From a5493365302384164af3bd8b62d89bcc91355c18 Mon Sep 17 00:00:00 2001
From: Bananymous <bananymousosq@gmail.com>
Date: Thu, 6 Jul 2023 23:17:54 +0300
Subject: [PATCH] Kernel/LibC: add basic dup2

---
 kernel/include/kernel/Process.h |  1 +
 kernel/kernel/Process.cpp       | 37 +++++++++++++++++++++++++++++++--
 kernel/kernel/Syscall.cpp       |  3 +++
 libc/include/sys/syscall.h      |  1 +
 libc/unistd.cpp                 | 12 +++++++++++
 5 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/kernel/include/kernel/Process.h b/kernel/include/kernel/Process.h
index 99e1b66d7e..738d78de1e 100644
--- a/kernel/include/kernel/Process.h
+++ b/kernel/include/kernel/Process.h
@@ -85,6 +85,7 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_creat(BAN::StringView name, mode_t);
 
 		BAN::ErrorOr<long> sys_pipe(int fildes[2]);
+		BAN::ErrorOr<long> sys_dup2(int fildes, int fildes2);
 
 		BAN::ErrorOr<long> sys_seek(int fd, off_t offset, int whence);
 		BAN::ErrorOr<long> sys_tell(int fd);
diff --git a/kernel/kernel/Process.cpp b/kernel/kernel/Process.cpp
index 0eede365da..cca4e63b82 100644
--- a/kernel/kernel/Process.cpp
+++ b/kernel/kernel/Process.cpp
@@ -135,8 +135,13 @@ namespace Kernel
 		}
 
 		m_threads.clear();
-		for (auto& open_fd : m_open_files)
-			open_fd.inode = nullptr;
+
+		for (int fd = 0; fd < (int)m_open_files.size(); fd++)
+		{
+			if (validate_fd(fd).is_error())
+				continue;
+			(void)sys_close(fd);
+		}
 
 		// NOTE: We must unmap ranges while the page table is still alive
 		for (auto* range : m_mapped_ranges)
@@ -624,6 +629,34 @@ namespace Kernel
 		return 0;
 	}
 
+	BAN::ErrorOr<long> Process::sys_dup2(int fildes, int fildes2)
+	{
+		// FIXME: m_open_files should be BAN::Array<BAN::RefPtr<OpenFileDescription>, OPEN_MAX> for accurate dup2
+
+		if (fildes2 < 0 || fildes2 >= 100)
+			return BAN::Error::from_errno(EBADF);
+
+		LockGuard _(m_lock);
+
+		TRY(validate_fd(fildes));
+		if (fildes == fildes2)
+			return fildes;
+
+		if (m_open_files.size() <= (size_t)fildes2)
+			TRY(m_open_files.resize(fildes2 + 1));
+		
+		if (!validate_fd(fildes2).is_error())
+			TRY(sys_close(fildes2));
+		
+		m_open_files[fildes2] = m_open_files[fildes];
+		m_open_files[fildes2].flags &= ~O_CLOEXEC;
+
+		if (m_open_files[fildes].flags & O_WRONLY && m_open_files[fildes].inode->is_pipe())
+			((Pipe*)m_open_files[fildes].inode.ptr())->clone_writing();
+
+		return fildes;
+	}
+
 	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 bfedb0edf9..c475829f25 100644
--- a/kernel/kernel/Syscall.cpp
+++ b/kernel/kernel/Syscall.cpp
@@ -135,6 +135,9 @@ namespace Kernel
 		case SYS_PIPE:
 			ret = Process::current().sys_pipe((int*)arg1);
 			break;
+		case SYS_DUP2:
+			ret = Process::current().sys_dup2((int)arg1, (int)arg2);
+			break;
 		default:
 			dwarnln("Unknown syscall {}", syscall);
 			break;
diff --git a/libc/include/sys/syscall.h b/libc/include/sys/syscall.h
index 6b2545a633..32be089eac 100644
--- a/libc/include/sys/syscall.h
+++ b/libc/include/sys/syscall.h
@@ -40,6 +40,7 @@ __BEGIN_DECLS
 #define SYS_SET_PWD 33
 #define SYS_CLOCK_GETTIME 34
 #define SYS_PIPE 35
+#define SYS_DUP2 36
 
 __END_DECLS
 
diff --git a/libc/unistd.cpp b/libc/unistd.cpp
index ff7a4ff085..9da86fe590 100644
--- a/libc/unistd.cpp
+++ b/libc/unistd.cpp
@@ -257,6 +257,13 @@ long syscall(long syscall, ...)
 			ret = Kernel::syscall(SYS_PIPE, (uintptr_t)fildes);
 			break;
 		}
+		case SYS_DUP2:
+		{
+			int fildes = va_arg(args, int);
+			int fildes2 = va_arg(args, int);
+			ret = Kernel::syscall(SYS_DUP2, fildes, fildes2);
+			break;
+		}
 		default:
 			puts("LibC: Unhandeled syscall");
 			ret = -ENOSYS;
@@ -289,6 +296,11 @@ ssize_t write(int fildes, const void* buf, size_t nbyte)
 	return syscall(SYS_WRITE, fildes, buf, nbyte);
 }
 
+int dup2(int fildes, int fildes2)
+{
+	return syscall(SYS_DUP2, fildes, fildes2);
+}
+
 int execl(const char* pathname, const char* arg0, ...)
 {
 	if (arg0 == nullptr)