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 fp = frame->fp;
  46
  47         if (fp & 0xf)
  48                 return -EINVAL;
  49
  50         if (!tsk)
  51                 tsk = current;
  52
  53         if (!on_accessible_stack(tsk, fp, NULL))
  54                 return -EINVAL;
  55
  56         frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
  57         frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
  58
  59 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  60         if (tsk->ret_stack &&
  61                         (frame->pc == (unsigned long)return_to_handler)) {
  62                 struct ftrace_ret_stack *ret_stack;
  63                 /*
  64                  * This is a case where function graph tracer has
  65                  * modified a return address (LR) in a stack frame
  66                  * to hook a function return.
  67                  * So replace it to an original value.
  68                  */
  69                 ret_stack = ftrace_graph_get_ret_stack(tsk, frame->graph++);
  70                 if (WARN_ON_ONCE(!ret_stack))
  71                         return -EINVAL;
  72                 frame->pc = ret_stack->ret;
  73         }
  74 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
  75
  76         /*
  77          * Frames created upon entry from EL0 have NULL FP and PC values, so
  78          * don't bother reporting these. Frames created by __noreturn functions
  79          * might have a valid FP even if PC is bogus, so only terminate where
  80          * both are NULL.
  81          */
  82         if (!frame->fp && !frame->pc)
  83                 return -EINVAL;
  84
  85         return 0;
  86 }
  87
  88 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
  89                      int (*fn)(struct stackframe *, void *), void *data)
  90 {
  91         while (1) {
  92                 int ret;
  93
  94                 if (fn(frame, data))
  95                         break;
  96                 ret = unwind_frame(tsk, frame);
  97                 if (ret < 0)
  98                         break;
  99         }
 100 }
 101
 102 #ifdef CONFIG_STACKTRACE
 103 struct stack_trace_data {
 104         struct stack_trace *trace;
 105         unsigned int no_sched_functions;
 106         unsigned int skip;
 107 };
 108
 109 static int save_trace(struct stackframe *frame, void *d)
 110 {
 111         struct stack_trace_data *data = d;
 112         struct stack_trace *trace = data->trace;
 113         unsigned long addr = frame->pc;
 114
 115         if (data->no_sched_functions && in_sched_functions(addr))
 116                 return 0;
 117         if (data->skip) {
 118                 data->skip--;
 119                 return 0;
 120         }
 121
 122         trace->entries[trace->nr_entries++] = addr;
 123
 124         return trace->nr_entries >= trace->max_entries;
 125 }
 126
 127 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 128 {
 129         struct stack_trace_data data;
 130         struct stackframe frame;
 131
 132         data.trace = trace;
 133         data.skip = trace->skip;
 134         data.no_sched_functions = 0;
 135
 136         frame.fp = regs->regs[29];
 137         frame.pc = regs->pc;
 138 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 139         frame.graph = 0;
 140 #endif
 141
 142         walk_stackframe(current, &frame, save_trace, &data);
 143 }
 144 EXPORT_SYMBOL_GPL(save_stack_trace_regs);
 145
 146 static noinline void __save_stack_trace(struct task_struct *tsk,
 147         struct stack_trace *trace, unsigned int nosched)
 148 {
 149         struct stack_trace_data data;
 150         struct stackframe frame;
 151
 152         if (!try_get_task_stack(tsk))
 153                 return;
 154
 155         data.trace = trace;
 156         data.skip = trace->skip;
 157         data.no_sched_functions = nosched;
 158
 159         if (tsk != current) {
 160                 frame.fp = thread_saved_fp(tsk);
 161                 frame.pc = thread_saved_pc(tsk);
 162         } else {
 163                 /* We don't want this function nor the caller */
 164                 data.skip += 2;
 165                 frame.fp = (unsigned long)__builtin_frame_address(0);
 166                 frame.pc = (unsigned long)__save_stack_trace;
 167         }
 168 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 169         frame.graph = 0;
 170 #endif
 171
 172         walk_stackframe(tsk, &frame, save_trace, &data);
 173
 174         put_task_stack(tsk);
 175 }
 176 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
 177
 178 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 179 {
 180         __save_stack_trace(tsk, trace, 1);
 181 }
 182
 183 void save_stack_trace(struct stack_trace *trace)
 184 {
 185         __save_stack_trace(current, trace, 0);
 186 }
 187
 188 EXPORT_SYMBOL_GPL(save_stack_trace);
 189 #endif