Prekernel: Move the generate_secure_seed function out of init.cpp

As part of a commit series trying to make the prekernel nicer, we should
move and refactor functions out of the init.cpp file if possible.

Kernel/Prekernel/CMakeLists.txt

@@ -12,6 +12,7 @@ set(SOURCES
     DebugOutput.cpp
     kmalloc.cpp
     Runtime.cpp
+    Random.cpp
     ../../Userland/Libraries/LibELF/Relocation.cpp
     )
 

Kernel/Prekernel/Prekernel.h

@@ -20,6 +20,9 @@
 #define KERNEL_MAPPING_BASE 0x2000000000
 
 #ifdef __cplusplus
+
+extern "C" multiboot_info_t* multiboot_info_ptr;
+
 namespace Kernel {
 
 #    if ARCH(X86_64)

Kernel/Prekernel/Random.cpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2024, Liav A. <[email protected]>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Platform.h>
+#include <Kernel/Boot/Multiboot.h>
+#include <Kernel/Prekernel/Prekernel.h>
+#include <Kernel/Prekernel/Random.h>
+#if ARCH(X86_64)
+#    include <Kernel/Arch/x86_64/ASM_wrapper.h>
+#    include <Kernel/Arch/x86_64/CPUID.h>
+#endif
+
+u64 generate_secure_seed()
+{
+    u32 seed = 0xFEEBDAED;
+
+#if ARCH(X86_64)
+    Kernel::CPUID processor_info(0x1);
+    if (processor_info.edx() & (1 << 4)) // TSC
+        seed ^= Kernel::read_tsc();
+
+    if (processor_info.ecx() & (1 << 30)) // RDRAND
+        seed ^= Kernel::read_rdrand();
+
+    Kernel::CPUID extended_features(0x7);
+    if (extended_features.ebx() & (1 << 18)) // RDSEED
+        seed ^= Kernel::read_rdseed();
+#else
+#    warning No native randomness source available for this architecture
+#endif
+
+    seed ^= multiboot_info_ptr->mods_addr;
+    seed ^= multiboot_info_ptr->framebuffer_addr;
+
+    return seed;
+}

Kernel/Prekernel/Random.h

@@ -0,0 +1,11 @@
+/*
+ * Copyright (c) 2024, Liav A. <[email protected]>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+
+u64 generate_secure_seed();

Kernel/Prekernel/init.cpp

@@ -12,15 +12,11 @@
 #include <Kernel/Memory/VirtualAddress.h>
 #include <Kernel/Prekernel/DebugOutput.h>
 #include <Kernel/Prekernel/Prekernel.h>
+#include <Kernel/Prekernel/Random.h>
 #include <Kernel/Prekernel/Runtime.h>
 #include <LibELF/ELFABI.h>
 #include <LibELF/Relocation.h>
 
-#if ARCH(X86_64)
-#    include <Kernel/Arch/x86_64/ASM_wrapper.h>
-#    include <Kernel/Arch/x86_64/CPUID.h>
-#endif
-
 // Defined in the linker script
 extern uintptr_t __stack_chk_guard;
 uintptr_t __stack_chk_guard __attribute__((used));
@@ -66,8 +62,6 @@ extern "C" [[noreturn]] void init();
 // This is where C++ execution begins, after boot.S transfers control here.
 //
 
-u64 generate_secure_seed();
-
 static void memmove_virt(void* dest_virt, FlatPtr dest_phys, void* src, size_t n)
 {
     if (dest_phys < (FlatPtr)src) {
@@ -258,31 +252,6 @@ extern "C" [[noreturn]] void init()
     __builtin_unreachable();
 }
 
-u64 generate_secure_seed()
-{
-    u32 seed = 0xFEEBDAED;
-
-#if ARCH(X86_64)
-    CPUID processor_info(0x1);
-    if (processor_info.edx() & (1 << 4)) // TSC
-        seed ^= read_tsc();
-
-    if (processor_info.ecx() & (1 << 30)) // RDRAND
-        seed ^= read_rdrand();
-
-    CPUID extended_features(0x7);
-    if (extended_features.ebx() & (1 << 18)) // RDSEED
-        seed ^= read_rdseed();
-#else
-#    warning No native randomness source available for this architecture
-#endif
-
-    seed ^= multiboot_info_ptr->mods_addr;
-    seed ^= multiboot_info_ptr->framebuffer_addr;
-
-    return seed;
-}
-
 // Define some Itanium C++ ABI methods to stop the linker from complaining.
 // If we actually call these something has gone horribly wrong
 void* __dso_handle __attribute__((visibility("hidden")));