EFI: Can't install the graphics output interface.

[Roman]

To learn about EFI programming I decided to write a small implementation of a EFI C library for writing EFI applications.

Here's my EFI system table structure:

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typedef struct {
	efi_tab_hdr_t header;
	char16_t *vendor;
	uint32_t revision;

	void *con_in_handle;
	efi_txt_input_proto_t *con_in;

	void *con_out_handle;
	efi_txt_output_proto_t *con_out;

	void *con_err_handle;
	efi_txt_output_proto_t *con_err;

	efi_rtsrv_t *rtsrv;
	efi_bsrv_t *bsrv;
} efi_systab_t;

Here's the boot services:

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typedef struct {
	efi_tab_hdr_t hdr;

	efi_tpl_t (*raise_tpl)(efi_tpl_t);
	void (*rstor_tpl)(efi_tpl_t);

	efi_status_t (*alloc_pages)(efi_alloc_type_t, efi_memory_type_t, native_int_t pages, native_int_t *memory);
	efi_status_t (*free_pages)(native_int_t, native_int_t);

	efi_status_t (*get_mmap)(native_int_t*, efi_mem_t*, native_int_t*, native_int_t*, uint32_t*);

	efi_status_t (*alloc_pool)(efi_memory_type_t, native_int_t, void**);
	efi_status_t (*free_pool)(void*);

	efi_status_t (*create_evt)(uint32_t, efi_tpl_t, efi_evt_notify_t, void*, void**);
	efi_status_t (*set_timer)(void*, efi_timer_delay_t, uint64_t);
	efi_status_t (*wait_evt)(native_int_t, void**, native_int_t*);
	efi_status_t (*sig_evt)(void*);
	efi_status_t (*close_evt)(void*);
	efi_status_t (*check_evt)(void*);

	efi_status_t (*install_proto)(void*, efi_guid_t*, efi_interface_t, void*);
} efi_bsrv_t;

And the problem:

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	void *graphics_handle = 0;
	efi_guid_t graphics_guid = EFI_GRAPHICS_PROTO_GUID;
	efi_graphics_proto_t *graphics = malloc(sizeof(efi_graphics_proto_t));
	status = efi_systab->bsrv->install_proto(&graphics_handle, &graphics_guid, EFI_NATIVE_INTERFACE, graphics);
	if (status != EFI_SUCCESS)
	{
		puts(L"Failed to install the graphics interface.");
		halt();
	}

	puts(L"Successfully installed the graphics interface.\n\r");

	hexdump(graphics, sizeof(efi_graphics_proto_t));
	halt();

install_proto() returns EFI_SUCCESS, points the handle somewhere, but the hexdump() function outputs something strange (see in the attachments).

[Icee]

Wait, what are you trying to do here? As far as I understand, the InstallProtocolInterface API call does just what its name implies -- it _installs_ your implementation of a protocol onto a handle. The call is not supposed to fill the structure, it is its input, not output, parameter.

You probably want to use LocateProtocol instead.

[Roman]

Wait, what are you trying to do here? As far as I understand, the InstallProtocolInterface API call does just what its name implies -- it _installs_ your implementation of a protocol onto a handle. The call is not supposed to fill the structure, it is its input, not output, parameter.

You probably want to use LocateProtocol instead.

Thank you. But now I have another problem.

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        efi_guid_t graphics_proto_guid[] = EFI_GRAPHICS_PROTO_GUID;
        efi_graphics_proto_t *graphics;
        status = efi_systab->bsrv->locate_proto(graphics_proto_guid, 0, (void**) &graphics);

The call returns EFI_INVALID_PARAMETER. The Phoenix Wiki says, that such status is returned, when the third argument is null, but it is not.

[Icee]

The call returns EFI_INVALID_PARAMETER. The Phoenix Wiki says, that such status is returned, when the third argument is null, but it is not.

The official UEFI 2.4 spec says the same. Are you sure that you have no link / call convention problems? Are you targetting 32- or 64-bit UEFI? Which toolchain are you using? I suspect a relocation problem.

[Roman]

The call returns EFI_INVALID_PARAMETER. The Phoenix Wiki says, that such status is returned, when the third argument is null, but it is not.

The official UEFI 2.4 spec says the same. Are you sure that you have no link / call convention problems? Are you targetting 32- or 64-bit UEFI? Which toolchain are you using? I suspect a relocation problem.

Toolchain: x86_64-w64-mingw32
Firmware: OVMF
Machine: QEMU
CFLAGS: -ffreestanding -c -nostdinc -Iinclude -Iinclude/arch/$(ARCH) -masm=intel -std=$(STDC_VERSION) -fno-stack-check -fno-stack-protector -mno-stack-arg-probe
LDFLAGS: -nostdlib -Wl,-dll -shared -Wl,--subsystem,10 -e efi_main
The updated boot services structure:

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typedef struct {
        efi_tab_hdr_t hdr;

        efi_tpl_t (*raise_tpl)(efi_tpl_t);
        void (*rstor_tpl)(efi_tpl_t);

        efi_status_t (*alloc_pages)(efi_alloc_type_t, efi_memory_type_t, native_int_t pages, native_int_t *memory);
        efi_status_t (*free_pages)(native_int_t, native_int_t);

        efi_status_t (*get_mmap)(native_int_t*, efi_mem_t*, native_int_t*, native_int_t*, uint32_t*);

        efi_status_t (*alloc_pool)(efi_memory_type_t, native_int_t, void**);
        efi_status_t (*free_pool)(void*);

        efi_status_t (*create_evt)(uint32_t, efi_tpl_t, efi_evt_notify_t, void*, void**);
        efi_status_t (*set_timer)(void*, efi_timer_delay_t, uint64_t);
        efi_status_t (*wait_evt)(native_int_t, void**, native_int_t*);
        efi_status_t (*sig_evt)(void*);
        efi_status_t (*close_evt)(void*);
        efi_status_t (*check_evt)(void*);

        efi_status_t (*install_proto)(void**, efi_guid_t*, efi_interface_t, void*);
        efi_status_t (*reinstall_proto)(void*, efi_guid_t*, void*, void*);
        efi_status_t (*uninstall_proto)(void*, efi_guid_t*, void*);
        efi_status_t (*handle_proto)(void*, efi_guid_t*, void**);

        void *reserved;

        efi_status_t (*reg_proto_notify)(efi_guid_t*, void*, void**);

        efi_status_t (*locate_handle)(efi_locate_search_t, efi_guid_t*, void*, native_int_t*, void**);
        efi_status_t (*locate_dev_path)(efi_guid_t*, efi_dev_path_proto_t**, void**);
        efi_status_t (*install_cfg_tab)(efi_guid_t*, void*);

        efi_status_t (*load_img)(bool, void*, efi_dev_path_proto_t*, void*, native_int_t, void**);
        efi_status_t (*start_img)(void*, native_int_t*, char16_t**);

        efi_status_t (*exit)(void*, efi_status_t, native_int_t, char16_t*);

        void *unknown_unload_img; // TODO: add unload_img here.

        efi_status_t (*exit_bsrv)(void*, native_int_t);

        efi_status_t (*get_next_monotonic_cnt)(uint64_t*);

        efi_status_t (*stall)(native_int_t);

        efi_status_t (*set_watchdog_timer)(native_int_t, uint64_t, native_int_t, char16_t*);

        // TODO: find information about these functions.
        void *unknown_connect_controller;
        void *unknown_disconnect_controller;

        efi_status_t (*open_proto)(void*, efi_guid_t*, void**, void*, void*, uint32_t);
        efi_status_t (*close_proto)(void*, efi_guid_t*, void*, void*);
        efi_status_t (*open_proto_info)(void*, efi_guid_t*, efi_proto_info_ent_t**, native_int_t*);

        void *unknown_locate_handle_buffer;
        efi_status_t (*locate_proto)(efi_guid_t*, void*, void**);
} efi_bsrv_t;

I should note, that some calls (e.g. stall, alloc_pool, free_pool, create_evt, set_timer...), I tested, work perfectly.

[Icee]

Could you also post an objdump -dr disassembly of the function where locate_proto is called?

EDIT: disregard that. Your boot services structure is missing a field: before LocateHandleBuffer you forgot ProtocolsPerHandle, so you are essentially calling LocateHandleBuffer instead of LocateProtocol.

[Roman]

Could you also post an objdump -dr disassembly of the function where locate_proto is called?

EDIT: disregard that. Your boot services structure is missing a field: before LocateHandleBuffer you forgot ProtocolsPerHandle, so you are essentially calling LocateHandleBuffer instead of LocateProtocol.

Thank you again! I've made a stupid mistake!

Edit: it looks like, it works!

[Roman]

I have another question: what is the actual size of a memory descriptor?
My code outputs some realistic values for the first entry (see in the attachment), but for the second one it shows some strange ones (too big value for a physical address).

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	native_int_t mmap_sz = sizeof(efi_mem_t) * 100;
	efi_mem_t *mmap = malloc(mmap_sz);
	native_int_t mmap_key;
	native_int_t mmap_ent_sz;
	uint32_t ver;
	//efi_mem_t *mmap = get_mmap(&mmap_key, &mmap_ent_n, &mmap_ent_sz);
	status = efi_systab->bsrv->get_mmap(&mmap_sz, mmap, &mmap_key, &mmap_ent_sz, &ver);
	if (status != EFI_SUCCESS)
	{
		puts(L"Failed to get the memory map: ");
		puts(ulltowcs(status, 10));
		halt();
	}

	puts(L"Memory map is at: 0x");
	puts(ulltowcs((uint64_t) mmap, 0x10));

	puts(L"\n\rMemory map entry size: 0x");
	puts(ulltowcs(mmap_ent_sz, 0x10));
	//mmap += sizeof(efi_mem_t);
	//mmap += mmap_ent_sz;

	puts(L"\n\rType: ");
	puts(ulltowcs(mmap->type, 10));

	puts(L"\n\rPhysical start: 0x");
	puts(ulltowcs(mmap->pstart, 0x10));

	puts(L"\n\rVirtual start: 0x");
	puts(ulltowcs(mmap->vstart, 0x10));

	puts(L"\n\rPage number: 0x");
	puts(ulltowcs(mmap->pnum, 0x10));

	puts(L"\n\rAttributes: 0x");
	puts(ulltowcs(mmap->attr, 0x10));

	halt();

My memory descriptor structure:

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typedef struct {
        uint32_t type;
        uint32_t pad;
        native_int_t pstart;
        native_int_t vstart;
        uint64_t pnum;
        uint64_t attr;
} efi_mem_t;

[jnc100]

The current defined EFI_MEMORY_DESCRIPTOR is as you define it, with the exception of the padding member which you don't need (the MS x64 ABI will automatically align the next member, PhysicalStart, on an 8 byte boundary).

To iterate through them, though, you need to use the DescriptorSize value returned. I see (in one of your commented attempts) you add this to a value of type efi_mem_t *, which will not advance the pointer by that number of bytes, but rather than by DesciptorType * sizeof(efi_mem_t *) bytes.

You'd want something like:

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uintptr_t offset = 0;
while(offset < mmap_sz)
{
    efi_mem_t *cur_entry = (efi_mem_t *)((uintptr_t)mmap + offset);

    // printf statements

    offset += mmap_ent_sz;
}

Regards,
John.

[Roman]

Thank you, jnc100. I've never used the += operator with pointers, I thought, it would increment by bytes.