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

Makefile

@@ -150,6 +150,15 @@ else
 endif
 endif
 
+# USE_DEBUGFS experimental feature recommended only in debug builds
+ifeq (${USE_DEBUGFS},1)
+ifeq (${DEBUG},1)
+        $(warning DEBUGFS experimental feature is enabled.)
+else
+        $(warning DEBUGFS experimental, recommended in DEBUG builds ONLY)
+endif
+endif
+
 ################################################################################
 # Toolchain
 ################################################################################
@@ -734,6 +743,7 @@ $(eval $(call assert_boolean,SPIN_ON_BL1_EXIT))
 $(eval $(call assert_boolean,SPM_MM))
 $(eval $(call assert_boolean,TRUSTED_BOARD_BOOT))
 $(eval $(call assert_boolean,USE_COHERENT_MEM))
+$(eval $(call assert_boolean,USE_DEBUGFS))
 $(eval $(call assert_boolean,USE_ROMLIB))
 $(eval $(call assert_boolean,USE_TBBR_DEFS))
 $(eval $(call assert_boolean,WARMBOOT_ENABLE_DCACHE_EARLY))
@@ -800,6 +810,7 @@ $(eval $(call add_define,SPIN_ON_BL1_EXIT))
 $(eval $(call add_define,SPM_MM))
 $(eval $(call add_define,TRUSTED_BOARD_BOOT))
 $(eval $(call add_define,USE_COHERENT_MEM))
+$(eval $(call add_define,USE_DEBUGFS))
 $(eval $(call add_define,USE_ROMLIB))
 $(eval $(call add_define,USE_TBBR_DEFS))
 $(eval $(call add_define,WARMBOOT_ENABLE_DCACHE_EARLY))

bl31/bl31.mk

@@ -43,6 +43,11 @@ ifeq (${ENABLE_PMF}, 1)
 BL31_SOURCES		+=	lib/pmf/pmf_main.c
 endif
 
+include lib/debugfs/debugfs.mk
+ifeq (${USE_DEBUGFS},1)
+	BL31_SOURCES	+= $(DEBUGFS_SRCS)
+endif
+
 ifeq (${EL3_EXCEPTION_HANDLING},1)
 BL31_SOURCES		+=	bl31/ehf.c
 endif

include/lib/debugfs.h

+/*
+ * Copyright (c) 2019, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef DEBUGFS_H
+#define DEBUGFS_H
+
+#define NAMELEN   13 /* Maximum length of a file name */
+#define PATHLEN   41 /* Maximum length of a path */
+#define STATLEN   41 /* Size of static part of dir format */
+#define ROOTLEN   (2 + 4) /* Size needed to encode root string */
+#define FILNAMLEN (2 + NAMELEN) /* Size needed to encode filename */
+#define DIRLEN    (STATLEN + FILNAMLEN + 3*ROOTLEN) /* Size of dir entry */
+
+#define KSEEK_SET 0
+#define KSEEK_CUR 1
+#define KSEEK_END 2
+
+#define NELEM(tab) (sizeof(tab) / sizeof((tab)[0]))
+
+typedef unsigned short qid_t; /* FIXME: short type not recommended? */
+
+/*******************************************************************************
+ * This structure contains the necessary information to represent a 9p
+ * directory.
+ ******************************************************************************/
+typedef struct {
+	char		name[NAMELEN];
+	long		length;
+	unsigned char	mode;
+	unsigned char	index;
+	unsigned char	dev;
+	qid_t		qid;
+} dir_t;
+
+/* Permission definitions used as flags */
+#define O_READ		(1 << 0)
+#define O_WRITE		(1 << 1)
+#define O_RDWR		(1 << 2)
+#define O_BIND		(1 << 3)
+#define O_DIR		(1 << 4)
+#define O_STAT		(1 << 5)
+
+/* 9p interface */
+int mount(const char *srv, const char *mnt, const char *spec);
+int create(const char *name, int flags);
+int open(const char *name, int flags);
+int close(int fd);
+int read(int fd, void *buf, int n);
+int write(int fd, void *buf, int n);
+int seek(int fd, long off, int whence);
+int bind(const char *path, const char *where);
+int stat(const char *path, dir_t *dir);
+
+/* DebugFS initialization */
+void debugfs_init(void);
+
+#endif /* DEBUGFS_H */

lib/debugfs/blobs.h

+/*
+ * Copyright (c) 2019, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include "dev.h"
+
+static const dirtab_t blobtab[] = {
+	{"ctl", DEV_ROOT_QBLOBCTL, 0, O_READ}
+};

lib/debugfs/debugfs.mk

+#
+# Copyright (c) 2019, ARM Limited and Contributors. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+
+DEBUGFS_SRCS	:=	$(addprefix lib/debugfs/,	\
+			dev.c				\
+			devc.c				\
+			devroot.c)

lib/debugfs/dev.c

+/*
+ * 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();
+}

lib/debugfs/dev.h

+/*
+ * Copyright (c) 2019, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef DEV_H
+#define DEV_H
+
+#include <cdefs.h>
+#include <lib/debugfs.h>
+#include <stddef.h>
+
+/* FIXME: need configurability */
+#define NR_CHANS  10
+#define NR_CONSS  1
+#define NR_BINDS  4
+#define NR_FILES  18
+
+#define NODEV     255
+#define CHDIR     (1 << 15)
+
+#define SYNCDEV   0
+#define SYNCALL   1
+
+typedef struct dev dev_t;
+typedef struct chan chan_t;
+typedef struct dirtab dirtab_t;
+typedef int devgen_t(chan_t *, const dirtab_t *, int, int, dir_t *);
+typedef struct attr attr_t;
+
+enum {
+	DEV_ROOT_QROOT,
+	DEV_ROOT_QDEV,
+	DEV_ROOT_QFIP,
+	DEV_ROOT_QBLOBS,
+	DEV_ROOT_QBLOBCTL,
+	DEV_ROOT_QPSCI
+};
+
+/*******************************************************************************
+ * This structure contains the necessary information to represent a directory
+ * of the filesystem.
+ ******************************************************************************/
+struct dirtab {
+	char		name[NAMELEN];
+	qid_t		qid;
+	long		length;
+	unsigned char	perm;
+	void		*data;
+};
+
+/*******************************************************************************
+ * This structure defines the interface of device drivers.
+ * Each driver must implement a subset of those functions.
+ * It is possible to redirect to default implementations defined in dev.c.
+ ******************************************************************************/
+/* FIXME: comments for the callbacks */
+struct dev {
+	char id;
+	int (*stat)(chan_t *c, const char *file, dir_t *dir);
+	int (*walk)(chan_t *c, const char *name);
+	int (*read)(chan_t *c, void *buf, int n);
+	int (*write)(chan_t *c, void *buf, int n);
+	int (*seek)(chan_t *c, long off, int whence);
+	chan_t *(*clone)(chan_t *c, chan_t *nc);
+	chan_t *(*attach)(int id, int dev);
+	chan_t *(*mount)(chan_t *c, const char *spec);
+};
+
+/*******************************************************************************
+ * This structure defines the channel structure.
+ * A channel is a handle on an element of the filesystem.
+ ******************************************************************************/
+struct chan {
+	long		offset;
+	qid_t		qid;
+	unsigned char	index;	/* device index in devtab */
+	unsigned char	dev;
+	unsigned char	mode;
+};
+
+/*******************************************************************************
+ * This structure defines an abstract argument passed to physical drivers from
+ * the configuration file.
+ ******************************************************************************/
+struct attr {
+	char	*key;
+	char	*value;
+};
+
+chan_t *path_to_channel(const char *path, int mode);
+chan_t *clone(chan_t *c, chan_t *nc);
+chan_t *attach(int id, int dev);
+void channel_close(chan_t *c);
+int buf_to_channel(chan_t *c, void *dst, void *src, int nbytes, long len);
+int dirread(chan_t *c, dir_t *dir, const dirtab_t *tab,
+	    int ntab, devgen_t *gen);
+void make_dir_entry(chan_t *c, dir_t *dir, const char *name, long length,
+		    qid_t qid, unsigned int mode);
+void devlink(void);
+
+chan_t *devattach(int id, int dev);
+int devseek(chan_t *c, long off, int whence);
+chan_t *devclone(chan_t *c, chan_t *nc);
+int devgen(chan_t *c, const dirtab_t *tab, int ntab, int n, dir_t *dir);
+int devwalk(chan_t *c, const char *name, const dirtab_t *tab, int ntab,
+		   devgen_t *gen);
+int devstat(chan_t *dirc, const char *file, dir_t *dir,
+		   const dirtab_t *tab, int ntab, devgen_t *gen);
+
+chan_t *deverrmount(chan_t *c, const char *spec);
+int deverrwrite(chan_t *c, void *buf, int n);
+int deverrseek(chan_t *c, long off, int whence);
+
+extern dev_t *const devtab[];
+
+void __dead2 devpanic(const char *cause);
+
+#endif /* DEV_H */

lib/debugfs/devc.c

+/*
+ * Copyright (c) 2019, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+typedef struct dev dev_t;
+
+extern dev_t rootdevtab;
+
+dev_t *const devtab[] = {
+	&rootdevtab,
+	0
+};
+
+void devlink(void)
+{
+}

lib/debugfs/devroot.c

+/*
+ * Copyright (c) 2019, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+#include <common/debug.h>
+#include <lib/debugfs.h>
+
+#include "blobs.h"
+#include "dev.h"
+
+/*******************************************************************************
+ * This array contains the directories available from the root directory.
+ ******************************************************************************/
+static const dirtab_t dirtab[] = {
+	{"dev",   CHDIR | DEV_ROOT_QDEV,   0, O_READ},
+	{"blobs", CHDIR | DEV_ROOT_QBLOBS, 0, O_READ},
+	{"fip",   CHDIR | DEV_ROOT_QFIP,   0, O_READ}
+};
+
+static const dirtab_t devfstab[] = {
+};
+
+/*******************************************************************************
+ * This function exposes the elements of the root directory.
+ * It also exposes the content of the dev and blobs directories.
+ ******************************************************************************/
+static int rootgen(chan_t *channel, const dirtab_t *tab, int ntab,
+		   int n, dir_t *dir)
+{
+	switch (channel->qid & ~CHDIR) {
+	case DEV_ROOT_QROOT:
+		tab = dirtab;
+		ntab = NELEM(dirtab);
+		break;
+	case DEV_ROOT_QDEV:
+		tab = devfstab;
+		ntab = NELEM(devfstab);
+		break;
+	case DEV_ROOT_QBLOBS:
+		tab = blobtab;
+		ntab = NELEM(blobtab);
+		break;
+	default:
+		return 0;
+	}
+
+	return devgen(channel, tab, ntab, n, dir);
+}
+
+static int rootwalk(chan_t *channel, const char *name)
+{
+	return devwalk(channel, name, NULL, 0, rootgen);
+}
+
+/*******************************************************************************
+ * This function copies at most n bytes from the element referred by c into buf.
+ ******************************************************************************/
+static int rootread(chan_t *channel, void *buf, int size)
+{
+	const dirtab_t *dp;
+	dir_t *dir;
+
+	if ((channel->qid & CHDIR) != 0) {
+		if (size < sizeof(dir_t)) {
+			return -1;
+		}
+
+		dir = buf;
+		return dirread(channel, dir, NULL, 0, rootgen);
+	}
+
+	/* Only makes sense when using debug language */
+	assert(channel->qid != DEV_ROOT_QBLOBCTL);
+
+	dp = &blobtab[channel->qid - DEV_ROOT_QBLOBCTL];
+	return buf_to_channel(channel, buf, dp->data, size, dp->length);
+}
+
+static int rootstat(chan_t *channel, const char *file, dir_t *dir)
+{
+	return devstat(channel, file, dir, NULL, 0, rootgen);
+}
+
+const dev_t rootdevtab = {
+	.id = '/',
+	.stat = rootstat,
+	.clone = devclone,
+	.attach = devattach,
+	.walk = rootwalk,
+	.read = rootread,
+	.write = deverrwrite,
+	.mount = deverrmount,
+	.seek = devseek
+};

make_helpers/defaults.mk

@@ -194,6 +194,9 @@ TRUSTED_BOARD_BOOT		:= 0
 # Build option to choose whether Trusted Firmware uses Coherent memory or not.
 USE_COHERENT_MEM		:= 1
 
+# Build option to add debugfs support
+USE_DEBUGFS			:= 0
+
 # Build option to choose whether Trusted Firmware uses library at ROM
 USE_ROMLIB			:= 0