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      1 /*	$NetBSD: copyout.c,v 1.10 2022/05/22 11:27:34 andvar Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2010, 2011 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Raytheon BBN Technologies Corp and Defense Advanced Research Projects
      9  * Agency and which was developed by Matt Thomas of 3am Software Foundry.
     10  *
     11  * This material is based upon work supported by the Defense Advanced Research
     12  * Projects Agency and Space and Naval Warfare Systems Center, Pacific, under
     13  * Contract No. N66001-09-C-2073.
     14  * Approved for Public Release, Distribution Unlimited
     15  *
     16  * Redistribution and use in source and binary forms, with or without
     17  * modification, are permitted provided that the following conditions
     18  * are met:
     19  * 1. Redistributions of source code must retain the above copyright
     20  *    notice, this list of conditions and the following disclaimer.
     21  * 2. Redistributions in binary form must reproduce the above copyright
     22  *    notice, this list of conditions and the following disclaimer in the
     23  *    documentation and/or other materials provided with the distribution.
     24  *
     25  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     26  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     27  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     28  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     29  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     30  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     31  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     32  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     33  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     34  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     35  * POSSIBILITY OF SUCH DAMAGE.
     36  */
     37 
     38 #define	__UFETCHSTORE_PRIVATE
     39 
     40 #include <sys/cdefs.h>
     41 __KERNEL_RCSID(0, "$NetBSD: copyout.c,v 1.10 2022/05/22 11:27:34 andvar Exp $");
     42 
     43 #include <sys/param.h>
     44 #include <sys/lwp.h>
     45 #include <sys/systm.h>
     46 
     47 #include <powerpc/pcb.h>
     48 
     49 #include <powerpc/booke/cpuvar.h>
     50 
     51 static inline void
     52 copyout_uint8(uint8_t *udaddr, uint8_t data, register_t ds_msr)
     53 {
     54 	register_t msr;
     55 	__asm volatile(
     56 		"mfmsr	%[msr]"				/* Save MSR */
     57 	"\n\t"	"mtmsr	%[ds_msr]; sync; isync"		/* DS on */
     58 	"\n\t"	"stb	%[data],0(%[udaddr])"		/* store user byte */
     59 	"\n\t"	"mtmsr	%[msr]; sync; isync"		/* DS off */
     60 	    : [msr] "=&r" (msr)
     61 	    : [ds_msr] "r" (ds_msr), [data] "r" (data), [udaddr] "b" (udaddr));
     62 }
     63 
     64 static inline void
     65 copyout_uint16(uint16_t *udaddr, uint8_t data, register_t ds_msr)
     66 {
     67 	register_t msr;
     68 	__asm volatile(
     69 		"mfmsr	%[msr]"				/* Save MSR */
     70 	"\n\t"	"mtmsr	%[ds_msr]; sync; isync"		/* DS on */
     71 	"\n\t"	"sth	%[data],0(%[udaddr])"		/* store user half */
     72 	"\n\t"	"mtmsr	%[msr]; sync; isync"		/* DS off */
     73 	    : [msr] "=&r" (msr)
     74 	    : [ds_msr] "r" (ds_msr), [data] "r" (data), [udaddr] "b" (udaddr));
     75 }
     76 
     77 static inline void
     78 copyout_uint32(uint32_t * const udaddr, uint32_t data, register_t ds_msr)
     79 {
     80 	register_t msr;
     81 	__asm volatile(
     82 		"mfmsr	%[msr]"				/* Save MSR */
     83 	"\n\t"	"mtmsr	%[ds_msr]; sync; isync"		/* DS on */
     84 	"\n\t"	"stw	%[data],0(%[udaddr])"		/* store user data */
     85 	"\n\t"	"mtmsr	%[msr]; sync; isync"		/* DS off */
     86 	    : [msr] "=&r" (msr)
     87 	    : [ds_msr] "r" (ds_msr), [data] "r" (data), [udaddr] "b" (udaddr));
     88 }
     89 
     90 #if 0
     91 static inline void
     92 copyout_le32(uint32_t * const udaddr, uint32_t data, register_t ds_msr)
     93 {
     94 	register_t msr;
     95 	__asm volatile(
     96 		"mfmsr	%[msr]"				/* Save MSR */
     97 	"\n\t"	"mtmsr	%[ds_msr]; sync; isync"		/* DS on */
     98 	"\n\t"	"stwbrx	%[data],0,%[udaddr]"		/* store user data */
     99 	"\n\t"	"mtmsr	%[msr]; sync; isync"		/* DS off */
    100 	    : [msr] "=&r" (msr)
    101 	    : [ds_msr] "r" (ds_msr), [data] "r" (data), [udaddr] "b" (udaddr));
    102 }
    103 
    104 static inline void
    105 copyout_le32_with_mask(uint32_t * const udaddr, uint32_t data,
    106 	uint32_t mask, register_t ds_msr)
    107 {
    108 	register_t msr;
    109 	uint32_t tmp;
    110 	KASSERT((data & ~mask) == 0);
    111 	__asm volatile(
    112 		"mfmsr	%[msr]"				/* Save MSR */
    113 	"\n\t"	"mtmsr	%[ds_msr]; sync; isync"		/* DS on */
    114 	"\n\t"	"lwbrx	%[tmp],0,%[udaddr]"		/* fetch user data */
    115 	"\n\t"	"andc	%[tmp],%[tmp],%[mask]"		/* mask out new data */
    116 	"\n\t"	"or	%[tmp],%[tmp],%[data]"		/* merge new data */
    117 	"\n\t"	"stwbrx	%[tmp],0,%[udaddr]"		/* store user data */
    118 	"\n\t"	"mtmsr	%[msr]; sync; isync"		/* DS off */
    119 	    : [msr] "=&r" (msr), [tmp] "=&r" (tmp)
    120 	    : [ds_msr] "r" (ds_msr), [data] "r" (data),
    121 	      [mask] "r" (mask), [udaddr] "b" (udaddr));
    122 }
    123 #endif
    124 
    125 static inline void
    126 copyout_16uint8s(const uint8_t *ksaddr8, uint8_t *udaddr8, register_t ds_msr)
    127 {
    128 	register_t msr;
    129 	__asm volatile(
    130 		"mfmsr	%[msr]"				/* Save MSR */
    131 	"\n\t"	"mtmsr	%[ds_msr]; sync; isync"		/* DS on */
    132 	"\n\t"	"stb	%[data0],0(%[udaddr8])"		/* store user data */
    133 	"\n\t"	"stb	%[data1],1(%[udaddr8])"		/* store user data */
    134 	"\n\t"	"stb	%[data2],2(%[udaddr8])"		/* store user data */
    135 	"\n\t"	"stb	%[data3],3(%[udaddr8])"		/* store user data */
    136 	"\n\t"	"stb	%[data4],4(%[udaddr8])"		/* store user data */
    137 	"\n\t"	"stb	%[data5],5(%[udaddr8])"		/* store user data */
    138 	"\n\t"	"stb	%[data6],6(%[udaddr8])"		/* store user data */
    139 	"\n\t"	"stb	%[data7],7(%[udaddr8])"		/* store user data */
    140 	"\n\t"	"stb	%[data8],8(%[udaddr8])"		/* store user data */
    141 	"\n\t"	"stb	%[data9],9(%[udaddr8])"		/* store user data */
    142 	"\n\t"	"stb	%[data10],10(%[udaddr8])"	/* store user data */
    143 	"\n\t"	"stb	%[data11],11(%[udaddr8])"	/* store user data */
    144 	"\n\t"	"stb	%[data12],12(%[udaddr8])"	/* store user data */
    145 	"\n\t"	"stb	%[data13],13(%[udaddr8])"	/* store user data */
    146 	"\n\t"	"stb	%[data14],14(%[udaddr8])"	/* store user data */
    147 	"\n\t"	"stb	%[data15],15(%[udaddr8])"	/* store user data */
    148 	"\n\t"	"mtmsr	%[msr]; sync; isync"		/* DS off */
    149 	    : [msr] "=&r" (msr)
    150 	    : [ds_msr] "r" (ds_msr), [udaddr8] "b" (udaddr8),
    151 	      [data0] "r" (ksaddr8[0]), [data1] "r" (ksaddr8[1]),
    152 	      [data2] "r" (ksaddr8[2]), [data3] "r" (ksaddr8[3]),
    153 	      [data4] "r" (ksaddr8[4]), [data5] "r" (ksaddr8[5]),
    154 	      [data6] "r" (ksaddr8[6]), [data7] "r" (ksaddr8[7]),
    155 	      [data8] "r" (ksaddr8[8]), [data9] "r" (ksaddr8[9]),
    156 	      [data10] "r" (ksaddr8[10]), [data11] "r" (ksaddr8[11]),
    157 	      [data12] "r" (ksaddr8[12]), [data13] "r" (ksaddr8[13]),
    158 	      [data14] "r" (ksaddr8[14]), [data15] "r" (ksaddr8[15]));
    159 }
    160 
    161 static inline void
    162 copyout_8uint32s(const uint32_t * const ksaddr32, uint32_t * const udaddr32,
    163 	const register_t ds_msr, const size_t line_mask)
    164 {
    165 	register_t msr;
    166 	register_t tmp;
    167 	__asm volatile(
    168 		"and.	%[tmp],%[line_mask],%[udaddr32]"
    169 	"\n\t"	"mfmsr	%[msr]"				/* Save MSR */
    170 	"\n\t"	"mtmsr	%[ds_msr]; sync; isync"		/* DS on */
    171 	"\n\t"	"bne	0,1f"
    172 	"\n\t"	"dcba	0,%[udaddr32]"
    173 	"\n"	"1:"
    174 	"\n\t"	"stw	%[data0],0(%[udaddr32])"	/* store user data */
    175 	"\n\t"	"stw	%[data1],4(%[udaddr32])"	/* store user data */
    176 	"\n\t"	"stw	%[data2],8(%[udaddr32])"	/* store user data */
    177 	"\n\t"	"stw	%[data3],12(%[udaddr32])"	/* store user data */
    178 	"\n\t"	"stw	%[data4],16(%[udaddr32])"	/* store user data */
    179 	"\n\t"	"stw	%[data5],20(%[udaddr32])"	/* store user data */
    180 	"\n\t"	"stw	%[data6],24(%[udaddr32])"	/* store user data */
    181 	"\n\t"	"stw	%[data7],28(%[udaddr32])"	/* store user data */
    182 	"\n\t"	"mtmsr	%[msr]; sync; isync"		/* DS off */
    183 	    : [msr] "=&r" (msr), [tmp] "=&r" (tmp)
    184 	    : [ds_msr] "r" (ds_msr), [udaddr32] "b" (udaddr32),
    185 	      [line_mask] "r" (line_mask),
    186 	      [data0] "r" (ksaddr32[0]), [data1] "r" (ksaddr32[1]),
    187 	      [data2] "r" (ksaddr32[2]), [data3] "r" (ksaddr32[3]),
    188 	      [data4] "r" (ksaddr32[4]), [data5] "r" (ksaddr32[5]),
    189 	      [data6] "r" (ksaddr32[6]), [data7] "r" (ksaddr32[7])
    190 	    : "cr0");
    191 }
    192 
    193 static inline void
    194 copyout_16uint32s(const uint32_t * const ksaddr32, uint32_t * const udaddr32,
    195 	const register_t ds_msr, const size_t line_mask)
    196 {
    197 	KASSERT(((uintptr_t)udaddr32 & line_mask) == 0);
    198 	register_t msr;
    199 	register_t tmp;
    200 	__asm volatile(
    201 		"and.	%[tmp],%[line_mask],%[udaddr32]"
    202 	"\n\t"	"cmplwi	2,%[line_size],32"
    203 	"\n\t"	"mfmsr	%[msr]"				/* Save MSR */
    204 	"\n\t"	"mtmsr	%[ds_msr]; sync; isync"		/* DS on */
    205 	"\n\t"	"bne	0,1f"
    206 	"\n\t"	"dcba	0,%[udaddr32]"
    207 	"\n\t"	"bne	2,1f"
    208 	"\n\t"	"dcba	%[line_size],%[udaddr32]"
    209 	"\n"	"1:"
    210 	"\n\t"	"stw	%[data0],0(%[udaddr32])"	/* store user data */
    211 	"\n\t"	"stw	%[data1],4(%[udaddr32])"	/* store user data */
    212 	"\n\t"	"stw	%[data2],8(%[udaddr32])"	/* store user data */
    213 	"\n\t"	"stw	%[data3],12(%[udaddr32])"	/* store user data */
    214 	"\n\t"	"stw	%[data4],16(%[udaddr32])"	/* store user data */
    215 	"\n\t"	"stw	%[data5],20(%[udaddr32])"	/* store user data */
    216 	"\n\t"	"stw	%[data6],24(%[udaddr32])"	/* store user data */
    217 	"\n\t"	"stw	%[data7],28(%[udaddr32])"	/* store user data */
    218 	"\n\t"	"stw	%[data8],32(%[udaddr32])"	/* store user data */
    219 	"\n\t"	"stw	%[data9],36(%[udaddr32])"	/* store user data */
    220 	"\n\t"	"stw	%[data10],40(%[udaddr32])"	/* store user data */
    221 	"\n\t"	"stw	%[data11],44(%[udaddr32])"	/* store user data */
    222 	"\n\t"	"stw	%[data12],48(%[udaddr32])"	/* store user data */
    223 	"\n\t"	"stw	%[data13],52(%[udaddr32])"	/* store user data */
    224 	"\n\t"	"stw	%[data14],56(%[udaddr32])"	/* store user data */
    225 	"\n\t"	"stw	%[data15],60(%[udaddr32])"	/* store user data */
    226 	"\n\t"	"mtmsr	%[msr]; sync; isync"		/* DS off */
    227 	    : [msr] "=&r" (msr), [tmp] "=&r" (tmp)
    228 	    : [ds_msr] "r" (ds_msr), [udaddr32] "b" (udaddr32),
    229 	      [line_size] "r" (line_mask + 1), [line_mask] "r" (line_mask),
    230 	      [data0] "r" (ksaddr32[0]), [data1] "r" (ksaddr32[1]),
    231 	      [data2] "r" (ksaddr32[2]), [data3] "r" (ksaddr32[3]),
    232 	      [data4] "r" (ksaddr32[4]), [data5] "r" (ksaddr32[5]),
    233 	      [data6] "r" (ksaddr32[6]), [data7] "r" (ksaddr32[7]),
    234 	      [data8] "r" (ksaddr32[8]), [data9] "r" (ksaddr32[9]),
    235 	      [data10] "r" (ksaddr32[10]), [data11] "r" (ksaddr32[11]),
    236 	      [data12] "r" (ksaddr32[12]), [data13] "r" (ksaddr32[13]),
    237 	      [data14] "r" (ksaddr32[14]), [data15] "r" (ksaddr32[15])
    238 	    : "cr0", "cr2");
    239 }
    240 
    241 static inline void
    242 copyout_uint8s(vaddr_t ksaddr, vaddr_t udaddr, size_t len, register_t ds_msr)
    243 {
    244 	const uint8_t *ksaddr8 = (void *)ksaddr;
    245 	uint8_t *udaddr8 = (void *)udaddr;
    246 
    247 	__builtin_prefetch(ksaddr8, 0, 1);
    248 
    249 	for (; len >= 16; len -= 16, ksaddr8 += 16, udaddr8 += 16) {
    250 		__builtin_prefetch(ksaddr8 + 16, 0, 1);
    251 		copyout_16uint8s(ksaddr8, udaddr8, ds_msr);
    252 	}
    253 
    254 	while (len-- > 0) {
    255 		copyout_uint8(udaddr8++, *ksaddr8++, ds_msr);
    256 	}
    257 }
    258 
    259 static inline void
    260 copyout_uint32s(vaddr_t ksaddr, vaddr_t udaddr, size_t len, register_t ds_msr)
    261 {
    262 	const size_t line_size = curcpu()->ci_ci.dcache_line_size;
    263 	const size_t line_mask = line_size - 1;
    264 	const size_t udalignment = udaddr & line_mask;
    265 	KASSERT((ksaddr & 3) == 0);
    266 	KASSERT((udaddr & 3) == 0);
    267 	const uint32_t *ksaddr32 = (void *)ksaddr;
    268 	uint32_t *udaddr32 = (void *)udaddr;
    269 	len >>= 2;
    270 	__builtin_prefetch(ksaddr32, 0, 1);
    271 	if (udalignment != 0 && udalignment + 4*len > line_size) {
    272 		size_t slen = (line_size - udalignment) >> 2;
    273 		len -= slen;
    274 		for (; slen >= 8; ksaddr32 += 8, udaddr32 += 8, slen -= 8) {
    275 			copyout_8uint32s(ksaddr32, udaddr32, ds_msr, line_mask);
    276 		}
    277 		while (slen-- > 0) {
    278 			copyout_uint32(udaddr32++, *ksaddr32++, ds_msr);
    279 		}
    280 		if (len == 0)
    281 			return;
    282 	}
    283 	__builtin_prefetch(ksaddr32, 0, 1);
    284 	while (len >= 16) {
    285 		__builtin_prefetch(ksaddr32 + 8, 0, 1);
    286 		__builtin_prefetch(ksaddr32 + 16, 0, 1);
    287 		copyout_16uint32s(ksaddr32, udaddr32, ds_msr, line_mask);
    288 		ksaddr32 += 16, udaddr32 += 16, len -= 16;
    289 	}
    290 	KASSERT(len <= 16);
    291 	if (len >= 8) {
    292 		__builtin_prefetch(ksaddr32 + 8, 0, 1);
    293 		copyout_8uint32s(ksaddr32, udaddr32, ds_msr, line_mask);
    294 		ksaddr32 += 8, udaddr32 += 8, len -= 8;
    295 	}
    296 	while (len-- > 0) {
    297 		copyout_uint32(udaddr32++, *ksaddr32++, ds_msr);
    298 	}
    299 }
    300 
    301 int
    302 _ustore_8(uint8_t *vusaddr, uint8_t val)
    303 {
    304 	struct pcb * const pcb = lwp_getpcb(curlwp);
    305 	struct faultbuf env;
    306 
    307 	if (setfault(&env) != 0) {
    308 		pcb->pcb_onfault = NULL;
    309 		return EFAULT;
    310 	}
    311 
    312 	copyout_uint8(vusaddr, val, mfmsr() | PSL_DS);
    313 
    314 	pcb->pcb_onfault = NULL;
    315 
    316 	return 0;
    317 }
    318 
    319 int
    320 _ustore_16(uint16_t *vusaddr, uint16_t val)
    321 {
    322 	struct pcb * const pcb = lwp_getpcb(curlwp);
    323 	struct faultbuf env;
    324 
    325 	if (setfault(&env) != 0) {
    326 		pcb->pcb_onfault = NULL;
    327 		return EFAULT;
    328 	}
    329 
    330 	copyout_uint16(vusaddr, val, mfmsr() | PSL_DS);
    331 
    332 	pcb->pcb_onfault = NULL;
    333 
    334 	return 0;
    335 }
    336 
    337 int
    338 _ustore_32(uint32_t *vusaddr, uint32_t val)
    339 {
    340 	struct pcb * const pcb = lwp_getpcb(curlwp);
    341 	struct faultbuf env;
    342 
    343 	if (setfault(&env) != 0) {
    344 		pcb->pcb_onfault = NULL;
    345 		return EFAULT;
    346 	}
    347 
    348 	copyout_uint32(vusaddr, val, mfmsr() | PSL_DS);
    349 
    350 	pcb->pcb_onfault = NULL;
    351 
    352 	return 0;
    353 }
    354 
    355 int
    356 copyout(const void *vksaddr, void *vudaddr, size_t len)
    357 {
    358 	struct pcb * const pcb = lwp_getpcb(curlwp);
    359 	struct faultbuf env;
    360 	vaddr_t udaddr = (vaddr_t) vudaddr;
    361 	vaddr_t ksaddr = (vaddr_t) vksaddr;
    362 
    363 	if (__predict_false(len == 0)) {
    364 		return 0;
    365 	}
    366 
    367 	const register_t ds_msr = mfmsr() | PSL_DS;
    368 
    369 	int rv = setfault(&env);
    370 	if (rv != 0) {
    371 		pcb->pcb_onfault = NULL;
    372 		return rv;
    373 	}
    374 
    375 	if (__predict_false(len < 4)) {
    376 		copyout_uint8s(ksaddr, udaddr, len, ds_msr);
    377 		pcb->pcb_onfault = NULL;
    378 		return 0;
    379 	}
    380 
    381 	const size_t alignment = (udaddr ^ ksaddr) & 3;
    382 	if (__predict_true(alignment == 0)) {
    383 		size_t slen;
    384 		if (__predict_false(ksaddr & 3)) {
    385 			slen = 4 - (ksaddr & 3);
    386 			copyout_uint8s(ksaddr, udaddr, slen, ds_msr);
    387 			udaddr += slen, ksaddr += slen, len -= slen;
    388 		}
    389 		slen = len & ~3;
    390 		if (__predict_true(slen >= 4)) {
    391 			copyout_uint32s(ksaddr, udaddr, slen, ds_msr);
    392 			udaddr += slen, ksaddr += slen, len -= slen;
    393 		}
    394 	}
    395 
    396 	if (len > 0) {
    397 		copyout_uint8s(ksaddr, udaddr, len, ds_msr);
    398 	}
    399 	pcb->pcb_onfault = NULL;
    400 	return 0;
    401 }
    402 
    403 #if 1
    404 int
    405 copyoutstr(const void *ksaddr, void *udaddr, size_t len, size_t *done)
    406 {
    407 	struct pcb * const pcb = lwp_getpcb(curlwp);
    408 	struct faultbuf env;
    409 	int rv;
    410 
    411 	if (__predict_false(len == 0)) {
    412 		if (done)
    413 			*done = 0;
    414 		return 0;
    415 	}
    416 
    417 	rv = setfault(&env);
    418 	if (rv != 0) {
    419 		pcb->pcb_onfault = NULL;
    420 		if (done)
    421 			*done = 0;
    422 		return rv;
    423 	}
    424 
    425 	const register_t ds_msr = mfmsr() | PSL_DS;
    426 	const uint8_t *ksaddr8 = ksaddr;
    427 	size_t copylen = 0;
    428 
    429 	uint8_t *udaddr8 = (void *)udaddr;
    430 
    431 	while (copylen++ < len) {
    432 		const uint8_t data = *ksaddr8++;
    433 		copyout_uint8(udaddr8++, data, ds_msr);
    434 		if (data == 0)
    435 			goto out;
    436 	}
    437 	rv = ENAMETOOLONG;
    438 
    439 out:
    440 	pcb->pcb_onfault = NULL;
    441 	if (done)
    442 		*done = copylen;
    443 	return rv;
    444 }
    445 #else
    446 /* XXX This version of copyoutstr(9) has never been enabled so far. */
    447 int
    448 copyoutstr(const void *ksaddr, void *udaddr, size_t len, size_t *lenp)
    449 {
    450 	struct pcb * const pcb = lwp_getpcb(curlwp);
    451 	struct faultbuf env;
    452 
    453 	if (__predict_false(len == 0)) {
    454 		if (lenp)
    455 			*lenp = 0;
    456 		return 0;
    457 	}
    458 
    459 	if (setfault(&env)) {
    460 		pcb->pcb_onfault = NULL;
    461 		if (lenp)
    462 			*lenp = 0;
    463 		return EFAULT;
    464 	}
    465 
    466 	const register_t ds_msr = mfmsr() | PSL_DS;
    467 	const uint8_t *ksaddr8 = ksaddr;
    468 	size_t copylen = 0;
    469 
    470 	uint32_t *udaddr32 = (void *)((uintptr_t)udaddr & ~3);
    471 
    472 	size_t boff = (uintptr_t)udaddr & 3;
    473 	bool done = false;
    474 	size_t wlen = 0;
    475 	size_t data = 0;
    476 
    477 	/*
    478 	 * If the destination buffer doesn't start on a 32-bit boundary
    479 	 * try to partially fill in the first word.  If we succeed we can
    480 	 * finish writing it while preserving the bytes on front.
    481 	 */
    482 	if (boff > 0) {
    483 		KASSERT(len > 0);
    484 		do {
    485 			data = (data << 8) | *ksaddr8++;
    486 			wlen++;
    487 			done = ((uint8_t)data == 0 || len == wlen);
    488 		} while (!done && boff + wlen < 4);
    489 		KASSERT(wlen > 0);
    490 		data <<= 8 * boff;
    491 		if (!done || boff + wlen == 4) {
    492 			uint32_t mask = 0xffffffff << (8 * boff);
    493 			copyout_le32_with_mask(udaddr32++, data, mask, ds_msr);
    494 			boff = 0;
    495 			copylen = wlen;
    496 			wlen = 0;
    497 			data = 0;
    498 		}
    499 	}
    500 
    501 	/*
    502 	 * Now we get to the heart of the routine.  Build up complete words
    503 	 * if possible.  When we have one, write it to the user's address
    504 	 * space and go for the next.  If we ran out of space or we found the
    505 	 * end of the string, stop building.  If we managed to build a complete
    506 	 * word, just write it and be happy.  Otherwise we have to deal with
    507 	 * the trailing bytes.
    508 	 */
    509 	KASSERT(done || boff == 0);
    510 	KASSERT(done || copylen < len);
    511 	while (!done) {
    512 		KASSERT(wlen == 0);
    513 		KASSERT(copylen < len);
    514 		do {
    515 			data = (data << 8) | *ksaddr8++;
    516 			wlen++;
    517 			done = ((uint8_t)data == 0 || copylen + wlen == len);
    518 		} while (!done && wlen < 4);
    519 		KASSERT(done || wlen == 4);
    520 		if (__predict_true(wlen == 4)) {
    521 			copyout_le32(udaddr32++, data, ds_msr);
    522 			data = 0;
    523 			copylen += wlen;
    524 			wlen = 0;
    525 			KASSERT(copylen < len || done);
    526 		}
    527 	}
    528 	KASSERT(wlen < 3);
    529 	if (wlen) {
    530 		/*
    531 		 * Remember even though we are running big-endian we are using
    532 		 * byte reversed load/stores so we need to deal with things as
    533 		 * little endian.
    534 		 *
    535 		 * wlen=1 boff=0:
    536 		 * (~(~0 <<  8) <<  0) -> (~(0xffffff00) <<  0) -> 0x000000ff
    537 		 * wlen=1 boff=1:
    538 		 * (~(~0 <<  8) <<  8) -> (~(0xffffff00) <<  8) -> 0x0000ff00
    539 		 * wlen=1 boff=2:
    540 		 * (~(~0 <<  8) << 16) -> (~(0xffffff00) << 16) -> 0x00ff0000
    541 		 * wlen=1 boff=3:
    542 		 * (~(~0 <<  8) << 24) -> (~(0xffffff00) << 24) -> 0xff000000
    543 		 * wlen=2 boff=0:
    544 		 * (~(~0 << 16) <<  0) -> (~(0xffff0000) <<  0) -> 0x0000ffff
    545 		 * wlen=2 boff=1:
    546 		 * (~(~0 << 16) <<  8) -> (~(0xffff0000) <<  8) -> 0x00ffff00
    547 		 * wlen=2 boff=2:
    548 		 * (~(~0 << 16) << 16) -> (~(0xffff0000) << 16) -> 0xffff0000
    549 		 * wlen=3 boff=0:
    550 		 * (~(~0 << 24) <<  0) -> (~(0xff000000) <<  0) -> 0x00ffffff
    551 		 * wlen=3 boff=1:
    552 		 * (~(~0 << 24) <<  8) -> (~(0xff000000) <<  8) -> 0xffffff00
    553 		 */
    554 		KASSERT(boff + wlen <= 4);
    555 		uint32_t mask = (~(~0 << (8 * wlen))) << (8 * boff);
    556 		KASSERT(mask != 0xffffffff);
    557 		copyout_le32_with_mask(udaddr32, data, mask, ds_msr);
    558 		copylen += wlen;
    559 	}
    560 
    561 	pcb->pcb_onfault = NULL;
    562 	if (lenp)
    563 		*lenp = copylen;
    564 	return 0;
    565 }
    566 #endif
    567