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.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