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         /*
  52          * -4 here because we care about the PC at time of bl,
  53          * not where the return will go.
  54          */
  55         frame->pc = *(unsigned long *)(fp + 8) - 4;
  56
  57         return 0;
  58 }
  59
  60 void notrace walk_stackframe(struct stackframe *frame,
  61                      int (*fn)(struct stackframe *, void *), void *data)
  62 {
  63         while (1) {
  64                 int ret;
  65
  66                 if (fn(frame, data))
  67                         break;
  68                 ret = unwind_frame(frame);
  69                 if (ret < 0)
  70                         break;
  71         }
  72 }
  73 EXPORT_SYMBOL(walk_stackframe);
  74
  75 #ifdef CONFIG_STACKTRACE
  76 struct stack_trace_data {
  77         struct stack_trace *trace;
  78         unsigned int no_sched_functions;
  79         unsigned int skip;
  80 };
  81
  82 static int save_trace(struct stackframe *frame, void *d)
  83 {
  84         struct stack_trace_data *data = d;
  85         struct stack_trace *trace = data->trace;
  86         unsigned long addr = frame->pc;
  87
  88         if (data->no_sched_functions && in_sched_functions(addr))
  89                 return 0;
  90         if (data->skip) {
  91                 data->skip--;
  92                 return 0;
  93         }
  94
  95         trace->entries[trace->nr_entries++] = addr;
  96
  97         return trace->nr_entries >= trace->max_entries;
  98 }
  99
 100 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 101 {
 102         struct stack_trace_data data;
 103         struct stackframe frame;
 104
 105         data.trace = trace;
 106         data.skip = trace->skip;
 107
 108         if (tsk != current) {
 109                 data.no_sched_functions = 1;
 110                 frame.fp = thread_saved_fp(tsk);
 111                 frame.sp = thread_saved_sp(tsk);
 112                 frame.pc = thread_saved_pc(tsk);
 113         } else {
 114                 register unsigned long current_sp asm("sp");
 115                 data.no_sched_functions = 0;
 116                 frame.fp = (unsigned long)__builtin_frame_address(0);
 117                 frame.sp = current_sp;
 118                 frame.pc = (unsigned long)save_stack_trace_tsk;
 119         }
 120
 121         walk_stackframe(&frame, save_trace, &data);
 122         if (trace->nr_entries < trace->max_entries)
 123                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 124 }
 125
 126 void save_stack_trace(struct stack_trace *trace)
 127 {
 128         save_stack_trace_tsk(current, trace);
 129 }
 130 EXPORT_SYMBOL_GPL(save_stack_trace);
 131 #endif