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 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); 93 !unwind_done(&state) && !unwind_error(&state); 94 unwind_next_frame(&state)) { 95 96 regs = unwind_get_entry_regs(&state, NULL); 97 if (regs) { 98 /* Success path for user tasks */ 99 if (user_mode(regs)) 100 goto success; 101 102 /* 103 * Kernel mode registers on the stack indicate an 104 * in-kernel interrupt or exception (e.g., preemption 105 * or a page fault), which can make frame pointers 106 * unreliable. 107 */ 108 109 if (IS_ENABLED(CONFIG_FRAME_POINTER)) 110 return -EINVAL; 111 } 112 113 addr = unwind_get_return_address(&state); 114 115 /* 116 * A NULL or invalid return address probably means there's some 117 * generated code which __kernel_text_address() doesn't know 118 * about. 119 */ 120 if (!addr) 121 return -EINVAL; 122 123 if (save_stack_address(trace, addr, false)) 124 return -EINVAL; 125 } 126 127 /* Check for stack corruption */ 128 if (unwind_error(&state)) 129 return -EINVAL; 130 131 /* Success path for non-user tasks, i.e. kthreads and idle tasks */ 132 if (!(task->flags & (PF_KTHREAD | PF_IDLE))) 133 return -EINVAL; 134 135 success: 136 if (trace->nr_entries < trace->max_entries) 137 trace->entries[trace->nr_entries++] = ULONG_MAX; 138 139 return 0; 140 } 141 142 /* 143 * This function returns an error if it detects any unreliable features of the 144 * stack. Otherwise it guarantees that the stack trace is reliable. 145 * 146 * If the task is not 'current', the caller *must* ensure the task is inactive. 147 */ 148 int save_stack_trace_tsk_reliable(struct task_struct *tsk, 149 struct stack_trace *trace) 150 { 151 int ret; 152 153 /* 154 * If the task doesn't have a stack (e.g., a zombie), the stack is 155 * "reliably" empty. 156 */ 157 if (!try_get_task_stack(tsk)) 158 return 0; 159 160 ret = __save_stack_trace_reliable(trace, tsk); 161 162 put_task_stack(tsk); 163 164 return ret; 165 } 166 #endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */ 167 168 /* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */ 169 170 struct stack_frame_user { 171 const void __user *next_fp; 172 unsigned long ret_addr; 173 }; 174 175 static int 176 copy_stack_frame(const void __user *fp, struct stack_frame_user *frame) 177 { 178 int ret; 179 180 if (!access_ok(VERIFY_READ, fp, sizeof(*frame))) 181 return 0; 182 183 ret = 1; 184 pagefault_disable(); 185 if (__copy_from_user_inatomic(frame, fp, sizeof(*frame))) 186 ret = 0; 187 pagefault_enable(); 188 189 return ret; 190 } 191 192 static inline void __save_stack_trace_user(struct stack_trace *trace) 193 { 194 const struct pt_regs *regs = task_pt_regs(current); 195 const void __user *fp = (const void __user *)regs->bp; 196 197 if (trace->nr_entries < trace->max_entries) 198 trace->entries[trace->nr_entries++] = regs->ip; 199 200 while (trace->nr_entries < trace->max_entries) { 201 struct stack_frame_user frame; 202 203 frame.next_fp = NULL; 204 frame.ret_addr = 0; 205 if (!copy_stack_frame(fp, &frame)) 206 break; 207 if ((unsigned long)fp < regs->sp) 208 break; 209 if (frame.ret_addr) { 210 trace->entries[trace->nr_entries++] = 211 frame.ret_addr; 212 } 213 if (fp == frame.next_fp) 214 break; 215 fp = frame.next_fp; 216 } 217 } 218 219 void save_stack_trace_user(struct stack_trace *trace) 220 { 221 /* 222 * Trace user stack if we are not a kernel thread 223 */ 224 if (current->mm) { 225 __save_stack_trace_user(trace); 226 } 227 if (trace->nr_entries < trace->max_entries) 228 trace->entries[trace->nr_entries++] = ULONG_MAX; 229 } 230