arch/riscv/kernel/stacktrace.c

   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 }