drivers/gator/gator_annotate.c

/**
 * Copyright (C) Arm Limited 2010-2016. 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 as
 * published by the Free Software Foundation.
 *
 */

#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/uaccess.h>
#include <asm/current.h>
#include <linux/spinlock.h>

static DEFINE_SPINLOCK(annotate_lock);
static bool collect_annotations;

static int annotate_copy(struct file *file, char const __user *buf, size_t count)
{
    int cpu = 0;
    int write = per_cpu(gator_buffer_write, cpu)[ANNOTATE_BUF];

    if (file == NULL) {
        /* copy from kernel */
        memcpy(&per_cpu(gator_buffer, cpu)[ANNOTATE_BUF][write], buf, count);
    } else {
        /* copy from user space */
        if (copy_from_user(&per_cpu(gator_buffer, cpu)[ANNOTATE_BUF][write], buf, count) != 0)
            return -1;
    }
    per_cpu(gator_buffer_write, cpu)[ANNOTATE_BUF] = (write + count) & gator_buffer_mask[ANNOTATE_BUF];

    return 0;
}

static ssize_t annotate_write(struct file *file, char const __user *buf, size_t count_orig, loff_t *offset)
{
    int pid, cpu, header_size, available, contiguous, length1, length2, size, count = count_orig & 0x7fffffff;
    bool interrupt_context;

    if (*offset)
        return -EINVAL;

    interrupt_context = in_interrupt();
    /* Annotations are not supported in interrupt context, but may work
     * if you comment out the the next four lines of code. By doing so,
     * annotations in interrupt context can result in deadlocks and lost
     * data.
     */
    if (interrupt_context) {
        pr_warning("gator: Annotations are not supported in interrupt context. Edit gator_annotate.c in the gator driver to enable annotations in interrupt context.\n");
        return -EINVAL;
    }

 retry:
    /* synchronize between cores and with collect_annotations */
    spin_lock(&annotate_lock);

    if (!collect_annotations) {
        /* Not collecting annotations, tell the caller everything was written */
        size = count_orig;
        goto annotate_write_out;
    }

    /* Annotation only uses a single per-cpu buffer as the data must be in order to the engine */
    cpu = 0;

    if (current == NULL)
        pid = 0;
    else
        pid = current->pid;

    /* determine total size of the payload */
    header_size = MAXSIZE_PACK32 * 3 + MAXSIZE_PACK64;
    available = buffer_bytes_available(cpu, ANNOTATE_BUF) - header_size;
    size = count < available ? count : available;

    if (size <= 0) {
        /* Buffer is full, wait until space is available */
        spin_unlock(&annotate_lock);

        /* Drop the annotation as blocking is not allowed in interrupt context */
        if (interrupt_context)
            return -EINVAL;

        wait_event_interruptible(gator_annotate_wait, buffer_bytes_available(cpu, ANNOTATE_BUF) > header_size || !collect_annotations);

        /* Check to see if a signal is pending */
        if (signal_pending(current))
            return -EINTR;

        goto retry;
    }

    /* synchronize shared variables annotateBuf and annotatePos */
    if (per_cpu(gator_buffer, cpu)[ANNOTATE_BUF]) {
        u64 time = gator_get_time();

        gator_buffer_write_packed_int(cpu, ANNOTATE_BUF, get_physical_cpu());
        gator_buffer_write_packed_int(cpu, ANNOTATE_BUF, pid);
        gator_buffer_write_packed_int64(cpu, ANNOTATE_BUF, time);
        gator_buffer_write_packed_int(cpu, ANNOTATE_BUF, size);

        /* determine the sizes to capture, length1 + length2 will equal size */
        contiguous = contiguous_space_available(cpu, ANNOTATE_BUF);
        if (size < contiguous) {
            length1 = size;
            length2 = 0;
        } else {
            length1 = contiguous;
            length2 = size - contiguous;
        }

        if (annotate_copy(file, buf, length1) != 0) {
            size = -EINVAL;
            goto annotate_write_out;
        }

        if (length2 > 0 && annotate_copy(file, &buf[length1], length2) != 0) {
            size = -EINVAL;
            goto annotate_write_out;
        }

        /* Check and commit; commit is set to occur once buffer is 3/4 full */
        buffer_check(cpu, ANNOTATE_BUF, time);
    }

annotate_write_out:
    spin_unlock(&annotate_lock);

    /* return the number of bytes written */
    return size;
}

#include "gator_annotate_kernel.c"

static int annotate_release(struct inode *inode, struct file *file)
{
    int cpu = 0;

    /* synchronize between cores */
    spin_lock(&annotate_lock);

    if (per_cpu(gator_buffer, cpu)[ANNOTATE_BUF] && buffer_check_space(cpu, ANNOTATE_BUF, MAXSIZE_PACK64 + 3 * MAXSIZE_PACK32)) {
        uint32_t pid = current->pid;

        gator_buffer_write_packed_int(cpu, ANNOTATE_BUF, get_physical_cpu());
        gator_buffer_write_packed_int(cpu, ANNOTATE_BUF, pid);
        /* time */
        gator_buffer_write_packed_int64(cpu, ANNOTATE_BUF, 0);
        /* size */
        gator_buffer_write_packed_int(cpu, ANNOTATE_BUF, 0);
    }

    /* Check and commit; commit is set to occur once buffer is 3/4 full */
    buffer_check(cpu, ANNOTATE_BUF, gator_get_time());

    spin_unlock(&annotate_lock);

    return 0;
}

static const struct file_operations annotate_fops = {
    .write = annotate_write,
    .release = annotate_release
};

static int gator_annotate_create_files(struct super_block *sb, struct dentry *root)
{
    return gatorfs_create_file_perm(sb, root, "annotate", &annotate_fops, 0666);
}

static int gator_annotate_start(void)
{
    collect_annotations = true;
    return 0;
}

static void gator_annotate_stop(void)
{
    /* the spinlock here will ensure that when this function exits, we are not in the middle of an annotation */
    spin_lock(&annotate_lock);
    collect_annotations = false;
    wake_up(&gator_annotate_wait);
    spin_unlock(&annotate_lock);
}