void __init efi_esrt_init()

in efi/esrt.c [241:340]

• 73 lines of code
• 16 McCabe index (conditional complexity)

void __init efi_esrt_init(void)
{
	void *va;
	struct efi_system_resource_table tmpesrt;
	size_t size, max, entry_size, entries_size;
	efi_memory_desc_t md;
	int rc;
	phys_addr_t end;

	if (!efi_enabled(EFI_MEMMAP))
		return;

	pr_debug("esrt-init: loading.\n");
	if (!esrt_table_exists())
		return;

	rc = efi_mem_desc_lookup(efi.esrt, &md);
	if (rc < 0 ||
	    (!(md.attribute & EFI_MEMORY_RUNTIME) &&
	     md.type != EFI_BOOT_SERVICES_DATA &&
	     md.type != EFI_RUNTIME_SERVICES_DATA)) {
		pr_warn("ESRT header is not in the memory map.\n");
		return;
	}

	max = efi_mem_desc_end(&md);
	if (max < efi.esrt) {
		pr_err("EFI memory descriptor is invalid. (esrt: %p max: %p)\n",
		       (void *)efi.esrt, (void *)max);
		return;
	}

	size = sizeof(*esrt);
	max -= efi.esrt;

	if (max < size) {
		pr_err("ESRT header doesn't fit on single memory map entry. (size: %zu max: %zu)\n",
		       size, max);
		return;
	}

	va = early_memremap(efi.esrt, size);
	if (!va) {
		pr_err("early_memremap(%p, %zu) failed.\n", (void *)efi.esrt,
		       size);
		return;
	}

	memcpy(&tmpesrt, va, sizeof(tmpesrt));
	early_memunmap(va, size);

	if (tmpesrt.fw_resource_version != 1) {
		pr_err("Unsupported ESRT version %lld.\n",
		       tmpesrt.fw_resource_version);
		return;
	}

	entry_size = sizeof(struct efi_system_resource_entry_v1);
	if (tmpesrt.fw_resource_count > 0 && max - size < entry_size) {
		pr_err("ESRT memory map entry can only hold the header. (max: %zu size: %zu)\n",
		       max - size, entry_size);
		return;
	}

	/*
	 * The format doesn't really give us any boundary to test here,
	 * so I'm making up 128 as the max number of individually updatable
	 * components we support.
	 * 128 should be pretty excessive, but there's still some chance
	 * somebody will do that someday and we'll need to raise this.
	 */
	if (tmpesrt.fw_resource_count > 128) {
		pr_err("ESRT says fw_resource_count has very large value %d.\n",
		       tmpesrt.fw_resource_count);
		return;
	}

	/*
	 * We know it can't be larger than N * sizeof() here, and N is limited
	 * by the previous test to a small number, so there's no overflow.
	 */
	entries_size = tmpesrt.fw_resource_count * entry_size;
	if (max < size + entries_size) {
		pr_err("ESRT does not fit on single memory map entry (size: %zu max: %zu)\n",
		       size, max);
		return;
	}

	size += entries_size;

	esrt_data = (phys_addr_t)efi.esrt;
	esrt_data_size = size;

	end = esrt_data + size;
	pr_info("Reserving ESRT space from %pa to %pa.\n", &esrt_data, &end);
	if (md.type == EFI_BOOT_SERVICES_DATA)
		efi_mem_reserve(esrt_data, esrt_data_size);

	pr_debug("esrt-init: loaded.\n");
}