scanlog.c

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/*
 *  c 2001 PPC 64 Team, IBM Corp
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 * scan-log-data driver for PPC64  Todd Inglett <[email protected]>
 *
 * When ppc64 hardware fails the service processor dumps internal state
 * of the system.  After a reboot the operating system can access a dump
 * of this data using this driver.  A dump exists if the device-tree
 * /chosen/ibm,scan-log-data property exists.
 *
 * This driver exports /proc/powerpc/scan-log-dump which can be read.
 * The driver supports only sequential reads.
 *
 * The driver looks at a write to the driver for the single word "reset".
 * If given, the driver will reset the scanlog so the platform can free it.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/rtas.h>
#include <asm/prom.h>

#define MODULE_VERS "1.0"
#define MODULE_NAME "scanlog"

/* Status returns from ibm,scan-log-dump */
#define SCANLOG_COMPLETE 0
#define SCANLOG_HWERROR -1
#define SCANLOG_CONTINUE 1


static unsigned int ibm_scan_log_dump;          /* RTAS token */
static struct proc_dir_entry *proc_ppc64_scan_log_dump; /* The proc file */

static ssize_t scanlog_read(struct file *file, char __user *buf,
                size_t count, loff_t *ppos)
{
        struct inode * inode = file->f_path.dentry->d_inode;
    struct proc_dir_entry *dp;
    unsigned int *data;
    int status;
    unsigned long len, off;
    unsigned int wait_time;

        dp = PDE(inode);
    data = (unsigned int *)dp->data;

    if (count > RTAS_DATA_BUF_SIZE)
        count = RTAS_DATA_BUF_SIZE;

    if (count < 1024) {
        /* This is the min supported by this RTAS call.  Rather
         * than do all the buffering we insist the user code handle
         * larger reads.  As long as cp works... :)
         */
        printk(KERN_ERR "scanlog: cannot perform a small read (%ld)\n", count);
        return -EINVAL;
    }

    if (!access_ok(VERIFY_WRITE, buf, count))
        return -EFAULT;

    for (;;) {
        wait_time = 500;    /* default wait if no data */
        spin_lock(&rtas_data_buf_lock);
        memcpy(rtas_data_buf, data, RTAS_DATA_BUF_SIZE);
        status = rtas_call(ibm_scan_log_dump, 2, 1, NULL,
                   (u32) __pa(rtas_data_buf), (u32) count);
        memcpy(data, rtas_data_buf, RTAS_DATA_BUF_SIZE);
        spin_unlock(&rtas_data_buf_lock);

        pr_debug("scanlog: status=%d, data[0]=%x, data[1]=%x, " \
             "data[2]=%x\n", status, data[0], data[1], data[2]);
        switch (status) {
            case SCANLOG_COMPLETE:
            pr_debug("scanlog: hit eof\n");
            return 0;
            case SCANLOG_HWERROR:
            pr_debug("scanlog: hardware error reading data\n");
            return -EIO;
            case SCANLOG_CONTINUE:
            /* We may or may not have data yet */
            len = data[1];
            off = data[2];
            if (len > 0) {
                if (copy_to_user(buf, ((char *)data)+off, len))
                    return -EFAULT;
                return len;
            }
            /* Break to sleep default time */
            break;
            default:
            /* Assume extended busy */
            wait_time = rtas_busy_delay_time(status);
            if (!wait_time) {
                printk(KERN_ERR "scanlog: unknown error " \
                       "from rtas: %d\n", status);
                return -EIO;
            }
        }
        /* Apparently no data yet.  Wait and try again. */
        msleep_interruptible(wait_time);
    }
    /*NOTREACHED*/
}

static ssize_t scanlog_write(struct file * file, const char __user * buf,
                 size_t count, loff_t *ppos)
{
    char stkbuf[20];
    int status;

    if (count > 19) count = 19;
    if (copy_from_user (stkbuf, buf, count)) {
        return -EFAULT;
    }
    stkbuf[count] = 0;

    if (buf) {
        if (strncmp(stkbuf, "reset", 5) == 0) {
            pr_debug("scanlog: reset scanlog\n");
            status = rtas_call(ibm_scan_log_dump, 2, 1, NULL, 0, 0);
            pr_debug("scanlog: rtas returns %d\n", status);
        }
    }
    return count;
}

static int scanlog_open(struct inode * inode, struct file * file)
{
    struct proc_dir_entry *dp = PDE(inode);
    unsigned int *data = (unsigned int *)dp->data;

    if (data[0] != 0) {
        /* This imperfect test stops a second copy of the
         * data (or a reset while data is being copied)
         */
        return -EBUSY;
    }

    data[0] = 0;    /* re-init so we restart the scan */

    return 0;
}

static int scanlog_release(struct inode * inode, struct file * file)
{
    struct proc_dir_entry *dp = PDE(inode);
    unsigned int *data = (unsigned int *)dp->data;

    data[0] = 0;

    return 0;
}

const struct file_operations scanlog_fops = {
    .owner      = THIS_MODULE,
    .read       = scanlog_read,
    .write      = scanlog_write,
    .open       = scanlog_open,
    .release    = scanlog_release,
    .llseek     = noop_llseek,
};

static int __init scanlog_init(void)
{
    struct proc_dir_entry *ent;
    void *data;
    int err = -ENOMEM;

    ibm_scan_log_dump = rtas_token("ibm,scan-log-dump");
    if (ibm_scan_log_dump == RTAS_UNKNOWN_SERVICE)
        return -ENODEV;

    /* Ideally we could allocate a buffer < 4G */
    data = kzalloc(RTAS_DATA_BUF_SIZE, GFP_KERNEL);
    if (!data)
        goto err;

    ent = proc_create_data("powerpc/rtas/scan-log-dump", S_IRUSR, NULL,
                   &scanlog_fops, data);
    if (!ent)
        goto err;

    proc_ppc64_scan_log_dump = ent;

    return 0;
err:
    kfree(data);
    return err;
}

static void __exit scanlog_cleanup(void)
{
    if (proc_ppc64_scan_log_dump) {
        kfree(proc_ppc64_scan_log_dump->data);
        remove_proc_entry("scan-log-dump", proc_ppc64_scan_log_dump->parent);
    }
}

module_init(scanlog_init);
module_exit(scanlog_cleanup);
MODULE_LICENSE("GPL");