kernel+libc: Add getcwd()

kernel/src/sys/chdir.cpp

@@ -36,3 +36,22 @@ Result<u64> sys_chdir(Registers*, SyscallArgs args)
         return 0;
     }
 }
+
+Result<u64> sys_getcwd(Registers*, SyscallArgs args)
+{
+    u8* buf = (u8*)args[0];
+    usize size = (usize)args[1];
+
+    Thread* current = Scheduler::current();
+
+    StringView cwd = current->current_directory_path.view();
+    if (cwd.is_empty()) cwd = "/"_sv;
+
+    usize cwd_size = cwd.length() + 1;
+
+    if (cwd_size > size) return cwd_size;
+
+    if (!MemoryManager::copy_to_user(buf, cwd.chars(), cwd_size)) return err(EFAULT);
+
+    return cwd_size;
+}

libc/include/unistd.h

@@ -100,6 +100,9 @@ extern "C"
     /* Change the current working directory. */
     int chdir(const char* path);
 
+    /* Retrieve the current working directory. */
+    char* getcwd(char* buf, size_t size);
+
 #ifdef __cplusplus
 }
 #endif

libc/src/unistd.cpp

@@ -235,4 +235,69 @@ extern "C"
         long rc = syscall(SYS_chdir, path);
         __errno_return(rc, int);
     }
+
+    static ssize_t __getcwd_wrapper(char* buf, size_t size)
+    {
+        long rc = syscall(SYS_getcwd, buf, size);
+        __errno_return(rc, ssize_t);
+    }
+
+    char* getcwd(char* buf, size_t size)
+    {
+        if (buf)
+        {
+            ssize_t rc = __getcwd_wrapper(buf, size);
+            if (rc < 0) return nullptr;
+
+            if (rc > (ssize_t)size)
+            {
+                errno = ERANGE;
+                return nullptr;
+            }
+
+            return buf;
+        }
+        else if (size)
+        {
+            buf = (char*)malloc(size);
+            if (!buf) return nullptr;
+
+            ssize_t rc = __getcwd_wrapper(buf, size);
+            if (rc < 0)
+            {
+                free(buf);
+                return nullptr;
+            }
+
+            if (rc > (ssize_t)size)
+            {
+                free(buf);
+                errno = ERANGE;
+                return nullptr;
+            }
+
+            return buf;
+        }
+        else
+        {
+            buf = (char*)malloc(1024);
+            if (!buf) return nullptr;
+
+            ssize_t rc = __getcwd_wrapper(buf, 1024);
+            if (rc < 0)
+            {
+                free(buf);
+                return nullptr;
+            }
+
+            if (rc > 1024)
+            {
+                free(buf);
+
+                return getcwd(NULL, rc);
+            }
+
+            return buf;
+        }
+    }
 }

libluna/include/luna/StringView.h

@@ -16,6 +16,8 @@ class StringView
 
     StringView(const StringView&);
 
+    StringView& operator=(const StringView&);
+
     Result<String> to_string();
 
     const char* chars() const

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(chdir)
+                _e(ioctl) _e(stat) _e(fstat) _e(chdir) _e(getcwd)
 
 enum Syscalls
 {

libluna/src/StringView.cpp

@@ -30,6 +30,16 @@ StringView::StringView(const char* c_str, usize length)
     m_length = length;
 }
 
+StringView& StringView::operator=(const StringView& other)
+{
+    if (&other == this) return *this;
+
+    m_string = other.m_string;
+    m_length = other.m_length;
+
+    return *this;
+}
+
 const char& StringView::operator[](usize index) const
 {
     expect(index < m_length, "index out of range");