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/sched/debug.h> 23 #include <linux/sched/task_stack.h> 24 #include <linux/stacktrace.h> 25 26 #include <asm/irq.h> 27 #include <asm/stack_pointer.h> 28 #include <asm/stacktrace.h> 29 30 /* 31 * AArch64 PCS assigns the frame pointer to x29. 32 * 33 * A simple function prologue looks like this: 34 * sub sp, sp, #0x10 35 * stp x29, x30, [sp] 36 * mov x29, sp 37 * 38 * A simple function epilogue looks like this: 39 * mov sp, x29 40 * ldp x29, x30, [sp] 41 * add sp, sp, #0x10 42 */ 43 int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) 44 { 45 unsigned long high, low; 46 unsigned long fp = frame->fp; 47 unsigned long irq_stack_ptr; 48 49 if (!tsk) 50 tsk = current; 51 52 /* 53 * Switching between stacks is valid when tracing current and in 54 * non-preemptible context. 55 */ 56 if (tsk == current && !preemptible()) 57 irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); 58 else 59 irq_stack_ptr = 0; 60 61 low = frame->sp; 62 /* irq stacks are not THREAD_SIZE aligned */ 63 if (on_irq_stack(frame->sp, raw_smp_processor_id())) 64 high = irq_stack_ptr; 65 else 66 high = ALIGN(low, THREAD_SIZE) - 0x20; 67 68 if (fp < low || fp > high || fp & 0xf) 69 return -EINVAL; 70 71 frame->sp = fp + 0x10; 72 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp)); 73 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8)); 74 75 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 76 if (tsk->ret_stack && 77 (frame->pc == (unsigned long)return_to_handler)) { 78 /* 79 * This is a case where function graph tracer has 80 * modified a return address (LR) in a stack frame 81 * to hook a function return. 82 * So replace it to an original value. 83 */ 84 frame->pc = tsk->ret_stack[frame->graph--].ret; 85 } 86 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 87 88 /* 89 * Check whether we are going to walk through from interrupt stack 90 * to task stack. 91 * If we reach the end of the stack - and its an interrupt stack, 92 * unpack the dummy frame to find the original elr. 93 * 94 * Check the frame->fp we read from the bottom of the irq_stack, 95 * and the original task stack pointer are both in current->stack. 96 */ 97 if (frame->sp == irq_stack_ptr) { 98 struct pt_regs *irq_args; 99 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr); 100 101 if (object_is_on_stack((void *)orig_sp) && 102 object_is_on_stack((void *)frame->fp)) { 103 frame->sp = orig_sp; 104 105 /* orig_sp is the saved pt_regs, find the elr */ 106 irq_args = (struct pt_regs *)orig_sp; 107 frame->pc = irq_args->pc; 108 } else { 109 /* 110 * This frame has a non-standard format, and we 111 * didn't fix it, because the data looked wrong. 112 * Refuse to output this frame. 113 */ 114 return -EINVAL; 115 } 116 } 117 118 return 0; 119 } 120 121 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame, 122 int (*fn)(struct stackframe *, void *), void *data) 123 { 124 while (1) { 125 int ret; 126 127 if (fn(frame, data)) 128 break; 129 ret = unwind_frame(tsk, frame); 130 if (ret < 0) 131 break; 132 } 133 } 134 135 #ifdef CONFIG_STACKTRACE 136 struct stack_trace_data { 137 struct stack_trace *trace; 138 unsigned int no_sched_functions; 139 unsigned int skip; 140 }; 141 142 static int save_trace(struct stackframe *frame, void *d) 143 { 144 struct stack_trace_data *data = d; 145 struct stack_trace *trace = data->trace; 146 unsigned long addr = frame->pc; 147 148 if (data->no_sched_functions && in_sched_functions(addr)) 149 return 0; 150 if (data->skip) { 151 data->skip--; 152 return 0; 153 } 154 155 trace->entries[trace->nr_entries++] = addr; 156 157 return trace->nr_entries >= trace->max_entries; 158 } 159 160 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace) 161 { 162 struct stack_trace_data data; 163 struct stackframe frame; 164 165 data.trace = trace; 166 data.skip = trace->skip; 167 data.no_sched_functions = 0; 168 169 frame.fp = regs->regs[29]; 170 frame.sp = regs->sp; 171 frame.pc = regs->pc; 172 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 173 frame.graph = current->curr_ret_stack; 174 #endif 175 176 walk_stackframe(current, &frame, save_trace, &data); 177 if (trace->nr_entries < trace->max_entries) 178 trace->entries[trace->nr_entries++] = ULONG_MAX; 179 } 180 181 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 182 { 183 struct stack_trace_data data; 184 struct stackframe frame; 185 186 if (!try_get_task_stack(tsk)) 187 return; 188 189 data.trace = trace; 190 data.skip = trace->skip; 191 192 if (tsk != current) { 193 data.no_sched_functions = 1; 194 frame.fp = thread_saved_fp(tsk); 195 frame.sp = thread_saved_sp(tsk); 196 frame.pc = thread_saved_pc(tsk); 197 } else { 198 data.no_sched_functions = 0; 199 frame.fp = (unsigned long)__builtin_frame_address(0); 200 frame.sp = current_stack_pointer; 201 frame.pc = (unsigned long)save_stack_trace_tsk; 202 } 203 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 204 frame.graph = tsk->curr_ret_stack; 205 #endif 206 207 walk_stackframe(tsk, &frame, save_trace, &data); 208 if (trace->nr_entries < trace->max_entries) 209 trace->entries[trace->nr_entries++] = ULONG_MAX; 210 211 put_task_stack(tsk); 212 } 213 EXPORT_SYMBOL_GPL(save_stack_trace_tsk); 214 215 void save_stack_trace(struct stack_trace *trace) 216 { 217 save_stack_trace_tsk(current, trace); 218 } 219 EXPORT_SYMBOL_GPL(save_stack_trace); 220 #endif 221