kernel: Add strdup_from_user()

kernel/src/memory/MemoryManager.cpp

@@ -8,6 +8,7 @@
 #include <luna/Spinlock.h>
 #include <luna/SystemError.h>
 #include <luna/Types.h>
+#include <luna/Vector.h>
 
 extern const u8 start_of_kernel_rodata[1];
 extern const u8 end_of_kernel_rodata[1];
@@ -420,6 +421,28 @@ namespace MemoryManager
         return true;
     }
 
+    // FIXME: Make this more efficient.
+    Result<OwnedStringView> strdup_from_user(u64 address)
+    {
+        if (!validate_user_readable_page(address)) return err(EFAULT);
+
+        Vector<char> result;
+
+        while (*(char*)address != 0)
+        {
+            TRY(result.try_append(*(char*)address));
+            address++;
+            if (address % ARCH_PAGE_SIZE)
+            {
+                if (!validate_user_readable_page(address)) return err(EFAULT);
+            }
+        }
+
+        TRY(result.try_append(0)); // null terminator
+
+        return OwnedStringView::from_string_literal(result.data());
+    }
+
     bool validate_user_write(void* user, usize size)
     {
         uintptr_t user_ptr = (uintptr_t)user;

kernel/src/memory/MemoryManager.h

@@ -1,4 +1,5 @@
 #pragma once
+#include <luna/OwnedStringView.h>
 #include <luna/Result.h>
 #include <luna/Types.h>
 
@@ -24,6 +25,7 @@ namespace MemoryManager
     bool validate_user_writable_page(u64 address);
 
     bool validate_userspace_string(u64 address);
+    Result<OwnedStringView> strdup_from_user(u64 address);
 
     bool validate_user_write(void* user, usize size);
     bool validate_user_read(const void* user, usize size);

kernel/src/sys/mkdir.cpp

@@ -5,14 +5,11 @@
 
 Result<u64> sys_mkdir(Registers*, SyscallArgs args)
 {
-    u64 path_address = args[0];
+    auto path = TRY(MemoryManager::strdup_from_user(args[0]));
-    if (!MemoryManager::validate_userspace_string(path_address)) return err(EFAULT);
 
-    const char* path = (const char*)path_address;
+    kinfoln("mkdir: attempting to create %s", path.chars());
 
-    kinfoln("mkdir: attempting to create %s", path);
+    TRY(VFS::create_directory(path.chars()));
-
-    TRY(VFS::create_directory(path));
 
     return 0;
 }

kernel/src/sys/open.cpp

@@ -10,25 +10,22 @@ constexpr int FLAGS_TO_KEEP = O_RDWR | O_APPEND;
 
 Result<u64> sys_open(Registers*, SyscallArgs args)
 {
-    u64 path_address = args[0];
+    auto path = TRY(MemoryManager::strdup_from_user(args[0]));
-    if (!MemoryManager::validate_userspace_string(path_address)) return err(EFAULT);
-
-    const char* path = (const char*)path_address;
     int flags = (int)args[1];
 
     Thread* current = Scheduler::current();
 
-    kinfoln("open: trying to open file %s, flags %d", path, flags);
+    kinfoln("open: trying to open file %s, flags %d", path.chars(), flags);
 
     SharedPtr<VFS::Inode> inode;
 
     // Caller did not pass either O_RDONLY, O_WRONLY or O_RDWR
     if ((flags & O_RDWR) == 0) { return err(EINVAL); }
 
-    auto maybe_inode = VFS::resolve_path(path);
+    auto maybe_inode = VFS::resolve_path(path.chars());
     if (maybe_inode.has_error())
     {
-        if (maybe_inode.error() == ENOENT && (flags & O_CREAT)) inode = TRY(VFS::create_file(path));
+        if (maybe_inode.error() == ENOENT && (flags & O_CREAT)) inode = TRY(VFS::create_file(path.chars()));
         else
             return maybe_inode.release_error();
     }