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    Subject[PATCH 1/3] debugfs utility routines for perf

    Add routines to locate the debugfs mount point and to manage the
    mounting and unmountin of the debugfs.

    Signed-off-by: Clark Williams <williams@redhat.com>
    ---
    tools/perf/util/debugfs.c | 241 +++++++++++++++++++++++++++++++++++++++++++++
    tools/perf/util/debugfs.h | 22 ++++
    2 files changed, 263 insertions(+), 0 deletions(-)
    create mode 100644 tools/perf/util/debugfs.c
    create mode 100644 tools/perf/util/debugfs.h

    diff --git a/tools/perf/util/debugfs.c b/tools/perf/util/debugfs.c
    new file mode 100644
    index 0000000..34f7983
    --- /dev/null
    +++ b/tools/perf/util/debugfs.c
    @@ -0,0 +1,241 @@
    +#include "util.h"
    +#include "debugfs.h"
    +#include "cache.h"
    +
    +static int debugfs_premounted = 0;
    +static char debugfs_mountpoint[MAX_PATH+1];
    +
    +static const char *debugfs_known_mountpoints[] = {
    + "/sys/kernel/debug/",
    + "/debug/",
    + 0,
    +};
    +
    +/* use this to force a umount */
    +void debugfs_force_cleanup(void)
    +{
    + debugfs_find_mountpoint();
    + debugfs_premounted = 0;
    + debugfs_umount();
    +}
    +
    +/* construct a full path to a debugfs element */
    +int debugfs_make_path(const char *element, char *buffer, int size)
    +{
    + int len;
    +
    + if (strlen(debugfs_mountpoint) == 0) {
    + buffer[0] = '\0';
    + return -1;
    + }
    +
    + len = strlen(debugfs_mountpoint) + strlen(element) + 1;
    + if (len >= size)
    + return len+1;
    +
    + snprintf(buffer, size-1, "%s/%s", debugfs_mountpoint, element);
    + return 0;
    +}
    +
    +/* find the path to the mounted debugfs */
    +const char *
    +debugfs_find_mountpoint(void)
    +{
    + static int debugfs_found = 0;
    + char type[100];
    + FILE *fp;
    + const char **ptr;
    +
    + 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 */
    + if ((fp = fopen("/proc/mounts","r")) == NULL)
    + die("Can't open /proc/mounts for read");
    +
    + while (fscanf(fp, "%*s %"
    + STR(MAX_PATH)
    + "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;
    +}
    +
    +
    +int
    +debugfs_valid_entry(const char *path)
    +{
    + struct stat st;
    +
    + if (stat(path, &st))
    + return -errno;
    + return 0;
    +}
    +
    +/* mount the debugfs somewhere */
    +
    +int
    +debugfs_mount(const char *mountpoint)
    +{
    + char mountcmd[128];
    +
    + /* see if it's already mounted */
    + if (debugfs_find_mountpoint()) {
    + debugfs_premounted = 1;
    + return 0;
    + }
    +
    + /* 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";
    + }
    +
    + /* save the mountpoint */
    + strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
    +
    + /* mount it */
    + snprintf(mountcmd, sizeof(mountcmd),
    + "/bin/mount -t debugfs debugfs %s", mountpoint);
    + return system(mountcmd);
    +}
    +
    +/* umount the debugfs */
    +
    +int
    +debugfs_umount(void)
    +{
    + int ret;
    + char umountcmd[128];
    +
    + /* if it was already mounted, leave it */
    + if (debugfs_premounted)
    + return 0;
    +
    + /* make sure it's a valid mount point */
    + if ((ret = debugfs_valid_mountpoint(debugfs_mountpoint)))
    + return ret;
    +
    + snprintf(umountcmd, sizeof(umountcmd),
    + "/bin/umount %s", debugfs_mountpoint);
    + return system(umountcmd);
    +}
    +
    +
    +int
    +debugfs_write(const char *entry, const char *value)
    +{
    + int ret, count;
    + int fd;
    + char path[MAX_PATH+1];
    +
    + /* construct the path */
    + snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
    +
    + /* verify that it exists */
    + if ((ret = debugfs_valid_entry(path)))
    + return ret;
    +
    + /* get how many chars we're going to write */
    + count = strlen(value);
    +
    + /* open the debugfs entry */
    + if ((fd = open(path, O_RDWR)) < 0)
    + return -errno;
    +
    + while (count > 0) {
    + /* write it */
    + ret = write(fd, value, count);
    + if (ret <= 0) {
    + if (ret == EAGAIN)
    + continue;
    + close(fd);
    + return -errno;
    + }
    + count -= ret;
    + }
    +
    + /* close it */
    + close(fd);
    +
    + /* return success */
    + return 0;
    +}
    +
    +/*
    + * read a debugfs entry
    + * returns the number of chars read or a negative errno
    + */
    +
    +int
    +debugfs_read(const char *entry, char *buffer, size_t size)
    +{
    + int ret;
    + int fd;
    + char path[MAX_PATH+1];
    +
    + /* construct the path */
    + snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
    +
    + /* verify that it exists */
    + if ((ret = debugfs_valid_entry(path)))
    + return ret;
    +
    + /* open the debugfs entry */
    + if ((fd = open(path, O_RDONLY)) < 0)
    + return -errno;
    +
    + do {
    + /* read it */
    + ret = read(fd, buffer, size);
    + if (ret == 0) {
    + close(fd);
    + return EOF;
    + }
    + } while (ret < 0 && errno == EAGAIN);
    +
    + /* close it */
    + close(fd);
    +
    + /* make *sure* there's a null character at the end */
    + buffer[ret] = '\0';
    +
    + /* return the number of chars read */
    + return ret;
    +}
    diff --git a/tools/perf/util/debugfs.h b/tools/perf/util/debugfs.h
    new file mode 100644
    index 0000000..df14c2a
    --- /dev/null
    +++ b/tools/perf/util/debugfs.h
    @@ -0,0 +1,22 @@
    +#ifndef __DEBUGFS_H__
    +#define __DEBUGFS_H__
    +#include <sys/mount.h>
    +#ifndef MAX_PATH
    +#define MAX_PATH 256
    +#endif
    +
    +#ifndef STR
    +#define _STR(x) #x
    +#define STR(x) _STR(x)
    +#endif
    +
    +extern const char * debugfs_find_mountpoint(void);
    +extern int debugfs_valid_mountpoint(const char *debugfs);
    +extern int debugfs_valid_entry(const char *path);
    +extern int debugfs_mount(const char *mountpoint);
    +extern int debugfs_umount(void);
    +extern int debugfs_write(const char *entry, const char *value);
    +extern int debugfs_read(const char *entry, char *buffer, size_t size);
    +extern void debugfs_force_cleanup(void);
    +extern int debugfs_make_path(const char *element, char *buffer, int size);
    +#endif
    --
    1.6.2.5

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