return -EINVAL;
 122
 123                 if (save_stack_address(trace, addr, false))
 124                         return -EINVAL;
 125         }
 126
 127         /* Check for stack corruption */
 128         if (unwind_error(&state))
 129                 return -EINVAL;
 130
 131         /* Success path for non-user tasks, i.e. kthreads and idle tasks */
 132         if (!(task->flags & (PF_KTHREAD | PF_IDLE)))
 133                 return -EINVAL;
 134
 135 success:
 136         if (trace->nr_entries < trace->max_entries)
 137                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 138
 139         return 0;
 140 }
 141
 142 /*
 143  * This function returns an error if it detects any unreliable features of the
 144  * stack.  Otherwise it guarantees that the stack trace is reliable.
 145  *
 146  * If the task is not 'current', the caller *must* ensure the task is inactive.
 147  */
 148 int save_stack_trace_tsk_reliable(struct task_struct *tsk,
 149                                   struct stack_trace *trace)
 150 {
 151         int ret;
 152
 153         /*
 154          * If the task doesn't have a stack (e.g., a zombie), the stack is
 155          * "reliably" empty.
 156          */
 157         if (!try_get_task_stack(tsk))
 158                 return 0;
 159
 160         ret = __save_stack_trace_reliable(trace, tsk);
 161
 162         put_task_stack(tsk);
 163
 164         return ret;
 165 }
 166 #endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */
 167
 168 /* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */
 169
 170 struct stack_frame_user {
 171         const void __user       *next_fp;
 172         unsigned long           ret_addr;
 173 };
 174
 175 static int
 176 copy_stack_frame(const void __user *fp, struct stack_frame_user *frame)
 177 {
 178         int ret;
 179
 180         if (!access_ok(fp, sizeof(*frame)))
 181                 return 0;
 182
 183         ret = 1;
 184         pagefault_disable();
 185         if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
 186                 ret = 0;
 187         pagefault_enable();
 188
 189         return ret;
 190 }
 191
 192 static inline void __save_stack_trace_user(struct stack_trace *trace)
 193 {
 194         const struct pt_regs *regs = task_pt_regs(current);
 195         const void __user *fp = (const void __user *)regs->bp;
 196
 197         if (trace->nr_entries < trace->max_entries)
 198                 trace->entries[trace->nr_entries++] = regs->ip;
 199
 200         while (trace->nr_entries < trace->max_entries) {
 201                 struct stack_frame_user frame;
 202
 203                 frame.next_fp = NULL;
 204                 frame.ret_addr = 0;
 205                 if (!copy_stack_frame(fp, &frame))
 206                         break;
 207                 if ((unsigned long)fp < regs->sp)
 208                         break;
 209                 if (frame.ret_addr) {
 210                         trace->entries[trace->nr_entries++] =
 211                                 frame.ret_addr;
 212                 }
 213                 if (fp == frame.next_fp)
 214                         break;
 215                 fp = frame.next_fp;
 216         }
 217 }
 218
 219 void save_stack_trace_user(struct stack_trace *trace)
 220 {
 221         /*
 222          * Trace user stack if we are not a kernel thread
 223          */
 224         if (current->mm) {
 225                 __save_stack_trace_user(trace);
 226         }
 227         if (trace->nr_entries < trace->max_entries)
 228                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 229 }