From 2a967f4b8b1ab477e344a156f57460f128c10612 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Tue, 11 Apr 2023 22:15:21 +0200
Subject: [PATCH] kernel+libc: Add chdir()

---
 kernel/CMakeLists.txt             |  1 +
 kernel/src/sys/chdir.cpp          | 38 +++++++++++++++++++++++++
 libc/include/unistd.h             |  3 ++
 libc/src/unistd.cpp               |  6 ++++
 libluna/include/luna/PathParser.h | 11 +++++++-
 libluna/include/luna/Syscall.h    |  2 +-
 libluna/src/PathParser.cpp        | 46 +++++++++++++++++++++++++++++++
 7 files changed, 105 insertions(+), 2 deletions(-)
 create mode 100644 kernel/src/sys/chdir.cpp

diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index b46efcc5..dc378736 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -35,6 +35,7 @@ set(SOURCES
     src/sys/waitpid.cpp
     src/sys/getdents.cpp
     src/sys/stat.cpp
+    src/sys/chdir.cpp
     src/fs/VFS.cpp
     src/fs/tmpfs/FileSystem.cpp
     src/fs/devices/DeviceRegistry.cpp
diff --git a/kernel/src/sys/chdir.cpp b/kernel/src/sys/chdir.cpp
new file mode 100644
index 00000000..1991e5bb
--- /dev/null
+++ b/kernel/src/sys/chdir.cpp
@@ -0,0 +1,38 @@
+#include "memory/MemoryManager.h"
+#include "sys/Syscall.h"
+#include "thread/Scheduler.h"
+#include <luna/PathParser.h>
+
+Result<u64> sys_chdir(Registers*, SyscallArgs args)
+{
+    auto path = TRY(MemoryManager::strdup_from_user(args[0]));
+
+    Thread* current = Scheduler::current();
+
+    if (PathParser::is_absolute(path.view()))
+    {
+        SharedPtr<VFS::Inode> inode = TRY(VFS::resolve_path(path.chars(), current->auth));
+
+        if (inode->type() != VFS::InodeType::Directory) return err(ENOTDIR);
+
+        current->current_directory = inode;
+        current->current_directory_path = move(path);
+
+        return 0;
+    }
+    else
+    {
+        SharedPtr<VFS::Inode> inode = TRY(VFS::resolve_path(path.chars(), current->auth, current->current_directory));
+
+        if (inode->type() != VFS::InodeType::Directory) return err(ENOTDIR);
+
+        auto old_wdir = current->current_directory_path.view();
+
+        String new_path = TRY(PathParser::join(old_wdir.is_empty() ? "/"_sv : old_wdir, path.view()));
+
+        current->current_directory = inode;
+        current->current_directory_path = move(new_path);
+
+        return 0;
+    }
+}
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index a8c1bcfc..49379ff2 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -97,6 +97,9 @@ extern "C"
     /* Duplicate a file descriptor. */
     int dup(int fd);
 
+    /* Change the current working directory. */
+    int chdir(const char* path);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/libc/src/unistd.cpp b/libc/src/unistd.cpp
index 845f0235..29b0c51c 100644
--- a/libc/src/unistd.cpp
+++ b/libc/src/unistd.cpp
@@ -229,4 +229,10 @@ extern "C"
     {
         return fcntl(fd, F_DUPFD, 0);
     }
+
+    int chdir(const char* path)
+    {
+        long rc = syscall(SYS_chdir, path);
+        __errno_return(rc, int);
+    }
 }
diff --git a/libluna/include/luna/PathParser.h b/libluna/include/luna/PathParser.h
index 44e9fbb9..cf6de4c0 100644
--- a/libluna/include/luna/PathParser.h
+++ b/libluna/include/luna/PathParser.h
@@ -11,11 +11,20 @@ class PathParser
     PathParser(PathParser&& other);
     PathParser(const PathParser&) = delete;
 
+    static Result<String> join(StringView path1, StringView path2);
+
+    static Result<String> realpath(StringView path);
+
+    static bool is_absolute(StringView path)
+    {
+        return *path.chars() == '/';
+    }
+
     ~PathParser();
 
     bool is_absolute() const
     {
-        return *m_original == '/';
+        return is_absolute(StringView { m_original });
     }
 
     Result<String> basename();
diff --git a/libluna/include/luna/Syscall.h b/libluna/include/luna/Syscall.h
index 00eb17dc..d01005a9 100644
--- a/libluna/include/luna/Syscall.h
+++ b/libluna/include/luna/Syscall.h
@@ -4,7 +4,7 @@
     _e(exit) _e(clock_gettime) _e(mmap) _e(munmap) _e(usleep) _e(open) _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(ioctl) _e(stat) _e(fstat) _e(chdir)
 
 enum Syscalls
 {
diff --git a/libluna/src/PathParser.cpp b/libluna/src/PathParser.cpp
index 6ae26b7c..3ddd8f4c 100644
--- a/libluna/src/PathParser.cpp
+++ b/libluna/src/PathParser.cpp
@@ -1,6 +1,7 @@
 #include <luna/CPath.h>
 #include <luna/PathParser.h>
 #include <luna/ScopeGuard.h>
+#include <luna/StringBuilder.h>
 
 Result<PathParser> PathParser::create(const char* path)
 {
@@ -59,3 +60,48 @@ Result<String> PathParser::dirname()
     // We must copy this as we cannot rely on the original string.
     return String::from_cstring(result);
 }
+
+Result<String> PathParser::join(StringView path1, StringView path2)
+{
+    StringBuilder sb;
+    TRY(sb.add(path1));
+
+    if (path1[path1.length() - 1] != '/') TRY(sb.add('/'));
+
+    TRY(sb.add(path2));
+
+    String result = TRY(sb.string());
+
+    return realpath(result.view());
+}
+
+Result<String> PathParser::realpath(StringView path)
+{
+    if (!is_absolute(path)) return String {};
+
+    Vector<StringView> parts;
+    PathParser parser = TRY(PathParser::create(path.chars()));
+
+    const char* part;
+    while (parser.next().try_set_value(part))
+    {
+        StringView view = part;
+        if (view == ".") continue;
+        if (view == "..")
+        {
+            parts.try_pop();
+            continue;
+        }
+
+        TRY(parts.try_append(view));
+    }
+
+    StringBuilder sb;
+    for (const auto& section : parts)
+    {
+        TRY(sb.add('/'));
+        TRY(sb.add(section));
+    }
+
+    return sb.string();
+}