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 #define STACKTRACE_DUMP_ONCE(task) ({                           \
  85         static bool __section(.data.unlikely) __dumped;         \
  86                                                                 \
  87         if (!__dumped) {                                        \
  88                 __dumped = true;                                \
  89                 WARN_ON(1);                                     \
  90                 show_stack(task, NULL);                         \
  91         }                                                       \
  92 })
  93
  94 static int __always_inline
  95 __save_stack_trace_reliable(struct stack_trace *trace,
  96                             struct task_struct *task)
  97 {
  98         struct unwind_state state;
  99         struct pt_regs *regs;
 100         unsigned long addr;
 101
 102         for (unwind_start(&state, task, NULL, NULL); !unwind_done(&state);
 103              unwind_next_frame(&state)) {
 104
 105                 regs = unwind_get_entry_regs(&state, NULL);
 106                 if (regs) {
 107                         /*
 108                          * Kernel mode registers on the stack indicate an
 109                          * in-kernel interrupt or exception (e.g., preemption
 110                          * or a page fault), which can make frame pointers
 111                          * unreliable.
 112                          */
 113                         if (!user_mode(regs))
 114                                 return -EINVAL;
 115
 116                         /*
 117                          * The last frame contains the user mode syscall
 118                          * pt_regs.  Skip it and finish the unwind.
 119                          */
 120                         unwind_next_frame(&state);
 121                         if (!unwind_done(&state)) {
 122                                 STACKTRACE_DUMP_ONCE(task);
 123                                 return -EINVAL;
 124                         }
 125                         break;
 126                 }
 127
 128                 addr = unwind_get_return_address(&state);
 129
 130                 /*
 131                  * A NULL or invalid return address probably means there's some
 132                  * generated code which __kernel_text_address() doesn't know
 133                  * about.
 134                  */
 135                 if (!addr) {
 136                         STACKTRACE_DUMP_ONCE(task);
 137                         return -EINVAL;
 138                 }
 139
 140                 if (save_stack_address(trace, addr, false))
 141                         return -EINVAL;
 142         }
 143
 144         /* Check for stack corruption */
 145         if (unwind_error(&state)) {
 146                 STACKTRACE_DUMP_ONCE(task);
 147                 return -EINVAL;
 148         }
 149
 150         if (trace->nr_entries < trace->max_entries)
 151                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 152
 153         return 0;
 154 }
 155
 156 /*
 157  * This function returns an error if it detects any unreliable features of the
 158  * stack.  Otherwise it guarantees that the stack trace is reliable.
 159  *
 160  * If the task is not 'current', the caller *must* ensure the task is inactive.
 161  */
 162 int save_stack_trace_tsk_reliable(struct task_struct *tsk,
 163                                   struct stack_trace *trace)
 164 {
 165         int ret;
 166
 167         /*
 168          * If the task doesn't have a stack (e.g., a zombie), the stack is
 169          * "reliably" empty.
 170          */
 171         if (!try_get_task_stack(tsk))
 172                 return 0;
 173
 174         ret = __save_stack_trace_reliable(trace, tsk);
 175
 176         put_task_stack(tsk);
 177
 178         return ret;
 179 }
 180 #endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */
 181
 182 /* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */
 183
 184 struct stack_frame_user {
 185         const void __user       *next_fp;
 186         unsigned long           ret_addr;
 187 };
 188
 189 static int
 190 copy_stack_frame(const void __user *fp, struct stack_frame_user *frame)
 191 {
 192         int ret;
 193
 194         if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
 195                 return 0;
 196
 197         ret = 1;
 198         pagefault_disable();
 199         if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
 200                 ret = 0;
 201         pagefault_enable();
 202
 203         return ret;
 204 }
 205
 206 static inline void __save_stack_trace_user(struct stack_trace *trace)
 207 {
 208         const struct pt_regs *regs = task_pt_regs(current);
 209         const void __user *fp = (const void __user *)regs->bp;
 210
 211         if (trace->nr_entries < trace->max_entries)
 212                 trace->entries[trace->nr_entries++] = regs->ip;
 213
 214         while (trace->nr_entries < trace->max_entries) {
 215                 struct stack_frame_user frame;
 216
 217                 frame.next_fp = NULL;
 218                 frame.ret_addr = 0;
 219                 if (!copy_stack_frame(fp, &frame))
 220                         break;
 221                 if ((unsigned long)fp < regs->sp)
 222                         break;
 223                 if (frame.ret_addr) {
 224                         trace->entries[trace->nr_entries++] =
 225                                 frame.ret_addr;
 226                 }
 227                 if (fp == frame.next_fp)
 228                         break;
 229                 fp = frame.next_fp;
 230         }
 231 }
 232
 233 void save_stack_trace_user(struct stack_trace *trace)
 234 {
 235         /*
 236          * Trace user stack if we are not a kernel thread
 237          */
 238         if (current->mm) {
 239                 __save_stack_trace_user(trace);
 240         }
 241         if (trace->nr_entries < trace->max_entries)
 242                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 243 }