debugfs: add 9p device interface
The 9p interface provides abstraction layers allowing the software
that uses devices to be independent from the hardware.
This patch provides a file system abstraction to link drivers to their
devices and propose a common interface to expose driver operations to
higher layers. This file system can be used to access and configure a
device by doing read/write operations.
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: Ia9662393baf489855dc0c8f389fe4a0afbc9c255
diff --git a/lib/debugfs/dev.c b/lib/debugfs/dev.c
new file mode 100644
index 0000000..0361437
--- /dev/null
+++ b/lib/debugfs/dev.c
@@ -0,0 +1,849 @@
+/*
+ * Copyright (c) 2019, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <cdefs.h>
+#include <common/debug.h>
+#include <lib/debugfs.h>
+#include <string.h>
+
+#include "dev.h"
+
+#define NR_MOUNT_POINTS 4
+
+struct mount_point {
+ chan_t *new;
+ chan_t *old;
+};
+
+/* This array contains all the available channels of the filesystem.
+ * A file descriptor is the index of a specific channel in this array.
+ */
+static chan_t fdset[NR_CHANS];
+
+/* This array contains all the available mount points of the filesystem. */
+static struct mount_point mount_points[NR_MOUNT_POINTS];
+
+/* This variable stores the channel associated to the root directory. */
+static chan_t slash_channel;
+
+/* This function creates a channel from a device index and registers
+ * it to fdset.
+ */
+static chan_t *create_new_channel(unsigned char index)
+{
+ chan_t *channel = NULL;
+ int i;
+
+ for (i = 0; i < NR_CHANS; i++) {
+ if (fdset[i].index == NODEV) {
+ channel = &fdset[i];
+ channel->index = index;
+ break;
+ }
+ }
+
+ return channel;
+}
+
+/*******************************************************************************
+ * This function returns a pointer to an existing channel in fdset from a file
+ * descriptor.
+ ******************************************************************************/
+static chan_t *fd_to_channel(int fd)
+{
+ if ((fd < 0) || (fd >= NR_CHANS) || (fdset[fd].index == NODEV)) {
+ return NULL;
+ }
+
+ return &fdset[fd];
+}
+
+/*******************************************************************************
+ * This function returns a file descriptor from a channel.
+ * The caller must be sure that the channel is registered in fdset.
+ ******************************************************************************/
+static int channel_to_fd(chan_t *channel)
+{
+ return (channel == NULL) ? -1 : (channel - fdset);
+}
+
+/*******************************************************************************
+ * This function checks the validity of a mode.
+ ******************************************************************************/
+static bool is_valid_mode(int mode)
+{
+ if ((mode & O_READ) && (mode & (O_WRITE | O_RDWR))) {
+ return false;
+ }
+ if ((mode & O_WRITE) && (mode & (O_READ | O_RDWR))) {
+ return false;
+ }
+ if ((mode & O_RDWR) && (mode & (O_READ | O_WRITE))) {
+ return false;
+ }
+
+ return true;
+}
+
+/*******************************************************************************
+ * This function extracts the next part of the given path contained and puts it
+ * in token. It returns a pointer to the remainder of the path.
+ ******************************************************************************/
+static const char *next(const char *path, char *token)
+{
+ int index;
+ const char *cursor;
+
+ while (*path == '/') {
+ ++path;
+ }
+
+ index = 0;
+ cursor = path;
+ if (*path != '\0') {
+ while (*cursor != '/' && *cursor != '\0') {
+ if (index == NAMELEN) {
+ return NULL;
+ }
+ token[index++] = *cursor++;
+ }
+ }
+ token[index] = '\0';
+
+ return cursor;
+}
+
+/*******************************************************************************
+ * This function returns the driver index in devtab of the driver
+ * identified by id.
+ ******************************************************************************/
+static int get_device_index(int id)
+{
+ int index;
+ dev_t * const *dp;
+
+ for (index = 0, dp = devtab; *dp && (*dp)->id != id; ++dp) {
+ index++;
+ }
+
+ if (*dp == NULL) {
+ return -1;
+ }
+
+ return index;
+}
+
+/*******************************************************************************
+ * This function clears a given channel fields
+ ******************************************************************************/
+static void channel_clear(chan_t *channel)
+{
+ channel->offset = 0;
+ channel->qid = 0;
+ channel->index = NODEV;
+ channel->dev = 0;
+ channel->mode = 0;
+}
+
+/*******************************************************************************
+ * This function closes the channel pointed to by c.
+ ******************************************************************************/
+void channel_close(chan_t *channel)
+{
+ if (channel != NULL) {
+ channel_clear(channel);
+ }
+}
+
+/*******************************************************************************
+ * This function copies data from src to dst after applying the offset of the
+ * channel c. nbytes bytes are expected to be copied unless the data goes over
+ * dst + len.
+ * It returns the actual number of bytes that were copied.
+ ******************************************************************************/
+int buf_to_channel(chan_t *channel, void *dst, void *src, int nbytes, long len)
+{
+ const char *addr = src;
+
+ if ((channel == NULL) || (dst == NULL) || (src == NULL)) {
+ return 0;
+ }
+
+ if (channel->offset >= len) {
+ return 0;
+ }
+
+ if ((channel->offset + nbytes) > len) {
+ nbytes = len - channel->offset;
+ }
+
+ memcpy(dst, addr + channel->offset, nbytes);
+
+ channel->offset += nbytes;
+
+ return nbytes;
+}
+
+/*******************************************************************************
+ * This function checks whether a channel (identified by its device index and
+ * qid) is registered as a mount point.
+ * Returns a pointer to the channel it is mounted to when found, NULL otherwise.
+ ******************************************************************************/
+static chan_t *mount_point_to_channel(int index, qid_t qid)
+{
+ chan_t *channel;
+ struct mount_point *mp;
+
+ for (mp = mount_points; mp < &mount_points[NR_MOUNT_POINTS]; mp++) {
+ channel = mp->new;
+ if (channel == NULL) {
+ continue;
+ }
+
+ if ((channel->index == index) && (channel->qid == qid)) {
+ return mp->old;
+ }
+ }
+
+ return NULL;
+}
+
+/*******************************************************************************
+ * This function calls the attach function of the driver identified by id.
+ ******************************************************************************/
+chan_t *attach(int id, int dev)
+{
+ /* Get the devtab index for the driver identified by id */
+ int index = get_device_index(id);
+
+ if (index < 0) {
+ return NULL;
+ }
+
+ return devtab[index]->attach(id, dev);
+}
+
+/*******************************************************************************
+ * This function is the default implementation of the driver attach function.
+ * It creates a new channel and returns a pointer to it.
+ ******************************************************************************/
+chan_t *devattach(int id, int dev)
+{
+ chan_t *channel;
+ int index;
+
+ index = get_device_index(id);
+ if (index < 0) {
+ return NULL;
+ }
+
+ channel = create_new_channel(index);
+ if (channel == NULL) {
+ return NULL;
+ }
+
+ channel->dev = dev;
+ channel->qid = CHDIR;
+
+ return channel;
+}
+
+/*******************************************************************************
+ * This function returns a channel given a path.
+ * It goes through the filesystem, from the root namespace ('/') or from a
+ * device namespace ('#'), switching channel on mount points.
+ ******************************************************************************/
+chan_t *path_to_channel(const char *path, int mode)
+{
+ int i, n;
+ const char *path_next;
+ chan_t *mnt, *channel;
+ char elem[NAMELEN];
+
+ if (path == NULL) {
+ return NULL;
+ }
+
+ switch (path[0]) {
+ case '/':
+ channel = clone(&slash_channel, NULL);
+ path_next = path;
+ break;
+ case '#':
+ path_next = next(path + 1, elem);
+ if (path_next == NULL) {
+ goto noent;
+ }
+
+ n = 0;
+ for (i = 1; (elem[i] >= '0') && (elem[i] <= '9'); i++) {
+ n += elem[i] - '0';
+ }
+
+ if (elem[i] != '\0') {
+ goto noent;
+ }
+
+ channel = attach(elem[0], n);
+ break;
+ default:
+ return NULL;
+ }
+
+ if (channel == NULL) {
+ return NULL;
+ }
+
+ for (path_next = next(path_next, elem); *elem;
+ path_next = next(path_next, elem)) {
+ if ((channel->qid & CHDIR) == 0) {
+ goto notfound;
+ }
+
+ if (devtab[channel->index]->walk(channel, elem) < 0) {
+ channel_close(channel);
+ goto notfound;
+ }
+
+ mnt = mount_point_to_channel(channel->index, channel->qid);
+ if (mnt != NULL) {
+ clone(mnt, channel);
+ }
+ }
+
+ if (path_next == NULL) {
+ goto notfound;
+ }
+
+ /* TODO: check mode */
+ return channel;
+
+notfound:
+ channel_close(channel);
+noent:
+ return NULL;
+}
+
+/*******************************************************************************
+ * This function calls the clone function of the driver associated to the
+ * channel c.
+ ******************************************************************************/
+chan_t *clone(chan_t *c, chan_t *nc)
+{
+ return devtab[c->index]->clone(c, nc);
+}
+
+/*******************************************************************************
+ * This function is the default implementation of the driver clone function.
+ * It creates a new channel and returns a pointer to it.
+ * It clones channel into new_channel.
+ ******************************************************************************/
+chan_t *devclone(chan_t *channel, chan_t *new_channel)
+{
+ if (channel == NULL) {
+ return NULL;
+ }
+
+ if (new_channel == NULL) {
+ new_channel = create_new_channel(channel->index);
+ if (new_channel == NULL) {
+ return NULL;
+ }
+ }
+
+ new_channel->qid = channel->qid;
+ new_channel->dev = channel->dev;
+ new_channel->mode = channel->mode;
+ new_channel->offset = channel->offset;
+ new_channel->index = channel->index;
+
+ return new_channel;
+}
+
+/*******************************************************************************
+ * This function is the default implementation of the driver walk function.
+ * It goes through all the elements of tab using the gen function until a match
+ * is found with name.
+ * If a match is found, it copies the qid of the new directory.
+ ******************************************************************************/
+int devwalk(chan_t *channel, const char *name, const dirtab_t *tab,
+ int ntab, devgen_t *gen)
+{
+ int i;
+ dir_t dir;
+
+ if ((channel == NULL) || (name == NULL) || (gen == NULL)) {
+ return -1;
+ }
+
+ if ((name[0] == '.') && (name[1] == '\0')) {
+ return 1;
+ }
+
+ for (i = 0; ; i++) {
+ switch ((*gen)(channel, tab, ntab, i, &dir)) {
+ case 0:
+ /* Intentional fall-through */
+ case -1:
+ return -1;
+ case 1:
+ if (strncmp(name, dir.name, NAMELEN) != 0) {
+ continue;
+ }
+ channel->qid = dir.qid;
+ return 1;
+ }
+ }
+}
+
+/*******************************************************************************
+ * This is a helper function which exposes the content of a directory, element
+ * by element. It is meant to be called until the end of the directory is
+ * reached or an error occurs.
+ * It returns -1 on error, 0 on end of directory and 1 when a new file is found.
+ ******************************************************************************/
+int dirread(chan_t *channel, dir_t *dir, const dirtab_t *tab,
+ int ntab, devgen_t *gen)
+{
+ int i, ret;
+
+ if ((channel == NULL) || (dir == NULL) || (gen == NULL)) {
+ return -1;
+ }
+
+ i = channel->offset/sizeof(dir_t);
+ ret = (*gen)(channel, tab, ntab, i, dir);
+ if (ret == 1) {
+ channel->offset += sizeof(dir_t);
+ }
+
+ return ret;
+}
+
+/*******************************************************************************
+ * This function sets the elements of dir.
+ ******************************************************************************/
+void make_dir_entry(chan_t *channel, dir_t *dir,
+ const char *name, long length, qid_t qid, unsigned int mode)
+{
+ if ((channel == NULL) || (dir == NULL) || (name == NULL)) {
+ return;
+ }
+
+ strlcpy(dir->name, name, sizeof(dir->name));
+ dir->length = length;
+ dir->qid = qid;
+ dir->mode = mode;
+
+ if ((qid & CHDIR) != 0) {
+ dir->mode |= O_DIR;
+ }
+
+ dir->index = channel->index;
+ dir->dev = channel->dev;
+}
+
+/*******************************************************************************
+ * This function is the default implementation of the internal driver gen
+ * function.
+ * It copies and formats the information of the nth element of tab into dir.
+ ******************************************************************************/
+int devgen(chan_t *channel, const dirtab_t *tab, int ntab, int n, dir_t *dir)
+{
+ const dirtab_t *dp;
+
+ if ((channel == NULL) || (dir == NULL) || (tab == NULL) ||
+ (n >= ntab)) {
+ return 0;
+ }
+
+ dp = &tab[n];
+ make_dir_entry(channel, dir, dp->name, dp->length, dp->qid, dp->perm);
+ return 1;
+}
+
+/*******************************************************************************
+ * This function returns a file descriptor identifying the channel associated to
+ * the given path.
+ ******************************************************************************/
+int open(const char *path, int mode)
+{
+ chan_t *channel;
+
+ if (path == NULL) {
+ return -1;
+ }
+
+ if (is_valid_mode(mode) == false) {
+ return -1;
+ }
+
+ channel = path_to_channel(path, mode);
+
+ return channel_to_fd(channel);
+}
+
+/*******************************************************************************
+ * This function closes the channel identified by the file descriptor fd.
+ ******************************************************************************/
+int close(int fd)
+{
+ chan_t *channel;
+
+ channel = fd_to_channel(fd);
+ if (channel == NULL) {
+ return -1;
+ }
+
+ channel_close(channel);
+ return 0;
+}
+
+/*******************************************************************************
+ * This function is the default implementation of the driver stat function.
+ * It goes through all the elements of tab using the gen function until a match
+ * is found with file.
+ * If a match is found, dir contains the information file.
+ ******************************************************************************/
+int devstat(chan_t *dirc, const char *file, dir_t *dir,
+ const dirtab_t *tab, int ntab, devgen_t *gen)
+{
+ int i, r = 0;
+ chan_t *c, *mnt;
+
+ if ((dirc == NULL) || (dir == NULL) || (gen == NULL)) {
+ return -1;
+ }
+
+ c = path_to_channel(file, O_STAT);
+ if (c == NULL) {
+ return -1;
+ }
+
+ for (i = 0; ; i++) {
+ switch ((*gen)(dirc, tab, ntab, i, dir)) {
+ case 0:
+ /* Intentional fall-through */
+ case -1:
+ r = -1;
+ goto leave;
+ case 1:
+ mnt = mount_point_to_channel(dir->index, dir->qid);
+ if (mnt != NULL) {
+ dir->qid = mnt->qid;
+ dir->index = mnt->index;
+ }
+
+ if ((dir->qid != c->qid) || (dir->index != c->index)) {
+ continue;
+ }
+
+ goto leave;
+ }
+ }
+
+leave:
+ channel_close(c);
+ return r;
+}
+
+/*******************************************************************************
+ * This function calls the stat function of the driver associated to the parent
+ * directory of the file in path.
+ * The result is stored in dir.
+ ******************************************************************************/
+int stat(const char *path, dir_t *dir)
+{
+ int r;
+ size_t len;
+ chan_t *channel;
+ char *p, dirname[PATHLEN];
+
+ if ((path == NULL) || (dir == NULL)) {
+ return -1;
+ }
+
+ len = strlen(path);
+ if ((len + 1) > sizeof(dirname)) {
+ return -1;
+ }
+
+ memcpy(dirname, path, len);
+ for (p = dirname + len; p > dirname; --p) {
+ if (*p != '/') {
+ break;
+ }
+ }
+
+ p = memrchr(dirname, '/', p - dirname);
+ if (p == NULL) {
+ return -1;
+ }
+
+ dirname[p - dirname + 1] = '\0';
+
+ channel = path_to_channel(dirname, O_STAT);
+ if (channel == NULL) {
+ return -1;
+ }
+
+ r = devtab[channel->index]->stat(channel, path, dir);
+ channel_close(channel);
+
+ return r;
+}
+
+/*******************************************************************************
+ * This function calls the read function of the driver associated to fd.
+ * It fills buf with at most n bytes.
+ * It returns the number of bytes that were actually read.
+ ******************************************************************************/
+int read(int fd, void *buf, int n)
+{
+ chan_t *channel;
+
+ if (buf == NULL) {
+ return -1;
+ }
+
+ channel = fd_to_channel(fd);
+ if (channel == NULL) {
+ return -1;
+ }
+
+ if (((channel->qid & CHDIR) != 0) && (n < sizeof(dir_t))) {
+ return -1;
+ }
+
+ return devtab[channel->index]->read(channel, buf, n);
+}
+
+/*******************************************************************************
+ * This function calls the write function of the driver associated to fd.
+ * It writes at most n bytes of buf.
+ * It returns the number of bytes that were actually written.
+ ******************************************************************************/
+int write(int fd, void *buf, int n)
+{
+ chan_t *channel;
+
+ if (buf == NULL) {
+ return -1;
+ }
+
+ channel = fd_to_channel(fd);
+ if (channel == NULL) {
+ return -1;
+ }
+
+ if ((channel->qid & CHDIR) != 0) {
+ return -1;
+ }
+
+ return devtab[channel->index]->write(channel, buf, n);
+}
+
+/*******************************************************************************
+ * This function calls the seek function of the driver associated to fd.
+ * It applies the offset off according to the strategy whence.
+ ******************************************************************************/
+int seek(int fd, long off, int whence)
+{
+ chan_t *channel;
+
+ channel = fd_to_channel(fd);
+ if (channel == NULL) {
+ return -1;
+ }
+
+ if ((channel->qid & CHDIR) != 0) {
+ return -1;
+ }
+
+ return devtab[channel->index]->seek(channel, off, whence);
+}
+
+/*******************************************************************************
+ * This function is the default error implementation of the driver mount
+ * function.
+ ******************************************************************************/
+chan_t *deverrmount(chan_t *channel, const char *spec)
+{
+ return NULL;
+}
+
+/*******************************************************************************
+ * This function is the default error implementation of the driver write
+ * function.
+ ******************************************************************************/
+int deverrwrite(chan_t *channel, void *buf, int n)
+{
+ return -1;
+}
+
+/*******************************************************************************
+ * This function is the default error implementation of the driver seek
+ * function.
+ ******************************************************************************/
+int deverrseek(chan_t *channel, long off, int whence)
+{
+ return -1;
+}
+
+/*******************************************************************************
+ * This function is the default implementation of the driver seek function.
+ * It applies the offset off according to the strategy whence to the channel c.
+ ******************************************************************************/
+int devseek(chan_t *channel, long off, int whence)
+{
+ switch (whence) {
+ case KSEEK_SET:
+ channel->offset = off;
+ break;
+ case KSEEK_CUR:
+ channel->offset += off;
+ break;
+ case KSEEK_END:
+ /* Not implemented */
+ return -1;
+ }
+
+ return 0;
+}
+
+/*******************************************************************************
+ * This function registers the channel associated to the path new as a mount
+ * point for the channel c.
+ ******************************************************************************/
+static int add_mount_point(chan_t *channel, const char *new)
+{
+ int i;
+ chan_t *cn;
+ struct mount_point *mp;
+
+ if (new == NULL) {
+ goto err0;
+ }
+
+ cn = path_to_channel(new, O_READ);
+ if (cn == NULL) {
+ goto err0;
+ }
+
+ if ((cn->qid & CHDIR) == 0) {
+ goto err1;
+ }
+
+ for (i = NR_MOUNT_POINTS - 1; i >= 0; i--) {
+ mp = &mount_points[i];
+ if (mp->new == NULL) {
+ break;
+ }
+ }
+
+ if (i < 0) {
+ goto err1;
+ }
+
+ mp->new = cn;
+ mp->old = channel;
+
+ return 0;
+
+err1:
+ channel_close(cn);
+err0:
+ return -1;
+}
+
+/*******************************************************************************
+ * This function registers the path new as a mount point for the path old.
+ ******************************************************************************/
+int bind(const char *old, const char *new)
+{
+ chan_t *channel;
+
+ channel = path_to_channel(old, O_BIND);
+ if (channel == NULL) {
+ return -1;
+ }
+
+ if (add_mount_point(channel, new) < 0) {
+ channel_close(channel);
+ return -1;
+ }
+
+ return 0;
+}
+
+/*******************************************************************************
+ * This function calls the mount function of the driver associated to the path
+ * srv.
+ * It mounts the path srv on the path where.
+ ******************************************************************************/
+int mount(const char *srv, const char *where, const char *spec)
+{
+ chan_t *channel, *mount_point_chan;
+ int ret;
+
+ channel = path_to_channel(srv, O_RDWR);
+ if (channel == NULL) {
+ goto err0;
+ }
+
+ mount_point_chan = devtab[channel->index]->mount(channel, spec);
+ if (mount_point_chan == NULL) {
+ goto err1;
+ }
+
+ ret = add_mount_point(mount_point_chan, where);
+ if (ret < 0) {
+ goto err2;
+ }
+
+ channel_close(channel);
+
+ return 0;
+
+err2:
+ channel_close(mount_point_chan);
+err1:
+ channel_close(channel);
+err0:
+ return -1;
+}
+
+/*******************************************************************************
+ * This function initializes the device environment.
+ * It creates the '/' channel.
+ * It links the device drivers to the physical drivers.
+ ******************************************************************************/
+void debugfs_init(void)
+{
+ chan_t *channel, *cloned_channel;
+
+ for (channel = fdset; channel < &fdset[NR_CHANS]; channel++) {
+ channel_clear(channel);
+ }
+
+ channel = devattach('/', 0);
+ if (channel == NULL) {
+ panic();
+ }
+
+ cloned_channel = clone(channel, &slash_channel);
+ if (cloned_channel == NULL) {
+ panic();
+ }
+
+ channel_close(channel);
+ devlink();
+}
+
+__dead2 void devpanic(const char *cause)
+{
+ panic();
+}