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