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kernel: Introduce *at() syscall framework, add openat() and fstatat()
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This commit is contained in:
apio 2023-04-15 20:26:15 +02:00
parent df95126ccd
commit 82e7b0e860
Signed by: apio
GPG Key ID: B8A7D06E42258954
11 changed files with 67 additions and 41 deletions
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2
kernel/src/fs/VFS.cpp
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@ -15,6 +15,8 @@ namespace VFS
Result<SharedPtr<Inode>> resolve_path(const char* path, Credentials auth, SharedPtr<Inode> working_directory)
{
if (*path == '\0') return err(ENOENT);
auto parser = TRY(PathParser::create(path));
SharedPtr<Inode> current_inode;

23
kernel/src/sys/open.cpp
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@ -9,11 +9,12 @@
// These flags are needed after open(), the rest only affect open().
constexpr int FLAGS_TO_KEEP = O_RDWR | O_APPEND | O_NONBLOCK | O_CLOEXEC;
Result<u64> sys_open(Registers*, SyscallArgs args)
Result<u64> sys_openat(Registers*, SyscallArgs args)
{
auto path = TRY(MemoryManager::strdup_from_user(args[0]));
int flags = (int)args[1];
mode_t mode = (mode_t)args[2];
int dirfd = (int)args[0];
auto path = TRY(MemoryManager::strdup_from_user(args[1]));
int flags = (int)args[2];
mode_t mode = (mode_t)args[3];
Thread* current = Scheduler::current();
@ -22,14 +23,16 @@ Result<u64> sys_open(Registers*, SyscallArgs args)
// Caller did not pass either O_RDONLY, O_WRONLY or O_RDWR
if ((flags & O_RDWR) == 0) { return err(EINVAL); }
if ((flags & O_DIRECTORY) & (flags & O_CREAT)) return err(EINVAL);
int error;
bool ok =
VFS::resolve_path(path.chars(), current->auth, current->current_directory).try_set_value_or_error(inode, error);
SharedPtr<VFS::Inode> parent_inode;
bool ok = current->resolve_atfile(dirfd, path, false, &parent_inode).try_set_value_or_error(inode, error);
if (!ok)
{
if (error == ENOENT && (flags & O_CREAT))
if (error == ENOENT && (flags & O_CREAT) && !path.is_empty())
{
inode = TRY(VFS::create_file(path.chars(), current->auth, current->current_directory));
inode = TRY(VFS::create_file(path.chars(), current->auth, parent_inode));
inode->chmod(mode);
inode->chown(current->auth.euid, current->auth.egid);
}
@ -50,9 +53,9 @@ Result<u64> sys_open(Registers*, SyscallArgs args)
int fd = TRY(current->allocate_fd(0));
current->fd_table[fd] = FileDescriptor { inode, 0, flags & FLAGS_TO_KEEP };
kinfoln("openat: opening file %s from dirfd %d, flags %d, mode %#o = fd %d", path.chars(), dirfd, flags, mode, fd);
kinfoln("open: opening file %s, flags %d, mode %#o = fd %d", path.chars(), flags, mode, fd);
current->fd_table[fd] = FileDescriptor { inode, 0, flags & FLAGS_TO_KEEP };
return (u64)fd;
}

36
kernel/src/sys/stat.cpp
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@ -1,6 +1,7 @@
#include "memory/MemoryManager.h"
#include "sys/Syscall.h"
#include "thread/Scheduler.h"
#include <bits/atfile.h>
#include <bits/modes.h>
#include <bits/struct_stat.h>
@ -19,8 +20,17 @@ static mode_t make_mode(mode_t mode, VFS::InodeType type)
return result;
}
static Result<u64> do_stat(SharedPtr<VFS::Inode> inode, stat* st)
Result<u64> sys_fstatat(Registers*, SyscallArgs args)
{
int dirfd = (int)args[0];
auto path = TRY(MemoryManager::strdup_from_user(args[1]));
stat* st = (stat*)args[2];
int flags = (int)args[3];
Thread* current = Scheduler::current();
auto inode = TRY(current->resolve_atfile(dirfd, path, flags & AT_EMPTY_PATH));
stat kstat;
kstat.st_ino = inode->inode_number();
@ -34,27 +44,3 @@ static Result<u64> do_stat(SharedPtr<VFS::Inode> inode, stat* st)
return 0;
}
Result<u64> sys_stat(Registers*, SyscallArgs args)
{
auto path = TRY(MemoryManager::strdup_from_user(args[0]));
stat* st = (stat*)args[1];
Thread* current = Scheduler::current();
auto inode = TRY(VFS::resolve_path(path.chars(), current->auth, current->current_directory));
return do_stat(inode, st);
}
Result<u64> sys_fstat(Registers*, SyscallArgs args)
{
int fd = (int)args[0];
stat* st = (stat*)args[1];
Thread* current = Scheduler::current();
auto descriptor = *TRY(current->resolve_fd(fd));
return do_stat(descriptor.inode, st);
}

21
kernel/src/thread/Thread.cpp
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@ -1,7 +1,10 @@
#include "thread/Thread.h"
#include "memory/MemoryManager.h"
#include <bits/atfile.h>
#include <bits/open-flags.h>
#include <luna/Alloc.h>
#include <luna/Atomic.h>
#include <luna/PathParser.h>
static Atomic<u64> g_next_id;
@ -45,6 +48,24 @@ Result<FileDescriptor*> Thread::resolve_fd(int fd)
return maybe_descriptor.value_ptr();
}
Result<SharedPtr<VFS::Inode>> Thread::resolve_atfile(int dirfd, const String& path, bool allow_empty_path,
SharedPtr<VFS::Inode>* parent_inode)
{
if (parent_inode) *parent_inode = this->current_directory;
if (PathParser::is_absolute(path.view())) return VFS::resolve_path(path.chars(), this->auth);
if (dirfd == AT_FDCWD) return VFS::resolve_path(path.chars(), this->auth, this->current_directory);
auto descriptor = TRY(resolve_fd(dirfd));
if (parent_inode) *parent_inode = descriptor->inode;
if (path.is_empty() && allow_empty_path) return descriptor->inode;
return VFS::resolve_path(path.chars(), this->auth, descriptor->inode);
}
bool FileDescriptor::should_append()
{
return flags & O_APPEND;

2
kernel/src/thread/Thread.h
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@ -73,6 +73,8 @@ struct Thread : public LinkedListNode<Thread>
Result<int> allocate_fd(int min);
Result<FileDescriptor*> resolve_fd(int fd);
Result<SharedPtr<VFS::Inode>> resolve_atfile(int dirfd, const String& path, bool allow_empty_path,
SharedPtr<VFS::Inode>* parent_inode = nullptr);
FPData fp_data;

10
libc/include/bits/atfile.h Normal file
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@ -0,0 +1,10 @@
/* bits/atfile.h: Definitions for *at() functions. */
#ifndef _BITS_ATFILE_H
#define _BITS_ATFILE_H
#define AT_FDCWD -100
#define AT_EMPTY_PATH 1
#endif

1
libc/include/fcntl.h
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@ -3,6 +3,7 @@
#ifndef _FCNTL_H
#define _FCNTL_H
#include <bits/atfile.h>
#include <bits/fcntl.h>
#include <bits/open-flags.h>
#include <sys/types.h>

2
libc/src/fcntl.cpp
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@ -13,7 +13,7 @@ extern "C"
mode_t mode = (mode_t)va_arg(ap, int);
long rc = syscall(SYS_open, path, flags, mode);
long rc = syscall(SYS_openat, AT_FDCWD, path, flags, mode);
va_end(ap);
__errno_return(rc, int);

5
libc/src/sys/stat.cpp
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@ -1,4 +1,5 @@
#include <bits/errno-return.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <unistd.h>
@ -19,13 +20,13 @@ extern "C"
int stat(const char* path, struct stat* st)
{
long rc = syscall(SYS_stat, path, st);
long rc = syscall(SYS_fstatat, AT_FDCWD, path, st, 0);
__errno_return(rc, int);
}
int fstat(int fd, struct stat* st)
{
long rc = syscall(SYS_fstat, fd, st);
long rc = syscall(SYS_fstatat, fd, "", st, AT_EMPTY_PATH);
__errno_return(rc, int);
}
}

4
libluna/include/luna/Syscall.h
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@ -1,10 +1,10 @@
#pragma once
#define enumerate_syscalls(_e) \
_e(exit) _e(clock_gettime) _e(mmap) _e(munmap) _e(usleep) _e(open) _e(close) _e(read) _e(getpid) _e(write) \
_e(exit) _e(clock_gettime) _e(mmap) _e(munmap) _e(usleep) _e(openat) _e(close) _e(read) _e(getpid) _e(write) \
_e(lseek) _e(mkdir) _e(execve) _e(mknod) _e(fork) _e(waitpid) _e(getppid) _e(fcntl) _e(getdents) _e(getuid) \
_e(geteuid) _e(getgid) _e(getegid) _e(setuid) _e(setgid) _e(seteuid) _e(setegid) _e(chmod) _e(chown) \
_e(ioctl) _e(stat) _e(fstat) _e(chdir) _e(getcwd) _e(unlink)
_e(ioctl) _e(fstatat) _e(chdir) _e(getcwd) _e(unlink)
enum Syscalls
{

2
libos/src/File.cpp
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@ -59,7 +59,7 @@ namespace os
{
auto file = TRY(adopt_shared_if_nonnull(new (std::nothrow) File({})));
long rc = syscall(SYS_open, path.chars(), flags, mode);
long rc = syscall(SYS_openat, AT_FDCWD, path.chars(), flags, mode);
int fd = TRY(Result<int>::from_syscall(rc));
file->m_fd = fd;