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