file.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Helper functions used by the EFI stub on multiple
 * architectures. This should be #included by the EFI stub
 * implementation files.
 *
 * Copyright 2011 Intel Corporation; author Matt Fleming
 */

#include <linux/efi.h>
#include <asm/efi.h>

#include "efistub.h"

#define MAX_FILENAME_SIZE	256

/*
 * Some firmware implementations have problems reading files in one go.
 * A read chunk size of 1MB seems to work for most platforms.
 *
 * Unfortunately, reading files in chunks triggers *other* bugs on some
 * platforms, so we provide a way to disable this workaround, which can
 * be done by passing "efi=nochunk" on the EFI boot stub command line.
 *
 * If you experience issues with initrd images being corrupt it's worth
 * trying efi=nochunk, but chunking is enabled by default on x86 because
 * there are far more machines that require the workaround than those that
 * break with it enabled.
 */
#define EFI_READ_CHUNK_SIZE	SZ_1M

struct finfo {
	efi_file_info_t info;
	efi_char16_t	filename[MAX_FILENAME_SIZE];
};

static efi_status_t efi_open_file(efi_file_protocol_t *volume,
				  struct finfo *fi,
				  efi_file_protocol_t **handle,
				  unsigned long *file_size)
{
	efi_guid_t info_guid = EFI_FILE_INFO_ID;
	efi_file_protocol_t *fh;
	unsigned long info_sz;
	efi_status_t status;

	status = volume->open(volume, &fh, fi->filename, EFI_FILE_MODE_READ, 0);
	if (status != EFI_SUCCESS) {
		efi_err("Failed to open file: %ls\n", fi->filename);
		return status;
	}

	info_sz = sizeof(struct finfo);
	status = fh->get_info(fh, &info_guid, &info_sz, fi);
	if (status != EFI_SUCCESS) {
		efi_err("Failed to get file info\n");
		fh->close(fh);
		return status;
	}

	*handle = fh;
	*file_size = fi->info.file_size;
	return EFI_SUCCESS;
}

static efi_status_t efi_open_volume(efi_loaded_image_t *image,
				    efi_file_protocol_t **fh)
{
	efi_guid_t fs_proto = EFI_FILE_SYSTEM_GUID;
	efi_simple_file_system_protocol_t *io;
	efi_status_t status;

	status = efi_bs_call(handle_protocol, image->device_handle, &fs_proto,
			     (void **)&io);
	if (status != EFI_SUCCESS) {
		efi_err("Failed to handle fs_proto\n");
		return status;
	}

	status = io->open_volume(io, fh);
	if (status != EFI_SUCCESS)
		efi_err("Failed to open volume\n");

	return status;
}

static int find_file_option(const efi_char16_t *cmdline, int cmdline_len,
			    const efi_char16_t *prefix, int prefix_size,
			    efi_char16_t *result, int result_len)
{
	int prefix_len = prefix_size / 2;
	bool found = false;
	int i;

	for (i = prefix_len; i < cmdline_len; i++) {
		if (!memcmp(&cmdline[i - prefix_len], prefix, prefix_size)) {
			found = true;
			break;
		}
	}

	if (!found)
		return 0;

	/* Skip any leading slashes */
	while (i < cmdline_len && (cmdline[i] == L'/' || cmdline[i] == L'\\'))
		i++;

	while (--result_len > 0 && i < cmdline_len) {
		efi_char16_t c = cmdline[i++];

		if (c == L'\0' || c == L'\n' || c == L' ')
			break;
		else if (c == L'/')
			/* Replace UNIX dir separators with EFI standard ones */
			*result++ = L'\\';
		else
			*result++ = c;
	}
	*result = L'\0';
	return i;
}

/*
 * Check the cmdline for a LILO-style file= arguments.
 *
 * We only support loading a file from the same filesystem as
 * the kernel image.
 */
efi_status_t handle_cmdline_files(efi_loaded_image_t *image,
				  const efi_char16_t *optstr,
				  int optstr_size,
				  unsigned long soft_limit,
				  unsigned long hard_limit,
				  unsigned long *load_addr,
				  unsigned long *load_size)
{
	const efi_char16_t *cmdline = image->load_options;
	int cmdline_len = image->load_options_size;
	unsigned long efi_chunk_size = ULONG_MAX;
	efi_file_protocol_t *volume = NULL;
	efi_file_protocol_t *file;
	unsigned long alloc_addr;
	unsigned long alloc_size;
	efi_status_t status;
	int offset;

	if (!load_addr || !load_size)
		return EFI_INVALID_PARAMETER;

	efi_apply_loadoptions_quirk((const void **)&cmdline, &cmdline_len);
	cmdline_len /= sizeof(*cmdline);

	if (IS_ENABLED(CONFIG_X86) && !efi_nochunk)
		efi_chunk_size = EFI_READ_CHUNK_SIZE;

	alloc_addr = alloc_size = 0;
	do {
		struct finfo fi;
		unsigned long size;
		void *addr;

		offset = find_file_option(cmdline, cmdline_len,
					  optstr, optstr_size,
					  fi.filename, ARRAY_SIZE(fi.filename));

		if (!offset)
			break;

		cmdline += offset;
		cmdline_len -= offset;

		if (!volume) {
			status = efi_open_volume(image, &volume);
			if (status != EFI_SUCCESS)
				return status;
		}

		status = efi_open_file(volume, &fi, &file, &size);
		if (status != EFI_SUCCESS)
			goto err_close_volume;

		/*
		 * Check whether the existing allocation can contain the next
		 * file. This condition will also trigger naturally during the
		 * first (and typically only) iteration of the loop, given that
		 * alloc_size == 0 in that case.
		 */
		if (round_up(alloc_size + size, EFI_ALLOC_ALIGN) >
		    round_up(alloc_size, EFI_ALLOC_ALIGN)) {
			unsigned long old_addr = alloc_addr;

			status = EFI_OUT_OF_RESOURCES;
			if (soft_limit < hard_limit)
				status = efi_allocate_pages(alloc_size + size,
							    &alloc_addr,
							    soft_limit);
			if (status == EFI_OUT_OF_RESOURCES)
				status = efi_allocate_pages(alloc_size + size,
							    &alloc_addr,
							    hard_limit);
			if (status != EFI_SUCCESS) {
				efi_err("Failed to allocate memory for files\n");
				goto err_close_file;
			}

			if (old_addr != 0) {
				/*
				 * This is not the first time we've gone
				 * around this loop, and so we are loading
				 * multiple files that need to be concatenated
				 * and returned in a single buffer.
				 */
				memcpy((void *)alloc_addr, (void *)old_addr, alloc_size);
				efi_free(alloc_size, old_addr);
			}
		}

		addr = (void *)alloc_addr + alloc_size;
		alloc_size += size;

		while (size) {
			unsigned long chunksize = min(size, efi_chunk_size);

			status = file->read(file, &chunksize, addr);
			if (status != EFI_SUCCESS) {
				efi_err("Failed to read file\n");
				goto err_close_file;
			}
			addr += chunksize;
			size -= chunksize;
		}
		file->close(file);
	} while (offset > 0);

	*load_addr = alloc_addr;
	*load_size = alloc_size;

	if (volume)
		volume->close(volume);

	if (*load_size == 0)
		return EFI_NOT_READY;
	return EFI_SUCCESS;

err_close_file:
	file->close(file);

err_close_volume:
	volume->close(volume);
	efi_free(alloc_size, alloc_addr);
	return status;
}