1 /* 2 * Stack tracing support 3 * 4 * Copyright (C) 2012 ARM Ltd. 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program. If not, see <http://www.gnu.org/licenses/>. 17 */ 18 #include <linux/kernel.h> 19 #include <linux/export.h> 20 #include <linux/ftrace.h> 21 #include <linux/sched.h> 22 #include <linux/stacktrace.h> 23 24 #include <asm/irq.h> 25 #include <asm/stacktrace.h> 26 27 /* 28 * AArch64 PCS assigns the frame pointer to x29. 29 * 30 * A simple function prologue looks like this: 31 * sub sp, sp, #0x10 32 * stp x29, x30, [sp] 33 * mov x29, sp 34 * 35 * A simple function epilogue looks like this: 36 * mov sp, x29 37 * ldp x29, x30, [sp] 38 * add sp, sp, #0x10 39 */ 40 int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) 41 { 42 unsigned long high, low; 43 unsigned long fp = frame->fp; 44 unsigned long irq_stack_ptr; 45 46 /* 47 * Use raw_smp_processor_id() to avoid false-positives from 48 * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping 49 * task stacks, we can be pre-empted in this case, so 50 * {raw_,}smp_processor_id() may give us the wrong value. Sleeping 51 * tasks can't ever be on an interrupt stack, so regardless of cpu, 52 * the checks will always fail. 53 */ 54 irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id()); 55 56 low = frame->sp; 57 /* irq stacks are not THREAD_SIZE aligned */ 58 if (on_irq_stack(frame->sp, raw_smp_processor_id())) 59 high = irq_stack_ptr; 60 else 61 high = ALIGN(low, THREAD_SIZE) - 0x20; 62 63 if (fp < low || fp > high || fp & 0xf) 64 return -EINVAL; 65 66 frame->sp = fp + 0x10; 67 frame->fp = *(unsigned long *)(fp); 68 frame->pc = *(unsigned long *)(fp + 8); 69 70 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 71 if (tsk && tsk->ret_stack && 72 (frame->pc == (unsigned long)return_to_handler)) { 73 /* 74 * This is a case where function graph tracer has 75 * modified a return address (LR) in a stack frame 76 * to hook a function return. 77 * So replace it to an original value. 78 */ 79 frame->pc = tsk->ret_stack[frame->graph--].ret; 80 } 81 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 82 83 /* 84 * Check whether we are going to walk through from interrupt stack 85 * to task stack. 86 * If we reach the end of the stack - and its an interrupt stack, 87 * unpack the dummy frame to find the original elr. 88 * 89 * Check the frame->fp we read from the bottom of the irq_stack, 90 * and the original task stack pointer are both in current->stack. 91 */ 92 if (frame->sp == irq_stack_ptr) { 93 struct pt_regs *irq_args; 94 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr); 95 96 if (object_is_on_stack((void *)orig_sp) && 97 object_is_on_stack((void *)frame->fp)) { 98 frame->sp = orig_sp; 99 100 /* orig_sp is the saved pt_regs, find the elr */ 101 irq_args = (struct pt_regs *)orig_sp; 102 frame->pc = irq_args->pc; 103 } else { 104 /* 105 * This frame has a non-standard format, and we 106 * didn't fix it, because the data looked wrong. 107 * Refuse to output this frame. 108 */ 109 return -EINVAL; 110 } 111 } 112 113 return 0; 114 } 115 116 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame, 117 int (*fn)(struct stackframe *, void *), void *data) 118 { 119 while (1) { 120 int ret; 121 122 if (fn(frame, data)) 123 break; 124 ret = unwind_frame(tsk, frame); 125 if (ret < 0) 126 break; 127 } 128 } 129 EXPORT_SYMBOL(walk_stackframe); 130 131 #ifdef CONFIG_STACKTRACE 132 struct stack_trace_data { 133 struct stack_trace *trace; 134 unsigned int no_sched_functions; 135 unsigned int skip; 136 }; 137 138 static int save_trace(struct stackframe *frame, void *d) 139 { 140 struct stack_trace_data *data = d; 141 struct stack_trace *trace = data->trace; 142 unsigned long addr = frame->pc; 143 144 if (data->no_sched_functions && in_sched_functions(addr)) 145 return 0; 146 if (data->skip) { 147 data->skip--; 148 return 0; 149 } 150 151 trace->entries[trace->nr_entries++] = addr; 152 153 return trace->nr_entries >= trace->max_entries; 154 } 155 156 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 157 { 158 struct stack_trace_data data; 159 struct stackframe frame; 160 161 data.trace = trace; 162 data.skip = trace->skip; 163 164 if (tsk != current) { 165 data.no_sched_functions = 1; 166 frame.fp = thread_saved_fp(tsk); 167 frame.sp = thread_saved_sp(tsk); 168 frame.pc = thread_saved_pc(tsk); 169 } else { 170 data.no_sched_functions = 0; 171 frame.fp = (unsigned long)__builtin_frame_address(0); 172 frame.sp = current_stack_pointer; 173 frame.pc = (unsigned long)save_stack_trace_tsk; 174 } 175 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 176 frame.graph = tsk->curr_ret_stack; 177 #endif 178 179 walk_stackframe(tsk, &frame, save_trace, &data); 180 if (trace->nr_entries < trace->max_entries) 181 trace->entries[trace->nr_entries++] = ULONG_MAX; 182 } 183 184 void save_stack_trace(struct stack_trace *trace) 185 { 186 save_stack_trace_tsk(current, trace); 187 } 188 EXPORT_SYMBOL_GPL(save_stack_trace); 189 #endif 190