WSL2-Linux-Kernel/drivers/firmware/efi/efi-pstore.c

#include <linux/efi.h>
#include <linux/module.h>
#include <linux/pstore.h>
#include <linux/slab.h>
#include <linux/ucs2_string.h>

#define DUMP_NAME_LEN 52

static bool efivars_pstore_disable =
	IS_ENABLED(CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE);

module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);

#define PSTORE_EFI_ATTRIBUTES \
	(EFI_VARIABLE_NON_VOLATILE | \
	 EFI_VARIABLE_BOOTSERVICE_ACCESS | \
	 EFI_VARIABLE_RUNTIME_ACCESS)

static int efi_pstore_open(struct pstore_info *psi)
{
	psi->data = NULL;
	return 0;
}

static int efi_pstore_close(struct pstore_info *psi)
{
	psi->data = NULL;
	return 0;
}

struct pstore_read_data {
	u64 *id;
	enum pstore_type_id *type;
	int *count;
	struct timespec *timespec;
	bool *compressed;
	char **buf;
};

static inline u64 generic_id(unsigned long timestamp,
			     unsigned int part, int count)
{
	return ((u64) timestamp * 100 + part) * 1000 + count;
}

static int efi_pstore_read_func(struct efivar_entry *entry, void *data)
{
	efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
	struct pstore_read_data *cb_data = data;
	char name[DUMP_NAME_LEN], data_type;
	int i;
	int cnt;
	unsigned int part;
	unsigned long time, size;

	if (efi_guidcmp(entry->var.VendorGuid, vendor))
		return 0;

	for (i = 0; i < DUMP_NAME_LEN; i++)
		name[i] = entry->var.VariableName[i];

	if (sscanf(name, "dump-type%u-%u-%d-%lu-%c",
		   cb_data->type, &part, &cnt, &time, &data_type) == 5) {
		*cb_data->id = generic_id(time, part, cnt);
		*cb_data->count = cnt;
		cb_data->timespec->tv_sec = time;
		cb_data->timespec->tv_nsec = 0;
		if (data_type == 'C')
			*cb_data->compressed = true;
		else
			*cb_data->compressed = false;
	} else if (sscanf(name, "dump-type%u-%u-%d-%lu",
		   cb_data->type, &part, &cnt, &time) == 4) {
		*cb_data->id = generic_id(time, part, cnt);
		*cb_data->count = cnt;
		cb_data->timespec->tv_sec = time;
		cb_data->timespec->tv_nsec = 0;
		*cb_data->compressed = false;
	} else if (sscanf(name, "dump-type%u-%u-%lu",
			  cb_data->type, &part, &time) == 3) {
		/*
		 * Check if an old format,
		 * which doesn't support holding
		 * multiple logs, remains.
		 */
		*cb_data->id = generic_id(time, part, 0);
		*cb_data->count = 0;
		cb_data->timespec->tv_sec = time;
		cb_data->timespec->tv_nsec = 0;
		*cb_data->compressed = false;
	} else
		return 0;

	entry->var.DataSize = 1024;
	__efivar_entry_get(entry, &entry->var.Attributes,
			   &entry->var.DataSize, entry->var.Data);
	size = entry->var.DataSize;
	memcpy(*cb_data->buf, entry->var.Data,
	       (size_t)min_t(unsigned long, EFIVARS_DATA_SIZE_MAX, size));

	return size;
}

/**
 * efi_pstore_scan_sysfs_enter
 * @entry: scanning entry
 * @next: next entry
 * @head: list head
 */
static void efi_pstore_scan_sysfs_enter(struct efivar_entry *pos,
					struct efivar_entry *next,
					struct list_head *head)
{
	pos->scanning = true;
	if (&next->list != head)
		next->scanning = true;
}

/**
 * __efi_pstore_scan_sysfs_exit
 * @entry: deleting entry
 * @turn_off_scanning: Check if a scanning flag should be turned off
 */
static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
						bool turn_off_scanning)
{
	if (entry->deleting) {
		list_del(&entry->list);
		efivar_entry_iter_end();
		efivar_unregister(entry);
		efivar_entry_iter_begin();
	} else if (turn_off_scanning)
		entry->scanning = false;
}

/**
 * efi_pstore_scan_sysfs_exit
 * @pos: scanning entry
 * @next: next entry
 * @head: list head
 * @stop: a flag checking if scanning will stop
 */
static void efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
				       struct efivar_entry *next,
				       struct list_head *head, bool stop)
{
	__efi_pstore_scan_sysfs_exit(pos, true);
	if (stop)
		__efi_pstore_scan_sysfs_exit(next, &next->list != head);
}

/**
 * efi_pstore_sysfs_entry_iter
 *
 * @data: function-specific data to pass to callback
 * @pos: entry to begin iterating from
 *
 * You MUST call efivar_enter_iter_begin() before this function, and
 * efivar_entry_iter_end() afterwards.
 *
 * It is possible to begin iteration from an arbitrary entry within
 * the list by passing @pos. @pos is updated on return to point to
 * the next entry of the last one passed to efi_pstore_read_func().
 * To begin iterating from the beginning of the list @pos must be %NULL.
 */
static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos)
{
	struct efivar_entry *entry, *n;
	struct list_head *head = &efivar_sysfs_list;
	int size = 0;

	if (!*pos) {
		list_for_each_entry_safe(entry, n, head, list) {
			efi_pstore_scan_sysfs_enter(entry, n, head);

			size = efi_pstore_read_func(entry, data);
			efi_pstore_scan_sysfs_exit(entry, n, head, size < 0);
			if (size)
				break;
		}
		*pos = n;
		return size;
	}

	list_for_each_entry_safe_from((*pos), n, head, list) {
		efi_pstore_scan_sysfs_enter((*pos), n, head);

		size = efi_pstore_read_func((*pos), data);
		efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0);
		if (size)
			break;
	}
	*pos = n;
	return size;
}

/**
 * efi_pstore_read
 *
 * This function returns a size of NVRAM entry logged via efi_pstore_write().
 * The meaning and behavior of efi_pstore/pstore are as below.
 *
 * size > 0: Got data of an entry logged via efi_pstore_write() successfully,
 *           and pstore filesystem will continue reading subsequent entries.
 * size == 0: Entry was not logged via efi_pstore_write(),
 *            and efi_pstore driver will continue reading subsequent entries.
 * size < 0: Failed to get data of entry logging via efi_pstore_write(),
 *           and pstore will stop reading entry.
 */
static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
			       int *count, struct timespec *timespec,
			       char **buf, bool *compressed,
			       struct pstore_info *psi)
{
	struct pstore_read_data data;
	ssize_t size;

	data.id = id;
	data.type = type;
	data.count = count;
	data.timespec = timespec;
	data.compressed = compressed;
	data.buf = buf;

	*data.buf = kzalloc(EFIVARS_DATA_SIZE_MAX, GFP_KERNEL);
	if (!*data.buf)
		return -ENOMEM;

	efivar_entry_iter_begin();
	size = efi_pstore_sysfs_entry_iter(&data,
					   (struct efivar_entry **)&psi->data);
	efivar_entry_iter_end();
	if (size <= 0)
		kfree(*data.buf);
	return size;
}

static int efi_pstore_write(enum pstore_type_id type,
		enum kmsg_dump_reason reason, u64 *id,
		unsigned int part, int count, bool compressed, size_t size,
		struct pstore_info *psi)
{
	char name[DUMP_NAME_LEN];
	efi_char16_t efi_name[DUMP_NAME_LEN];
	efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
	int i, ret = 0;

	sprintf(name, "dump-type%u-%u-%d-%lu-%c", type, part, count,
		get_seconds(), compressed ? 'C' : 'D');

	for (i = 0; i < DUMP_NAME_LEN; i++)
		efi_name[i] = name[i];

	efivar_entry_set_safe(efi_name, vendor, PSTORE_EFI_ATTRIBUTES,
			      !pstore_cannot_block_path(reason),
			      size, psi->buf);

	if (reason == KMSG_DUMP_OOPS)
		efivar_run_worker();

	*id = part;
	return ret;
};

struct pstore_erase_data {
	u64 id;
	enum pstore_type_id type;
	int count;
	struct timespec time;
	efi_char16_t *name;
};

/*
 * Clean up an entry with the same name
 */
static int efi_pstore_erase_func(struct efivar_entry *entry, void *data)
{
	struct pstore_erase_data *ed = data;
	efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
	efi_char16_t efi_name_old[DUMP_NAME_LEN];
	efi_char16_t *efi_name = ed->name;
	unsigned long ucs2_len = ucs2_strlen(ed->name);
	char name_old[DUMP_NAME_LEN];
	int i;

	if (efi_guidcmp(entry->var.VendorGuid, vendor))
		return 0;

	if (ucs2_strncmp(entry->var.VariableName,
			  efi_name, (size_t)ucs2_len)) {
		/*
		 * Check if an old format, which doesn't support
		 * holding multiple logs, remains.
		 */
		sprintf(name_old, "dump-type%u-%u-%lu", ed->type,
			(unsigned int)ed->id, ed->time.tv_sec);

		for (i = 0; i < DUMP_NAME_LEN; i++)
			efi_name_old[i] = name_old[i];

		if (ucs2_strncmp(entry->var.VariableName, efi_name_old,
				  ucs2_strlen(efi_name_old)))
			return 0;
	}

	if (entry->scanning) {
		/*
		 * Skip deletion because this entry will be deleted
		 * after scanning is completed.
		 */
		entry->deleting = true;
	} else
		list_del(&entry->list);

	/* found */
	__efivar_entry_delete(entry);

	return 1;
}

static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
			    struct timespec time, struct pstore_info *psi)
{
	struct pstore_erase_data edata;
	struct efivar_entry *entry = NULL;
	char name[DUMP_NAME_LEN];
	efi_char16_t efi_name[DUMP_NAME_LEN];
	int found, i;
	unsigned int part;

	do_div(id, 1000);
	part = do_div(id, 100);
	sprintf(name, "dump-type%u-%u-%d-%lu", type, part, count, time.tv_sec);

	for (i = 0; i < DUMP_NAME_LEN; i++)
		efi_name[i] = name[i];

	edata.id = part;
	edata.type = type;
	edata.count = count;
	edata.time = time;
	edata.name = efi_name;

	efivar_entry_iter_begin();
	found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry);

	if (found && !entry->scanning) {
		efivar_entry_iter_end();
		efivar_unregister(entry);
	} else
		efivar_entry_iter_end();

	return 0;
}

static struct pstore_info efi_pstore_info = {
	.owner		= THIS_MODULE,
	.name		= "efi",
	.flags		= PSTORE_FLAGS_FRAGILE,
	.open		= efi_pstore_open,
	.close		= efi_pstore_close,
	.read		= efi_pstore_read,
	.write		= efi_pstore_write,
	.erase		= efi_pstore_erase,
};

static __init int efivars_pstore_init(void)
{
	if (!efi_enabled(EFI_RUNTIME_SERVICES))
		return 0;

	if (!efivars_kobject())
		return 0;

	if (efivars_pstore_disable)
		return 0;

	efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
	if (!efi_pstore_info.buf)
		return -ENOMEM;

	efi_pstore_info.bufsize = 1024;
	spin_lock_init(&efi_pstore_info.buf_lock);

	if (pstore_register(&efi_pstore_info)) {
		kfree(efi_pstore_info.buf);
		efi_pstore_info.buf = NULL;
		efi_pstore_info.bufsize = 0;
	}

	return 0;
}

static __exit void efivars_pstore_exit(void)
{
}

module_init(efivars_pstore_init);
module_exit(efivars_pstore_exit);

MODULE_DESCRIPTION("EFI variable backend for pstore");
MODULE_LICENSE("GPL");