From 5aed186827c19931f349a71df0a46fcade7b5147 Mon Sep 17 00:00:00 2001
From: Bananymous <bananymousosq@gmail.com>
Date: Sun, 11 Jun 2023 03:27:56 +0300
Subject: [PATCH] Kernel: Add SYS_OPENAT

---
 kernel/include/kernel/Process.h |  1 +
 kernel/kernel/Process.cpp       | 16 ++++++++++++++++
 kernel/kernel/Syscall.cpp       | 11 +++++++++++
 libc/fcntl.cpp                  |  5 +++++
 libc/include/sys/syscall.h      | 29 +++++++++++++++--------------
 5 files changed, 48 insertions(+), 14 deletions(-)

diff --git a/kernel/include/kernel/Process.h b/kernel/include/kernel/Process.h
index 88e731045..6430b2061 100644
--- a/kernel/include/kernel/Process.h
+++ b/kernel/include/kernel/Process.h
@@ -58,6 +58,7 @@ namespace Kernel
 		BAN::ErrorOr<void> setenvp(char** envp);
 
 		BAN::ErrorOr<int> open(BAN::StringView, int);
+		BAN::ErrorOr<int> openat(int, BAN::StringView, int);
 		BAN::ErrorOr<void> close(int fd);
 		BAN::ErrorOr<size_t> read(int fd, void* buffer, size_t count);
 		BAN::ErrorOr<size_t> write(int fd, const void* buffer, size_t count);
diff --git a/kernel/kernel/Process.cpp b/kernel/kernel/Process.cpp
index 3a77a6d72..9bab81249 100644
--- a/kernel/kernel/Process.cpp
+++ b/kernel/kernel/Process.cpp
@@ -469,6 +469,22 @@ namespace Kernel
 		return fd;
 	}
 
+	BAN::ErrorOr<int> Process::openat(int fd, BAN::StringView path, int flags)
+	{
+		BAN::String absolute_path;
+		
+		{
+			LockGuard _(m_lock);
+			TRY(validate_fd(fd));
+			TRY(absolute_path.append(open_file_description(fd).path));
+		}
+		
+		TRY(absolute_path.push_back('/'));
+		TRY(absolute_path.append(path));
+
+		return open(absolute_path, flags);
+	}
+
 	BAN::ErrorOr<void> Process::close(int fd)
 	{
 		LockGuard _(m_lock);
diff --git a/kernel/kernel/Syscall.cpp b/kernel/kernel/Syscall.cpp
index 648af54d8..7d3f6c3a8 100644
--- a/kernel/kernel/Syscall.cpp
+++ b/kernel/kernel/Syscall.cpp
@@ -48,6 +48,14 @@ namespace Kernel
 			return -res.error().get_error_code();
 		return res.value();
 	}
+	
+	int sys_openat(int fd, const char* path, int oflags)
+	{
+		auto res = Process::current().openat(fd, path, oflags);
+		if (res.is_error())
+			return -res.error().get_error_code();
+		return res.value();
+	}
 
 	long sys_alloc(size_t bytes)
 	{
@@ -187,6 +195,9 @@ namespace Kernel
 		case SYS_OPEN:
 			ret = sys_open((const char*)arg1, (int)arg2);
 			break;
+		case SYS_OPENAT:
+			ret = sys_openat((int)arg1, (const char*)arg2, (int)arg3);
+			break;
 		case SYS_ALLOC:
 			ret = sys_alloc((size_t)arg1);
 			break;
diff --git a/libc/fcntl.cpp b/libc/fcntl.cpp
index 6be03408e..d4e05ded9 100644
--- a/libc/fcntl.cpp
+++ b/libc/fcntl.cpp
@@ -7,3 +7,8 @@ int open(const char* path, int oflag, ...)
 {
 	return syscall(SYS_OPEN, path, oflag);
 }
+
+int openat(int fd, const char* path, int oflag, ...)
+{
+	return syscall(SYS_OPENAT, fd, path, oflag);
+}
diff --git a/libc/include/sys/syscall.h b/libc/include/sys/syscall.h
index 5fc7c9a9a..78af2442b 100644
--- a/libc/include/sys/syscall.h
+++ b/libc/include/sys/syscall.h
@@ -11,20 +11,21 @@ __BEGIN_DECLS
 #define SYS_TERMID 4
 #define SYS_CLOSE 5
 #define SYS_OPEN 6
-#define SYS_ALLOC 7
-#define SYS_FREE 8
-#define SYS_SEEK 9
-#define SYS_TELL 10
-#define SYS_GET_TERMIOS 11
-#define SYS_SET_TERMIOS 12
-#define SYS_FORK 13
-#define SYS_SLEEP 14
-#define SYS_EXEC 15
-#define SYS_REALLOC 16
-#define SYS_WAIT 17
-#define SYS_FSTAT 18
-#define SYS_SETENVP 19
-#define SYS_READ_DIR_ENTRIES 20
+#define SYS_OPENAT 7
+#define SYS_ALLOC 8
+#define SYS_REALLOC 9
+#define SYS_FREE 10
+#define SYS_SEEK 11
+#define SYS_TELL 12
+#define SYS_GET_TERMIOS 13
+#define SYS_SET_TERMIOS 14
+#define SYS_FORK 15
+#define SYS_EXEC 16
+#define SYS_SLEEP 17
+#define SYS_WAIT 18
+#define SYS_FSTAT 19
+#define SYS_SETENVP 20
+#define SYS_READ_DIR_ENTRIES 21
 
 __END_DECLS