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))
  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                 if (WARN_ON_ONCE(frame->graph == -1))
  63                         return -EINVAL;
  64                 if (frame->graph < -1)
  65                         frame->graph += FTRACE_NOTRACE_DEPTH;
  66
  67                 /*
  68                  * This is a case where function graph tracer has
  69                  * modified a return address (LR) in a stack frame
  70                  * to hook a function return.
  71                  * So replace it to an original value.
  72                  */
  73                 frame->pc = tsk->ret_stack[frame->graph--].ret;
  74         }
  75 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
  76
  77         /*
  78          * Frames created upon entry from EL0 have NULL FP and PC values, so
  79          * don't bother reporting these. Frames created by __noreturn functions
  80          * might have a valid FP even if PC is bogus, so only terminate where
  81          * both are NULL.
  82          */
  83         if (!frame->fp && !frame->pc)
  84                 return -EINVAL;
  85
  86         return 0;
  87 }
  88
  89 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
  90                      int (*fn)(struct stackframe *, void *), void *data)
  91 {
  92         while (1) {
  93                 int ret;
  94
  95                 if (fn(frame, data))
  96                         break;
  97                 ret = unwind_frame(tsk, frame);
  98                 if (ret < 0)
  99                         break;
 100         }
 101 }
 102
 103 #ifdef CONFIG_STACKTRACE
 104 struct stack_trace_data {
 105         struct stack_trace *trace;
 106         unsigned int no_sched_functions;
 107         unsigned int skip;
 108 };
 109
 110 static int save_trace(struct stackframe *frame, void *d)
 111 {
 112         struct stack_trace_data *data = d;
 113         struct stack_trace *trace = data->trace;
 114         unsigned long addr = frame->pc;
 115
 116         if (data->no_sched_functions && in_sched_functions(addr))
 117                 return 0;
 118         if (data->skip) {
 119                 data->skip--;
 120                 return 0;
 121         }
 122
 123         trace->entries[trace->nr_entries++] = addr;
 124
 125         return trace->nr_entries >= trace->max_entries;
 126 }
 127
 128 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 129 {
 130         struct stack_trace_data data;
 131         struct stackframe frame;
 132
 133         data.trace = trace;
 134         data.skip = trace->skip;
 135         data.no_sched_functions = 0;
 136
 137         frame.fp = regs->regs[29];
 138         frame.pc = regs->pc;
 139 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 140         frame.graph = current->curr_ret_stack;
 141 #endif
 142
 143         walk_stackframe(current, &frame, save_trace, &data);
 144         if (trace->nr_entries < trace->max_entries)
 145                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 146 }
 147
 148 static noinline void __save_stack_trace(struct task_struct *tsk,
 149         struct stack_trace *trace, unsigned int nosched)
 150 {
 151         struct stack_trace_data data;
 152         struct stackframe frame;
 153
 154         if (!try_get_task_stack(tsk))
 155                 return;
 156
 157         data.trace = trace;
 158         data.skip = trace->skip;
 159         data.no_sched_functions = nosched;
 160
 161         if (tsk != current) {
 162                 frame.fp = thread_saved_fp(tsk);
 163                 frame.pc = thread_saved_pc(tsk);
 164         } else {
 165                 /* We don't want this function nor the caller */
 166                 data.skip += 2;
 167                 frame.fp = (unsigned long)__builtin_frame_address(0);
 168                 frame.pc = (unsigned long)__save_stack_trace;
 169         }
 170 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 171         frame.graph = tsk->curr_ret_stack;
 172 #endif
 173
 174         walk_stackframe(tsk, &frame, save_trace, &data);
 175         if (trace->nr_entries < trace->max_entries)
 176                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 177
 178         put_task_stack(tsk);
 179 }
 180 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
 181
 182 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 183 {
 184         __save_stack_trace(tsk, trace, 1);
 185 }
 186
 187 void save_stack_trace(struct stack_trace *trace)
 188 {
 189         __save_stack_trace(current, trace, 0);
 190 }
 191
 192 EXPORT_SYMBOL_GPL(save_stack_trace);
 193 #endif