arch/arm64/kernel/stacktrace.c

   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/sched.h>
  21 #include <linux/stacktrace.h>
  22
  23 #include <asm/stacktrace.h>
  24
  25 /*
  26  * AArch64 PCS assigns the frame pointer to x29.
  27  *
  28  * A simple function prologue looks like this:
  29  *      sub     sp, sp, #0x10
  30  *      stp     x29, x30, [sp]
  31  *      mov     x29, sp
  32  *
  33  * A simple function epilogue looks like this:
  34  *      mov     sp, x29
  35  *      ldp     x29, x30, [sp]
  36  *      add     sp, sp, #0x10
  37  */
  38 int unwind_frame(struct stackframe *frame)
  39 {
  40         unsigned long high, low;
  41         unsigned long fp = frame->fp;
  42
  43         low  = frame->sp;
  44         high = ALIGN(low, THREAD_SIZE);
  45
  46         if (fp < low || fp > high || fp & 0xf)
  47                 return -EINVAL;
  48
  49         frame->sp = fp + 0x10;
  50         frame->fp = *(unsigned long *)(fp);
  51         frame->pc = *(unsigned long *)(fp + 8);
  52
  53         return 0;
  54 }
  55
  56 void notrace walk_stackframe(struct stackframe *frame,
  57                      int (*fn)(struct stackframe *, void *), void *data)
  58 {
  59         while (1) {
  60                 int ret;
  61
  62                 if (fn(frame, data))
  63                         break;
  64                 ret = unwind_frame(frame);
  65                 if (ret < 0)
  66                         break;
  67         }
  68 }
  69 EXPORT_SYMBOL(walk_stackframe);
  70
  71 #ifdef CONFIG_STACKTRACE
  72 struct stack_trace_data {
  73         struct stack_trace *trace;
  74         unsigned int no_sched_functions;
  75         unsigned int skip;
  76 };
  77
  78 static int save_trace(struct stackframe *frame, void *d)
  79 {
  80         struct stack_trace_data *data = d;
  81         struct stack_trace *trace = data->trace;
  82         unsigned long addr = frame->pc;
  83
  84         if (data->no_sched_functions && in_sched_functions(addr))
  85                 return 0;
  86         if (data->skip) {
  87                 data->skip--;
  88                 return 0;
  89         }
  90
  91         trace->entries[trace->nr_entries++] = addr;
  92
  93         return trace->nr_entries >= trace->max_entries;
  94 }
  95
  96 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
  97 {
  98         struct stack_trace_data data;
  99         struct stackframe frame;
 100
 101         data.trace = trace;
 102         data.skip = trace->skip;
 103
 104         if (tsk != current) {
 105                 data.no_sched_functions = 1;
 106                 frame.fp = thread_saved_fp(tsk);
 107                 frame.sp = thread_saved_sp(tsk);
 108                 frame.pc = thread_saved_pc(tsk);
 109         } else {
 110                 register unsigned long current_sp asm("sp");
 111                 data.no_sched_functions = 0;
 112                 frame.fp = (unsigned long)__builtin_frame_address(0);
 113                 frame.sp = current_sp;
 114                 frame.pc = (unsigned long)save_stack_trace_tsk;
 115         }
 116
 117         walk_stackframe(&frame, save_trace, &data);
 118         if (trace->nr_entries < trace->max_entries)
 119                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 120 }
 121
 122 void save_stack_trace(struct stack_trace *trace)
 123 {
 124         save_stack_trace_tsk(current, trace);
 125 }
 126 EXPORT_SYMBOL_GPL(save_stack_trace);
 127 #endif