mirror_zfs/module/os/linux/spl/spl-generic.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
 *  Copyright (C) 2007 The Regents of the University of California.
 *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
 *  Written by Brian Behlendorf <behlendorf1@llnl.gov>.
 *  UCRL-CODE-235197
 *
 *  This file is part of the SPL, Solaris Porting Layer.
 *
 *  The SPL is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License as published by the
 *  Free Software Foundation; either version 2 of the License, or (at your
 *  option) any later version.
 *
 *  The SPL is distributed in the hope that it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
 *
 *  Solaris Porting Layer (SPL) Generic Implementation.
 */

#include <sys/isa_defs.h>
#include <sys/sysmacros.h>
#include <sys/systeminfo.h>
#include <sys/vmsystm.h>
#include <sys/kmem.h>
#include <sys/kmem_cache.h>
#include <sys/vmem.h>
#include <sys/mutex.h>
#include <sys/rwlock.h>
#include <sys/taskq.h>
#include <sys/tsd.h>
#include <sys/zmod.h>
#include <sys/debug.h>
#include <sys/proc.h>
#include <sys/kstat.h>
#include <sys/file.h>
#include <sys/sunddi.h>
#include <linux/ctype.h>
#include <sys/disp.h>
#include <sys/random.h>
#include <sys/string.h>
#include <linux/kmod.h>
#include <linux/mod_compat.h>
#include <sys/cred.h>
#include <sys/vnode.h>
#include <sys/misc.h>
#include <linux/mod_compat.h>

unsigned long spl_hostid = 0;
EXPORT_SYMBOL(spl_hostid);

module_param(spl_hostid, ulong, 0644);
MODULE_PARM_DESC(spl_hostid, "The system hostid.");

proc_t p0;
EXPORT_SYMBOL(p0);

/*
 * xoshiro256++ 1.0 PRNG by David Blackman and Sebastiano Vigna
 *
 * "Scrambled Linear Pseudorandom Number Generators∗"
 * https://vigna.di.unimi.it/ftp/papers/ScrambledLinear.pdf
 *
 * random_get_pseudo_bytes() is an API function on Illumos whose sole purpose
 * is to provide bytes containing random numbers. It is mapped to /dev/urandom
 * on Illumos, which uses a "FIPS 186-2 algorithm". No user of the SPL's
 * random_get_pseudo_bytes() needs bytes that are of cryptographic quality, so
 * we can implement it using a fast PRNG that we seed using Linux' actual
 * equivalent to random_get_pseudo_bytes(). We do this by providing each CPU
 * with an independent seed so that all calls to random_get_pseudo_bytes() are
 * free of atomic instructions.
 *
 * A consequence of using a fast PRNG is that using random_get_pseudo_bytes()
 * to generate words larger than 256 bits will paradoxically be limited to
 * `2^256 - 1` possibilities. This is because we have a sequence of `2^256 - 1`
 * 256-bit words and selecting the first will implicitly select the second. If
 * a caller finds this behavior undesirable, random_get_bytes() should be used
 * instead.
 *
 * XXX: Linux interrupt handlers that trigger within the critical section
 * formed by `s[3] = xp[3];` and `xp[0] = s[0];` and call this function will
 * see the same numbers. Nothing in the code currently calls this in an
 * interrupt handler, so this is considered to be okay. If that becomes a
 * problem, we could create a set of per-cpu variables for interrupt handlers
 * and use them when in_interrupt() from linux/preempt_mask.h evaluates to
 * true.
 */
static void __percpu *spl_pseudo_entropy;

/*
 * rotl()/spl_rand_next()/spl_rand_jump() are copied from the following CC-0
 * licensed file:
 *
 * https://prng.di.unimi.it/xoshiro256plusplus.c
 */

static inline uint64_t rotl(const uint64_t x, int k)
{
	return ((x << k) | (x >> (64 - k)));
}

static inline uint64_t
spl_rand_next(uint64_t *s)
{
	const uint64_t result = rotl(s[0] + s[3], 23) + s[0];

	const uint64_t t = s[1] << 17;

	s[2] ^= s[0];
	s[3] ^= s[1];
	s[1] ^= s[2];
	s[0] ^= s[3];

	s[2] ^= t;

	s[3] = rotl(s[3], 45);

	return (result);
}

static inline void
spl_rand_jump(uint64_t *s)
{
	static const uint64_t JUMP[] = { 0x180ec6d33cfd0aba,
	    0xd5a61266f0c9392c, 0xa9582618e03fc9aa, 0x39abdc4529b1661c };

	uint64_t s0 = 0;
	uint64_t s1 = 0;
	uint64_t s2 = 0;
	uint64_t s3 = 0;
	int i, b;
	for (i = 0; i < sizeof (JUMP) / sizeof (*JUMP); i++)
		for (b = 0; b < 64; b++) {
			if (JUMP[i] & 1ULL << b) {
				s0 ^= s[0];
				s1 ^= s[1];
				s2 ^= s[2];
				s3 ^= s[3];
			}
			(void) spl_rand_next(s);
		}

	s[0] = s0;
	s[1] = s1;
	s[2] = s2;
	s[3] = s3;
}

int
random_get_pseudo_bytes(uint8_t *ptr, size_t len)
{
	uint64_t *xp, s[4];

	ASSERT(ptr);

	xp = get_cpu_ptr(spl_pseudo_entropy);

	s[0] = xp[0];
	s[1] = xp[1];
	s[2] = xp[2];
	s[3] = xp[3];

	while (len) {
		union {
			uint64_t ui64;
			uint8_t byte[sizeof (uint64_t)];
		}entropy;
		int i = MIN(len, sizeof (uint64_t));

		len -= i;
		entropy.ui64 = spl_rand_next(s);

		/*
		 * xoshiro256++ has low entropy lower bytes, so we copy the
		 * higher order bytes first.
		 */
		while (i--)
#ifdef _ZFS_BIG_ENDIAN
			*ptr++ = entropy.byte[i];
#else
			*ptr++ = entropy.byte[7 - i];
#endif
	}

	xp[0] = s[0];
	xp[1] = s[1];
	xp[2] = s[2];
	xp[3] = s[3];

	put_cpu_ptr(spl_pseudo_entropy);

	return (0);
}
EXPORT_SYMBOL(random_get_pseudo_bytes);

/*
 * NOTE: The strtoxx behavior is solely based on my reading of the Solaris
 * ddi_strtol(9F) man page.  I have not verified the behavior of these
 * functions against their Solaris counterparts.  It is possible that I
 * may have misinterpreted the man page or the man page is incorrect.
 */
int ddi_strtol(const char *, char **, int, long *);
int ddi_strtoull(const char *, char **, int, unsigned long long *);
int ddi_strtoll(const char *, char **, int, long long *);

#define	define_ddi_strtox(type, valtype)				\
int ddi_strto##type(const char *str, char **endptr,			\
    int base, valtype *result)						\
{									\
	valtype last_value, value = 0;					\
	char *ptr = (char *)str;					\
	int digit, minus = 0;						\
									\
	while (strchr(" \t\n\r\f", *ptr))				\
		++ptr;							\
									\
	if (strlen(ptr) == 0)						\
		return (EINVAL);					\
									\
	switch (*ptr) {							\
	case '-':							\
		minus = 1;						\
		zfs_fallthrough;					\
	case '+':							\
		++ptr;							\
		break;							\
	}								\
									\
	/* Auto-detect base based on prefix */				\
	if (!base) {							\
		if (str[0] == '0') {					\
			if (tolower(str[1]) == 'x' && isxdigit(str[2])) { \
				base = 16; /* hex */			\
				ptr += 2;				\
			} else if (str[1] >= '0' && str[1] < '8') {	\
				base = 8; /* octal */			\
				ptr += 1;				\
			} else {					\
				return (EINVAL);			\
			}						\
		} else {						\
			base = 10; /* decimal */			\
		}							\
	}								\
									\
	while (1) {							\
		if (isdigit(*ptr))					\
			digit = *ptr - '0';				\
		else if (isalpha(*ptr))					\
			digit = tolower(*ptr) - 'a' + 10;		\
		else							\
			break;						\
									\
		if (digit >= base)					\
			break;						\
									\
		last_value = value;					\
		value = value * base + digit;				\
		if (last_value > value) /* Overflow */			\
			return (ERANGE);				\
									\
		ptr++;							\
	}								\
									\
	*result = minus ? -value : value;				\
									\
	if (endptr)							\
		*endptr = ptr;						\
									\
	return (0);							\
}									\

define_ddi_strtox(l, long)
define_ddi_strtox(ull, unsigned long long)
define_ddi_strtox(ll, long long)

EXPORT_SYMBOL(ddi_strtol);
EXPORT_SYMBOL(ddi_strtoll);
EXPORT_SYMBOL(ddi_strtoull);

int
ddi_copyin(const void *from, void *to, size_t len, int flags)
{
	/* Fake ioctl() issued by kernel, 'from' is a kernel address */
	if (flags & FKIOCTL) {
		memcpy(to, from, len);
		return (0);
	}

	return (copyin(from, to, len));
}
EXPORT_SYMBOL(ddi_copyin);

/*
 * Post a uevent to userspace whenever a new vdev adds to the pool. It is
 * necessary to sync blkid information with udev, which zed daemon uses
 * during device hotplug to identify the vdev.
 */
void
spl_signal_kobj_evt(struct block_device *bdev)
{
#if defined(HAVE_BDEV_KOBJ) || defined(HAVE_PART_TO_DEV)
#ifdef HAVE_BDEV_KOBJ
	struct kobject *disk_kobj = bdev_kobj(bdev);
#else
	struct kobject *disk_kobj = &part_to_dev(bdev->bd_part)->kobj;
#endif
	if (disk_kobj) {
		int ret = kobject_uevent(disk_kobj, KOBJ_CHANGE);
		if (ret) {
			pr_warn("ZFS: Sending event '%d' to kobject: '%s'"
			    " (%p): failed(ret:%d)\n", KOBJ_CHANGE,
			    kobject_name(disk_kobj), disk_kobj, ret);
		}
	}
#else
/*
 * This is encountered if neither bdev_kobj() nor part_to_dev() is available
 * in the kernel - likely due to an API change that needs to be chased down.
 */
#error "Unsupported kernel: unable to get struct kobj from bdev"
#endif
}
EXPORT_SYMBOL(spl_signal_kobj_evt);

int
ddi_copyout(const void *from, void *to, size_t len, int flags)
{
	/* Fake ioctl() issued by kernel, 'from' is a kernel address */
	if (flags & FKIOCTL) {
		memcpy(to, from, len);
		return (0);
	}

	return (copyout(from, to, len));
}
EXPORT_SYMBOL(ddi_copyout);

static int
spl_getattr(struct file *filp, struct kstat *stat)
{
	int rc;

	ASSERT(filp);
	ASSERT(stat);

	rc = vfs_getattr(&filp->f_path, stat, STATX_BASIC_STATS,
	    AT_STATX_SYNC_AS_STAT);
	if (rc)
		return (-rc);

	return (0);
}

/*
 * Read the unique system identifier from the /etc/hostid file.
 *
 * The behavior of /usr/bin/hostid on Linux systems with the
 * regular eglibc and coreutils is:
 *
 *   1. Generate the value if the /etc/hostid file does not exist
 *      or if the /etc/hostid file is less than four bytes in size.
 *
 *   2. If the /etc/hostid file is at least 4 bytes, then return
 *      the first four bytes [0..3] in native endian order.
 *
 *   3. Always ignore bytes [4..] if they exist in the file.
 *
 * Only the first four bytes are significant, even on systems that
 * have a 64-bit word size.
 *
 * See:
 *
 *   eglibc: sysdeps/unix/sysv/linux/gethostid.c
 *   coreutils: src/hostid.c
 *
 * Notes:
 *
 * The /etc/hostid file on Solaris is a text file that often reads:
 *
 *   # DO NOT EDIT
 *   "0123456789"
 *
 * Directly copying this file to Linux results in a constant
 * hostid of 4f442023 because the default comment constitutes
 * the first four bytes of the file.
 *
 */

static char *spl_hostid_path = HW_HOSTID_PATH;
module_param(spl_hostid_path, charp, 0444);
MODULE_PARM_DESC(spl_hostid_path, "The system hostid file (/etc/hostid)");

static int
hostid_read(uint32_t *hostid)
{
	uint64_t size;
	uint32_t value = 0;
	int error;
	loff_t off;
	struct file *filp;
	struct kstat stat;

	filp = filp_open(spl_hostid_path, 0, 0);

	if (IS_ERR(filp))
		return (ENOENT);

	error = spl_getattr(filp, &stat);
	if (error) {
		filp_close(filp, 0);
		return (error);
	}
	size = stat.size;
	// cppcheck-suppress sizeofwithnumericparameter
	if (size < sizeof (HW_HOSTID_MASK)) {
		filp_close(filp, 0);
		return (EINVAL);
	}

	off = 0;
	/*
	 * Read directly into the variable like eglibc does.
	 * Short reads are okay; native behavior is preserved.
	 */
	error = kernel_read(filp, &value, sizeof (value), &off);
	if (error < 0) {
		filp_close(filp, 0);
		return (EIO);
	}

	/* Mask down to 32 bits like coreutils does. */
	*hostid = (value & HW_HOSTID_MASK);
	filp_close(filp, 0);

	return (0);
}

/*
 * Return the system hostid.  Preferentially use the spl_hostid module option
 * when set, otherwise use the value in the /etc/hostid file.
 */
uint32_t
zone_get_hostid(void *zone)
{
	uint32_t hostid;

	ASSERT0P(zone);

	if (spl_hostid != 0)
		return ((uint32_t)(spl_hostid & HW_HOSTID_MASK));

	if (hostid_read(&hostid) == 0)
		return (hostid);

	return (0);
}
EXPORT_SYMBOL(zone_get_hostid);

static int
spl_kvmem_init(void)
{
	int rc = 0;

	rc = spl_kmem_init();
	if (rc)
		return (rc);

	rc = spl_vmem_init();
	if (rc) {
		spl_kmem_fini();
		return (rc);
	}

	return (rc);
}

/*
 * We initialize the random number generator with 128 bits of entropy from the
 * system random number generator. In the improbable case that we have a zero
 * seed, we fallback to the system jiffies, unless it is also zero, in which
 * situation we use a preprogrammed seed. We step forward by 2^64 iterations to
 * initialize each of the per-cpu seeds so that the sequences generated on each
 * CPU are guaranteed to never overlap in practice.
 */
static int __init
spl_random_init(void)
{
	uint64_t s[4];
	int i = 0;

	spl_pseudo_entropy = __alloc_percpu(4 * sizeof (uint64_t),
	    sizeof (uint64_t));

	if (!spl_pseudo_entropy)
		return (-ENOMEM);

	get_random_bytes(s, sizeof (s));

	if (s[0] == 0 && s[1] == 0 && s[2] == 0 && s[3] == 0) {
		if (jiffies != 0) {
			s[0] = jiffies;
			s[1] = ~0 - jiffies;
			s[2] = ~jiffies;
			s[3] = jiffies - ~0;
		} else {
			(void) memcpy(s, "improbable seed", 16);
		}
		printk("SPL: get_random_bytes() returned 0 "
		    "when generating random seed. Setting initial seed to "
		    "0x%016llx%016llx%016llx%016llx.\n", cpu_to_be64(s[0]),
		    cpu_to_be64(s[1]), cpu_to_be64(s[2]), cpu_to_be64(s[3]));
	}

	for_each_possible_cpu(i) {
		uint64_t *wordp = per_cpu_ptr(spl_pseudo_entropy, i);

		spl_rand_jump(s);

		wordp[0] = s[0];
		wordp[1] = s[1];
		wordp[2] = s[2];
		wordp[3] = s[3];
	}

	return (0);
}

static void
spl_random_fini(void)
{
	free_percpu(spl_pseudo_entropy);
}

static void
spl_kvmem_fini(void)
{
	spl_vmem_fini();
	spl_kmem_fini();
}

static int __init
spl_init(void)
{
	int rc = 0;

	if ((rc = spl_random_init()))
		goto out0;

	if ((rc = spl_kvmem_init()))
		goto out1;

	if ((rc = spl_tsd_init()))
		goto out2;

	if ((rc = spl_proc_init()))
		goto out3;

	if ((rc = spl_kstat_init()))
		goto out4;

	if ((rc = spl_taskq_init()))
		goto out5;

	if ((rc = spl_kmem_cache_init()))
		goto out6;

	if ((rc = spl_zlib_init()))
		goto out7;

	if ((rc = spl_zone_init()))
		goto out8;

	return (rc);

out8:
	spl_zlib_fini();
out7:
	spl_kmem_cache_fini();
out6:
	spl_taskq_fini();
out5:
	spl_kstat_fini();
out4:
	spl_proc_fini();
out3:
	spl_tsd_fini();
out2:
	spl_kvmem_fini();
out1:
	spl_random_fini();
out0:
	return (rc);
}

static void __exit
spl_fini(void)
{
	spl_zone_fini();
	spl_zlib_fini();
	spl_kmem_cache_fini();
	spl_taskq_fini();
	spl_kstat_fini();
	spl_proc_fini();
	spl_tsd_fini();
	spl_kvmem_fini();
	spl_random_fini();
}

module_init(spl_init);
module_exit(spl_fini);

MODULE_DESCRIPTION("Solaris Porting Layer");
MODULE_AUTHOR(ZFS_META_AUTHOR);
MODULE_LICENSE("GPL");
MODULE_VERSION(ZFS_META_VERSION "-" ZFS_META_RELEASE);