efi_status_t handle_kernel_image()

in efi/libstub/arm64-stub.c [82:170]

• 62 lines of code
• 15 McCabe index (conditional complexity)

efi_status_t handle_kernel_image(unsigned long *image_addr,
				 unsigned long *image_size,
				 unsigned long *reserve_addr,
				 unsigned long *reserve_size,
				 efi_loaded_image_t *image)
{
	efi_status_t status;
	unsigned long kernel_size, kernel_memsize = 0;
	u32 phys_seed = 0;

	/*
	 * Although relocatable kernels can fix up the misalignment with
	 * respect to MIN_KIMG_ALIGN, the resulting virtual text addresses are
	 * subtly out of sync with those recorded in the vmlinux when kaslr is
	 * disabled but the image required relocation anyway. Therefore retain
	 * 2M alignment if KASLR was explicitly disabled, even if it was not
	 * going to be activated to begin with.
	 */
	u64 min_kimg_align = efi_nokaslr ? MIN_KIMG_ALIGN : EFI_KIMG_ALIGN;

	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
		if (!efi_nokaslr) {
			status = efi_get_random_bytes(sizeof(phys_seed),
						      (u8 *)&phys_seed);
			if (status == EFI_NOT_FOUND) {
				efi_info("EFI_RNG_PROTOCOL unavailable\n");
				efi_nokaslr = true;
			} else if (status != EFI_SUCCESS) {
				efi_err("efi_get_random_bytes() failed (0x%lx)\n",
					status);
				efi_nokaslr = true;
			}
		} else {
			efi_info("KASLR disabled on kernel command line\n");
		}
	}

	if (image->image_base != _text)
		efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has bogus value\n");

	if (!IS_ALIGNED((u64)_text, EFI_KIMG_ALIGN))
		efi_err("FIRMWARE BUG: kernel image not aligned on %ldk boundary\n",
			EFI_KIMG_ALIGN >> 10);

	kernel_size = _edata - _text;
	kernel_memsize = kernel_size + (_end - _edata);
	*reserve_size = kernel_memsize;

	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
		/*
		 * If KASLR is enabled, and we have some randomness available,
		 * locate the kernel at a randomized offset in physical memory.
		 */
		status = efi_random_alloc(*reserve_size, min_kimg_align,
					  reserve_addr, phys_seed);
		if (status != EFI_SUCCESS)
			efi_warn("efi_random_alloc() failed: 0x%lx\n", status);
	} else {
		status = EFI_OUT_OF_RESOURCES;
	}

	if (status != EFI_SUCCESS) {
		if (!check_image_region((u64)_text, kernel_memsize)) {
			efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");
		} else if (IS_ALIGNED((u64)_text, min_kimg_align)) {
			/*
			 * Just execute from wherever we were loaded by the
			 * UEFI PE/COFF loader if the alignment is suitable.
			 */
			*image_addr = (u64)_text;
			*reserve_size = 0;
			return EFI_SUCCESS;
		}

		status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
						    ULONG_MAX, min_kimg_align);

		if (status != EFI_SUCCESS) {
			efi_err("Failed to relocate kernel\n");
			*reserve_size = 0;
			return status;
		}
	}

	*image_addr = *reserve_addr;
	memcpy((void *)*image_addr, _text, kernel_size);

	return EFI_SUCCESS;
}