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