Luna/kernel/src/sys/link.cpp

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#include "Log.h"
#include "memory/MemoryManager.h"
#include "sys/Syscall.h"
#include "thread/Scheduler.h"
#include <bits/atfile.h>
#include <luna/PathParser.h>
Result<u64> sys_unlinkat(Registers*, SyscallArgs args)
{
int dirfd = (int)args[0];
auto path = TRY(MemoryManager::strdup_from_user(args[1]));
int flags = (int)args[2];
Thread* current = Scheduler::current();
auto dirname = TRY(PathParser::dirname(path.view()));
auto basename = TRY(PathParser::basename(path.view()));
if (basename.view() == ".") return err(EINVAL);
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kinfoln("unlinkat: remove %s from directory %s, dirfd is %d", basename.chars(), dirname.chars(), dirfd);
auto inode = TRY(current->resolve_atfile(dirfd, dirname, false, false));
if (!VFS::can_write(inode, current->auth)) return err(EACCES);
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auto child = TRY(inode->find(basename.chars()));
if (flags == AT_REMOVEDIR && child->type() != VFS::InodeType::Directory) return err(ENOTDIR);
if (current->auth.euid != 0 && VFS::is_sticky(inode) && current->auth.euid != inode->metadata().uid &&
current->auth.euid != child->metadata().uid)
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return err(EACCES);
TRY(inode->remove_entry(basename.chars()));
return 0;
}
Result<u64> sys_symlinkat(Registers*, SyscallArgs args)
{
auto target = TRY(MemoryManager::strdup_from_user(args[0]));
int dirfd = (int)args[1];
auto linkpath = TRY(MemoryManager::strdup_from_user(args[2]));
if (target.is_empty()) return err(ENOENT);
auto* current = Scheduler::current();
auto parent = TRY(PathParser::dirname(linkpath.view()));
auto parent_inode = TRY(current->resolve_atfile(dirfd, parent, false, true));
if (!VFS::can_write(parent_inode, current->auth)) return err(EACCES);
auto child_name = TRY(PathParser::basename(linkpath.view()));
TRY(VFS::validate_filename(child_name.view()));
auto inode = TRY(parent_inode->fs()->create_symlink_inode(target.view()));
auto metadata = inode->metadata();
metadata.uid = current->auth.euid;
metadata.gid = current->auth.egid;
TRY(inode->set_metadata(metadata));
TRY(parent_inode->add_entry(inode, child_name.chars()));
return 0;
}
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Result<u64> sys_readlinkat(Registers*, SyscallArgs args)
{
int dirfd = (int)args[0];
auto path = TRY(MemoryManager::strdup_from_user(args[1]));
char* buf = (char*)args[2];
usize bufsiz = (usize)args[3];
auto* current = Scheduler::current();
auto symlink = TRY(current->resolve_atfile(dirfd, path, true, false));
if (symlink->type() != VFS::InodeType::Symlink) return err(EINVAL);
auto linkpath = TRY(symlink->readlink());
check(!linkpath.is_empty());
usize nread = linkpath.length();
if (nread > bufsiz) nread = bufsiz;
if (!MemoryManager::copy_to_user(buf, linkpath.chars(), nread)) return err(EFAULT);
return nread;
}
Result<u64> sys_linkat(Registers*, SyscallArgs args)
{
int olddirfd = (int)args[0];
auto oldpath = TRY(MemoryManager::strdup_from_user(args[1]));
int newdirfd = (int)args[2];
auto newpath = TRY(MemoryManager::strdup_from_user(args[3]));
int flags = (int)args[4];
auto* current = Scheduler::current();
auto parent = TRY(PathParser::dirname(newpath.view()));
// FIXME: Use AT_SYMLINK_FOLLOW.
auto target = TRY(current->resolve_atfile(olddirfd, oldpath, flags & AT_EMPTY_PATH, false));
if (target->type() == VFS::InodeType::Directory) return err(EPERM);
auto parent_inode = TRY(current->resolve_atfile(newdirfd, parent, false, true));
if (target->fs() != parent_inode->fs()) return err(EXDEV);
if (!VFS::can_write(parent_inode, current->auth)) return err(EACCES);
auto child_name = TRY(PathParser::basename(newpath.view()));
TRY(VFS::validate_filename(child_name.view()));
TRY(parent_inode->add_entry(target, child_name.chars()));
return 0;
}