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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Checksum library
4 *
5 * Influenced by arch/arm64/lib/csum.c
6 * Copyright (C) 2023 Rivos Inc.
7 */
8#include <linux/bitops.h>
9#include <linux/compiler.h>
10#include <linux/jump_label.h>
11#include <linux/kasan-checks.h>
12#include <linux/kernel.h>
13
14#include <asm/cpufeature.h>
15
16#include <net/checksum.h>
17
18/* Default version is sufficient for 32 bit */
19#ifndef CONFIG_32BIT
20__sum16 csum_ipv6_magic(const struct in6_addr *saddr,
21 const struct in6_addr *daddr,
22 __u32 len, __u8 proto, __wsum csum)
23{
24 unsigned int ulen, uproto;
25 unsigned long sum = (__force unsigned long)csum;
26
27 sum += (__force unsigned long)saddr->s6_addr32[0];
28 sum += (__force unsigned long)saddr->s6_addr32[1];
29 sum += (__force unsigned long)saddr->s6_addr32[2];
30 sum += (__force unsigned long)saddr->s6_addr32[3];
31
32 sum += (__force unsigned long)daddr->s6_addr32[0];
33 sum += (__force unsigned long)daddr->s6_addr32[1];
34 sum += (__force unsigned long)daddr->s6_addr32[2];
35 sum += (__force unsigned long)daddr->s6_addr32[3];
36
37 ulen = (__force unsigned int)htonl((unsigned int)len);
38 sum += ulen;
39
40 uproto = (__force unsigned int)htonl(proto);
41 sum += uproto;
42
43 /*
44 * Zbb support saves 4 instructions, so not worth checking without
45 * alternatives if supported
46 */
47 if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) &&
48 IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) {
49 unsigned long fold_temp;
50
51 /*
52 * Zbb is likely available when the kernel is compiled with Zbb
53 * support, so nop when Zbb is available and jump when Zbb is
54 * not available.
55 */
56 asm goto(ALTERNATIVE("j %l[no_zbb]", "nop", 0,
57 RISCV_ISA_EXT_ZBB, 1)
58 :
59 :
60 :
61 : no_zbb);
62 asm(".option push \n\
63 .option arch,+zbb \n\
64 rori %[fold_temp], %[sum], 32 \n\
65 add %[sum], %[fold_temp], %[sum] \n\
66 srli %[sum], %[sum], 32 \n\
67 not %[fold_temp], %[sum] \n\
68 roriw %[sum], %[sum], 16 \n\
69 subw %[sum], %[fold_temp], %[sum] \n\
70 .option pop"
71 : [sum] "+r" (sum), [fold_temp] "=&r" (fold_temp));
72 return (__force __sum16)(sum >> 16);
73 }
74no_zbb:
75 sum += ror64(sum, 32);
76 sum >>= 32;
77 return csum_fold((__force __wsum)sum);
78}
79EXPORT_SYMBOL(csum_ipv6_magic);
80#endif /* !CONFIG_32BIT */
81
82#ifdef CONFIG_32BIT
83#define OFFSET_MASK 3
84#elif CONFIG_64BIT
85#define OFFSET_MASK 7
86#endif
87
88static inline __no_sanitize_address unsigned long
89do_csum_common(const unsigned long *ptr, const unsigned long *end,
90 unsigned long data)
91{
92 unsigned int shift;
93 unsigned long csum = 0, carry = 0;
94
95 /*
96 * Do 32-bit reads on RV32 and 64-bit reads otherwise. This should be
97 * faster than doing 32-bit reads on architectures that support larger
98 * reads.
99 */
100 while (ptr < end) {
101 csum += data;
102 carry += csum < data;
103 data = *(ptr++);
104 }
105
106 /*
107 * Perform alignment (and over-read) bytes on the tail if any bytes
108 * leftover.
109 */
110 shift = ((long)ptr - (long)end) * 8;
111#ifdef __LITTLE_ENDIAN
112 data = (data << shift) >> shift;
113#else
114 data = (data >> shift) << shift;
115#endif
116 csum += data;
117 carry += csum < data;
118 csum += carry;
119 csum += csum < carry;
120
121 return csum;
122}
123
124/*
125 * Algorithm accounts for buff being misaligned.
126 * If buff is not aligned, will over-read bytes but not use the bytes that it
127 * shouldn't. The same thing will occur on the tail-end of the read.
128 */
129static inline __no_sanitize_address unsigned int
130do_csum_with_alignment(const unsigned char *buff, int len)
131{
132 unsigned int offset, shift;
133 unsigned long csum, data;
134 const unsigned long *ptr, *end;
135
136 /*
137 * Align address to closest word (double word on rv64) that comes before
138 * buff. This should always be in the same page and cache line.
139 * Directly call KASAN with the alignment we will be using.
140 */
141 offset = (unsigned long)buff & OFFSET_MASK;
142 kasan_check_read(buff, len);
143 ptr = (const unsigned long *)(buff - offset);
144
145 /*
146 * Clear the most significant bytes that were over-read if buff was not
147 * aligned.
148 */
149 shift = offset * 8;
150 data = *(ptr++);
151#ifdef __LITTLE_ENDIAN
152 data = (data >> shift) << shift;
153#else
154 data = (data << shift) >> shift;
155#endif
156 end = (const unsigned long *)(buff + len);
157 csum = do_csum_common(ptr, end, data);
158
159#ifdef CC_HAS_ASM_GOTO_TIED_OUTPUT
160 /*
161 * Zbb support saves 6 instructions, so not worth checking without
162 * alternatives if supported
163 */
164 if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) &&
165 IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) {
166 unsigned long fold_temp;
167
168 /*
169 * Zbb is likely available when the kernel is compiled with Zbb
170 * support, so nop when Zbb is available and jump when Zbb is
171 * not available.
172 */
173 asm goto(ALTERNATIVE("j %l[no_zbb]", "nop", 0,
174 RISCV_ISA_EXT_ZBB, 1)
175 :
176 :
177 :
178 : no_zbb);
179
180#ifdef CONFIG_32BIT
181 asm_goto_output(".option push \n\
182 .option arch,+zbb \n\
183 rori %[fold_temp], %[csum], 16 \n\
184 andi %[offset], %[offset], 1 \n\
185 add %[csum], %[fold_temp], %[csum] \n\
186 beq %[offset], zero, %l[end] \n\
187 rev8 %[csum], %[csum] \n\
188 .option pop"
189 : [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
190 : [offset] "r" (offset)
191 :
192 : end);
193
194 return (unsigned short)csum;
195#else /* !CONFIG_32BIT */
196 asm_goto_output(".option push \n\
197 .option arch,+zbb \n\
198 rori %[fold_temp], %[csum], 32 \n\
199 add %[csum], %[fold_temp], %[csum] \n\
200 srli %[csum], %[csum], 32 \n\
201 roriw %[fold_temp], %[csum], 16 \n\
202 addw %[csum], %[fold_temp], %[csum] \n\
203 andi %[offset], %[offset], 1 \n\
204 beq %[offset], zero, %l[end] \n\
205 rev8 %[csum], %[csum] \n\
206 .option pop"
207 : [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
208 : [offset] "r" (offset)
209 :
210 : end);
211
212 return (csum << 16) >> 48;
213#endif /* !CONFIG_32BIT */
214end:
215 return csum >> 16;
216 }
217no_zbb:
218#endif /* CC_HAS_ASM_GOTO_TIED_OUTPUT */
219#ifndef CONFIG_32BIT
220 csum += ror64(csum, 32);
221 csum >>= 32;
222#endif
223 csum = (u32)csum + ror32((u32)csum, 16);
224 if (offset & 1)
225 return (u16)swab32(csum);
226 return csum >> 16;
227}
228
229/*
230 * Does not perform alignment, should only be used if machine has fast
231 * misaligned accesses, or when buff is known to be aligned.
232 */
233static inline __no_sanitize_address unsigned int
234do_csum_no_alignment(const unsigned char *buff, int len)
235{
236 unsigned long csum, data;
237 const unsigned long *ptr, *end;
238
239 ptr = (const unsigned long *)(buff);
240 data = *(ptr++);
241
242 kasan_check_read(buff, len);
243
244 end = (const unsigned long *)(buff + len);
245 csum = do_csum_common(ptr, end, data);
246
247 /*
248 * Zbb support saves 6 instructions, so not worth checking without
249 * alternatives if supported
250 */
251 if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) &&
252 IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) {
253 unsigned long fold_temp;
254
255 /*
256 * Zbb is likely available when the kernel is compiled with Zbb
257 * support, so nop when Zbb is available and jump when Zbb is
258 * not available.
259 */
260 asm goto(ALTERNATIVE("j %l[no_zbb]", "nop", 0,
261 RISCV_ISA_EXT_ZBB, 1)
262 :
263 :
264 :
265 : no_zbb);
266
267#ifdef CONFIG_32BIT
268 asm (".option push \n\
269 .option arch,+zbb \n\
270 rori %[fold_temp], %[csum], 16 \n\
271 add %[csum], %[fold_temp], %[csum] \n\
272 .option pop"
273 : [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
274 :
275 : );
276
277#else /* !CONFIG_32BIT */
278 asm (".option push \n\
279 .option arch,+zbb \n\
280 rori %[fold_temp], %[csum], 32 \n\
281 add %[csum], %[fold_temp], %[csum] \n\
282 srli %[csum], %[csum], 32 \n\
283 roriw %[fold_temp], %[csum], 16 \n\
284 addw %[csum], %[fold_temp], %[csum] \n\
285 .option pop"
286 : [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
287 :
288 : );
289#endif /* !CONFIG_32BIT */
290 return csum >> 16;
291 }
292no_zbb:
293#ifndef CONFIG_32BIT
294 csum += ror64(csum, 32);
295 csum >>= 32;
296#endif
297 csum = (u32)csum + ror32((u32)csum, 16);
298 return csum >> 16;
299}
300
301/*
302 * Perform a checksum on an arbitrary memory address.
303 * Will do a light-weight address alignment if buff is misaligned, unless
304 * cpu supports fast misaligned accesses.
305 */
306unsigned int do_csum(const unsigned char *buff, int len)
307{
308 if (unlikely(len <= 0))
309 return 0;
310
311 /*
312 * Significant performance gains can be seen by not doing alignment
313 * on machines with fast misaligned accesses.
314 *
315 * There is some duplicate code between the "with_alignment" and
316 * "no_alignment" implmentations, but the overlap is too awkward to be
317 * able to fit in one function without introducing multiple static
318 * branches. The largest chunk of overlap was delegated into the
319 * do_csum_common function.
320 */
321 if (static_branch_likely(&fast_misaligned_access_speed_key))
322 return do_csum_no_alignment(buff, len);
323
324 if (((unsigned long)buff & OFFSET_MASK) == 0)
325 return do_csum_no_alignment(buff, len);
326
327 return do_csum_with_alignment(buff, len);
328}