[PATCH] ARM: Add support for semihosting
Andrey Smirnov
andrew.smirnov at gmail.com
Sun Oct 18 22:33:57 PDT 2015
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 at gmail.com>
---
Documentation/filesystems/smhfs.rst | 20 ++++
arch/arm/Kconfig | 9 ++
arch/arm/include/asm/semihosting.h | 19 +++
arch/arm/lib/Makefile | 1 +
arch/arm/lib/semihosting-trap.S | 28 +++++
arch/arm/lib/semihosting.c | 227 ++++++++++++++++++++++++++++++++++++
fs/Kconfig | 9 ++
fs/Makefile | 1 +
fs/smhfs.c | 177 ++++++++++++++++++++++++++++
9 files changed, 491 insertions(+)
create mode 100644 Documentation/filesystems/smhfs.rst
create mode 100644 arch/arm/include/asm/semihosting.h
create mode 100644 arch/arm/lib/semihosting-trap.S
create mode 100644 arch/arm/lib/semihosting.c
create mode 100644 fs/smhfs.c
diff --git a/Documentation/filesystems/smhfs.rst b/Documentation/filesystems/smhfs.rst
new file mode 100644
index 0000000..06b24b7
--- /dev/null
+++ b/Documentation/filesystems/smhfs.rst
@@ -0,0 +1,20 @@
+.. index:: smhfs (filesystem)
+
+.. _filesystems_smhfs:
+
+File I/O over ARM semihosting support
+=====================================
+
+barebox can communicate with debug programms attached via SWD/JTAG by
+means of ARM semihosting protocol.
+
+Not all of the I/O primitives neccessary to implement a full
+filesystem are exposed in ARM semihosting API and because of that some
+aspects of filesystem funcionality are missing. Implementation does
+not have support for listing directories. This means a
+:ref:`command_ls` to a SMHFS-mounted path will show an empty
+directory. Nevertheless, the files are there.
+
+Example::
+
+ mount -t smhfs /dev/null /mnt/smhfs
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 304b6e6..1bccca3 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -326,6 +326,15 @@ config ARM_UNWIND
the performance is not affected. Currently, this feature
only works with EABI compilers. If unsure say Y.
+config ARM_SEMIHOSTING
+ bool "enable ARM semihosting support"
+ help
+ This option enables ARM semihosting support in barebox. ARM
+ semihosting is a communication discipline that allows code
+ running on target ARM cpu perform system calls and access
+ the data on the host computer connected to the target via
+ debugging channel (JTAG, SWD). If unsure say N
+
endmenu
source common/Kconfig
diff --git a/arch/arm/include/asm/semihosting.h b/arch/arm/include/asm/semihosting.h
new file mode 100644
index 0000000..b478dad
--- /dev/null
+++ b/arch/arm/include/asm/semihosting.h
@@ -0,0 +1,19 @@
+#ifndef __ASM_ARM_SEMIHOSTING_H
+#define __ASM_ARM_SEMIHOSTING_H
+
+int semihosting_open(const char *fname, int flags);
+int semihosting_close(int fd);
+int semihosting_writec(char c);
+int semihosting_write0(const char *str);
+ssize_t semihosting_write(int fd, const void *buf, size_t count);
+ssize_t semihosting_read(int fd, void *buf, size_t count);
+int semihosting_readc(void);
+int semihosting_isatty(int fd);
+int semihosting_seek(int fd, loff_t pos);
+int semihosting_flen(int fd);
+int semihosting_remove(const char *fname);
+int semihosting_rename(const char *fname1, const char *fname2);
+int semihosting_errno(void);
+int semihosting_system(const char *command);
+
+#endif
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index a328795..e1c6f5b 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -20,6 +20,7 @@ pbl-y += runtime-offset.o
obj-$(CONFIG_ARM_OPTIMZED_STRING_FUNCTIONS) += memcpy.o
obj-$(CONFIG_ARM_OPTIMZED_STRING_FUNCTIONS) += memset.o
obj-$(CONFIG_ARM_UNWIND) += unwind.o
+obj-$(CONFIG_ARM_SEMIHOSTING) += semihosting-trap.o semihosting.o
obj-$(CONFIG_MODULES) += module.o
extra-y += barebox.lds
diff --git a/arch/arm/lib/semihosting-trap.S b/arch/arm/lib/semihosting-trap.S
new file mode 100644
index 0000000..9e40ebf
--- /dev/null
+++ b/arch/arm/lib/semihosting-trap.S
@@ -0,0 +1,28 @@
+/*
+ * semihosting-trap.S -- Assembly code needed to make a semihosting call
+ *
+ * Copyright (c) 2015 Zodiac Inflight Innovations
+ * Author: Andrey Smirnov <andrew.smirnov at 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 <linux/linkage.h>
+#include <asm/unified.h>
+
+.section .text.semihosting_trap
+ENTRY(semihosting_trap)
+ @ In supervisor mode SVC would clobber LR
+ push {lr}
+ ARM( svc #0x123456 )
+ THUMB( svc #0xAB )
+ pop {pc}
+ENDPROC(semihosting_trap)
diff --git a/arch/arm/lib/semihosting.c b/arch/arm/lib/semihosting.c
new file mode 100644
index 0000000..a735196
--- /dev/null
+++ b/arch/arm/lib/semihosting.c
@@ -0,0 +1,227 @@
+/*
+ * semihosting.c -- ARM Semihoting API implementation
+ *
+ * Copyright (c) 2015 Zodiac Inflight Innovations
+ * Author: Andrey Smirnov <andrew.smirnov at gmail.com>
+ *
+ * based on a smiliar code from U-Boot
+ * Copyright (c) 2014 Broadcom Corporation
+ *
+ * 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 <fcntl.h>
+
+#ifndef O_BINARY
+#define O_BINARY 0
+#endif
+
+
+enum {
+ SEMIHOSTING_SYS_OPEN = 0x01,
+ SEMIHOSTING_SYS_CLOSE = 0x02,
+ SEMIHOSTING_SYS_WRITEC = 0x03,
+ SEMIHOSTING_SYS_WRITE0 = 0x04,
+ SEMIHOSTING_SYS_WRITE = 0x05,
+ SEMIHOSTING_SYS_READ = 0x06,
+ SEMIHOSTING_SYS_READC = 0x07,
+ /* SYS_ISERROR is not implemented */
+ SEMIHOSTING_SYS_ISATTY = 0x09,
+ SEMIHOSTING_SYS_SEEK = 0x0a,
+ SEMIHOSTING_SYS_FLEN = 0x0c,
+ SEMIHOSTING_SYS_REMOVE = 0x0e,
+ SEMIHOSTING_SYS_RENAME = 0x0f,
+ SEMIHOSTING_SYS_TIME = 0x11,
+ SEMIHOSTING_SYS_ERRNO = 0x13,
+ /* SYS_GET_CMDLINE is not implemented */
+ /* SYS_HEAPINFO is not implemented */
+ /* angel_SWIreason_ReportException is not implemented */
+ SEMIHOSTING_SYS_SYSTEM = 0x12,
+};
+
+uint32_t semihosting_trap(uint32_t sysnum, void *addr);
+
+static uint32_t semihosting_flags_to_mode(int flags)
+{
+ static const int semihosting_open_modeflags[12] = {
+ O_RDONLY,
+ O_RDONLY | O_BINARY,
+ O_RDWR,
+ O_RDWR | O_BINARY,
+ O_WRONLY | O_CREAT | O_TRUNC,
+ O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
+ O_RDWR | O_CREAT | O_TRUNC,
+ O_RDWR | O_CREAT | O_TRUNC | O_BINARY,
+ O_WRONLY | O_CREAT | O_APPEND,
+ O_WRONLY | O_CREAT | O_APPEND | O_BINARY,
+ O_RDWR | O_CREAT | O_APPEND,
+ O_RDWR | O_CREAT | O_APPEND | O_BINARY
+ };
+
+ int i;
+ for (i = 0; i < ARRAY_SIZE(semihosting_open_modeflags); i++) {
+ if (semihosting_open_modeflags[i] == flags)
+ return i;
+ }
+
+ return 0;
+}
+
+int semihosting_open(const char *fname, int flags)
+{
+ struct __packed {
+ uint32_t fname;
+ uint32_t mode;
+ uint32_t len;
+ } open = {
+ .fname = (uint32_t)fname,
+ .len = strlen(fname),
+ .mode = semihosting_flags_to_mode(flags),
+ };
+
+ return semihosting_trap(SEMIHOSTING_SYS_OPEN, &open);
+}
+EXPORT_SYMBOL(semihosting_open);
+
+int semihosting_close(int fd)
+{
+ return semihosting_trap(SEMIHOSTING_SYS_CLOSE, &fd);
+}
+EXPORT_SYMBOL(semihosting_close);
+
+int semihosting_writec(char c)
+{
+ return semihosting_trap(SEMIHOSTING_SYS_WRITEC, &c);
+}
+EXPORT_SYMBOL(semihosting_writec);
+
+int semihosting_write0(const char *str)
+{
+ return semihosting_trap(SEMIHOSTING_SYS_WRITE0, (void *)str);
+}
+EXPORT_SYMBOL(semihosting_write0);
+
+struct __packed semihosting_file_io {
+ uint32_t fd;
+ uint32_t memp;
+ uint32_t len;
+};
+
+ssize_t semihosting_write(int fd, const void *buf, size_t count)
+{
+ struct semihosting_file_io write = {
+ .fd = fd,
+ .memp = (uint32_t)buf,
+ .len = count,
+ };
+
+ return semihosting_trap(SEMIHOSTING_SYS_WRITE, &write);
+}
+EXPORT_SYMBOL(semihosting_write);
+
+ssize_t semihosting_read(int fd, void *buf, size_t count)
+{
+ struct semihosting_file_io read = {
+ .fd = fd,
+ .memp = (uint32_t)buf,
+ .len = count,
+ };
+
+ return semihosting_trap(SEMIHOSTING_SYS_READ, &read);
+}
+EXPORT_SYMBOL(semihosting_read);
+
+int semihosting_readc(void)
+{
+ return semihosting_trap(SEMIHOSTING_SYS_READC, NULL);
+}
+EXPORT_SYMBOL(semihosting_readc);
+
+int semihosting_isatty(int fd)
+{
+ return semihosting_trap(SEMIHOSTING_SYS_ISATTY, &fd);
+}
+EXPORT_SYMBOL(semihosting_isatty);
+
+int semihosting_seek(int fd, off_t pos)
+{
+ struct __packed {
+ uint32_t fd;
+ uint32_t pos;
+ } seek = {
+ .fd = fd,
+ .pos = pos,
+ };
+
+ return semihosting_trap(SEMIHOSTING_SYS_SEEK, &seek);
+}
+EXPORT_SYMBOL(semihosting_seek);
+
+int semihosting_flen(int fd)
+{
+ return semihosting_trap(SEMIHOSTING_SYS_FLEN, &fd);
+}
+EXPORT_SYMBOL(semihosting_flen);
+
+int semihosting_remove(const char *fname)
+{
+ struct __packed {
+ uint32_t fname;
+ uint32_t fname_length;
+ } remove = {
+ .fname = (uint32_t)fname,
+ .fname_length = strlen(fname),
+ };
+
+ return semihosting_trap(SEMIHOSTING_SYS_REMOVE, &remove);
+}
+EXPORT_SYMBOL(semihosting_remove);
+
+int semihosting_rename(const char *fname1, const char *fname2)
+{
+ struct __packed {
+ uint32_t fname1;
+ uint32_t fname1_length;
+ uint32_t fname2;
+ uint32_t fname2_length;
+ } rename = {
+ .fname1 = (uint32_t)fname1,
+ .fname1_length = strlen(fname1),
+ .fname2 = (uint32_t)fname2,
+ .fname2_length = strlen(fname2),
+ };
+
+ return semihosting_trap(SEMIHOSTING_SYS_RENAME, &rename);
+}
+EXPORT_SYMBOL(semihosting_rename);
+
+int semihosting_errno(void)
+{
+ return semihosting_trap(SEMIHOSTING_SYS_ERRNO, NULL);
+}
+EXPORT_SYMBOL(semihosting_errno);
+
+
+int semihosting_system(const char *command)
+{
+ struct __packed {
+ uint32_t cmd;
+ uint32_t cmd_len;
+ } system = {
+ .cmd = (uint32_t)command,
+ .cmd_len = strlen(command),
+ };
+
+ return semihosting_trap(SEMIHOSTING_SYS_SYSTEM, &system);
+}
+EXPORT_SYMBOL(semihosting_system);
diff --git a/fs/Kconfig b/fs/Kconfig
index feab537..9217bc8 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 f5aae91..4693205 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 0000000..d38afe6
--- /dev/null
+++ b/fs/smhfs.c
@@ -0,0 +1,177 @@
+/*
+ * smhfs.c -- Driver implementing pseudo FS interface on top of ARM
+ * semihosting
+ *
+ * Copyright (c) 2015 Zodiac Inflight Innovations
+ * Author: Andrey Smirnov <andrew.smirnov at 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_remove(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)
+{
+ /* Get rid of leading '/' */
+ filename = &filename[1];
+
+ const int 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 {
+ file->pos = pos;
+ return file->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_remove,
+ .mkdir = smhfs_mkdir,
+ .rmdir = smhfs_remove,
+ .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);
--
2.1.4
More information about the barebox
mailing list