From ec8b9640e2cdad763cc008a5263abf70276effa4 Mon Sep 17 00:00:00 2001
From: Bananymous <bananymousosq@gmail.com>
Date: Sat, 22 Apr 2023 15:35:32 +0300
Subject: [PATCH] Kernel: Usespace programs are now ran through ELF files

only 64 bit elf files are supported for now.
---
 kernel/include/kernel/Process.h |  2 +-
 kernel/kernel/Process.cpp       | 52 ++++++++++++++++++++++++++++++---
 kernel/kernel/kernel.cpp        | 11 +------
 userspace/test.c                |  4 ++-
 4 files changed, 53 insertions(+), 16 deletions(-)

diff --git a/kernel/include/kernel/Process.h b/kernel/include/kernel/Process.h
index 826af39d..4b392c74 100644
--- a/kernel/include/kernel/Process.h
+++ b/kernel/include/kernel/Process.h
@@ -24,7 +24,7 @@ namespace Kernel
 
 	public:
 		static BAN::ErrorOr<Process*> create_kernel(entry_t, void*);
-		static BAN::ErrorOr<Process*> create_userspace(void(*)());
+		static BAN::ErrorOr<Process*> create_userspace(BAN::StringView);
 		~Process();
 
 		[[noreturn]] void exit();
diff --git a/kernel/kernel/Process.cpp b/kernel/kernel/Process.cpp
index 496ffb16..f0824a9c 100644
--- a/kernel/kernel/Process.cpp
+++ b/kernel/kernel/Process.cpp
@@ -1,8 +1,11 @@
 #include <BAN/StringView.h>
 #include <kernel/FS/VirtualFileSystem.h>
 #include <kernel/LockGuard.h>
+#include <kernel/Memory/Heap.h>
 #include <kernel/Process.h>
 #include <kernel/Scheduler.h>
+#include <LibELF/ELF.h>
+#include <LibELF/Values.h>
 
 #include <fcntl.h>
 
@@ -33,25 +36,65 @@ namespace Kernel
 		return process;
 	}
 
-	BAN::ErrorOr<Process*> Process::create_userspace(void(*entry)())
+	BAN::ErrorOr<Process*> Process::create_userspace(BAN::StringView path)
 	{
+		auto* elf = TRY(LibELF::ELF::load_from_file(path));	
+		
 		auto* process = create_process();
 		TRY(process->m_working_directory.push_back('/'));
 		TRY(process->init_stdio());
 		process->m_mmu = new MMU();
 		ASSERT(process->m_mmu);
 		
+		auto& elf_file_header = elf->file_header64();
+		for (size_t i = 0; i < elf_file_header.e_phnum; i++)
+		{
+			auto& elf_program_header = elf->program_header64(i);
+
+			switch (elf_program_header.p_type)
+			{
+			case LibELF::PT_NULL:
+				break;
+			case LibELF::PT_LOAD:
+			{
+				size_t page_start = elf_program_header.p_vaddr / 4096;
+				size_t page_end = BAN::Math::div_round_up<size_t>(elf_program_header.p_vaddr + elf_program_header.p_memsz, 4096);
+				for (size_t page = page_start; page <= page_end; page++)
+				{
+					auto addr = Memory::Heap::get().take_free_page();
+					process->m_mmu->map_page_at(addr, page * 4096, MMU::Flags::UserSupervisor | MMU::Flags::ReadWrite | MMU::Flags::Present);
+				}
+				process->m_mmu->load();
+				memset((void*)elf_program_header.p_vaddr, 0, elf_program_header.p_memsz);
+				memcpy((void*)elf_program_header.p_vaddr, elf->data() + elf_program_header.p_offset, elf_program_header.p_filesz);
+				Process::current().mmu().load();
+
+				dwarnln("mapped {8H}->{8H} to {8H}->{8H}",
+					elf_program_header.p_offset,
+					elf_program_header.p_offset + elf_program_header.p_filesz,
+					elf_program_header.p_vaddr,
+					elf_program_header.p_vaddr + elf_program_header.p_memsz
+				);
+				break;
+			}
+			default:
+				ASSERT_NOT_REACHED();
+			}
+		}
+
 		TRY(process->add_thread(
-			[](void* entry_func)
+			[](void* entry)
 			{
 				Thread& current = Thread::current();
 				current.process().m_mmu->map_range(current.stack_base(), current.stack_size(), MMU::Flags::UserSupervisor | MMU::Flags::ReadWrite | MMU::Flags::Present);
 				current.process().m_mmu->load();
-				current.jump_userspace((uintptr_t)entry_func);
+				current.jump_userspace((uintptr_t)entry);
 				ASSERT_NOT_REACHED();
-			}, (void*)entry
+			}, (void*)elf_file_header.e_entry
 		));
 
+		delete elf;
+
 		return process;
 	}
 
@@ -105,6 +148,7 @@ namespace Kernel
 				s_processes.remove(i);
 		s_process_lock.unlock();
 
+		// FIXME: we can't assume this is the current process
 		Scheduler::get().set_current_process_done();
 	}
 
diff --git a/kernel/kernel/kernel.cpp b/kernel/kernel/kernel.cpp
index 0cd3f722..042b60be 100644
--- a/kernel/kernel/kernel.cpp
+++ b/kernel/kernel/kernel.cpp
@@ -186,15 +186,6 @@ static void init2(void* tty1)
 
 	((TTY*)tty1)->initialize_device();
 
-	MUST(Process::create_kernel(
-		[](void*)
-		{
-			if (auto res = LibELF::ELF::load_from_file("/boot/banan-os.kernel"sv); res.is_error())
-				dwarnln("{}", res.error());
-			Process::current().exit();
-		}, nullptr
-	));
-
 	jump_userspace();
 	return;
 
@@ -216,5 +207,5 @@ static void jump_userspace()
 	MMU::get().map_range((uintptr_t)&g_userspace_start, (uintptr_t)&g_userspace_end - (uintptr_t)&g_userspace_start, MMU::Flags::UserSupervisor | MMU::Flags::Present);
 	MMU::get().map_range((uintptr_t)&g_kernel_start,    (uintptr_t)&g_kernel_end    - (uintptr_t)&g_kernel_start,    MMU::Flags::UserSupervisor | MMU::Flags::Present);
 
-	MUST(Process::create_userspace(userspace_entry));
+	MUST(Process::create_userspace("/bin/test"sv));
 }
diff --git a/userspace/test.c b/userspace/test.c
index ffacf6e6..04e7f20a 100644
--- a/userspace/test.c
+++ b/userspace/test.c
@@ -1,5 +1,7 @@
+#include <stdio.h>
+
 int main()
 {
+	puts("Hello World!");
 	return 0;
 }
-