Revert "mprotect(): Validate the entire range to protect is in userspace memory"

This reverts commit 4ef764e62e.

README.md

@@ -1,18 +1,6 @@
 # Luna
 A simple kernel and userspace for the x86_64 platform, written mostly in C++ and C.
 
-## WARNING
-This branch is no longer actively updated. I have started rewriting the kernel for three different reasons:
-
-- To switch to CMake, which is a lot more convenient than manually writing Makefiles. 
-- The code in this branch is so unportable that it doesn't have ANY hope of moving outside x86_64. I wanted to change that.
-- To start fresh without my 3-month-old bad code, with a new way of doing things, kind of inspired by my recent adventures with the Rust programming language (it's still C++ though, I found Rust to be too limiting for kernel development).
-
-The code for this rewrite can be found in the [restart](https://git.cloudapio.eu/apio/Luna/src/branch/restart) branch.
-The changes in this branch will be merged as soon as the rewrite has reached a level of functionality similar to the `main` branch.
-
-Until then, this version of Luna will stay in the `main` branch, although not actively developed.
-
 ## Features
 - x86_64-compatible [kernel](kernel/).
 - Keeps track of which [memory](kernel/src/memory/) is used and which memory is free, and can allocate memory for itself and [user programs](kernel/src/sys/mem.cpp).

kernel/src/memory/Memory.cpp

@@ -45,10 +45,10 @@ uint64_t Memory::get_usable()
 
 bool Memory::is_kernel_address(uintptr_t address)
 {
-    return address >= 0xffff800000000000;
+    return address >= 0xfffffffff8000000;
 }
 
 bool Memory::is_user_address(uintptr_t address)
 {
-    return address && address < 0x00007fffffffffff;
+    return address && address < 0xfffffffff8000000;
 }

kernel/src/sys/mem.cpp

@@ -55,9 +55,9 @@ void sys_mmap(Context* context, void* address, size_t size, int prot, int fd, of
     if (address)
     {
         kdbgln("mmap(): %ld pages at address %p, %s, fd %d", size / PAGE_SIZE, address, format_prot(prot), fd);
-        if (!Memory::is_user_address((uintptr_t)address))
+        if (Memory::is_kernel_address((uintptr_t)address))
         {
-            kwarnln("mmap() failed: attempted to map a non-user page");
+            kwarnln("munmap() failed: attempted to unmap a kernel page");
             context->rax = MAP_FAIL(ENOMEM);
             return;
         }
@@ -153,9 +153,9 @@ void sys_munmap(Context* context, void* address, size_t size)
         context->rax = -EINVAL;
         return;
     }
-    if (!Memory::is_user_address((uintptr_t)address))
+    if (Memory::is_kernel_address((uintptr_t)address))
     {
-        kwarnln("munmap() failed: attempted to unmap a non-user page");
+        kwarnln("munmap() failed: attempted to unmap a kernel page");
         context->rax = -EINVAL;
         return;
     }
@@ -202,19 +202,12 @@ void sys_mprotect(Context* context, void* address, size_t size, int prot)
         context->rax = -EINVAL;
         return;
     }
-    if (!Memory::is_user_address((uintptr_t)address))
+    if (Memory::is_kernel_address((uintptr_t)address))
     {
-        kwarnln("mprotect() failed: attempted to protect a non-user page");
+        kwarnln("mprotect() failed: attempted to protect a kernel page");
         context->rax = -EINVAL;
         return;
     }
-    // FIXME: Check for overflow when adding address + size.
-    if (!Memory::is_user_address((uintptr_t)address + size))
-    {
-	kwarnln("mprotect() failed: end of given range is out of user memory");
-	context->rax = -EINVAL;
-	return;
-    }
     uint64_t flags = VMM::get_flags((uint64_t)address);
     if (flags == (uint64_t)-1)
     {