efi.c

 * method enabled the runtime services to be called without having to
 * thunk back into physical mode for every invocation.
 *
 * The new method does a pagetable switch in a preemption-safe manner
 * so that we're in a different address space when calling a runtime
 * function. For function arguments passing we do copy the PGDs of the
 * kernel page table into ->trampoline_pgd prior to each call.
 *
 * Specially for kexec boot, efi runtime maps in previous kernel should
 * be passed in via setup_data. In that case runtime ranges will be mapped
 * to the same virtual addresses as the first kernel.
 */
void __init efi_enter_virtual_mode(void)
{
	int err, count = 0, pg_shift = 0;
	void *new_memmap = NULL;
	efi_status_t status;

	efi.systab = NULL;

	/*
	 * We don't do virtual mode, since we don't do runtime services, on
	 * non-native EFI
	 */
	if (!efi_is_native()) {
		efi_unmap_memmap();
		return;
	}

	if (efi_setup) {
		efi_map_regions_fixed();
	} else {
		efi_merge_regions();
		new_memmap = efi_map_regions(&count, &pg_shift);
		if (!new_memmap) {
			pr_err("Error reallocating memory, EFI runtime non-functional!\n");
			return;
		}

		err = save_runtime_map();
		if (err)
			pr_err("Error saving runtime map, efi runtime on kexec non-functional!!\n");
	}

	BUG_ON(!efi.systab);

	if (!efi_setup) {
		if (efi_setup_page_tables(__pa(new_memmap), 1 << pg_shift))
			return;
	}

	efi_sync_low_kernel_mappings();
	efi_dump_pagetable();

	if (!efi_setup) {
		status = phys_efi_set_virtual_address_map(
			memmap.desc_size * count,
			memmap.desc_size,
			memmap.desc_version,
			(efi_memory_desc_t *)__pa(new_memmap));

		if (status != EFI_SUCCESS) {
			pr_alert("Unable to switch EFI into virtual mode (status=%lx)!\n",
				 status);
			panic("EFI call to SetVirtualAddressMap() failed!");
		}
	}

	/*
	 * Now that EFI is in virtual mode, update the function
	 * pointers in the runtime service table to the new virtual addresses.
	 *
	 * Call EFI services through wrapper functions.
	 */
	efi.runtime_version = efi_systab.hdr.revision;
	efi.get_time = virt_efi_get_time;
	efi.set_time = virt_efi_set_time;
	efi.get_wakeup_time = virt_efi_get_wakeup_time;
	efi.set_wakeup_time = virt_efi_set_wakeup_time;
	efi.get_variable = virt_efi_get_variable;
	efi.get_next_variable = virt_efi_get_next_variable;
	efi.set_variable = virt_efi_set_variable;
	efi.get_next_high_mono_count = virt_efi_get_next_high_mono_count;
	efi.reset_system = virt_efi_reset_system;
	efi.set_virtual_address_map = NULL;
	efi.query_variable_info = virt_efi_query_variable_info;
	efi.update_capsule = virt_efi_update_capsule;
	efi.query_capsule_caps = virt_efi_query_capsule_caps;

	efi_runtime_mkexec();


	/*
	 * We mapped the descriptor array into the EFI pagetable above but we're
	 * not unmapping it here. Here's why:
	 *
	 * We're copying select PGDs from the kernel page table to the EFI page
	 * table and when we do so and make changes to those PGDs like unmapping
	 * stuff from them, those changes appear in the kernel page table and we
	 * go boom.
	 *
	 * From setup_real_mode():
	 *
	 * ...
	 * trampoline_pgd[0] = init_level4_pgt[pgd_index(__PAGE_OFFSET)].pgd;
	 *
	 * In this particular case, our allocation is in PGD 0 of the EFI page
	 * table but we've copied that PGD from PGD[272] of the EFI page table:
	 *
	 *	pgd_index(__PAGE_OFFSET = 0xffff880000000000) = 272
	 *
	 * where the direct memory mapping in kernel space is.
	 *
	 * new_memmap's VA comes from that direct mapping and thus clearing it,
	 * it would get cleared in the kernel page table too.
	 *
	 * efi_cleanup_page_tables(__pa(new_memmap), 1 << pg_shift);
	 */
	if (!efi_setup)
		free_pages((unsigned long)new_memmap, pg_shift);

	/* clean DUMMY object */
	efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
			 EFI_VARIABLE_NON_VOLATILE |
			 EFI_VARIABLE_BOOTSERVICE_ACCESS |
			 EFI_VARIABLE_RUNTIME_ACCESS,
			 0, NULL);
}

/*
 * Convenience functions to obtain memory types and attributes
 */
u32 efi_mem_type(unsigned long phys_addr)
{
	efi_memory_desc_t *md;
	void *p;

	if (!efi_enabled(EFI_MEMMAP))
		return 0;

	for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
		md = p;
		if ((md->phys_addr <= phys_addr) &&
		    (phys_addr < (md->phys_addr +
				  (md->num_pages << EFI_PAGE_SHIFT))))
			return md->type;
	}
	return 0;
}

u64 efi_mem_attributes(unsigned long phys_addr)
{
	efi_memory_desc_t *md;
	void *p;

	for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
		md = p;
		if ((md->phys_addr <= phys_addr) &&
		    (phys_addr < (md->phys_addr +
				  (md->num_pages << EFI_PAGE_SHIFT))))
			return md->attribute;
	}
	return 0;
}

/*
 * Some firmware implementations refuse to boot if there's insufficient space
 * in the variable store. Ensure that we never use more than a safe limit.
 *
 * Return EFI_SUCCESS if it is safe to write 'size' bytes to the variable
 * store.
 */
efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
{
	efi_status_t status;
	u64 storage_size, remaining_size, max_size;

	if (!(attributes & EFI_VARIABLE_NON_VOLATILE))
		return 0;

	status = efi.query_variable_info(attributes, &storage_size,
					 &remaining_size, &max_size);
	if (status != EFI_SUCCESS)
		return status;

	/*
	 * We account for that by refusing the write if permitting it would
	 * reduce the available space to under 5KB. This figure was provided by
	 * Samsung, so should be safe.
	 */
	if ((remaining_size - size < EFI_MIN_RESERVE) &&
		!efi_no_storage_paranoia) {

		/*
		 * Triggering garbage collection may require that the firmware
		 * generate a real EFI_OUT_OF_RESOURCES error. We can force
		 * that by attempting to use more space than is available.
		 */
		unsigned long dummy_size = remaining_size + 1024;
		void *dummy = kzalloc(dummy_size, GFP_ATOMIC);

		if (!dummy)
			return EFI_OUT_OF_RESOURCES;

		status = efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
					  EFI_VARIABLE_NON_VOLATILE |
					  EFI_VARIABLE_BOOTSERVICE_ACCESS |
					  EFI_VARIABLE_RUNTIME_ACCESS,
					  dummy_size, dummy);

		if (status == EFI_SUCCESS) {
			/*
			 * This should have failed, so if it didn't make sure
			 * that we delete it...
			 */
			efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
					 EFI_VARIABLE_NON_VOLATILE |
					 EFI_VARIABLE_BOOTSERVICE_ACCESS |
					 EFI_VARIABLE_RUNTIME_ACCESS,
					 0, dummy);
		}

		kfree(dummy);

		/*
		 * The runtime code may now have triggered a garbage collection
		 * run, so check the variable info again
		 */
		status = efi.query_variable_info(attributes, &storage_size,
						 &remaining_size, &max_size);

		if (status != EFI_SUCCESS)
			return status;

		/*
		 * There still isn't enough room, so return an error
		 */
		if (remaining_size - size < EFI_MIN_RESERVE)
			return EFI_OUT_OF_RESOURCES;
	}

	return EFI_SUCCESS;
}
EXPORT_SYMBOL_GPL(efi_query_variable_store);

static int __init parse_efi_cmdline(char *str)
{
	if (*str == '=')
		str++;

	if (!strncmp(str, "old_map", 7))
		set_bit(EFI_OLD_MEMMAP, &efi.flags);

	return 0;
}
early_param("efi", parse_efi_cmdline);