From 6f002c926a06b7667939754f803d3b8e7b14a577 Mon Sep 17 00:00:00 2001
From: Bananymous <bananymousosq@gmail.com>
Date: Mon, 4 Sep 2023 12:57:09 +0300
Subject: [PATCH] Kernel: add basic fcntl() with couple of commands and no
 validation

---
 kernel/include/kernel/OpenFileDescriptorSet.h |  2 ++
 kernel/include/kernel/Process.h               |  2 ++
 kernel/kernel/OpenFileDescriptorSet.cpp       | 26 +++++++++++++++++++
 kernel/kernel/Process.cpp                     |  6 +++++
 kernel/kernel/Syscall.cpp                     |  3 +++
 libc/fcntl.cpp                                | 10 +++++++
 libc/include/sys/syscall.h                    |  1 +
 7 files changed, 50 insertions(+)

diff --git a/kernel/include/kernel/OpenFileDescriptorSet.h b/kernel/include/kernel/OpenFileDescriptorSet.h
index ec5a5bcb..c4551be4 100644
--- a/kernel/include/kernel/OpenFileDescriptorSet.h
+++ b/kernel/include/kernel/OpenFileDescriptorSet.h
@@ -28,6 +28,8 @@ namespace Kernel
 		BAN::ErrorOr<int> dup(int);
 		BAN::ErrorOr<int> dup2(int, int);
 
+		BAN::ErrorOr<int> fcntl(int fd, int cmd, int extra);
+
 		BAN::ErrorOr<void> seek(int fd, off_t offset, int whence);
 		BAN::ErrorOr<off_t> tell(int) const;
 
diff --git a/kernel/include/kernel/Process.h b/kernel/include/kernel/Process.h
index 152d8875..2a808fa4 100644
--- a/kernel/include/kernel/Process.h
+++ b/kernel/include/kernel/Process.h
@@ -99,6 +99,8 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_dup(int fildes);
 		BAN::ErrorOr<long> sys_dup2(int fildes, int fildes2);
 
+		BAN::ErrorOr<long> sys_fcntl(int fildes, int cmd, int extra);
+
 		BAN::ErrorOr<long> sys_seek(int fd, off_t offset, int whence);
 		BAN::ErrorOr<long> sys_tell(int fd);
 
diff --git a/kernel/kernel/OpenFileDescriptorSet.cpp b/kernel/kernel/OpenFileDescriptorSet.cpp
index 607c6a52..46e6f794 100644
--- a/kernel/kernel/OpenFileDescriptorSet.cpp
+++ b/kernel/kernel/OpenFileDescriptorSet.cpp
@@ -118,6 +118,32 @@ namespace Kernel
 		return fildes;
 	}
 
+	BAN::ErrorOr<int> OpenFileDescriptorSet::fcntl(int fd, int cmd, int extra)
+	{
+		TRY(validate_fd(fd));
+
+		constexpr int creation_flags = O_CLOEXEC | O_CREAT | O_DIRECTORY | O_EXCL | O_NOCTTY | O_NOFOLLOW | O_TRUNC | O_TTY_INIT;
+
+		switch (cmd)
+		{
+			case F_GETFD:
+				return m_open_files[fd]->flags;
+			case F_SETFD:
+				// FIXME: validate permissions to set access flags
+				m_open_files[fd]->flags = extra;
+				return 0;
+			case F_GETFL:
+				return m_open_files[fd]->flags & ~creation_flags;
+			case F_SETFL:
+				m_open_files[fd]->flags |= extra & ~(O_ACCMODE | creation_flags);
+				return 0;
+			default:
+				break;
+		}
+		
+		return BAN::Error::from_errno(ENOTSUP);
+	}
+
 	BAN::ErrorOr<void> OpenFileDescriptorSet::seek(int fd, off_t offset, int whence)
 	{
 		TRY(validate_fd(fd));
diff --git a/kernel/kernel/Process.cpp b/kernel/kernel/Process.cpp
index 753ab5d5..9bafe0cf 100644
--- a/kernel/kernel/Process.cpp
+++ b/kernel/kernel/Process.cpp
@@ -669,6 +669,12 @@ namespace Kernel
 		return TRY(m_open_file_descriptors.dup2(fildes, fildes2));
 	}
 
+	BAN::ErrorOr<long> Process::sys_fcntl(int fildes, int cmd, int extra)
+	{
+		LockGuard _(m_lock);
+		return TRY(m_open_file_descriptors.fcntl(fildes, cmd, extra));
+	}
+
 	BAN::ErrorOr<long> Process::sys_seek(int fd, off_t offset, int whence)
 	{
 		LockGuard _(m_lock);
diff --git a/kernel/kernel/Syscall.cpp b/kernel/kernel/Syscall.cpp
index fd9df89a..c919c39d 100644
--- a/kernel/kernel/Syscall.cpp
+++ b/kernel/kernel/Syscall.cpp
@@ -179,6 +179,9 @@ namespace Kernel
 		case SYS_SET_PGID:
 			ret = Process::current().sys_setpgid((pid_t)arg1, (pid_t)arg2);
 			break;
+		case SYS_FCNTL:
+			ret = Process::current().sys_fcntl((int)arg1, (int)arg2, (int)arg3);
+			break;
 		default:
 			dwarnln("Unknown syscall {}", syscall);
 			break;
diff --git a/libc/fcntl.cpp b/libc/fcntl.cpp
index 429f6480..4a796461 100644
--- a/libc/fcntl.cpp
+++ b/libc/fcntl.cpp
@@ -23,3 +23,13 @@ int openat(int fd, const char* path, int oflag, ...)
 
 	return syscall(SYS_OPENAT, fd, path, oflag, mode);
 }
+
+int fcntl(int fildes, int cmd, ...)
+{
+	va_list args;
+	va_start(args, cmd);
+	int extra = va_arg(args, int);
+	va_end(args);
+
+	return syscall(SYS_FCNTL, fildes, cmd, extra);
+}
\ No newline at end of file
diff --git a/libc/include/sys/syscall.h b/libc/include/sys/syscall.h
index 25ba52dc..ae177acd 100644
--- a/libc/include/sys/syscall.h
+++ b/libc/include/sys/syscall.h
@@ -50,6 +50,7 @@ __BEGIN_DECLS
 #define SYS_GET_PID 43
 #define SYS_GET_PGID 44
 #define SYS_SET_PGID 45
+#define SYS_FCNTL 46
 
 __END_DECLS