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/sched/debug.h>
  23 #include <linux/sched/task_stack.h>
  24 #include <linux/stacktrace.h>
  25
  26 #include <asm/irq.h>
  27 #include <asm/stack_pointer.h>
  28 #include <asm/stacktrace.h>
  29
  30 /*
  31  * AArch64 PCS assigns the frame pointer to x29.
  32  *
  33  * A simple function prologue looks like this:
  34  *      sub     sp, sp, #0x10
  35  *      stp     x29, x30, [sp]
  36  *      mov     x29, sp
  37  *
  38  * A simple function epilogue looks like this:
  39  *      mov     sp, x29
  40  *      ldp     x29, x30, [sp]
  41  *      add     sp, sp, #0x10
  42  */
  43 int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
  44 {
  45         unsigned long high, low;
  46         unsigned long fp = frame->fp;
  47         unsigned long irq_stack_ptr;
  48
  49         if (!tsk)
  50                 tsk = current;
  51
  52         /*
  53          * Switching between stacks is valid when tracing current and in
  54          * non-preemptible context.
  55          */
  56         if (tsk == current && !preemptible())
  57                 irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
  58         else
  59                 irq_stack_ptr = 0;
  60
  61         low  = frame->sp;
  62         /* irq stacks are not THREAD_SIZE aligned */
  63         if (on_irq_stack(frame->sp, raw_smp_processor_id()))
  64                 high = irq_stack_ptr;
  65         else
  66                 high = ALIGN(low, THREAD_SIZE) - 0x20;
  67
  68         if (fp < low || fp > high || fp & 0xf)
  69                 return -EINVAL;
  70
  71         frame->sp = fp + 0x10;
  72         frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
  73         frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
  74
  75 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  76         if (tsk->ret_stack &&
  77                         (frame->pc == (unsigned long)return_to_handler)) {
  78                 /*
  79                  * This is a case where function graph tracer has
  80                  * modified a return address (LR) in a stack frame
  81                  * to hook a function return.
  82                  * So replace it to an original value.
  83                  */
  84                 frame->pc = tsk->ret_stack[frame->graph--].ret;
  85         }
  86 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
  87
  88         /*
  89          * Check whether we are going to walk through from interrupt stack
  90          * to task stack.
  91          * If we reach the end of the stack - and its an interrupt stack,
  92          * unpack the dummy frame to find the original elr.
  93          *
  94          * Check the frame->fp we read from the bottom of the irq_stack,
  95          * and the original task stack pointer are both in current->stack.
  96          */
  97         if (frame->sp == irq_stack_ptr) {
  98                 struct pt_regs *irq_args;
  99                 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
 100
 101                 if (object_is_on_stack((void *)orig_sp) &&
 102                    object_is_on_stack((void *)frame->fp)) {
 103                         frame->sp = orig_sp;
 104
 105                         /* orig_sp is the saved pt_regs, find the elr */
 106                         irq_args = (struct pt_regs *)orig_sp;
 107                         frame->pc = irq_args->pc;
 108                 } else {
 109                         /*
 110                          * This frame has a non-standard format, and we
 111                          * didn't fix it, because the data looked wrong.
 112                          * Refuse to output this frame.
 113                          */
 114                         return -EINVAL;
 115                 }
 116         }
 117
 118         return 0;
 119 }
 120
 121 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 122                      int (*fn)(struct stackframe *, void *), void *data)
 123 {
 124         while (1) {
 125                 int ret;
 126
 127                 if (fn(frame, data))
 128                         break;
 129                 ret = unwind_frame(tsk, frame);
 130                 if (ret < 0)
 131                         break;
 132         }
 133 }
 134
 135 #ifdef CONFIG_STACKTRACE
 136 struct stack_trace_data {
 137         struct stack_trace *trace;
 138         unsigned int no_sched_functions;
 139         unsigned int skip;
 140 };
 141
 142 static int save_trace(struct stackframe *frame, void *d)
 143 {
 144         struct stack_trace_data *data = d;
 145         struct stack_trace *trace = data->trace;
 146         unsigned long addr = frame->pc;
 147
 148         if (data->no_sched_functions && in_sched_functions(addr))
 149                 return 0;
 150         if (data->skip) {
 151                 data->skip--;
 152                 return 0;
 153         }
 154
 155         trace->entries[trace->nr_entries++] = addr;
 156
 157         return trace->nr_entries >= trace->max_entries;
 158 }
 159
 160 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 161 {
 162         struct stack_trace_data data;
 163         struct stackframe frame;
 164
 165         data.trace = trace;
 166         data.skip = trace->skip;
 167         data.no_sched_functions = 0;
 168
 169         frame.fp = regs->regs[29];
 170         frame.sp = regs->sp;
 171         frame.pc = regs->pc;
 172 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 173         frame.graph = current->curr_ret_stack;
 174 #endif
 175
 176         walk_stackframe(current, &frame, save_trace, &data);
 177         if (trace->nr_entries < trace->max_entries)
 178                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 179 }
 180
 181 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 182 {
 183         struct stack_trace_data data;
 184         struct stackframe frame;
 185
 186         if (!try_get_task_stack(tsk))
 187                 return;
 188
 189         data.trace = trace;
 190         data.skip = trace->skip;
 191
 192         if (tsk != current) {
 193                 data.no_sched_functions = 1;
 194                 frame.fp = thread_saved_fp(tsk);
 195                 frame.sp = thread_saved_sp(tsk);
 196                 frame.pc = thread_saved_pc(tsk);
 197         } else {
 198                 data.no_sched_functions = 0;
 199                 frame.fp = (unsigned long)__builtin_frame_address(0);
 200                 frame.sp = current_stack_pointer;
 201                 frame.pc = (unsigned long)save_stack_trace_tsk;
 202         }
 203 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 204         frame.graph = tsk->curr_ret_stack;
 205 #endif
 206
 207         walk_stackframe(tsk, &frame, save_trace, &data);
 208         if (trace->nr_entries < trace->max_entries)
 209                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 210
 211         put_task_stack(tsk);
 212 }
 213
 214 void save_stack_trace(struct stack_trace *trace)
 215 {
 216         save_stack_trace_tsk(current, trace);
 217 }
 218 EXPORT_SYMBOL_GPL(save_stack_trace);
 219 #endif