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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 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 }
244 

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