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Linux/arch/x86/kernel/stacktrace.c

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  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 __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         __save_stack_trace(trace, current, NULL, false);
 60 }
 61 EXPORT_SYMBOL_GPL(save_stack_trace);
 62 
 63 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 64 {
 65         __save_stack_trace(trace, current, regs, false);
 66 }
 67 
 68 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 69 {
 70         if (!try_get_task_stack(tsk))
 71                 return;
 72 
 73         __save_stack_trace(trace, tsk, NULL, true);
 74 
 75         put_task_stack(tsk);
 76 }
 77 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
 78 
 79 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
 80 
 81 #define STACKTRACE_DUMP_ONCE(task) ({                           \
 82         static bool __section(.data.unlikely) __dumped;         \
 83                                                                 \
 84         if (!__dumped) {                                        \
 85                 __dumped = true;                                \
 86                 WARN_ON(1);                                     \
 87                 show_stack(task, NULL);                         \
 88         }                                                       \
 89 })
 90 
 91 static int __save_stack_trace_reliable(struct stack_trace *trace,
 92                                        struct task_struct *task)
 93 {
 94         struct unwind_state state;
 95         struct pt_regs *regs;
 96         unsigned long addr;
 97 
 98         for (unwind_start(&state, task, NULL, NULL); !unwind_done(&state);
 99              unwind_next_frame(&state)) {
100 
101                 regs = unwind_get_entry_regs(&state);
102                 if (regs) {
103                         /*
104                          * Kernel mode registers on the stack indicate an
105                          * in-kernel interrupt or exception (e.g., preemption
106                          * or a page fault), which can make frame pointers
107                          * unreliable.
108                          */
109                         if (!user_mode(regs))
110                                 return -EINVAL;
111 
112                         /*
113                          * The last frame contains the user mode syscall
114                          * pt_regs.  Skip it and finish the unwind.
115                          */
116                         unwind_next_frame(&state);
117                         if (!unwind_done(&state)) {
118                                 STACKTRACE_DUMP_ONCE(task);
119                                 return -EINVAL;
120                         }
121                         break;
122                 }
123 
124                 addr = unwind_get_return_address(&state);
125 
126                 /*
127                  * A NULL or invalid return address probably means there's some
128                  * generated code which __kernel_text_address() doesn't know
129                  * about.
130                  */
131                 if (!addr) {
132                         STACKTRACE_DUMP_ONCE(task);
133                         return -EINVAL;
134                 }
135 
136                 if (save_stack_address(trace, addr, false))
137                         return -EINVAL;
138         }
139 
140         /* Check for stack corruption */
141         if (unwind_error(&state)) {
142                 STACKTRACE_DUMP_ONCE(task);
143                 return -EINVAL;
144         }
145 
146         if (trace->nr_entries < trace->max_entries)
147                 trace->entries[trace->nr_entries++] = ULONG_MAX;
148 
149         return 0;
150 }
151 
152 /*
153  * This function returns an error if it detects any unreliable features of the
154  * stack.  Otherwise it guarantees that the stack trace is reliable.
155  *
156  * If the task is not 'current', the caller *must* ensure the task is inactive.
157  */
158 int save_stack_trace_tsk_reliable(struct task_struct *tsk,
159                                   struct stack_trace *trace)
160 {
161         int ret;
162 
163         if (!try_get_task_stack(tsk))
164                 return -EINVAL;
165 
166         ret = __save_stack_trace_reliable(trace, tsk);
167 
168         put_task_stack(tsk);
169 
170         return ret;
171 }
172 #endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */
173 
174 /* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */
175 
176 struct stack_frame_user {
177         const void __user       *next_fp;
178         unsigned long           ret_addr;
179 };
180 
181 static int
182 copy_stack_frame(const void __user *fp, struct stack_frame_user *frame)
183 {
184         int ret;
185 
186         if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
187                 return 0;
188 
189         ret = 1;
190         pagefault_disable();
191         if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
192                 ret = 0;
193         pagefault_enable();
194 
195         return ret;
196 }
197 
198 static inline void __save_stack_trace_user(struct stack_trace *trace)
199 {
200         const struct pt_regs *regs = task_pt_regs(current);
201         const void __user *fp = (const void __user *)regs->bp;
202 
203         if (trace->nr_entries < trace->max_entries)
204                 trace->entries[trace->nr_entries++] = regs->ip;
205 
206         while (trace->nr_entries < trace->max_entries) {
207                 struct stack_frame_user frame;
208 
209                 frame.next_fp = NULL;
210                 frame.ret_addr = 0;
211                 if (!copy_stack_frame(fp, &frame))
212                         break;
213                 if ((unsigned long)fp < regs->sp)
214                         break;
215                 if (frame.ret_addr) {
216                         trace->entries[trace->nr_entries++] =
217                                 frame.ret_addr;
218                 }
219                 if (fp == frame.next_fp)
220                         break;
221                 fp = frame.next_fp;
222         }
223 }
224 
225 void save_stack_trace_user(struct stack_trace *trace)
226 {
227         /*
228          * Trace user stack if we are not a kernel thread
229          */
230         if (current->mm) {
231                 __save_stack_trace_user(trace);
232         }
233         if (trace->nr_entries < trace->max_entries)
234                 trace->entries[trace->nr_entries++] = ULONG_MAX;
235 }
236 

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