From a933fabb8617b3905a328aa712ed0f7fcb87b5ee Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Tue, 15 Apr 2025 23:07:22 +0300
Subject: [PATCH] Kernel: Define constant USERSPACE_END

This should be used for userspace generic allocations. Currently I used
KERNEL_OFFSET, but I want to limit userspace to the actual lower half of
the address space
---
 kernel/include/kernel/Memory/Types.h | 2 ++
 kernel/kernel/Process.cpp            | 6 +++---
 kernel/kernel/Thread.cpp             | 4 ++--
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/include/kernel/Memory/Types.h b/kernel/include/kernel/Memory/Types.h
index f4587b1c..db37994d 100644
--- a/kernel/include/kernel/Memory/Types.h
+++ b/kernel/include/kernel/Memory/Types.h
@@ -4,8 +4,10 @@
 
 #if ARCH(x86_64)
 	#define KERNEL_OFFSET 0xFFFFFFFF80000000
+	#define USERSPACE_END 0xFFFF800000000000
 #elif ARCH(i686)
 	#define KERNEL_OFFSET 0xC0000000
+	#define USERSPACE_END 0xC0000000
 #else
 	#error
 #endif
diff --git a/kernel/kernel/Process.cpp b/kernel/kernel/Process.cpp
index 6fc41015..b2b1165f 100644
--- a/kernel/kernel/Process.cpp
+++ b/kernel/kernel/Process.cpp
@@ -1622,7 +1622,7 @@ namespace Kernel
 		else
 			page_flags |= PageTable::Flags::UserSupervisor;
 
-		AddressRange address_range { .start = 0x400000, .end = KERNEL_OFFSET };
+		AddressRange address_range { .start = 0x400000, .end = USERSPACE_END };
 		if (args->flags & MAP_FIXED)
 		{
 			vaddr_t base_addr = reinterpret_cast<vaddr_t>(args->addr);
@@ -1767,7 +1767,7 @@ namespace Kernel
 
 	BAN::ErrorOr<long> Process::sys_smo_map(SharedMemoryObjectManager::Key key)
 	{
-		auto region = TRY(SharedMemoryObjectManager::get().map_object(key, page_table(), { .start = 0x400000, .end = KERNEL_OFFSET }));
+		auto region = TRY(SharedMemoryObjectManager::get().map_object(key, page_table(), { .start = 0x400000, .end = USERSPACE_END }));
 
 		LockGuard _(m_process_lock);
 		TRY(m_mapped_regions.push_back(BAN::move(region)));
@@ -2522,7 +2522,7 @@ namespace Kernel
 			goto unauthorized_access;
 
 		// trying to access kernel space memory
-		if (vaddr + size > KERNEL_OFFSET)
+		if (vaddr + size > USERSPACE_END)
 			goto unauthorized_access;
 
 		if (vaddr == 0)
diff --git a/kernel/kernel/Thread.cpp b/kernel/kernel/Thread.cpp
index f6812b79..4318b2a2 100644
--- a/kernel/kernel/Thread.cpp
+++ b/kernel/kernel/Thread.cpp
@@ -103,7 +103,7 @@ namespace Kernel
 
 		thread->m_kernel_stack = TRY(VirtualRange::create_to_vaddr_range(
 			page_table,
-			0x200000, KERNEL_OFFSET,
+			0x200000, USERSPACE_END,
 			kernel_stack_size,
 			PageTable::Flags::ReadWrite | PageTable::Flags::Present,
 			true
@@ -111,7 +111,7 @@ namespace Kernel
 
 		thread->m_userspace_stack = TRY(VirtualRange::create_to_vaddr_range(
 			page_table,
-			0x200000, KERNEL_OFFSET,
+			0x200000, USERSPACE_END,
 			userspace_stack_size,
 			PageTable::Flags::UserSupervisor | PageTable::Flags::ReadWrite | PageTable::Flags::Present,
 			true