1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * INET An implementation of the TCP/IP protocol suite for the LINUX 4 * operating system. INET is implemented using the BSD Socket 5 * interface as the means of communication with the user level. 6 * 7 * MIPS specific IP/TCP/UDP checksumming routines 8 * 9 * Authors: Ralf Baechle, <ralf@waldorf-gmbh.de> 10 * Lots of code moved from tcp.c and ip.c; see those files 11 * for more names. 12 */ 13 #include <linux/module.h> 14 #include <linux/types.h> 15 16 #include <net/checksum.h> 17 #include <asm/byteorder.h> 18 #include <asm/string.h> 19 #include <linux/uaccess.h> 20 21 #define addc(_t,_r) \ 22 __asm__ __volatile__ ( \ 23 " add %0, %1, %0\n" \ 24 " addc %0, %%r0, %0\n" \ 25 : "=r"(_t) \ 26 : "r"(_r), "0"(_t)); 27 28 static inline unsigned int do_csum(const unsigned char * buff, int len) 29 { 30 int odd, count; 31 unsigned int result = 0; 32 33 if (len <= 0) 34 goto out; 35 odd = 1 & (unsigned long) buff; 36 if (odd) { 37 result = be16_to_cpu(*buff); 38 len--; 39 buff++; 40 } 41 count = len >> 1; /* nr of 16-bit words.. */ 42 if (count) { 43 if (2 & (unsigned long) buff) { 44 result += *(unsigned short *) buff; 45 count--; 46 len -= 2; 47 buff += 2; 48 } 49 count >>= 1; /* nr of 32-bit words.. */ 50 if (count) { 51 while (count >= 4) { 52 unsigned int r1, r2, r3, r4; 53 r1 = *(unsigned int *)(buff + 0); 54 r2 = *(unsigned int *)(buff + 4); 55 r3 = *(unsigned int *)(buff + 8); 56 r4 = *(unsigned int *)(buff + 12); 57 addc(result, r1); 58 addc(result, r2); 59 addc(result, r3); 60 addc(result, r4); 61 count -= 4; 62 buff += 16; 63 } 64 while (count) { 65 unsigned int w = *(unsigned int *) buff; 66 count--; 67 buff += 4; 68 addc(result, w); 69 } 70 result = (result & 0xffff) + (result >> 16); 71 } 72 if (len & 2) { 73 result += *(unsigned short *) buff; 74 buff += 2; 75 } 76 } 77 if (len & 1) 78 result += le16_to_cpu(*buff); 79 result = csum_from32to16(result); 80 if (odd) 81 result = swab16(result); 82 out: 83 return result; 84 } 85 86 /* 87 * computes a partial checksum, e.g. for TCP/UDP fragments 88 */ 89 /* 90 * why bother folding? 91 */ 92 __wsum csum_partial(const void *buff, int len, __wsum sum) 93 { 94 unsigned int result = do_csum(buff, len); 95 addc(result, sum); 96 return (__force __wsum)csum_from32to16(result); 97 } 98 99 EXPORT_SYMBOL(csum_partial); 100