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 #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 break; 117 } 118 119 addr = unwind_get_return_address(&state); 120 121 /* 122 * A NULL or invalid return address probably means there's some 123 * generated code which __kernel_text_address() doesn't know 124 * about. 125 */ 126 if (!addr) { 127 STACKTRACE_DUMP_ONCE(task); 128 return -EINVAL; 129 } 130 131 if (save_stack_address(trace, addr, false)) 132 return -EINVAL; 133 } 134 135 /* Check for stack corruption */ 136 if (unwind_error(&state)) { 137 STACKTRACE_DUMP_ONCE(task); 138 return -EINVAL; 139 } 140 141 if (trace->nr_entries < trace->max_entries) 142 trace->entries[trace->nr_entries++] = ULONG_MAX; 143 144 return 0; 145 } 146 147 /* 148 * This function returns an error if it detects any unreliable features of the 149 * stack. Otherwise it guarantees that the stack trace is reliable. 150 * 151 * If the task is not 'current', the caller *must* ensure the task is inactive. 152 */ 153 int save_stack_trace_tsk_reliable(struct task_struct *tsk, 154 struct stack_trace *trace) 155 { 156 int ret; 157 158 /* 159 * If the task doesn't have a stack (e.g., a zombie), the stack is 160 * "reliably" empty. 161 */ 162 if (!try_get_task_stack(tsk)) 163 return 0; 164 165 ret = __save_stack_trace_reliable(trace, tsk); 166 167 put_task_stack(tsk); 168 169 return ret; 170 } 171 #endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */ 172 173 /* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */ 174 175 struct stack_frame_user { 176 const void __user *next_fp; 177 unsigned long ret_addr; 178 }; 179 180 static int 181 copy_stack_frame(const void __user *fp, struct stack_frame_user *frame) 182 { 183 int ret; 184 185 if (!access_ok(VERIFY_READ, fp, sizeof(*frame))) 186 return 0; 187 188 ret = 1; 189 pagefault_disable(); 190 if (__copy_from_user_inatomic(frame, fp, sizeof(*frame))) 191 ret = 0; 192 pagefault_enable(); 193 194 return ret; 195 } 196 197 static inline void __save_stack_trace_user(struct stack_trace *trace) 198 { 199 const struct pt_regs *regs = task_pt_regs(current); 200 const void __user *fp = (const void __user *)regs->bp; 201 202 if (trace->nr_entries < trace->max_entries) 203 trace->entries[trace->nr_entries++] = regs->ip; 204 205 while (trace->nr_entries < trace->max_entries) { 206 struct stack_frame_user frame; 207 208 frame.next_fp = NULL; 209 frame.ret_addr = 0; 210 if (!copy_stack_frame(fp, &frame)) 211 break; 212 if ((unsigned long)fp < regs->sp) 213 break; 214 if (frame.ret_addr) { 215 trace->entries[trace->nr_entries++] = 216 frame.ret_addr; 217 } 218 if (fp == frame.next_fp) 219 break; 220 fp = frame.next_fp; 221 } 222 } 223 224 void save_stack_trace_user(struct stack_trace *trace) 225 { 226 /* 227 * Trace user stack if we are not a kernel thread 228 */ 229 if (current->mm) { 230 __save_stack_trace_user(trace); 231 } 232 if (trace->nr_entries < trace->max_entries) 233 trace->entries[trace->nr_entries++] = ULONG_MAX; 234 } 235