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         if (!tsk)
  47                 tsk = current;
  48
  49         /*
  50          * Switching between stacks is valid when tracing current and in
  51          * non-preemptible context.
  52          */
  53         if (tsk == current && !preemptible())
  54                 irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
  55         else
  56                 irq_stack_ptr = 0;
  57
  58         low  = frame->sp;
  59         /* irq stacks are not THREAD_SIZE aligned */
  60         if (on_irq_stack(frame->sp, raw_smp_processor_id()))
  61                 high = irq_stack_ptr;
  62         else
  63                 high = ALIGN(low, THREAD_SIZE) - 0x20;
  64
  65         if (fp < low || fp > high || fp & 0xf)
  66                 return -EINVAL;
  67
  68         frame->sp = fp + 0x10;
  69         frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
  70         frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
  71
  72 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  73         if (tsk->ret_stack &&
  74                         (frame->pc == (unsigned long)return_to_handler)) {
  75                 /*
  76                  * This is a case where function graph tracer has
  77                  * modified a return address (LR) in a stack frame
  78                  * to hook a function return.
  79                  * So replace it to an original value.
  80                  */
  81                 frame->pc = tsk->ret_stack[frame->graph--].ret;
  82         }
  83 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
  84
  85         /*
  86          * Check whether we are going to walk through from interrupt stack
  87          * to task stack.
  88          * If we reach the end of the stack - and its an interrupt stack,
  89          * unpack the dummy frame to find the original elr.
  90          *
  91          * Check the frame->fp we read from the bottom of the irq_stack,
  92          * and the original task stack pointer are both in current->stack.
  93          */
  94         if (frame->sp == irq_stack_ptr) {
  95                 struct pt_regs *irq_args;
  96                 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
  97
  98                 if (object_is_on_stack((void *)orig_sp) &&
  99                    object_is_on_stack((void *)frame->fp)) {
 100                         frame->sp = orig_sp;
 101
 102                         /* orig_sp is the saved pt_regs, find the elr */
 103                         irq_args = (struct pt_regs *)orig_sp;
 104                         frame->pc = irq_args->pc;
 105                 } else {
 106                         /*
 107                          * This frame has a non-standard format, and we
 108                          * didn't fix it, because the data looked wrong.
 109                          * Refuse to output this frame.
 110                          */
 111                         return -EINVAL;
 112                 }
 113         }
 114
 115         return 0;
 116 }
 117
 118 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 119                      int (*fn)(struct stackframe *, void *), void *data)
 120 {
 121         while (1) {
 122                 int ret;
 123
 124                 if (fn(frame, data))
 125                         break;
 126                 ret = unwind_frame(tsk, frame);
 127                 if (ret < 0)
 128                         break;
 129         }
 130 }
 131 EXPORT_SYMBOL(walk_stackframe);
 132
 133 #ifdef CONFIG_STACKTRACE
 134 struct stack_trace_data {
 135         struct stack_trace *trace;
 136         unsigned int no_sched_functions;
 137         unsigned int skip;
 138 };
 139
 140 static int save_trace(struct stackframe *frame, void *d)
 141 {
 142         struct stack_trace_data *data = d;
 143         struct stack_trace *trace = data->trace;
 144         unsigned long addr = frame->pc;
 145
 146         if (data->no_sched_functions && in_sched_functions(addr))
 147                 return 0;
 148         if (data->skip) {
 149                 data->skip--;
 150                 return 0;
 151         }
 152
 153         trace->entries[trace->nr_entries++] = addr;
 154
 155         return trace->nr_entries >= trace->max_entries;
 156 }
 157
 158 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 159 {
 160         struct stack_trace_data data;
 161         struct stackframe frame;
 162
 163         data.trace = trace;
 164         data.skip = trace->skip;
 165
 166         if (tsk != current) {
 167                 data.no_sched_functions = 1;
 168                 frame.fp = thread_saved_fp(tsk);
 169                 frame.sp = thread_saved_sp(tsk);
 170                 frame.pc = thread_saved_pc(tsk);
 171         } else {
 172                 data.no_sched_functions = 0;
 173                 frame.fp = (unsigned long)__builtin_frame_address(0);
 174                 frame.sp = current_stack_pointer;
 175                 frame.pc = (unsigned long)save_stack_trace_tsk;
 176         }
 177 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 178         frame.graph = tsk->curr_ret_stack;
 179 #endif
 180
 181         walk_stackframe(tsk, &frame, save_trace, &data);
 182         if (trace->nr_entries < trace->max_entries)
 183                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 184 }
 185
 186 void save_stack_trace(struct stack_trace *trace)
 187 {
 188         save_stack_trace_tsk(current, trace);
 189 }
 190 EXPORT_SYMBOL_GPL(save_stack_trace);
 191 #endif