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