my-kern/kernel/vfs/vfs.c

//
// Created by rick on 12-08-21.
//

#include <stddef.h>
#include <stdlib.h>
#include <string.h>

#include <myke/tasks/locking.h>
#include <myke/vfs/vfs.h>
#include <myke/vfs/vfs-driver.h>
#include <myke/util/init.h>
#include <myke/libk/libk.h>

vfs_mount_t *first_mount = NULL;
mutex_t *mount_lock = NULL;

extern vfs_driver_t __start_vfs_driver[];
extern vfs_driver_t __stop_vfs_driver[];
#define NUM_DRIVERS ((size_t)(__stop_vfs_driver - __start_vfs_driver))
#define DRIVER(i) ((__start_vfs_driver) + (i))

vfs_driver_t *vfs_get_driver_by_name(const char *name) {
    for (size_t i = 0; i < NUM_DRIVERS; ++i) {
        if (strcmp(DRIVER(i)->name, name) == 0) {
            return DRIVER(i);
        }
    }
    return NULL;
}

void vfs_register_mount(vfs_mount_t *mount) {
    mutex_acquire(mount_lock);
    if (first_mount == NULL) {
        first_mount = mount;
    } else {
        vfs_mount_t *last_mount = first_mount;
        while (last_mount->next != NULL) last_mount = last_mount->next;
        last_mount->next = mount;
    }
    mutex_release(mount_lock);
}

vfs_mount_t *vfs_get_mount_for_path(const char *path) {
    if (first_mount == NULL) {
        return NULL;
    }
    mutex_acquire(mount_lock);
    size_t max_length = strlen(path);
    vfs_mount_t *longest_match = NULL;
    size_t match_length = 0;
    vfs_mount_t *last_mount = NULL;
    do {
        if (last_mount == NULL) {
            last_mount = first_mount;
        } else if ((last_mount = last_mount->next) == NULL) {
            break;
        }
        size_t mount_length = strlen(last_mount->prefix);
        if (mount_length > max_length || mount_length < match_length) {
            continue;
        }
        if (strncmp(last_mount->prefix, path, strlen(last_mount->prefix)) == 0) {
            longest_match = last_mount;
            match_length = mount_length;
        }
    } while (true);
    mutex_release(mount_lock);
    return longest_match;
}

int vfs_mount(const char *path, const char *device, const char *driver) {
    vfs_driver_t *driver_impl = vfs_get_driver_by_name(driver);
    if (driver_impl == NULL) {
        return VFS_MOUNT_ERROR;
    }
    vfs_mount_t *mount = malloc(sizeof(vfs_mount_t));
    mount->driver = driver_impl;
    mount->device = device;
    mount->prefix = path;
    int result = driver_impl->vfs_mount(mount);
    if (result != VFS_MOUNT_OK) {
        free(mount);
        return result;
    }
    vfs_register_mount(mount);
    return VFS_MOUNT_OK;
}

vfs_fd_t *vfs_open_intermediate(vfs_mount_t *mount, const char *path, int flags, int mode) {
    vfs_fd_t *intermediate_dir = malloc(sizeof(vfs_fd_t));
    vfs_fd_t *out = malloc(sizeof(vfs_fd_t));
    out->mount = mount;
    intermediate_dir->mount = mount;
    char *full_path = strdup(path);
    char *current_path = full_path;
    while (strlen(current_path) > 0) {
        if (current_path[0] == '/') {
            // root
            if (((vfs_driver_t *) mount->driver)->open(mount, NULL, NULL, flags, out) != VFS_OPEN_OK) {
                free(out);
                free(intermediate_dir);
                free(full_path);
                return NULL;
            }
            current_path = &current_path[1];
        } else {
            char *next_dir = strchr(current_path, '/');
            if (next_dir != NULL) {
                next_dir[0] = 0;
            }
            if (((vfs_driver_t *) mount->driver)->open(mount, intermediate_dir, current_path, flags, out) !=
                VFS_OPEN_OK) {
                ((vfs_driver_t *) mount->driver)->close(mount, intermediate_dir);
                free(out);
                free(intermediate_dir);
                free(full_path);
                return NULL;
            }
            if (next_dir == NULL) {
                current_path = &current_path[strlen(current_path)];
            } else {
                current_path = &next_dir[1];
            }
            if (((vfs_driver_t *) mount->driver)->close(mount, intermediate_dir) != VFS_CLOSE_OK) {
                free(out);
                free(intermediate_dir);
                free(full_path);
                return NULL;
            }
        }
        memcpy(intermediate_dir, out, sizeof(vfs_fd_t));
    }
    free(full_path);
    free(intermediate_dir);
    return out;
}

// https://man7.org/linux/man-pages/man2/open.2.html
vfs_fd_t *vfs_open(const char *path, int flags, int mode) {
    vfs_mount_t *mount = vfs_get_mount_for_path(path);
    if (mount == NULL) {
        return NULL;
    }
    return vfs_open_intermediate(mount, &path[strlen(mount->prefix) - 1], flags, mode);
}

void vfs_close(vfs_fd_t *fd) {
    ((vfs_driver_t *) (fd->mount->driver))->close(fd->mount, fd);
    free(fd);
}

// https://man7.org/linux/man-pages/man2/stat.2.html
int vfs_fstat(vfs_fd_t *dirfd, stat_t *target, int flags) {
    return ((vfs_driver_t *) (dirfd->mount->driver))->fstat(dirfd->mount, dirfd, target, flags);
}

// https://man7.org/linux/man-pages/man2/read.2.html
int vfs_read(vfs_fd_t *fd, void *target, size_t size) {
    return ((vfs_driver_t *) (fd->mount->driver))->fread(fd->mount, fd, target, size);
}

// inspiration https://man7.org/linux/man-pages/man2/getdents.2.html
int vfs_getdents(vfs_fd_t *fd, void *target, int count) {
    return ((vfs_driver_t *) fd->mount->driver)->dgetent(fd->mount, fd, target, count);
}

void vfs_mk_dirent_record(vfs_dirent_t *ent, uint32_t inode, uint32_t cur_offset, uint8_t type, char *name,
                          size_t name_length) {
    ent->inode = inode;
    strncpy(ent->name, name, name_length);
    ent->name[name_length] = 0;
    ent->type = type;
    ent->reclen = VFS_DIRENT_SIZE(name_length);
    ent->offset_next = cur_offset + ent->reclen;
}

void vfs_init() {
    mount_lock = mutex_create();
}

INIT_FUNCTION(100) = {
        .name = "vfs-task",
        .stage = INIT_STAGE_PRE_TASKING,
        .init = vfs_init,
};