--- /dev/null
+/*
+ * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/** @file
+ *
+ * TCP/IP checksum
+ *
+ */
+
+#include <limits.h>
+#include <ipxe/tcpip.h>
+
+extern char x86_tcpip_loop_end[];
+
+/**
+ * Calculate continued TCP/IP checkum
+ *
+ * @v partial Checksum of already-summed data, in network byte order
+ * @v data Data buffer
+ * @v len Length of data buffer
+ * @ret cksum Updated checksum, in network byte order
+ */
+uint16_t x86_tcpip_continue_chksum ( uint16_t partial,
+ const void *data, size_t len ) {
+ unsigned long sum = ( ( ~partial ) & 0xffff );
+ unsigned long initial_word_count;
+ unsigned long loop_count;
+ unsigned long loop_partial_count;
+ unsigned long final_word_count;
+ unsigned long final_byte;
+ unsigned long discard_S;
+ unsigned long discard_c;
+ unsigned long discard_a;
+ unsigned long discard_r1;
+ unsigned long discard_r2;
+
+ /* Calculate number of initial 16-bit words required to bring
+ * the main loop into alignment. (We don't care about the
+ * speed for data aligned to less than 16 bits, since this
+ * situation won't occur in practice.)
+ */
+ if ( len >= sizeof ( sum ) ) {
+ initial_word_count = ( ( -( ( intptr_t ) data ) &
+ ( sizeof ( sum ) - 1 ) ) >> 1 );
+ } else {
+ initial_word_count = 0;
+ }
+ len -= ( initial_word_count * 2 );
+
+ /* Calculate number of iterations of the main loop. This loop
+ * processes native machine words (32-bit or 64-bit), and is
+ * unrolled 16 times. We calculate an overall iteration
+ * count, and a starting point for the first iteration.
+ */
+ loop_count = ( len / ( sizeof ( sum ) * 16 ) );
+ loop_partial_count =
+ ( ( len % ( sizeof ( sum ) * 16 ) ) / sizeof ( sum ) );
+
+ /* Calculate number of 16-bit words remaining after the main
+ * loop completes.
+ */
+ final_word_count = ( ( len % sizeof ( sum ) ) / 2 );
+
+ /* Calculate whether or not a final byte remains at the end */
+ final_byte = ( len & 1 );
+
+ /* Calculate the checksum */
+ __asm__ ( /* Calculate position at which to jump into the
+ * unrolled loop.
+ */
+ "imul $( -x86_tcpip_loop_step_size ), %4\n\t"
+ "add %5, %4\n\t"
+
+ /* Clear carry flag before starting checksumming */
+ "clc\n\t"
+
+ /* Checksum initial words */
+ "jmp 2f\n\t"
+ "\n1:\n\t"
+ "lodsw\n\t"
+ "adcw %w2, %w0\n\t"
+ "\n2:\n\t"
+ "loop 1b\n\t"
+
+ /* Main "lods;adc" loop, unrolled x16 */
+ "mov %12, %3\n\t"
+ "jmp *%4\n\t"
+ "\nx86_tcpip_loop_start:\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "lods%z2\n\tadc %2, %0\n\t"
+ "\nx86_tcpip_loop_end:\n\t"
+ "loop x86_tcpip_loop_start\n\t"
+ ".equ x86_tcpip_loop_step_size, "
+ " ( ( x86_tcpip_loop_end - x86_tcpip_loop_start ) >> 4 )\n\t"
+
+ /* Checksum remaining whole words */
+ "mov %13, %3\n\t"
+ "jmp 2f\n\t"
+ "\n1:\n\t"
+ "lodsw\n\t"
+ "adcw %w2, %w0\n\t"
+ "\n2:\n\t"
+ "loop 1b\n\t"
+
+ /* Checksum final byte if applicable */
+ "mov %14, %3\n\t"
+ "loop 1f\n\t"
+ "adcb (%1), %b0\n\t"
+ "adcb $0, %h0\n\t"
+ "\n1:\n\t"
+
+ /* Fold down to a uint16_t */
+ "push %0\n\t"
+ "popw %w0\n\t"
+ "popw %w2\n\t"
+ "adcw %w2, %w0\n\t"
+#if ULONG_MAX > 0xffffffffUL /* 64-bit only */
+ "popw %w2\n\t"
+ "adcw %w2, %w0\n\t"
+ "popw %w2\n\t"
+ "adcw %w2, %w0\n\t"
+#endif /* 64-bit only */
+
+ /* Consume CF */
+ "adcw $0, %w0\n\t"
+ "adcw $0, %w0\n\t"
+
+ : "=&Q" ( sum ), "=&S" ( discard_S ), "=&a" ( discard_a ),
+ "=&c" ( discard_c ), "=&r" ( discard_r1 ),
+ "=&r" ( discard_r2 )
+ : "0" ( sum ), "1" ( data ), "2" ( 0 ),
+ "3" ( initial_word_count + 1 ), "4" ( loop_partial_count ),
+ "5" ( x86_tcpip_loop_end ), "g" ( loop_count + 1 ),
+ "g" ( final_word_count + 1 ), "g" ( final_byte ) );
+
+ return ( ~sum & 0xffff );
+}
Code Review / kvmfornfv.git / blobdiff