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libos_stat.c
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libos_stat.c
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/* SPDX-License-Identifier: LGPL-3.0-or-later */
/* Copyright (C) 2014 Stony Brook University */
/*
* Implementation of system calls "stat", "lstat", "fstat" and "readlink".
*/
#include "libos_fs.h"
#include "libos_handle.h"
#include "libos_internal.h"
#include "libos_process.h"
#include "libos_table.h"
#include "linux_abi/errors.h"
#include "linux_abi/fs.h"
#include "stat.h"
static int do_stat(struct libos_dentry* dent, struct stat* stat) {
assert(locked(&g_dcache_lock));
assert(dent->inode);
struct libos_fs* fs = dent->inode->fs;
if (!fs || !fs->d_ops || !fs->d_ops->stat)
return -EACCES;
int ret = fs->d_ops->stat(dent, stat);
if (ret < 0)
return ret;
/* Update `st_ino` from dentry */
stat->st_ino = dentry_ino(dent);
return 0;
}
static int do_hstat(struct libos_handle* hdl, struct stat* stat) {
struct libos_fs* fs = hdl->fs;
if (!fs || !fs->fs_ops || !fs->fs_ops->hstat)
return -EACCES;
int ret = fs->fs_ops->hstat(hdl, stat);
if (ret < 0)
return ret;
/* Update `st_ino` from dentry */
lock(&hdl->lock);
if (hdl->dentry)
stat->st_ino = dentry_ino(hdl->dentry);
unlock(&hdl->lock);
return 0;
}
long libos_syscall_stat(const char* file, struct stat* stat) {
if (!is_user_string_readable(file))
return -EFAULT;
if (!is_user_memory_writable(stat, sizeof(*stat)))
return -EFAULT;
int ret;
struct libos_dentry* dent = NULL;
lock(&g_dcache_lock);
ret = path_lookupat(/*start=*/NULL, file, LOOKUP_FOLLOW, &dent);
if (ret < 0)
goto out;
ret = do_stat(dent, stat);
out:
unlock(&g_dcache_lock);
if (dent)
put_dentry(dent);
return ret;
}
long libos_syscall_lstat(const char* file, struct stat* stat) {
if (!is_user_string_readable(file))
return -EFAULT;
if (!is_user_memory_writable(stat, sizeof(*stat)))
return -EFAULT;
int ret;
struct libos_dentry* dent = NULL;
lock(&g_dcache_lock);
ret = path_lookupat(/*start=*/NULL, file, LOOKUP_NO_FOLLOW, &dent);
if (ret < 0)
goto out;
ret = do_stat(dent, stat);
out:
unlock(&g_dcache_lock);
if (dent)
put_dentry(dent);
return ret;
}
long libos_syscall_fstat(int fd, struct stat* stat) {
struct libos_handle* hdl = get_fd_handle(fd, NULL, NULL);
if (!hdl)
return -EBADF;
if (!is_user_memory_writable(stat, sizeof(*stat)))
return -EFAULT;
int ret = do_hstat(hdl, stat);
put_handle(hdl);
return ret;
}
long libos_syscall_readlinkat(int dirfd, const char* file, char* buf, int bufsize) {
int ret;
char* target = NULL;
if (!is_user_string_readable(file))
return -EFAULT;
if (bufsize <= 0)
return -EINVAL;
if (!is_user_memory_writable(buf, bufsize))
return -EFAULT;
struct libos_dentry* dent = NULL;
struct libos_dentry* dir = NULL;
if (*file != '/' && (ret = get_dirfd_dentry(dirfd, &dir)) < 0)
goto out;
lock(&g_dcache_lock);
ret = path_lookupat(dir, file, LOOKUP_NO_FOLLOW, &dent);
if (ret < 0)
goto out;
ret = -EINVAL;
/* The correct behavior is to return -EINVAL if file is not a
symbolic link */
if (dent->inode->type != S_IFLNK)
goto out;
struct libos_fs* fs = dent->inode->fs;
if (!fs->d_ops || !fs->d_ops->follow_link)
goto out;
ret = fs->d_ops->follow_link(dent, &target);
if (ret < 0)
goto out;
size_t target_len = strlen(target);
ret = bufsize;
if (target_len < (size_t)bufsize)
ret = target_len;
memcpy(buf, target, ret);
out:
unlock(&g_dcache_lock);
if (dent) {
put_dentry(dent);
}
if (dir) {
put_dentry(dir);
}
free(target);
return ret;
}
long libos_syscall_readlink(const char* file, char* buf, int bufsize) {
return libos_syscall_readlinkat(AT_FDCWD, file, buf, bufsize);
}
static int __do_statfs(struct libos_mount* mount, struct statfs* buf) {
__UNUSED(mount);
if (!is_user_memory_writable(buf, sizeof(*buf)))
return -EFAULT;
memset(buf, 0, sizeof(*buf));
buf->f_bsize = 4096;
buf->f_blocks = 20000000;
buf->f_bfree = 10000000;
buf->f_bavail = 10000000;
log_debug("statfs: %ld %ld %ld", buf->f_blocks, buf->f_bfree, buf->f_bavail);
return 0;
}
long libos_syscall_statfs(const char* path, struct statfs* buf) {
if (!is_user_string_readable(path))
return -EFAULT;
int ret;
struct libos_dentry* dent = NULL;
lock(&g_dcache_lock);
ret = path_lookupat(/*start=*/NULL, path, LOOKUP_FOLLOW, &dent);
unlock(&g_dcache_lock);
if (ret < 0)
return ret;
struct libos_mount* mount = dent->mount;
put_dentry(dent);
return __do_statfs(mount, buf);
}
long libos_syscall_fstatfs(int fd, struct statfs* buf) {
struct libos_handle* hdl = get_fd_handle(fd, NULL, NULL);
if (!hdl)
return -EBADF;
lock(&hdl->lock);
struct libos_mount* mount = hdl->dentry ? hdl->dentry->mount : NULL;
unlock(&hdl->lock);
put_handle(hdl);
return __do_statfs(mount, buf);
}
/*
* Handle the special case of `fstatat` with empty path (permitted with AT_EMPTY_PATH). Note that in
* this case `dirfd` can point to a non-directory file, so we cannot use `get_dirfd_dentry`.
*/
static int do_fstatat_empty_path(int dirfd, struct stat* statbuf) {
if (dirfd != AT_FDCWD)
return libos_syscall_fstat(dirfd, statbuf);
lock(&g_process.fs_lock);
struct libos_dentry* dent = g_process.cwd;
get_dentry(dent);
unlock(&g_process.fs_lock);
lock(&g_dcache_lock);
int ret;
if (!dent->inode) {
ret = -ENOENT;
goto out;
}
ret = do_stat(dent, statbuf);
out:
unlock(&g_dcache_lock);
put_dentry(dent);
return ret;
}
long libos_syscall_newfstatat(int dirfd, const char* pathname, struct stat* statbuf, int flags) {
if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW))
return -EINVAL;
if (!is_user_string_readable(pathname))
return -EFAULT;
if (!is_user_memory_writable(statbuf, sizeof(*statbuf)))
return -EFAULT;
int lookup_flags = LOOKUP_FOLLOW;
if (flags & AT_SYMLINK_NOFOLLOW)
lookup_flags &= ~LOOKUP_FOLLOW;
if (flags & AT_NO_AUTOMOUNT) {
/* Do nothing as automount isn't supported */
log_warning("newfstatat: ignoring AT_NO_AUTOMOUNT.");
}
if (!*pathname) {
if (!(flags & AT_EMPTY_PATH))
return -ENOENT;
return do_fstatat_empty_path(dirfd, statbuf);
}
int ret;
struct libos_dentry* dir = NULL;
if (*pathname != '/') {
ret = get_dirfd_dentry(dirfd, &dir);
if (ret < 0)
return ret;
}
lock(&g_dcache_lock);
struct libos_dentry* dent = NULL;
ret = path_lookupat(dir, pathname, lookup_flags, &dent);
if (ret < 0)
goto out;
ret = do_stat(dent, statbuf);
out:
unlock(&g_dcache_lock);
if (dent)
put_dentry(dent);
if (dir)
put_dentry(dir);
return ret;
}