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 /* 20 * This disables KASAN checking when reading a value from another task's stack, 21 * since the other task could be running on another CPU and could have poisoned 22 * the stack in the meantime. 23 */ 24 #define READ_ONCE_TASK_STACK(task, x) \ 25 ({ \ 26 unsigned long val; \ 27 unsigned long addr = x; \ 28 if ((task) == current) \ 29 val = READ_ONCE(addr); \ 30 else \ 31 val = READ_ONCE_NOCHECK(addr); \ 32 val; \ 33 }) 34 35 extern asmlinkage void handle_exception(void); 36 extern unsigned long ret_from_exception_end; 37 38 static inline int fp_is_valid(unsigned long fp, unsigned long sp) 39 { 40 unsigned long low, high; 41 42 low = sp + sizeof(struct stackframe); 43 high = ALIGN(sp, THREAD_SIZE); 44 45 return !(fp < low || fp > high || fp & 0x07); 46 } 47 48 void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs, 49 bool (*fn)(void *, unsigned long), void *arg) 50 { 51 unsigned long fp, sp, pc; 52 int graph_idx = 0; 53 int level = 0; 54 55 if (regs) { 56 fp = frame_pointer(regs); 57 sp = user_stack_pointer(regs); 58 pc = instruction_pointer(regs); 59 } else if (task == NULL || task == current) { 60 fp = (unsigned long)__builtin_frame_address(0); 61 sp = current_stack_pointer; 62 pc = (unsigned long)walk_stackframe; 63 level = -1; 64 } else { 65 /* task blocked in __switch_to */ 66 fp = task->thread.s[0]; 67 sp = task->thread.sp; 68 pc = task->thread.ra; 69 } 70 71 for (;;) { 72 struct stackframe *frame; 73 74 if (unlikely(!__kernel_text_address(pc) || (level++ >= 0 && !fn(arg, pc)))) 75 break; 76 77 if (unlikely(!fp_is_valid(fp, sp))) 78 break; 79 80 /* Unwind stack frame */ 81 frame = (struct stackframe *)fp - 1; 82 sp = fp; 83 if (regs && (regs->epc == pc) && fp_is_valid(frame->ra, sp)) { 84 /* We hit function where ra is not saved on the stack */ 85 fp = frame->ra; 86 pc = regs->ra; 87 } else { 88 fp = READ_ONCE_TASK_STACK(task, frame->fp); 89 pc = READ_ONCE_TASK_STACK(task, frame->ra); 90 pc = ftrace_graph_ret_addr(current, &graph_idx, pc, 91 &frame->ra); 92 if (pc >= (unsigned long)handle_exception && 93 pc < (unsigned long)&ret_from_exception_end) { 94 if (unlikely(!fn(arg, pc))) 95 break; 96 97 pc = ((struct pt_regs *)sp)->epc; 98 fp = ((struct pt_regs *)sp)->s0; 99 } 100 } 101 102 } 103 } 104 105 #else /* !CONFIG_FRAME_POINTER */ 106 107 void notrace walk_stackframe(struct task_struct *task, 108 struct pt_regs *regs, bool (*fn)(void *, unsigned long), void *arg) 109 { 110 unsigned long sp, pc; 111 unsigned long *ksp; 112 113 if (regs) { 114 sp = user_stack_pointer(regs); 115 pc = instruction_pointer(regs); 116 } else if (task == NULL || task == current) { 117 sp = current_stack_pointer; 118 pc = (unsigned long)walk_stackframe; 119 } else { 120 /* task blocked in __switch_to */ 121 sp = task->thread.sp; 122 pc = task->thread.ra; 123 } 124 125 if (unlikely(sp & 0x7)) 126 return; 127 128 ksp = (unsigned long *)sp; 129 while (!kstack_end(ksp)) { 130 if (__kernel_text_address(pc) && unlikely(!fn(arg, pc))) 131 break; 132 pc = READ_ONCE_NOCHECK(*ksp++) - 0x4; 133 } 134 } 135 136 #endif /* CONFIG_FRAME_POINTER */ 137 138 static bool print_trace_address(void *arg, unsigned long pc) 139 { 140 const char *loglvl = arg; 141 142 print_ip_sym(loglvl, pc); 143 return true; 144 } 145 146 noinline void dump_backtrace(struct pt_regs *regs, struct task_struct *task, 147 const char *loglvl) 148 { 149 walk_stackframe(task, regs, print_trace_address, (void *)loglvl); 150 } 151 152 void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl) 153 { 154 pr_cont("%sCall Trace:\n", loglvl); 155 dump_backtrace(NULL, task, loglvl); 156 } 157 158 static bool save_wchan(void *arg, unsigned long pc) 159 { 160 if (!in_sched_functions(pc)) { 161 unsigned long *p = arg; 162 *p = pc; 163 return false; 164 } 165 return true; 166 } 167 168 unsigned long __get_wchan(struct task_struct *task) 169 { 170 unsigned long pc = 0; 171 172 if (!try_get_task_stack(task)) 173 return 0; 174 walk_stackframe(task, NULL, save_wchan, &pc); 175 put_task_stack(task); 176 return pc; 177 } 178 179 noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie, 180 struct task_struct *task, struct pt_regs *regs) 181 { 182 walk_stackframe(task, regs, consume_entry, cookie); 183 } 184 185 /* 186 * Get the return address for a single stackframe and return a pointer to the 187 * next frame tail. 188 */ 189 static unsigned long unwind_user_frame(stack_trace_consume_fn consume_entry, 190 void *cookie, unsigned long fp, 191 unsigned long reg_ra) 192 { 193 struct stackframe buftail; 194 unsigned long ra = 0; 195 unsigned long __user *user_frame_tail = 196 (unsigned long __user *)(fp - sizeof(struct stackframe)); 197 198 /* Check accessibility of one struct frame_tail beyond */ 199 if (!access_ok(user_frame_tail, sizeof(buftail))) 200 return 0; 201 if (__copy_from_user_inatomic(&buftail, user_frame_tail, 202 sizeof(buftail))) 203 return 0; 204 205 ra = reg_ra ? : buftail.ra; 206 207 fp = buftail.fp; 208 if (!ra || !consume_entry(cookie, ra)) 209 return 0; 210 211 return fp; 212 } 213 214 void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie, 215 const struct pt_regs *regs) 216 { 217 unsigned long fp = 0; 218 219 fp = regs->s0; 220 if (!consume_entry(cookie, regs->epc)) 221 return; 222 223 fp = unwind_user_frame(consume_entry, cookie, fp, regs->ra); 224 while (fp && !(fp & 0x7)) 225 fp = unwind_user_frame(consume_entry, cookie, fp, 0); 226 } 227