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