ARM: Add support for semihosting

Add semihosting API implementation and implement a filesystem driver
to access debugging host filesystem using it.

Tested on Freescale SabreSD board (i.MX6Q) using OpenOCD

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

3 files changed, 188 insertions, 0 deletions

diff --git a/fs/Kconfig b/fs/Kconfig
index feab537b98..9217bc81ea 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -80,4 +80,13 @@ config FS_UIMAGEFS
 	select CRC32
 	prompt "uImage FS support"
 
+config FS_SMHFS
+	depends on ARM_SEMIHOSTING
+	bool
+	prompt "Semihosting FS support"
+	help
+	  If enabled this filesystem provides access to the files
+	  located on a debugging host connected to the target running
+	  Barebox
+
 endmenu
diff --git a/fs/Makefile b/fs/Makefile
index f5aae91a60..46932057c1 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_FS_BPKFS) += bpkfs.o
 obj-$(CONFIG_FS_UIMAGEFS)	+= uimagefs.o
 obj-$(CONFIG_FS_EFI)	 += efi.o
 obj-$(CONFIG_FS_EFIVARFS) += efivarfs.o
+obj-$(CONFIG_FS_SMHFS) += smhfs.o
diff --git a/fs/smhfs.c b/fs/smhfs.c
new file mode 100644
index 0000000000..a0df06c31e
--- /dev/null
+++ b/fs/smhfs.c
@@ -0,0 +1,178 @@
+/*
+ * smhfs.c -- Driver implementing pseudo FS interface on top of ARM
+ *            semihosting
+ *
+ * Copyright (c) 2015 Zodiac Inflight Innovations
+ * Author: Andrey Smirnov <andrew.smirnov@gmail.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <common.h>
+#include <command.h>
+#include <init.h>
+#include <fs.h>
+#include <errno.h>
+#include <linux/stat.h>
+#include <asm/semihosting.h>
+
+static int file_to_fd(const FILE *f)
+{
+	return (int)f->priv;
+}
+
+static int smhfs_create(struct device_d __always_unused *dev,
+			const char __always_unused *pathname,
+			mode_t __always_unused mode)
+{
+	return 0;
+}
+
+static int smhfs_mkdir(struct device_d __always_unused *dev,
+		       const char __always_unused *pathname)
+{
+	return -ENOSYS;
+}
+
+static int smhfs_rm(struct device_d __always_unused *dev,
+		    const char *pathname)
+{
+	/* Get rid of leading '/' */
+	pathname = &pathname[1];
+
+	if (semihosting_remove(pathname) != 0)
+		return -semihosting_errno();
+	else
+		return 0;
+}
+
+static int smhfs_truncate(struct device_d __always_unused *dev,
+			  FILE __always_unused *f,
+			  ulong __always_unused size)
+{
+	return -ENOSYS;
+}
+
+static int smhfs_open(struct device_d __always_unused *dev,
+		      FILE *file, const char *filename)
+{
+	int fd;
+	/* Get rid of leading '/' */
+	filename = &filename[1];
+
+	fd = semihosting_open(filename, file->flags);
+	if (fd < 0)
+		goto error;
+
+	file->priv = (void *)fd;
+	file->size = semihosting_flen(fd);
+	if (file->size < 0)
+		goto error;
+
+	return 0;
+error:
+	return -semihosting_errno();
+}
+
+static int smhfs_close(struct device_d __always_unused *dev,
+		       FILE *f)
+{
+	if (semihosting_close(file_to_fd(f)))
+		return -semihosting_errno();
+	else
+		return 0;
+}
+
+static int smhfs_write(struct device_d __always_unused *dev,
+		       FILE *f, const void *inbuf, size_t insize)
+{
+	if (semihosting_write(file_to_fd(f), inbuf, insize))
+		return -semihosting_errno();
+	else
+		return insize;
+}
+
+static int smhfs_read(struct device_d __always_unused *dev,
+		      FILE *f, void *buf, size_t insize)
+{
+	if (!semihosting_read(file_to_fd(f), buf, insize))
+		return insize;
+	else
+		return -semihosting_errno();
+}
+
+static loff_t smhfs_lseek(struct device_d __always_unused *dev,
+			  FILE *f, loff_t pos)
+{
+	if (semihosting_seek(file_to_fd(f), pos)) {
+		return -semihosting_errno();
+	} else {
+		f->pos = pos;
+		return f->pos;
+	}
+}
+
+static DIR* smhfs_opendir(struct device_d __always_unused *dev,
+			  const char __always_unused *pathname)
+{
+	return NULL;
+}
+
+static int smhfs_stat(struct device_d __always_unused *dev,
+		      const char *filename, struct stat *s)
+{
+	FILE file;
+
+	if (smhfs_open(NULL, &file, filename) == 0) {
+		s->st_mode = S_IFREG | S_IRWXU | S_IRWXG | S_IRWXO;
+		s->st_size = file.size;
+	}
+	smhfs_close(NULL, &file);
+
+	return 0;
+}
+
+static int smhfs_probe(struct device_d __always_unused *dev)
+{
+	/* TODO: Add provisions to detect if debugger is connected */
+	return 0;
+}
+
+static void smhfs_remove(struct device_d __always_unused *dev)
+{
+}
+
+static struct fs_driver_d smhfs_driver = {
+	.open      = smhfs_open,
+	.close     = smhfs_close,
+	.read      = smhfs_read,
+	.lseek     = smhfs_lseek,
+	.opendir   = smhfs_opendir,
+	.stat      = smhfs_stat,
+	.create    = smhfs_create,
+	.unlink    = smhfs_rm,
+	.mkdir     = smhfs_mkdir,
+	.rmdir     = smhfs_rm,
+	.write     = smhfs_write,
+	.truncate  = smhfs_truncate,
+	.flags     = FS_DRIVER_NO_DEV,
+	.drv = {
+		.probe  = smhfs_probe,
+		.remove = smhfs_remove,
+		.name = "smhfs",
+	}
+};
+
+static int smhfs_init(void)
+{
+	return register_fs_driver(&smhfs_driver);
+}
+coredevice_initcall(smhfs_init);