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          * Switching between stacks is valid when tracing current and in
  48          * non-preemptible context.
  49          */
  50         if (tsk == current && !preemptible())
  51                 irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
  52         else
  53                 irq_stack_ptr = 0;
  54
  55         low  = frame->sp;
  56         /* irq stacks are not THREAD_SIZE aligned */
  57         if (on_irq_stack(frame->sp, raw_smp_processor_id()))
  58                 high = irq_stack_ptr;
  59         else
  60                 high = ALIGN(low, THREAD_SIZE) - 0x20;
  61
  62         if (fp < low || fp > high || fp & 0xf)
  63                 return -EINVAL;
  64
  65         frame->sp = fp + 0x10;
  66         frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
  67         frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
  68
  69 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  70         if (tsk && tsk->ret_stack &&
  71                         (frame->pc == (unsigned long)return_to_handler)) {
  72                 /*
  73                  * This is a case where function graph tracer has
  74                  * modified a return address (LR) in a stack frame
  75                  * to hook a function return.
  76                  * So replace it to an original value.
  77                  */
  78                 frame->pc = tsk->ret_stack[frame->graph--].ret;
  79         }
  80 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
  81
  82         /*
  83          * Check whether we are going to walk through from interrupt stack
  84          * to task stack.
  85          * If we reach the end of the stack - and its an interrupt stack,
  86          * unpack the dummy frame to find the original elr.
  87          *
  88          * Check the frame->fp we read from the bottom of the irq_stack,
  89          * and the original task stack pointer are both in current->stack.
  90          */
  91         if (frame->sp == irq_stack_ptr) {
  92                 struct pt_regs *irq_args;
  93                 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
  94
  95                 if (object_is_on_stack((void *)orig_sp) &&
  96                    object_is_on_stack((void *)frame->fp)) {
  97                         frame->sp = orig_sp;
  98
  99                         /* orig_sp is the saved pt_regs, find the elr */
 100                         irq_args = (struct pt_regs *)orig_sp;
 101                         frame->pc = irq_args->pc;
 102                 } else {
 103                         /*
 104                          * This frame has a non-standard format, and we
 105                          * didn't fix it, because the data looked wrong.
 106                          * Refuse to output this frame.
 107                          */
 108                         return -EINVAL;
 109                 }
 110         }
 111
 112         return 0;
 113 }
 114
 115 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 116                      int (*fn)(struct stackframe *, void *), void *data)
 117 {
 118         while (1) {
 119                 int ret;
 120
 121                 if (fn(frame, data))
 122                         break;
 123                 ret = unwind_frame(tsk, frame);
 124                 if (ret < 0)
 125                         break;
 126         }
 127 }
 128 EXPORT_SYMBOL(walk_stackframe);
 129
 130 #ifdef CONFIG_STACKTRACE
 131 struct stack_trace_data {
 132         struct stack_trace *trace;
 133         unsigned int no_sched_functions;
 134         unsigned int skip;
 135 };
 136
 137 static int save_trace(struct stackframe *frame, void *d)
 138 {
 139         struct stack_trace_data *data = d;
 140         struct stack_trace *trace = data->trace;
 141         unsigned long addr = frame->pc;
 142
 143         if (data->no_sched_functions && in_sched_functions(addr))
 144                 return 0;
 145         if (data->skip) {
 146                 data->skip--;
 147                 return 0;
 148         }
 149
 150         trace->entries[trace->nr_entries++] = addr;
 151
 152         return trace->nr_entries >= trace->max_entries;
 153 }
 154
 155 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 156 {
 157         struct stack_trace_data data;
 158         struct stackframe frame;
 159
 160         data.trace = trace;
 161         data.skip = trace->skip;
 162
 163         if (tsk != current) {
 164                 data.no_sched_functions = 1;
 165                 frame.fp = thread_saved_fp(tsk);
 166                 frame.sp = thread_saved_sp(tsk);
 167                 frame.pc = thread_saved_pc(tsk);
 168         } else {
 169                 data.no_sched_functions = 0;
 170                 frame.fp = (unsigned long)__builtin_frame_address(0);
 171                 frame.sp = current_stack_pointer;
 172                 frame.pc = (unsigned long)save_stack_trace_tsk;
 173         }
 174 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 175         frame.graph = tsk->curr_ret_stack;
 176 #endif
 177
 178         walk_stackframe(tsk, &frame, save_trace, &data);
 179         if (trace->nr_entries < trace->max_entries)
 180                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 181 }
 182
 183 void save_stack_trace(struct stack_trace *trace)
 184 {
 185         save_stack_trace_tsk(current, trace);
 186 }
 187 EXPORT_SYMBOL_GPL(save_stack_trace);
 188 #endif