Kernel: Improve strdup_from_user and add copy to and from user

Still a bit funky, that's why we're not using it in read() and write() yet.

kernel/include/sys/UserMemory.h

@@ -16,6 +16,9 @@ bool validate_user_writable_page(uintptr_t address);
 bool validate_user_read(uintptr_t address, size_t size);
 bool validate_user_write(uintptr_t address, size_t size);
 
+bool copy_from_user(const void* user_ptr, void* ptr, size_t size);
+bool copy_to_user(void* user_ptr, const void* ptr, size_t size);
+
 // FIXME: Map the physical addresses into kernel address space. Right now, something overwrites KernelHeap and crashes
 // it, so that's not really possible. But it should be done in the future.
 

kernel/src/sys/UserMemory.cpp

@@ -1,14 +1,44 @@
 #include "sys/UserMemory.h"
 #include "memory/Memory.h"
+#include "memory/MemoryManager.h"
+#include "std/stdlib.h"
 #include "std/string.h"
 #include "utils/Addresses.h"
 
-char* strdup_from_user(
-    const char* user_string) // FIXME: This function is a little hacky. Use the obtain_user_ref and similar functions.
+struct dynamic_string
 {
-    uint64_t phys = VMM::get_physical((uint64_t)user_string);
-    if (phys == (uint64_t)-1) { return nullptr; }
-    return strdup((const char*)phys);
+    char* buf;
+    long capacity;
+    long size;
+};
+
+bool dynamic_expand(dynamic_string* str, long new_capacity)
+{
+    char* buffer = (char*)krealloc(str->buf, new_capacity);
+    if (!buffer) { return false; }
+    str->buf = buffer;
+    str->capacity = new_capacity;
+    return true;
+}
+
+bool dynamic_push(dynamic_string* str, char c)
+{
+    if (str->size == str->capacity)
+    {
+        if (!dynamic_expand(str, str->capacity + 16)) return false;
+    }
+    str->buf[str->size] = c;
+    str->size++;
+    return true;
+}
+
+bool dynamic_init(dynamic_string* str)
+{
+    str->buf = (char*)kmalloc(10);
+    if (!str->buf) return false;
+    str->capacity = 10;
+    str->size = 0;
+    return true;
 }
 
 bool validate_user_readable_page(uintptr_t address)
@@ -29,6 +59,54 @@ bool validate_user_writable_page(uintptr_t address)
     return false;
 }
 
+char* strdup_from_user(const char* user_string)
+{
+    uintptr_t user_ptr = (uintptr_t)user_string;
+    auto aligned = round_down_to_nearest_page(user_ptr);
+    char* ptr = nullptr;
+    uintptr_t index = 0;
+    if (aligned != user_ptr) // Otherwise, we already do this check below.
+    {
+        if (!validate_user_readable_page(aligned)) return nullptr;
+        ptr = (char*)MemoryManager::get_mapping((void*)VMM::get_physical(aligned), 0);
+        index = user_ptr - aligned;
+    }
+    dynamic_string str;
+    if (!dynamic_init(&str))
+    {
+        if (ptr) MemoryManager::release_mapping(ptr);
+        return nullptr;
+    }
+    while (true) // FIXME: set a limit for this and fail with ENAMETOOLONG otherwise.
+    {
+        if (user_ptr % PAGE_SIZE == 0)
+        {
+            index = 0;
+            if (ptr) MemoryManager::release_mapping(ptr);
+            if (!validate_user_readable_page(user_ptr))
+            {
+                kfree(str.buf);
+                return nullptr;
+            }
+            ptr = (char*)MemoryManager::get_mapping((void*)VMM::get_physical(user_ptr), 0);
+        }
+        char c = ptr[index];
+        if (!dynamic_push(&str, c))
+        {
+            MemoryManager::release_mapping(ptr);
+            kfree(str.buf);
+            return nullptr;
+        }
+        if (!c) // We reached the null terminator!!
+        {
+            MemoryManager::release_mapping(ptr);
+            return str.buf;
+        }
+        user_ptr++;
+        index++;
+    }
+}
+
 bool validate_user_read(uintptr_t address, size_t size)
 {
     auto aligned = round_down_to_nearest_page(address);
@@ -64,3 +142,71 @@ bool validate_user_write(uintptr_t address, size_t size)
     }
     return true;
 }
+
+bool do_copy_from_user(const char* uptr, char* ptr, size_t size)
+{
+    uintptr_t user_ptr = (uintptr_t)uptr;
+    auto aligned = round_down_to_nearest_page(user_ptr);
+    char* mapping = nullptr;
+    uintptr_t index = 0;
+    if (aligned != user_ptr) // Otherwise, we already do this check below.
+    {
+        if (!validate_user_readable_page(aligned)) return false;
+        mapping = (char*)MemoryManager::get_mapping((void*)VMM::get_physical(aligned), 0);
+        index = user_ptr - aligned;
+    }
+    while (size--)
+    {
+        if (user_ptr % PAGE_SIZE == 0)
+        {
+            if (mapping) MemoryManager::release_mapping(mapping);
+            index = 0;
+            if (!validate_user_readable_page(user_ptr)) return false;
+            mapping = (char*)MemoryManager::get_mapping((void*)VMM::get_physical(user_ptr), 0);
+        }
+        *ptr = mapping[index];
+        user_ptr++;
+        ptr++;
+        index++;
+    }
+    return true;
+}
+
+bool do_copy_to_user(char* uptr, const char* ptr, size_t size)
+{
+    uintptr_t user_ptr = (uintptr_t)uptr;
+    auto aligned = round_down_to_nearest_page(user_ptr);
+    char* mapping = nullptr;
+    uintptr_t index = 0;
+    if (aligned != user_ptr) // Otherwise, we already do this check below.
+    {
+        if (!validate_user_writable_page(aligned)) return false;
+        mapping = (char*)MemoryManager::get_mapping((void*)VMM::get_physical(aligned));
+        index = user_ptr - aligned;
+    }
+    while (size--)
+    {
+        if (user_ptr % PAGE_SIZE == 0)
+        {
+            if (mapping) MemoryManager::release_mapping(mapping);
+            index = 0;
+            if (!validate_user_writable_page(user_ptr)) return false;
+            mapping = (char*)MemoryManager::get_mapping((void*)VMM::get_physical(user_ptr));
+        }
+        mapping[index] = *ptr;
+        user_ptr++;
+        ptr++;
+        index++;
+    }
+    return true;
+}
+
+bool copy_from_user(const void* user_ptr, void* ptr, size_t size)
+{
+    return do_copy_from_user((const char*)user_ptr, (char*)ptr, size);
+}
+
+bool copy_to_user(void* user_ptr, const void* ptr, size_t size)
+{
+    return do_copy_to_user((char*)user_ptr, (const char*)ptr, size);
+}