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/ftrace.h>
  21 #include <linux/sched.h>
  22 #include <linux/stacktrace.h>
  23
  24 #include <asm/irq.h>
  25 #include <asm/stacktrace.h>
  26
  27 /*
  28  * AArch64 PCS assigns the frame pointer to x29.
  29  *
  30  * A simple function prologue looks like this:
  31  *      sub     sp, sp, #0x10
  32  *      stp     x29, x30, [sp]
  33  *      mov     x29, sp
  34  *
  35  * A simple function epilogue looks like this:
  36  *      mov     sp, x29
  37  *      ldp     x29, x30, [sp]
  38  *      add     sp, sp, #0x10
  39  */
  40 int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
  41 {
  42         unsigned long high, low;
  43         unsigned long fp = frame->fp;
  44         unsigned long irq_stack_ptr;
  45
  46         /*
  47          * Use raw_smp_processor_id() to avoid false-positives from
  48          * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping
  49          * task stacks, we can be pre-empted in this case, so
  50          * {raw_,}smp_processor_id() may give us the wrong value. Sleeping
  51          * tasks can't ever be on an interrupt stack, so regardless of cpu,
  52          * the checks will always fail.
  53          */
  54         irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id());
  55
  56         low  = frame->sp;
  57         /* irq stacks are not THREAD_SIZE aligned */
  58         if (on_irq_stack(frame->sp, raw_smp_processor_id()))
  59                 high = irq_stack_ptr;
  60         else
  61                 high = ALIGN(low, THREAD_SIZE) - 0x20;
  62
  63         if (fp < low || fp > high || fp & 0xf)
  64                 return -EINVAL;
  65
  66         frame->sp = fp + 0x10;
  67         frame->fp = *(unsigned long *)(fp);
  68         frame->pc = *(unsigned long *)(fp + 8);
  69
  70 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  71         if (tsk && tsk->ret_stack &&
  72                         (frame->pc == (unsigned long)return_to_handler)) {
  73                 /*
  74                  * This is a case where function graph tracer has
  75                  * modified a return address (LR) in a stack frame
  76                  * to hook a function return.
  77                  * So replace it to an original value.
  78                  */
  79                 frame->pc = tsk->ret_stack[frame->graph--].ret;
  80         }
  81 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
  82
  83         /*
  84          * Check whether we are going to walk through from interrupt stack
  85          * to task stack.
  86          * If we reach the end of the stack - and its an interrupt stack,
  87          * unpack the dummy frame to find the original elr.
  88          *
  89          * Check the frame->fp we read from the bottom of the irq_stack,
  90          * and the original task stack pointer are both in current->stack.
  91          */
  92         if (frame->sp == irq_stack_ptr) {
  93                 struct pt_regs *irq_args;
  94                 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
  95
  96                 if (object_is_on_stack((void *)orig_sp) &&
  97                    object_is_on_stack((void *)frame->fp)) {
  98                         frame->sp = orig_sp;
  99
 100                         /* orig_sp is the saved pt_regs, find the elr */
 101                         irq_args = (struct pt_regs *)orig_sp;
 102                         frame->pc = irq_args->pc;
 103                 } else {
 104                         /*
 105                          * This frame has a non-standard format, and we
 106                          * didn't fix it, because the data looked wrong.
 107                          * Refuse to output this frame.
 108                          */
 109                         return -EINVAL;
 110                 }
 111         }
 112
 113         return 0;
 114 }
 115
 116 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 117                      int (*fn)(struct stackframe *, void *), void *data)
 118 {
 119         while (1) {
 120                 int ret;
 121
 122                 if (fn(frame, data))
 123                         break;
 124                 ret = unwind_frame(tsk, frame);
 125                 if (ret < 0)
 126                         break;
 127         }
 128 }
 129 EXPORT_SYMBOL(walk_stackframe);
 130
 131 #ifdef CONFIG_STACKTRACE
 132 struct stack_trace_data {
 133         struct stack_trace *trace;
 134         unsigned int no_sched_functions;
 135         unsigned int skip;
 136 };
 137
 138 static int save_trace(struct stackframe *frame, void *d)
 139 {
 140         struct stack_trace_data *data = d;
 141         struct stack_trace *trace = data->trace;
 142         unsigned long addr = frame->pc;
 143
 144         if (data->no_sched_functions && in_sched_functions(addr))
 145                 return 0;
 146         if (data->skip) {
 147                 data->skip--;
 148                 return 0;
 149         }
 150
 151         trace->entries[trace->nr_entries++] = addr;
 152
 153         return trace->nr_entries >= trace->max_entries;
 154 }
 155
 156 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 157 {
 158         struct stack_trace_data data;
 159         struct stackframe frame;
 160
 161         data.trace = trace;
 162         data.skip = trace->skip;
 163
 164         if (tsk != current) {
 165                 data.no_sched_functions = 1;
 166                 frame.fp = thread_saved_fp(tsk);
 167                 frame.sp = thread_saved_sp(tsk);
 168                 frame.pc = thread_saved_pc(tsk);
 169         } else {
 170                 data.no_sched_functions = 0;
 171                 frame.fp = (unsigned long)__builtin_frame_address(0);
 172                 frame.sp = current_stack_pointer;
 173                 frame.pc = (unsigned long)save_stack_trace_tsk;
 174         }
 175 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 176         frame.graph = tsk->curr_ret_stack;
 177 #endif
 178
 179         walk_stackframe(tsk, &frame, save_trace, &data);
 180         if (trace->nr_entries < trace->max_entries)
 181                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 182 }
 183
 184 void save_stack_trace(struct stack_trace *trace)
 185 {
 186         save_stack_trace_tsk(current, trace);
 187 }
 188 EXPORT_SYMBOL_GPL(save_stack_trace);
 189 #endif