linux/arch/arm64/kernel/stacktrace.c
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   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/sched.h>
  21#include <linux/stacktrace.h>
  22
  23#include <asm/stacktrace.h>
  24
  25/*
  26 * AArch64 PCS assigns the frame pointer to x29.
  27 *
  28 * A simple function prologue looks like this:
  29 *      sub     sp, sp, #0x10
  30 *      stp     x29, x30, [sp]
  31 *      mov     x29, sp
  32 *
  33 * A simple function epilogue looks like this:
  34 *      mov     sp, x29
  35 *      ldp     x29, x30, [sp]
  36 *      add     sp, sp, #0x10
  37 */
  38int unwind_frame(struct stackframe *frame)
  39{
  40        unsigned long high, low;
  41        unsigned long fp = frame->fp;
  42
  43        low  = frame->sp;
  44        high = ALIGN(low, THREAD_SIZE);
  45
  46        if (fp < low || fp > high || fp & 0xf)
  47                return -EINVAL;
  48
  49        frame->sp = fp + 0x10;
  50        frame->fp = *(unsigned long *)(fp);
  51        frame->pc = *(unsigned long *)(fp + 8);
  52
  53        return 0;
  54}
  55
  56void notrace walk_stackframe(struct stackframe *frame,
  57                     int (*fn)(struct stackframe *, void *), void *data)
  58{
  59        while (1) {
  60                int ret;
  61
  62                if (fn(frame, data))
  63                        break;
  64                ret = unwind_frame(frame);
  65                if (ret < 0)
  66                        break;
  67        }
  68}
  69EXPORT_SYMBOL(walk_stackframe);
  70
  71#ifdef CONFIG_STACKTRACE
  72struct stack_trace_data {
  73        struct stack_trace *trace;
  74        unsigned int no_sched_functions;
  75        unsigned int skip;
  76};
  77
  78static int save_trace(struct stackframe *frame, void *d)
  79{
  80        struct stack_trace_data *data = d;
  81        struct stack_trace *trace = data->trace;
  82        unsigned long addr = frame->pc;
  83
  84        if (data->no_sched_functions && in_sched_functions(addr))
  85                return 0;
  86        if (data->skip) {
  87                data->skip--;
  88                return 0;
  89        }
  90
  91        trace->entries[trace->nr_entries++] = addr;
  92
  93        return trace->nr_entries >= trace->max_entries;
  94}
  95
  96void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
  97{
  98        struct stack_trace_data data;
  99        struct stackframe frame;
 100
 101        data.trace = trace;
 102        data.skip = trace->skip;
 103
 104        if (tsk != current) {
 105                data.no_sched_functions = 1;
 106                frame.fp = thread_saved_fp(tsk);
 107                frame.sp = thread_saved_sp(tsk);
 108                frame.pc = thread_saved_pc(tsk);
 109        } else {
 110                register unsigned long current_sp asm("sp");
 111                data.no_sched_functions = 0;
 112                frame.fp = (unsigned long)__builtin_frame_address(0);
 113                frame.sp = current_sp;
 114                frame.pc = (unsigned long)save_stack_trace_tsk;
 115        }
 116
 117        walk_stackframe(&frame, save_trace, &data);
 118        if (trace->nr_entries < trace->max_entries)
 119                trace->entries[trace->nr_entries++] = ULONG_MAX;
 120}
 121
 122void save_stack_trace(struct stack_trace *trace)
 123{
 124        save_stack_trace_tsk(current, trace);
 125}
 126EXPORT_SYMBOL_GPL(save_stack_trace);
 127#endif
 128