eir: support booting with framebuffers at over 4 GiB

This is needed when booting with a passed-through Intel GPU. This commit
changes the behavior to not fail boot in this case, but instead to not
use the framebuffer in eir, but to map it for thor. This means that in
such cases, eir will only output over serial.

kernel/eir/arch/x86/multiboot2/multiboot2.cpp

@@ -175,8 +175,9 @@ extern "C" void eirMultiboot2Main(uint32_t info, uint32_t magic){
 			case kMb2TagFramebuffer: {
 				auto *framebuffer_tag = reinterpret_cast<Mb2TagFramebuffer*>(tag);
 				if(framebuffer_tag->address + framebuffer_tag->width * framebuffer_tag->pitch >= UINTPTR_MAX) {
-					eir::panicLogger() << "eir: Framebuffer outside of addressable memory!"
+					eir::infoLogger() << "eir: Framebuffer outside of addressable memory!"
 						<< frg::endlog;
+					framebuffer = framebuffer_tag;
 				}else if(framebuffer_tag->bpp != 32) {
 					eir::panicLogger() << "eir: Framebuffer does not use 32 bpp!"
 						<< frg::endlog;
@@ -336,7 +337,7 @@ extern "C" void eirMultiboot2Main(uint32_t info, uint32_t magic){
 	framebuf->fbType = framebuffer->type;
 
 	// Map the framebuffer.
-	assert(framebuffer->address & ~(pageSize - 1));
+	assert(framebuffer->address & ~static_cast<EirPtr>(pageSize - 1));
 	for(address_t pg = 0; pg < framebuffer->pitch * framebuffer->height; pg += 0x1000)
 		mapSingle4kPage(0xFFFF'FE00'4000'0000 + pg, framebuffer->address + pg,
 				PageFlags::write, CachingMode::writeCombine);