vfs: Adds semihosting VFS driver

components/vfs/CMakeLists.txt

@@ -1,5 +1,6 @@
 set(COMPONENT_SRCS "vfs.c"
-                   "vfs_uart.c")
+                   "vfs_uart.c"
+                   "vfs_semihost.c")
 set(COMPONENT_ADD_INCLUDEDIRS "include")
 
 set(COMPONENT_REQUIRES)

components/vfs/Kconfig

@@ -15,4 +15,20 @@ menu "Virtual file system"
         help
             Disabling this option can save memory when the support for termios.h is not required.
 
+    menu "Host File System I/O (Semihosting)"
+        config SEMIHOSTFS_MAX_MOUNT_POINTS
+            int "Maximum number of the host filesystem mount points"
+            default 1
+            help
+                Define maximum number of host filesystem mount points.
+
+        config SEMIHOSTFS_HOST_PATH_MAX_LEN
+            int "Maximum path length for the host base directory"
+            default 128
+            help
+                Define maximum path length for the host base directory which is to be mounted.
+                If host path passed to esp_vfs_semihost_register() is longer than this value
+                it will be truncated.
+    endmenu
+
 endmenu

components/vfs/include/esp_vfs_semihost.h

@@ -0,0 +1,46 @@
+// Copyright 2019 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include "esp_vfs.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief add virtual filesystem semihosting driver
+ *
+ * @param base_path VFS path to mount host directory
+ * @param host_path host path to mount; if NULL default dirctory will be used (see OpenOCD configuration)
+ * @return
+ *      - ESP_OK on success
+ *      - ESP_ERR_INVALID_ARG if esp_vfs_semihost_register was already called for specified VFS path
+ *      - ESP_ERR_NO_MEM if there are no slots to register new mount point
+ */
+esp_err_t esp_vfs_semihost_register(const char* base_path, const char* host_path);
+
+/**
+ * @brief Un-register semihosting driver from VFS
+ *
+ * @return
+ *      - ESP_OK on success
+ *      - ESP_ERR_INVALID_ARG if semihosting driver is not registered in VFS at that path
+ */
+esp_err_t esp_vfs_semihost_unregister(const char* base_path);
+
+#ifdef __cplusplus
+}
+#endif

components/vfs/vfs_semihost.c

@@ -0,0 +1,216 @@
+// Copyright 2019 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <string.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <sys/errno.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include "soc/cpu.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "esp_vfs.h"
+
+#define LOG_LOCAL_LEVEL ESP_LOG_NONE
+#include "esp_log.h"
+const static char *TAG = "esp_semihost";
+
+#define SYSCALL_INSTR           "break 1,1\n"
+#define SYS_OPEN                0x01
+#define SYS_CLOSE               0x02
+#define SYS_WRITE               0x05
+#define SYS_READ                0x06
+#define SYS_SEEK                0x0A
+
+/** ESP-specific file open flag. Indicates that path passed to open() is absolute host path. */
+#define ESP_O_SEMIHOST_ABSPATH  0x80000000
+
+typedef struct {
+    char base_path[ESP_VFS_PATH_MAX+1];                 /* base path in VFS where host semohosting dir is mounted */
+    char host_path[CONFIG_SEMIHOSTFS_HOST_PATH_MAX_LEN+1];    /* host path to use as base dir for open files */
+} vfs_semihost_ctx_t;
+
+static vfs_semihost_ctx_t s_semhost_ctx[CONFIG_SEMIHOSTFS_MAX_MOUNT_POINTS];
+
+
+static inline int generic_syscall(int sys_nr, int arg1, int arg2, int arg3, int arg4, int* ret_errno)
+{
+    int host_ret, host_errno;
+
+    if (!esp_cpu_in_ocd_debug_mode()) {
+        *ret_errno = EIO;
+        return -1;
+    }
+    __asm__ volatile (
+        "mov a2, %[sys_nr]\n" \
+        "mov a3, %[arg1]\n" \
+        "mov a4, %[arg2]\n" \
+        "mov a5, %[arg3]\n" \
+        "mov a6, %[arg4]\n" \
+        SYSCALL_INSTR \
+        "mov %[host_ret], a2\n" \
+        "mov %[host_errno], a3\n" \
+        :[host_ret]"=r"(host_ret),[host_errno]"=r"(host_errno)
+        :[sys_nr]"r"(sys_nr),[arg1]"r"(arg1),[arg2]"r"(arg2),[arg3]"r"(arg3),[arg4]"r"(arg4)
+        :"a2","a3","a4","a5","a6");
+    *ret_errno = host_errno;
+    return host_ret;
+}
+
+inline bool ctx_is_unused(const vfs_semihost_ctx_t* ctx)
+{
+    return ctx->base_path[0] == 0;
+}
+
+inline bool ctx_uses_abspath(const vfs_semihost_ctx_t* ctx)
+{
+    return ctx->host_path[0];
+}
+
+static int vfs_semihost_open(void* ctx, const char * path, int flags, int mode)
+{
+    int fd = -1, host_err = 0;
+    char *host_path;
+    vfs_semihost_ctx_t *semi_ctx = ctx;
+
+    ESP_LOGV(TAG, "%s: %p '%s 0x%x 0x%x'", __func__, semi_ctx, path, flags, mode);
+    if (ctx_uses_abspath(semi_ctx)) {
+        flags |= ESP_O_SEMIHOST_ABSPATH;
+        host_path = malloc(strlen(semi_ctx->host_path)+strlen(path)+1);
+        if(host_path == NULL) {
+            errno = ENOMEM;
+            return -1;
+        }
+        strcpy(host_path, semi_ctx->host_path);
+        strcat(host_path, path);
+    } else {
+        host_path = (char *)path;
+    }
+    fd = generic_syscall(SYS_OPEN, (int)host_path, strlen(host_path), flags, mode, &host_err);
+    if (ctx_uses_abspath(semi_ctx)) {
+        free(host_path);
+    }
+    if (fd == -1) {
+        errno = host_err;
+    }
+    return fd;
+}
+
+static ssize_t vfs_semihost_write(void* ctx, int fd, const void * data, size_t size)
+{
+    int host_err = 0;
+    size_t ret = -1;
+
+    ESP_LOGV(TAG, "%s: %d %u bytes", __func__, fd, size);
+    ret = generic_syscall(SYS_WRITE, fd, (int)data, size, 0, &host_err);
+    if (ret == -1) {
+        errno = host_err;
+    }
+    return (ssize_t)ret;
+}
+
+static ssize_t vfs_semihost_read(void* ctx, int fd, void* data, size_t size)
+{
+    int host_err = 0;
+    size_t ret = -1;
+
+    ESP_LOGV(TAG, "%s: %d %u bytes", __func__, fd, size);
+    ret = generic_syscall(SYS_READ, fd, (int)data, size, 0, &host_err);
+    if (ret == -1) {
+        errno = host_err;
+    }
+    return (ssize_t)ret;
+}
+
+static int vfs_semihost_close(void* ctx, int fd)
+{
+    int ret = -1, host_err = 0;
+
+    ESP_LOGV(TAG, "%s: %d", __func__, fd);
+    ret = generic_syscall(SYS_CLOSE, fd, 0, 0, 0, &host_err);
+    if (ret == -1) {
+        errno = host_err;
+    }
+    return ret;
+}
+
+static off_t vfs_semihost_lseek(void* ctx, int fd, off_t size, int mode)
+{
+    int ret = -1, host_err = 0;
+
+    ESP_LOGV(TAG, "%s: %d %ld %d", __func__, fd, size, mode);
+    ret = generic_syscall(SYS_SEEK, fd, size, mode, 0, &host_err);
+    if (ret == -1) {
+        errno = host_err;
+    }
+    return (off_t)ret;
+}
+
+esp_err_t esp_vfs_semihost_register(const char* base_path, const char* host_path)
+{
+    const esp_vfs_t vfs = {
+        .flags = ESP_VFS_FLAG_CONTEXT_PTR,
+        .write_p = &vfs_semihost_write,
+        .open_p = &vfs_semihost_open,
+        .close_p = &vfs_semihost_close,
+        .read_p = &vfs_semihost_read,
+        .lseek_p = &vfs_semihost_lseek,
+    };
+    ESP_LOGD(TAG, "Register semihosting driver '%s' -> '%s'", base_path, host_path ? host_path : "null");
+    if (!esp_cpu_in_ocd_debug_mode()) {
+        ESP_LOGE(TAG, "OpenOCD is not connected!");
+        return ESP_ERR_NOT_SUPPORTED;
+    }
+    int i = 0;
+    for (i = 0; i < CONFIG_SEMIHOSTFS_MAX_MOUNT_POINTS; i++) {
+        if (ctx_is_unused(&s_semhost_ctx[i])) {
+            break;
+        }
+        if (strcmp(base_path, s_semhost_ctx[i].base_path) == 0) {
+            return ESP_ERR_INVALID_STATE;
+        }
+    }
+    if (i == CONFIG_SEMIHOSTFS_MAX_MOUNT_POINTS) {
+        return ESP_ERR_NO_MEM;
+    }
+    strlcpy(s_semhost_ctx[i].base_path, base_path, sizeof(s_semhost_ctx[i].base_path) - 1);
+    if (host_path) {
+        strlcpy(s_semhost_ctx[i].host_path, host_path, sizeof(s_semhost_ctx[i].host_path) - 1);
+    }
+    ESP_LOGD(TAG, "Register semihosting driver %d %p", i, &s_semhost_ctx[i]);
+    return esp_vfs_register(base_path, &vfs, &s_semhost_ctx[i]);
+}
+
+esp_err_t esp_vfs_semihost_unregister(const char* base_path)
+{
+    ESP_LOGD(TAG, "Unregister semihosting driver @ '%s'", base_path);
+    int i = 0;
+    for (i = 0; i < CONFIG_SEMIHOSTFS_MAX_MOUNT_POINTS; i++) {
+        if (s_semhost_ctx[i].base_path[0] != 0 && strcmp(base_path, s_semhost_ctx[i].base_path) == 0) {
+            break;
+        }
+    }
+    if (i == CONFIG_SEMIHOSTFS_MAX_MOUNT_POINTS) {
+        return ESP_ERR_INVALID_ARG;
+    }
+    esp_err_t ret = esp_vfs_unregister(s_semhost_ctx[i].base_path);
+    if (ret != ESP_OK) {
+        return ret;
+    }
+    s_semhost_ctx[i].base_path[0] = 0;
+    s_semhost_ctx[i].host_path[0] = 0;
+    ESP_LOGD(TAG, "Unregistered semihosting driver @ '%s'", base_path);
+    return ESP_OK;
+}

docs/Doxyfile

@@ -137,6 +137,7 @@ INPUT = \
     ## Virtual Filesystem
     ../../components/vfs/include/esp_vfs.h \
     ../../components/vfs/include/esp_vfs_dev.h \
+    ../../components/vfs/include/esp_vfs_semihost.h \
     ## FAT Filesystem
     ## NOTE: for two lines below header_file.inc is not used
     ../../components/fatfs/src/esp_vfs_fat.h \