arch/arm/kernel/stacktrace.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/export.h>
   3 #include <linux/sched.h>
   4 #include <linux/sched/debug.h>
   5 #include <linux/stacktrace.h>
   6
   7 #include <asm/sections.h>
   8 #include <asm/stacktrace.h>
   9 #include <asm/traps.h>
  10
  11 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
  12 /*
  13  * Unwind the current stack frame and store the new register values in the
  14  * structure passed as argument. Unwinding is equivalent to a function return,
  15  * hence the new PC value rather than LR should be used for backtrace.
  16  *
  17  * With framepointer enabled, a simple function prologue looks like this:
  18  *      mov     ip, sp
  19  *      stmdb   sp!, {fp, ip, lr, pc}
  20  *      sub     fp, ip, #4
  21  *
  22  * A simple function epilogue looks like this:
  23  *      ldm     sp, {fp, sp, pc}
  24  *
  25  * Note that with framepointer enabled, even the leaf functions have the same
  26  * prologue and epilogue, therefore we can ignore the LR value in this case.
  27  */
  28 int notrace unwind_frame(struct stackframe *frame)
  29 {
  30         unsigned long high, low;
  31         unsigned long fp = frame->fp;
  32
  33         /* only go to a higher address on the stack */
  34         low = frame->sp;
  35         high = ALIGN(low, THREAD_SIZE);
  36
  37         /* check current frame pointer is within bounds */
  38         if (fp < low + 12 || fp > high - 4)
  39                 return -EINVAL;
  40
  41         /* restore the registers from the stack frame */
  42         frame->fp = *(unsigned long *)(fp - 12);
  43         frame->sp = *(unsigned long *)(fp - 8);
  44         frame->pc = *(unsigned long *)(fp - 4);
  45
  46         return 0;
  47 }
  48 #endif
  49
  50 void notrace walk_stackframe(struct stackframe *frame,
  51                      int (*fn)(struct stackframe *, void *), void *data)
  52 {
  53         while (1) {
  54                 int ret;
  55
  56                 if (fn(frame, data))
  57                         break;
  58                 ret = unwind_frame(frame);
  59                 if (ret < 0)
  60                         break;
  61         }
  62 }
  63 EXPORT_SYMBOL(walk_stackframe);
  64
  65 #ifdef CONFIG_STACKTRACE
  66 struct stack_trace_data {
  67         struct stack_trace *trace;
  68         unsigned int no_sched_functions;
  69         unsigned int skip;
  70 };
  71
  72 static int save_trace(struct stackframe *frame, void *d)
  73 {
  74         struct stack_trace_data *data = d;
  75         struct stack_trace *trace = data->trace;
  76         struct pt_regs *regs;
  77         unsigned long addr = frame->pc;
  78
  79         if (data->no_sched_functions && in_sched_functions(addr))
  80                 return 0;
  81         if (data->skip) {
  82                 data->skip--;
  83                 return 0;
  84         }
  85
  86         trace->entries[trace->nr_entries++] = addr;
  87
  88         if (trace->nr_entries >= trace->max_entries)
  89                 return 1;
  90
  91         if (!in_entry_text(frame->pc))
  92                 return 0;
  93
  94         regs = (struct pt_regs *)frame->sp;
  95         if ((unsigned long)&regs[1] > ALIGN(frame->sp, THREAD_SIZE))
  96                 return 0;
  97
  98         trace->entries[trace->nr_entries++] = regs->ARM_pc;
  99
 100         return trace->nr_entries >= trace->max_entries;
 101 }
 102
 103 /* This must be noinline to so that our skip calculation works correctly */
 104 static noinline void __save_stack_trace(struct task_struct *tsk,
 105         struct stack_trace *trace, unsigned int nosched)
 106 {
 107         struct stack_trace_data data;
 108         struct stackframe frame;
 109
 110         data.trace = trace;
 111         data.skip = trace->skip;
 112         data.no_sched_functions = nosched;
 113
 114         if (tsk != current) {
 115 #ifdef CONFIG_SMP
 116                 /*
 117                  * What guarantees do we have here that 'tsk' is not
 118                  * running on another CPU?  For now, ignore it as we
 119                  * can't guarantee we won't explode.
 120                  */
 121                 return;
 122 #else
 123                 frame.fp = thread_saved_fp(tsk);
 124                 frame.sp = thread_saved_sp(tsk);
 125                 frame.lr = 0;           /* recovered from the stack */
 126                 frame.pc = thread_saved_pc(tsk);
 127 #endif
 128         } else {
 129                 /* We don't want this function nor the caller */
 130                 data.skip += 2;
 131                 frame.fp = (unsigned long)__builtin_frame_address(0);
 132                 frame.sp = current_stack_pointer;
 133                 frame.lr = (unsigned long)__builtin_return_address(0);
 134                 frame.pc = (unsigned long)__save_stack_trace;
 135         }
 136
 137         walk_stackframe(&frame, save_trace, &data);
 138 }
 139
 140 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 141 {
 142         struct stack_trace_data data;
 143         struct stackframe frame;
 144
 145         data.trace = trace;
 146         data.skip = trace->skip;
 147         data.no_sched_functions = 0;
 148
 149         frame.fp = regs->ARM_fp;
 150         frame.sp = regs->ARM_sp;
 151         frame.lr = regs->ARM_lr;
 152         frame.pc = regs->ARM_pc;
 153
 154         walk_stackframe(&frame, save_trace, &data);
 155 }
 156
 157 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 158 {
 159         __save_stack_trace(tsk, trace, 1);
 160 }
 161 EXPORT_SYMBOL(save_stack_trace_tsk);
 162
 163 void save_stack_trace(struct stack_trace *trace)
 164 {
 165         __save_stack_trace(current, trace, 0);
 166 }
 167 EXPORT_SYMBOL_GPL(save_stack_trace);
 168 #endif