stacktrace.c

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/*
 * Stacktrace support for Hexagon
 *
 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#include <linux/sched.h>
#include <linux/stacktrace.h>
#include <linux/thread_info.h>
#include <linux/module.h>

register unsigned long current_frame_pointer asm("r30");

struct stackframe {
    unsigned long fp;
    unsigned long rets;
};

/*
 * Save stack-backtrace addresses into a stack_trace buffer.
 */
void save_stack_trace(struct stack_trace *trace)
{
    unsigned long low, high;
    unsigned long fp;
    struct stackframe *frame;
    int skip = trace->skip;

    low = (unsigned long)task_stack_page(current);
    high = low + THREAD_SIZE;
    fp = current_frame_pointer;

    while (fp >= low && fp <= (high - sizeof(*frame))) {
        frame = (struct stackframe *)fp;

        if (skip) {
            skip--;
        } else {
            trace->entries[trace->nr_entries++] = frame->rets;
            if (trace->nr_entries >= trace->max_entries)
                break;
        }

        /*
         * The next frame must be at a higher address than the
         * current frame.
         */
        low = fp + sizeof(*frame);
        fp = frame->fp;
    }
}
EXPORT_SYMBOL_GPL(save_stack_trace);