1 /* 2 * Stack trace management functions 3 * 4 * Copyright (C) 2006-2009 Red Hat, Inc., Ingo Molnar <[email protected]> 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 51 /* 52 * Save stack-backtrace addresses into a stack_trace buffer. 53 */ 54 void save_stack_trace(struct stack_trace *trace) 55 { 56 trace->skip++; 57 __save_stack_trace(trace, current, NULL, false); 58 } 59 EXPORT_SYMBOL_GPL(save_stack_trace); 60 61 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace) 62 { 63 __save_stack_trace(trace, current, regs, false); 64 } 65 66 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 67 { 68 if (!try_get_task_stack(tsk)) 69 return; 70 71 if (tsk == current) 72 trace->skip++; 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 static int __always_inline 82 __save_stack_trace_reliable(struct stack_trace *trace, 83 struct task_struct *task) 84 { 85 struct unwind_state state; 86 struct pt_regs *regs; 87 unsigned long addr; 88 89 for (unwind_start(&state, task, NULL, NULL); 90 !unwind_done(&state) && !unwind_error(&state); 91 unwind_next_frame(&state)) { 92 93 regs = unwind_get_entry_regs(&state, NULL); 94 if (regs) { 95 /* Success path for user tasks */ 96 if (user_mode(regs)) 97 return 0; 98 99 /* 100 * Kernel mode registers on the stack indicate an 101 * in-kernel interrupt or exception (e.g., preemption 102 * or a page fault), which can make frame pointers 103 * unreliable. 104 */ 105 106 if (IS_ENABLED(CONFIG_FRAME_POINTER)) 107 return -EINVAL; 108 } 109 110 addr = unwind_get_return_address(&state); 111 112 /* 113 * A NULL or invalid return address probably means there's some 114 * generated code which __kernel_text_address() doesn't know 115 * about. 116 */ 117 if (!addr) 118 return -EINVAL; 119 120 if (save_stack_address(trace, addr, false)) 121 return -EINVAL; 122 } 123 124 /* Check for stack corruption */ 125 if (unwind_error(&state)) 126 return -EINVAL; 127 128 /* Success path for non-user tasks, i.e. kthreads and idle tasks */ 129 if (!(task->flags & (PF_KTHREAD | PF_IDLE))) 130 return -EINVAL; 131 132 return 0; 133 } 134 135 /* 136 * This function returns an error if it detects any unreliable features of the 137 * stack. Otherwise it guarantees that the stack trace is reliable. 138 * 139 * If the task is not 'current', the caller *must* ensure the task is inactive. 140 */ 141 int save_stack_trace_tsk_reliable(struct task_struct *tsk, 142 struct stack_trace *trace) 143 { 144 int ret; 145 146 /* 147 * If the task doesn't have a stack (e.g., a zombie), the stack is 148 * "reliably" empty. 149 */ 150 if (!try_get_task_stack(tsk)) 151 return 0; 152 153 ret = __save_stack_trace_reliable(trace, tsk); 154 155 put_task_stack(tsk); 156 157 return ret; 158 } 159 #endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */ 160 161 /* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */ 162 163 struct stack_frame_user { 164 const void __user *next_fp; 165 unsigned long ret_addr; 166 }; 167 168 static int 169 copy_stack_frame(const void __user *fp, struct stack_frame_user *frame) 170 { 171 int ret; 172 173 if (!access_ok(fp, sizeof(*frame))) 174 return 0; 175 176 ret = 1; 177 pagefault_disable(); 178 if (__copy_from_user_inatomic(frame, fp, sizeof(*frame))) 179 ret = 0; 180 pagefault_enable(); 181 182 return ret; 183 } 184 185 static inline void __save_stack_trace_user(struct stack_trace *trace) 186 { 187 const struct pt_regs *regs = task_pt_regs(current); 188 const void __user *fp = (const void __user *)regs->bp; 189 190 if (trace->nr_entries < trace->max_entries) 191 trace->entries[trace->nr_entries++] = regs->ip; 192 193 while (trace->nr_entries < trace->max_entries) { 194 struct stack_frame_user frame; 195 196 frame.next_fp = NULL; 197 frame.ret_addr = 0; 198 if (!copy_stack_frame(fp, &frame)) 199 break; 200 if ((unsigned long)fp < regs->sp) 201 break; 202 if (frame.ret_addr) { 203 trace->entries[trace->nr_entries++] = 204 frame.ret_addr; 205 } 206 if (fp == frame.next_fp) 207 break; 208 fp = frame.next_fp; 209 } 210 } 211 212 void save_stack_trace_user(struct stack_trace *trace) 213 { 214 /* 215 * Trace user stack if we are not a kernel thread 216 */ 217 if (current->mm) 218 __save_stack_trace_user(trace); 219 } 220