1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2008 ARM Limited 4 * Copyright (C) 2014 Regents of the University of California 5 */ 6 7 #include <linux/export.h> 8 #include <linux/kallsyms.h> 9 #include <linux/sched.h> 10 #include <linux/sched/debug.h> 11 #include <linux/sched/task_stack.h> 12 #include <linux/stacktrace.h> 13 #include <linux/ftrace.h> 14 15 #include <asm/stacktrace.h> 16 17 #ifdef CONFIG_FRAME_POINTER 18 19 extern asmlinkage void handle_exception(void); 20 21 static inline int fp_is_valid(unsigned long fp, unsigned long sp) 22 { 23 unsigned long low, high; 24 25 low = sp + sizeof(struct stackframe); 26 high = ALIGN(sp, THREAD_SIZE); 27 28 return !(fp < low || fp > high || fp & 0x07); 29 } 30 31 void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs, 32 bool (*fn)(void *, unsigned long), void *arg) 33 { 34 unsigned long fp, sp, pc; 35 int graph_idx = 0; 36 int level = 0; 37 38 if (regs) { 39 fp = frame_pointer(regs); 40 sp = user_stack_pointer(regs); 41 pc = instruction_pointer(regs); 42 } else if (task == NULL || task == current) { 43 fp = (unsigned long)__builtin_frame_address(0); 44 sp = current_stack_pointer; 45 pc = (unsigned long)walk_stackframe; 46 level = -1; 47 } else { 48 /* task blocked in __switch_to */ 49 fp = task->thread.s[0]; 50 sp = task->thread.sp; 51 pc = task->thread.ra; 52 } 53 54 for (;;) { 55 struct stackframe *frame; 56 57 if (unlikely(!__kernel_text_address(pc) || (level++ >= 0 && !fn(arg, pc)))) 58 break; 59 60 if (unlikely(!fp_is_valid(fp, sp))) 61 break; 62 63 /* Unwind stack frame */ 64 frame = (struct stackframe *)fp - 1; 65 sp = fp; 66 if (regs && (regs->epc == pc) && fp_is_valid(frame->ra, sp)) { 67 /* We hit function where ra is not saved on the stack */ 68 fp = frame->ra; 69 pc = regs->ra; 70 } else { 71 fp = frame->fp; 72 pc = ftrace_graph_ret_addr(current, &graph_idx, frame->ra, 73 &frame->ra); 74 if (pc == (unsigned long)handle_exception) { 75 if (unlikely(!__kernel_text_address(pc) || !fn(arg, pc))) 76 break; 77 78 pc = ((struct pt_regs *)sp)->epc; 79 fp = ((struct pt_regs *)sp)->s0; 80 } 81 } 82 83 } 84 } 85 86 #else /* !CONFIG_FRAME_POINTER */ 87 88 void notrace walk_stackframe(struct task_struct *task, 89 struct pt_regs *regs, bool (*fn)(void *, unsigned long), void *arg) 90 { 91 unsigned long sp, pc; 92 unsigned long *ksp; 93 94 if (regs) { 95 sp = user_stack_pointer(regs); 96 pc = instruction_pointer(regs); 97 } else if (task == NULL || task == current) { 98 sp = current_stack_pointer; 99 pc = (unsigned long)walk_stackframe; 100 } else { 101 /* task blocked in __switch_to */ 102 sp = task->thread.sp; 103 pc = task->thread.ra; 104 } 105 106 if (unlikely(sp & 0x7)) 107 return; 108 109 ksp = (unsigned long *)sp; 110 while (!kstack_end(ksp)) { 111 if (__kernel_text_address(pc) && unlikely(!fn(arg, pc))) 112 break; 113 pc = READ_ONCE_NOCHECK(*ksp++) - 0x4; 114 } 115 } 116 117 #endif /* CONFIG_FRAME_POINTER */ 118 119 static bool print_trace_address(void *arg, unsigned long pc) 120 { 121 const char *loglvl = arg; 122 123 print_ip_sym(loglvl, pc); 124 return true; 125 } 126 127 noinline void dump_backtrace(struct pt_regs *regs, struct task_struct *task, 128 const char *loglvl) 129 { 130 walk_stackframe(task, regs, print_trace_address, (void *)loglvl); 131 } 132 133 void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl) 134 { 135 pr_cont("%sCall Trace:\n", loglvl); 136 dump_backtrace(NULL, task, loglvl); 137 } 138 139 static bool save_wchan(void *arg, unsigned long pc) 140 { 141 if (!in_sched_functions(pc)) { 142 unsigned long *p = arg; 143 *p = pc; 144 return false; 145 } 146 return true; 147 } 148 149 unsigned long __get_wchan(struct task_struct *task) 150 { 151 unsigned long pc = 0; 152 153 if (!try_get_task_stack(task)) 154 return 0; 155 walk_stackframe(task, NULL, save_wchan, &pc); 156 put_task_stack(task); 157 return pc; 158 } 159 160 noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie, 161 struct task_struct *task, struct pt_regs *regs) 162 { 163 walk_stackframe(task, regs, consume_entry, cookie); 164 } 165 166 /* 167 * Get the return address for a single stackframe and return a pointer to the 168 * next frame tail. 169 */ 170 static unsigned long unwind_user_frame(stack_trace_consume_fn consume_entry, 171 void *cookie, unsigned long fp, 172 unsigned long reg_ra) 173 { 174 struct stackframe buftail; 175 unsigned long ra = 0; 176 unsigned long __user *user_frame_tail = 177 (unsigned long __user *)(fp - sizeof(struct stackframe)); 178 179 /* Check accessibility of one struct frame_tail beyond */ 180 if (!access_ok(user_frame_tail, sizeof(buftail))) 181 return 0; 182 if (__copy_from_user_inatomic(&buftail, user_frame_tail, 183 sizeof(buftail))) 184 return 0; 185 186 ra = reg_ra ? : buftail.ra; 187 188 fp = buftail.fp; 189 if (!ra || !consume_entry(cookie, ra)) 190 return 0; 191 192 return fp; 193 } 194 195 void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie, 196 const struct pt_regs *regs) 197 { 198 unsigned long fp = 0; 199 200 fp = regs->s0; 201 if (!consume_entry(cookie, regs->epc)) 202 return; 203 204 fp = unwind_user_frame(consume_entry, cookie, fp, regs->ra); 205 while (fp && !(fp & 0x7)) 206 fp = unwind_user_frame(consume_entry, cookie, fp, 0); 207 } 208