[boot] Fix call to exit_boot_services

Exiting boot services can't actually be done from inside
`bootloader_uefi_main`, because there are objects in that scope that run
code requiring boot services in their destructors.

Also added `support.cpp` with `memcpy` because clang will emit
references to `memcpy` even in freestanding mode.

Added a `debug_break` function to allow for faking breakpoints when
connecting to the bootloader with GDB.

Tags: debug

modules.yaml

@@ -62,6 +62,7 @@ modules:
             - src/boot/hardware.cpp
             - src/boot/loader.cpp
             - src/boot/memory.cpp
+            - src/boot/support.cpp
 
     nulldrv:
         kind: exe

scripts/templates/exe.boot.j2

@@ -3,6 +3,7 @@
 {{ super() }}
 
 ccflags = $ccflags $
+    -g3 $
     -DKERNEL_FILENAME=L\"jsix.elf\" $
     -I${srcroot}/external/include $
     -I${srcroot}/external/include/X64

src/boot/error.cpp

@@ -89,6 +89,8 @@ cpu_assert_handler::handle(uefi::status s, const wchar_t *message)
 } // namespace error
 } // namespace boot
 
-extern "C" int _purecall() { ::boot::error::raise(uefi::status::unsupported, L"Pure virtual call"); }
-void operator delete (void *) {}
-
+void debug_break()
+{
+	volatile int go = 0;
+	while (!go);
+}

src/boot/error.h

@@ -58,6 +58,9 @@ public:
 } // namespace error
 } // namespace boot
 
+/// Debugging psuedo-breakpoint.
+void debug_break();
+
 /// Helper macro to raise an error if an operation fails.
 /// \arg s  An expression evaluating to a UEFI status
 /// \arg m  The error message to use on failure

src/boot/main.cpp

@@ -144,7 +144,7 @@ load_module(
 /// UEFI is still in control of the machine. (ie, while the loader still
 /// has access to boot services.
 loader::loaded_elf
-bootloader_main_uefi(uefi::handle image, uefi::system_table *st, console &con)
+bootloader_main_uefi(uefi::handle image, uefi::system_table *st, console &con, size_t *map_key)
 {
 	error::uefi_handler handler(con);
 
@@ -174,6 +174,9 @@ bootloader_main_uefi(uefi::handle image, uefi::system_table *st, console &con)
 	memory::efi_mem_map efi_map = memory::get_uefi_mappings(bs);
 	memory::build_kernel_mem_map(efi_map, args, bs);
 
+	efi_map = memory::get_uefi_mappings(bs);
+	*map_key = efi_map.key;
+
 	return kernel_elf;
 }
 
@@ -288,10 +291,15 @@ efi_main(uefi::handle image_handle, uefi::system_table *st)
 	error::cpu_assert_handler handler;
 	console con(st->boot_services, st->con_out);
 
+	size_t map_key;
 	loader::loaded_elf kernel =
-		bootloader_main_uefi(image_handle, st, con);
+		bootloader_main_uefi(image_handle, st, con, &map_key);
 
-	while(1);
+	try_or_raise(
+		st->boot_services->exit_boot_services(image_handle, map_key),
+		L"Failed to exit boot services");
+
+	debug_break();
 	return uefi::status::unsupported;
 }
 

src/boot/memory.cpp

@@ -67,6 +67,8 @@ init_pointer_fixup(uefi::boot_services *bs, uefi::runtime_services *rs)
 	status_line status(L"Initializing pointer virtualization event");
 
 	uefi::event event;
+	bs->set_mem(&fixup_pointers, sizeof(fixup_pointers), 0);
+	fixup_pointer_index = 0;
 
 	try_or_raise(
 		bs->create_event(

src/boot/support.cpp

@@ -0,0 +1,27 @@
+#include <stdint.h>
+
+#include "error.h"
+
+extern "C" {
+
+/// Basic memcpy() implementation for clang. Clang requires freestanding code
+/// implement memcpy(), as it may emit references to it. This basic memcpy is
+/// not the most efficient, but will get linked if no other memcpy exists.
+__attribute__ ((__weak__))
+void *memcpy(void *dest, const void *src, size_t n)
+{
+	uint8_t *cdest = reinterpret_cast<uint8_t*>(dest);
+	const uint8_t *csrc = reinterpret_cast<const uint8_t*>(src);
+	for (size_t i = 0; i < n; ++i)
+		cdest[i] = csrc[i];
+	return dest;
+}
+
+int _purecall()
+{
+	::boot::error::raise(uefi::status::unsupported, L"Pure virtual call");
+}
+
+} // extern "C"
+
+void operator delete (void *) {}