From df7ddfb8035ed133e01edb3ed3aba0cf2088e8b0 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Tue, 2 Feb 2021 19:59:15 +0100
Subject: [PATCH] LibELF: Mark libc.so and libpthread.so as syscall regions

Also, before calling the main program entry function, inform the kernel
that no more syscall regions can be registered.

This effectively bans syscalls from everywhere except LibC and
LibPthread. Pretty neat! :^)
---
 Userland/Libraries/LibELF/DynamicLinker.cpp | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/Userland/Libraries/LibELF/DynamicLinker.cpp b/Userland/Libraries/LibELF/DynamicLinker.cpp
index f3273ea87c2..746adbc3ee4 100644
--- a/Userland/Libraries/LibELF/DynamicLinker.cpp
+++ b/Userland/Libraries/LibELF/DynamicLinker.cpp
@@ -31,6 +31,7 @@
 #include <AK/LexicalPath.h>
 #include <AK/LogStream.h>
 #include <AK/ScopeGuard.h>
+#include <Kernel/API/Syscall.h>
 #include <LibC/mman.h>
 #include <LibC/stdio.h>
 #include <LibC/sys/internals.h>
@@ -214,6 +215,14 @@ static NonnullRefPtr<DynamicLoader> commit_elf(const String& name)
 
     auto object = loader->load_stage_3(RTLD_GLOBAL | RTLD_LAZY, g_total_tls_size);
     ASSERT(object);
+
+
+    if (name.is_one_of("libc.so", "libpthread.so")) {
+        if (syscall(SC_msyscall, object->base_address().as_ptr())) {
+            ASSERT_NOT_REACHED();
+        }
+    }
+
     if (name == "libc.so") {
         initialize_libc(*object);
     }
@@ -263,7 +272,13 @@ void ELF::DynamicLinker::linker_main(String&& main_program_name, int main_progra
     if (g_do_breakpoint_trap_before_entry) {
         asm("int3");
     }
-    int rc = main_function(argc, argv, envp);
+
+    int rc = syscall(SC_msyscall, nullptr);
+    if (rc < 0) {
+        ASSERT_NOT_REACHED();
+    }
+
+    rc = main_function(argc, argv, envp);
     dbgln<DYNAMIC_LOAD_DEBUG>("rc: {}", rc);
     if (g_libc_exit != nullptr) {
         g_libc_exit(rc);