stacktrace.c

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/*
 * Stack tracing support
 *
 * Copyright (C) 2012 ARM Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/stacktrace.h>

#include <asm/stacktrace.h>

/*
 * AArch64 PCS assigns the frame pointer to x29.
 *
 * A simple function prologue looks like this:
 *  sub sp, sp, #0x10
 *      stp x29, x30, [sp]
 *  mov x29, sp
 *
 * A simple function epilogue looks like this:
 *  mov sp, x29
 *  ldp x29, x30, [sp]
 *  add sp, sp, #0x10
 */
int unwind_frame(struct stackframe *frame)
{
    unsigned long high, low;
    unsigned long fp = frame->fp;

    low  = frame->sp;
    high = ALIGN(low, THREAD_SIZE);

    if (fp < low || fp > high || fp & 0xf)
        return -EINVAL;

    frame->sp = fp + 0x10;
    frame->fp = *(unsigned long *)(fp);
    frame->pc = *(unsigned long *)(fp + 8);

    return 0;
}

void notrace walk_stackframe(struct stackframe *frame,
             int (*fn)(struct stackframe *, void *), void *data)
{
    while (1) {
        int ret;

        if (fn(frame, data))
            break;
        ret = unwind_frame(frame);
        if (ret < 0)
            break;
    }
}
EXPORT_SYMBOL(walk_stackframe);

#ifdef CONFIG_STACKTRACE
struct stack_trace_data {
    struct stack_trace *trace;
    unsigned int no_sched_functions;
    unsigned int skip;
};

static int save_trace(struct stackframe *frame, void *d)
{
    struct stack_trace_data *data = d;
    struct stack_trace *trace = data->trace;
    unsigned long addr = frame->pc;

    if (data->no_sched_functions && in_sched_functions(addr))
        return 0;
    if (data->skip) {
        data->skip--;
        return 0;
    }

    trace->entries[trace->nr_entries++] = addr;

    return trace->nr_entries >= trace->max_entries;
}

void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
    struct stack_trace_data data;
    struct stackframe frame;

    data.trace = trace;
    data.skip = trace->skip;

    if (tsk != current) {
        data.no_sched_functions = 1;
        frame.fp = thread_saved_fp(tsk);
        frame.sp = thread_saved_sp(tsk);
        frame.pc = thread_saved_pc(tsk);
    } else {
        register unsigned long current_sp asm("sp");
        data.no_sched_functions = 0;
        frame.fp = (unsigned long)__builtin_frame_address(0);
        frame.sp = current_sp;
        frame.pc = (unsigned long)save_stack_trace_tsk;
    }

    walk_stackframe(&frame, save_trace, &data);
    if (trace->nr_entries < trace->max_entries)
        trace->entries[trace->nr_entries++] = ULONG_MAX;
}

void save_stack_trace(struct stack_trace *trace)
{
    save_stack_trace_tsk(current, trace);
}
EXPORT_SYMBOL_GPL(save_stack_trace);
#endif