debugfs.c

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#include "util.h"
#include "debugfs.h"
#include "cache.h"

#include <linux/kernel.h>
#include <sys/mount.h>

static int debugfs_premounted;
char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
char tracing_events_path[PATH_MAX + 1] = "/sys/kernel/debug/tracing/events";

static const char *debugfs_known_mountpoints[] = {
    "/sys/kernel/debug/",
    "/debug/",
    0,
};

static int debugfs_found;

/* find the path to the mounted debugfs */
const char *debugfs_find_mountpoint(void)
{
    const char **ptr;
    char type[100];
    FILE *fp;

    if (debugfs_found)
        return (const char *) debugfs_mountpoint;

    ptr = debugfs_known_mountpoints;
    while (*ptr) {
        if (debugfs_valid_mountpoint(*ptr) == 0) {
            debugfs_found = 1;
            strcpy(debugfs_mountpoint, *ptr);
            return debugfs_mountpoint;
        }
        ptr++;
    }

    /* give up and parse /proc/mounts */
    fp = fopen("/proc/mounts", "r");
    if (fp == NULL)
        return NULL;

    while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
              debugfs_mountpoint, type) == 2) {
        if (strcmp(type, "debugfs") == 0)
            break;
    }
    fclose(fp);

    if (strcmp(type, "debugfs") != 0)
        return NULL;

    debugfs_found = 1;

    return debugfs_mountpoint;
}

/* verify that a mountpoint is actually a debugfs instance */

int debugfs_valid_mountpoint(const char *debugfs)
{
    struct statfs st_fs;

    if (statfs(debugfs, &st_fs) < 0)
        return -ENOENT;
    else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
        return -ENOENT;

    return 0;
}

static void debugfs_set_tracing_events_path(const char *mountpoint)
{
    snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s",
         mountpoint, "tracing/events");
}

/* mount the debugfs somewhere if it's not mounted */

char *debugfs_mount(const char *mountpoint)
{
    /* see if it's already mounted */
    if (debugfs_find_mountpoint()) {
        debugfs_premounted = 1;
        goto out;
    }

    /* if not mounted and no argument */
    if (mountpoint == NULL) {
        /* see if environment variable set */
        mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
        /* if no environment variable, use default */
        if (mountpoint == NULL)
            mountpoint = "/sys/kernel/debug";
    }

    if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
        return NULL;

    /* save the mountpoint */
    debugfs_found = 1;
    strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
out:
    debugfs_set_tracing_events_path(debugfs_mountpoint);
    return debugfs_mountpoint;
}

void debugfs_set_path(const char *mountpoint)
{
    snprintf(debugfs_mountpoint, sizeof(debugfs_mountpoint), "%s", mountpoint);
    debugfs_set_tracing_events_path(mountpoint);
}