LXR linux/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/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 notrace 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 - 0x18 || fp & 0xf)
  47                return -EINVAL;
  48
  49        frame->sp = fp + 0x10;
  50        frame->fp = *(unsigned long *)(fp);
  51        /*
  52         * -4 here because we care about the PC at time of bl,
  53         * not where the return will go.
  54         */
  55        frame->pc = *(unsigned long *)(fp + 8) - 4;
  56
  57        return 0;
  58}
  59
  60void notrace walk_stackframe(struct stackframe *frame,
  61                     int (*fn)(struct stackframe *, void *), void *data)
  62{
  63        while (1) {
  64                int ret;
  65
  66                if (fn(frame, data))
  67                        break;
  68                ret = unwind_frame(frame);
  69                if (ret < 0)
  70                        break;
  71        }
  72}
  73EXPORT_SYMBOL(walk_stackframe);
  74
  75#ifdef CONFIG_STACKTRACE
  76struct stack_trace_data {
  77        struct stack_trace *trace;
  78        unsigned int no_sched_functions;
  79        unsigned int skip;
  80};
  81
  82static int save_trace(struct stackframe *frame, void *d)
  83{
  84        struct stack_trace_data *data = d;
  85        struct stack_trace *trace = data->trace;
  86        unsigned long addr = frame->pc;
  87
  88        if (data->no_sched_functions && in_sched_functions(addr))
  89                return 0;
  90        if (data->skip) {
  91                data->skip--;
  92                return 0;
  93        }
  94
  95        trace->entries[trace->nr_entries++] = addr;
  96
  97        return trace->nr_entries >= trace->max_entries;
  98}
  99
 100void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 101{
 102        struct stack_trace_data data;
 103        struct stackframe frame;
 104
 105        data.trace = trace;
 106        data.skip = trace->skip;
 107
 108        if (tsk != current) {
 109                data.no_sched_functions = 1;
 110                frame.fp = thread_saved_fp(tsk);
 111                frame.sp = thread_saved_sp(tsk);
 112                frame.pc = thread_saved_pc(tsk);
 113        } else {
 114                register unsigned long current_sp asm("sp");
 115                data.no_sched_functions = 0;
 116                frame.fp = (unsigned long)__builtin_frame_address(0);
 117                frame.sp = current_sp;
 118                frame.pc = (unsigned long)save_stack_trace_tsk;
 119        }
 120
 121        walk_stackframe(&frame, save_trace, &data);
 122        if (trace->nr_entries < trace->max_entries)
 123                trace->entries[trace->nr_entries++] = ULONG_MAX;
 124}
 125
 126void save_stack_trace(struct stack_trace *trace)
 127{
 128        save_stack_trace_tsk(current, trace);
 129}
 130EXPORT_SYMBOL_GPL(save_stack_trace);
 131#endif
 132