1 #include <linux/export.h> 2 #include <linux/sched.h> 3 #include <linux/stacktrace.h> 4 5 #include <asm/stacktrace.h> 6 7 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) 8 /* 9 * Unwind the current stack frame and store the new register values in the 10 * structure passed as argument. Unwinding is equivalent to a function return, 11 * hence the new PC value rather than LR should be used for backtrace. 12 * 13 * With framepointer enabled, a simple function prologue looks like this: 14 * mov ip, sp 15 * stmdb sp!, {fp, ip, lr, pc} 16 * sub fp, ip, #4 17 * 18 * A simple function epilogue looks like this: 19 * ldm sp, {fp, sp, pc} 20 * 21 * Note that with framepointer enabled, even the leaf functions have the same 22 * prologue and epilogue, therefore we can ignore the LR value in this case. 23 */ 24 int notrace unwind_frame(struct stackframe *frame) 25 { 26 unsigned long high, low; 27 unsigned long fp = frame->fp; 28 29 /* only go to a higher address on the stack */ 30 low = frame->sp; 31 high = ALIGN(low, THREAD_SIZE); 32 33 /* check current frame pointer is within bounds */ 34 if (fp < (low + 12) || fp + 4 >= high) 35 return -EINVAL; 36 37 /* restore the registers from the stack frame */ 38 frame->fp = *(unsigned long *)(fp - 12); 39 frame->sp = *(unsigned long *)(fp - 8); 40 frame->pc = *(unsigned long *)(fp - 4); 41 42 return 0; 43 } 44 #endif 45 46 void notrace walk_stackframe(struct stackframe *frame, 47 int (*fn)(struct stackframe *, void *), void *data) 48 { 49 while (1) { 50 int ret; 51 52 if (fn(frame, data)) 53 break; 54 ret = unwind_frame(frame); 55 if (ret < 0) 56 break; 57 } 58 } 59 EXPORT_SYMBOL(walk_stackframe); 60 61 #ifdef CONFIG_STACKTRACE 62 struct stack_trace_data { 63 struct stack_trace *trace; 64 unsigned int no_sched_functions; 65 unsigned int skip; 66 }; 67 68 static int save_trace(struct stackframe *frame, void *d) 69 { 70 struct stack_trace_data *data = d; 71 struct stack_trace *trace = data->trace; 72 unsigned long addr = frame->pc; 73 74 if (data->no_sched_functions && in_sched_functions(addr)) 75 return 0; 76 if (data->skip) { 77 data->skip--; 78 return 0; 79 } 80 81 trace->entries[trace->nr_entries++] = addr; 82 83 return trace->nr_entries >= trace->max_entries; 84 } 85 86 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 87 { 88 struct stack_trace_data data; 89 struct stackframe frame; 90 91 data.trace = trace; 92 data.skip = trace->skip; 93 94 if (tsk != current) { 95 #ifdef CONFIG_SMP 96 /* 97 * What guarantees do we have here that 'tsk' is not 98 * running on another CPU? For now, ignore it as we 99 * can't guarantee we won't explode. 100 */ 101 if (trace->nr_entries < trace->max_entries) 102 trace->entries[trace->nr_entries++] = ULONG_MAX; 103 return; 104 #else 105 data.no_sched_functions = 1; 106 frame.fp = thread_saved_fp(tsk); 107 frame.sp = thread_saved_sp(tsk); 108 frame.lr = 0; /* recovered from the stack */ 109 frame.pc = thread_saved_pc(tsk); 110 #endif 111 } else { 112 register unsigned long current_sp asm ("sp"); 113 114 data.no_sched_functions = 0; 115 frame.fp = (unsigned long)__builtin_frame_address(0); 116 frame.sp = current_sp; 117 frame.lr = (unsigned long)__builtin_return_address(0); 118 frame.pc = (unsigned long)save_stack_trace_tsk; 119 } 120 121 walk_stackframe(&frame, save_trace, &data); 122 if (trace->nr_entries < trace->max_entries) 123 trace->entries[trace->nr_entries++] = ULONG_MAX; 124 } 125 126 void save_stack_trace(struct stack_trace *trace) 127 { 128 save_stack_trace_tsk(current, trace); 129 } 130 EXPORT_SYMBOL_GPL(save_stack_trace); 131 #endif 132