UEFI: break down when calling LocateProtocol

[Oython]

I just try to develop my boot loader using UEFI, but I immediately encounter a problem.I am using GNU-efi and my code is simple:

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#include "efi.h"
#include "efilib.h"

EFI_STATUS
EFIAPI
efi_main (EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
{
    InitializeLib(ImageHandle, SystemTable);
    EFI_GUID gop_guid = EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID;
    EFI_GRAPHICS_OUTPUT_PROTOCOL *GOP;
    
    SystemTable->BootServices->SetWatchdogTimer(0, 0, 0, NULL);
    SystemTable->BootServices->LocateProtocol(&gop_guid, NULL, (void**) &GOP);
    return EFI_SUCCESS;
}

I tried to run it in VmWare but it breaks down.
I have tried to recompile the library but it doesn't work.
Is there any problem with my code?

[Octocontrabass]

I tried to run it in VmWare but it breaks down.

Can you be more specific? What exactly is happening that you don't expect your code to do?

Is there any problem with my code?

I don't see anything wrong with the code you posted, but there might be a problem with how you're building your code.

[Oython]

Thanks for your reply.

Can you be more specific? What exactly is happening that you don't expect your code to do?

VmWare just halts and pops out a window saying that the UEFI loader occurs an error.

I don't see anything wrong with the code you posted, but there might be a problem with how you're building your code.

I use the following code to compile my loader:

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all: BOOTX64.EFI

loader.o: loader.c Makefile
	x86_64-pc-cygwin-gcc -I./inc -fpic -ffreestanding -fno-stack-protector -fno-stack-check -fshort-wchar -mno-red-zone -maccumulate-outgoing-args -c loader.c -o loader.o -fPIC

loader.so: loader.o Makefile
	ld -shared -Bsymbolic -L./x86_64/lib -L./x86_64/gnuefi -T./gnuefi/elf_x86_64_efi.lds ./x86_64/gnuefi/crt0-efi-x86_64.o loader.o -o loader.so -lgnuefi -lefi -fPIC

BOOTX64.EFI: loader.so Makefile
	objcopy -j .text -j .sdata -j .data -j .rodata -j .dynamic -j .dynsym  -j .rel -j .rela -j .rel.* -j .rela.* -j .reloc --target efi-app-x86_64 --subsystem=10 loader.so BOOTX64.EFI

In fact, it's adapted from https://wiki.osdev.org/GNU-EFI
My environment is WSL.

[Octocontrabass]

VmWare just halts and pops out a window saying that the UEFI loader occurs an error.

Is that because your bootloader returns? Normally a bootloader returning means there was an error. Try adding an infinite loop so it won't return.

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x86_64-pc-cygwin-gcc

That seems wrong. Why aren't you using x86_64-elf-gcc or just plain gcc?

In fact, it's adapted from https://wiki.osdev.org/GNU-EFI

Those instructions might be outdated, you don't need objcopy when ld can directly link an EFI PE executable.

[Oython]

Now I give up compiling with gnu-efi and just use the api from uefi.And finally I succeed in runing my code.
I guess that there is a problem in the prior way I compiled the code.