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Kernel+LibC: Implement futimens(3)

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Implement futimes() in terms of utimensat(). Now, utimensat() strays
from POSIX compliance because it also accepts a combination of a file
descriptor of a regular file and an empty path. utimensat() then uses
this file descriptor instead of the path to update the last access
and/or modification time of a file. That being said, its prior behavior
remains intact.

With the new behavior of utimensat(), `path` must point to a valid
string; given a null pointer instead of an empty string, utimensat()
sets `errno` to `EFAULT` and returns a failure.
This commit is contained in:
Ariel Don 2022-05-03 14:52:08 -05:00 • committed by Andreas Kling
parent 9a6bd85924
commit 8a854ba309
3 changed files with 36 additions and 12 deletions
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41
Kernel/Syscalls/utimensat.cpp
View file

@ -20,6 +20,9 @@ ErrorOr<FlatPtr> Process::sys$utimensat(Userspace<Syscall::SC_utimensat_params c
auto params = TRY(copy_typed_from_user(user_params));
auto now = kgettimeofday().to_truncated_seconds();
int dirfd = params.dirfd;
int follow_symlink = params.flag & AT_SYMLINK_NOFOLLOW ? O_NOFOLLOW_NOERROR : 0;
timespec times[2];
if (params.times) {
TRY(copy_from_user(times, params.times, sizeof(times)));
@ -36,24 +39,38 @@ ErrorOr<FlatPtr> Process::sys$utimensat(Userspace<Syscall::SC_utimensat_params c
times[1].tv_nsec = UTIME_NOW;
}
int dirfd = params.dirfd;
auto path = TRY(get_syscall_path_argument(params.path));
OwnPtr<KString> path;
RefPtr<OpenFileDescription> description;
RefPtr<Custody> base;
if (dirfd == AT_FDCWD) {
base = current_directory();
auto path_or_error = get_syscall_path_argument(params.path);
if (path_or_error.is_error()) {
// If the path is empty ("") but not a nullptr, attempt to get a path
// from the file descriptor. This allows futimens() to be implemented
// in terms of utimensat().
if (params.path.characters && params.path.length == 0) {
description = TRY(open_file_description(dirfd));
path = TRY(description->original_absolute_path());
base = description->custody();
} else {
return path_or_error.release_error();
}
} else {
auto base_description = TRY(open_file_description(dirfd));
if (!KLexicalPath::is_absolute(path->view()) && !base_description->is_directory())
return ENOTDIR;
if (!base_description->custody())
return EINVAL;
base = base_description->custody();
path = path_or_error.release_value();
if (dirfd == AT_FDCWD) {
base = current_directory();
} else {
description = TRY(open_file_description(dirfd));
if (!KLexicalPath::is_absolute(path->view()) && !description->is_directory())
return ENOTDIR;
if (!description->custody())
return EINVAL;
base = description->custody();
}
}
auto& atime = times[0];
auto& mtime = times[1];
int follow_symlink = params.flag & AT_SYMLINK_NOFOLLOW ? O_NOFOLLOW_NOERROR : 0;
TRY(VirtualFileSystem::the().utimensat(path->view(), *base, atime, mtime, follow_symlink));
return 0;
}