Kernel: Add a few convenience functions to manipulate userland memory

kernel/include/sys/Syscall.h

@@ -25,8 +25,6 @@
 namespace Syscall
 {
     void entry(Context* context);
-
-    char* strdup_from_user(const char* user_string);
 }
 
 void sys_exit(Context* context, int status);

kernel/include/sys/UserMemory.h

@@ -0,0 +1,29 @@
+#pragma once
+#include "memory/MemoryManager.h"
+#include "memory/VMM.h"
+#include "misc/utils.h"
+
+char* strdup_from_user(const char* user_string);
+
+template <typename T, unsigned long S = sizeof(T), typename V> T* user_address_to_typed_pointer(V address)
+{
+    uint64_t phys = VMM::get_physical((uint64_t)address);
+    if (phys == (uint64_t)-1) return nullptr;
+    return (T*)MemoryManager::get_unaligned_mappings((void*)phys, Utilities::get_blocks_from_size(PAGE_SIZE, S),
+                                                     MAP_READ_WRITE);
+}
+
+template <typename T, unsigned long S = sizeof(T)> void free_user_typed_pointer(T* ptr)
+{
+    MemoryManager::release_unaligned_mappings(ptr, Utilities::get_blocks_from_size(PAGE_SIZE, S));
+}
+
+template <typename T> T* obtain_user_ref(T* user_ptr)
+{
+    return user_address_to_typed_pointer<T>(user_ptr);
+}
+
+template <typename T> void release_user_ref(T* ptr)
+{
+    return free_user_typed_pointer(ptr);
+}

kernel/src/sys/Syscall.cpp

@@ -33,11 +33,4 @@ void Syscall::entry(Context* context)
     default: context->rax = -ENOSYS; break;
     }
     VMM::exit_syscall_context();
-}
-
-char* Syscall::strdup_from_user(const char* user_string) // FIXME: This function is a little hacky.
-{
-    uint64_t phys = VMM::get_physical((uint64_t)user_string);
-    if (phys == (uint64_t)-1) { return nullptr; }
-    return strdup((const char*)phys);
 }

kernel/src/sys/UserMemory.cpp

@@ -0,0 +1,10 @@
+#include "sys/UserMemory.h"
+#include "std/string.h"
+
+char* strdup_from_user(
+    const char* user_string) // FIXME: This function is a little hacky. Use the obtain_user_ref and similar functions.
+{
+    uint64_t phys = VMM::get_physical((uint64_t)user_string);
+    if (phys == (uint64_t)-1) { return nullptr; }
+    return strdup((const char*)phys);
+}

kernel/src/sys/exec.cpp

@@ -10,6 +10,7 @@
 #include "std/stdlib.h"
 #include "std/string.h"
 #include "sys/Syscall.h"
+#include "sys/UserMemory.h"
 #include "sys/elf/ELFLoader.h"
 #include "thread/Scheduler.h"
 
@@ -57,7 +58,7 @@ void sys_fork(Context* context)
 
 void sys_exec(Context* context, const char* pathname)
 {
-    char* kpathname = Syscall::strdup_from_user(pathname);
+    char* kpathname = strdup_from_user(pathname);
     if (!kpathname)
     {
         context->rax = -EFAULT;

kernel/src/sys/stdio.cpp

@@ -8,6 +8,7 @@
 #include "render/TextRenderer.h"
 #include "std/stdlib.h"
 #include "sys/Syscall.h"
+#include "sys/UserMemory.h"
 #include "thread/Scheduler.h"
 #include "thread/Task.h"
 
@@ -145,7 +146,7 @@ void sys_open(Context* context, const char* filename, int flags)
         return;
     }
 
-    char* kernel_filename = Syscall::strdup_from_user(filename);
+    char* kernel_filename = strdup_from_user(filename);
     if (!kernel_filename)
     {
         context->rax = -EFAULT;
@@ -225,7 +226,7 @@ void sys_close(Context* context, int fd)
 
 void sys_mkdir(Context* context, const char* filename)
 {
-    char* kfilename = Syscall::strdup_from_user(filename);
+    char* kfilename = strdup_from_user(filename);
     if (!kfilename)
     {
         context->rax = -EFAULT;