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-rw-r--r--src/arch/riscv/core/riscv_string.c233
1 files changed, 233 insertions, 0 deletions
diff --git a/src/arch/riscv/core/riscv_string.c b/src/arch/riscv/core/riscv_string.c
new file mode 100644
index 000000000..e28dc8951
--- /dev/null
+++ b/src/arch/riscv/core/riscv_string.c
@@ -0,0 +1,233 @@
+/*
+ * Copyright (C) 2024 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 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.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+/** @file
+ *
+ * Optimised string operations
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <string.h>
+
+/**
+ * Copy memory area
+ *
+ * @v dest Destination address
+ * @v src Source address
+ * @v len Length
+ * @ret dest Destination address
+ */
+void riscv_memcpy ( void *dest, const void *src, size_t len ) {
+ size_t len_pre;
+ size_t len_mid;
+ size_t len_post;
+ unsigned long discard_data;
+
+ /* Calculate pre-aligned, aligned, and post-aligned lengths.
+ * (Align on the destination address, on the assumption that
+ * misaligned stores are likely to be more expensive than
+ * misaligned loads.)
+ */
+ len_pre = ( ( sizeof ( unsigned long ) - ( ( intptr_t ) dest ) ) &
+ ( sizeof ( unsigned long ) - 1 ) );
+ if ( len_pre > len )
+ len_pre = len;
+ len -= len_pre;
+ len_mid = ( len & ~( sizeof ( unsigned long ) - 1 ) );
+ len -= len_mid;
+ len_post = len;
+
+ /* Copy pre-aligned section */
+ __asm__ __volatile__ ( "j 2f\n\t"
+ "\n1:\n\t"
+ "lb %2, (%1)\n\t"
+ "sb %2, (%0)\n\t"
+ "addi %0, %0, 1\n\t"
+ "addi %1, %1, 1\n\t"
+ "\n2:\n\t"
+ "bne %0, %3, 1b\n\t"
+ : "+r" ( dest ), "+r" ( src ),
+ "=&r" ( discard_data )
+ : "r" ( dest + len_pre )
+ : "memory" );
+
+ /* Copy aligned section */
+ __asm__ __volatile__ ( "j 2f\n\t"
+ "\n1:\n\t"
+ LOADN " %2, (%1)\n\t"
+ STOREN " %2, (%0)\n\t"
+ "addi %0, %0, %4\n\t"
+ "addi %1, %1, %4\n\t"
+ "\n2:\n\t"
+ "bne %0, %3, 1b\n\t"
+ : "+r" ( dest ), "+r" ( src ),
+ "=&r" ( discard_data )
+ : "r" ( dest + len_mid ),
+ "i" ( sizeof ( unsigned long ) )
+ : "memory" );
+
+ /* Copy post-aligned section */
+ __asm__ __volatile__ ( "j 2f\n\t"
+ "\n1:\n\t"
+ "lb %2, (%1)\n\t"
+ "sb %2, (%0)\n\t"
+ "addi %0, %0, 1\n\t"
+ "addi %1, %1, 1\n\t"
+ "\n2:\n\t"
+ "bne %0, %3, 1b\n\t"
+ : "+r" ( dest ), "+r" ( src ),
+ "=&r" ( discard_data )
+ : "r" ( dest + len_post )
+ : "memory" );
+}
+
+/**
+ * Zero memory region
+ *
+ * @v dest Destination region
+ * @v len Length
+ */
+void riscv_bzero ( void *dest, size_t len ) {
+ size_t len_pre;
+ size_t len_mid;
+ size_t len_post;
+
+ /* Calculate pre-aligned, aligned, and post-aligned lengths */
+ len_pre = ( ( sizeof ( unsigned long ) - ( ( intptr_t ) dest ) ) &
+ ( sizeof ( unsigned long ) - 1 ) );
+ if ( len_pre > len )
+ len_pre = len;
+ len -= len_pre;
+ len_mid = ( len & ~( sizeof ( unsigned long ) - 1 ) );
+ len -= len_mid;
+ len_post = len;
+
+ /* Zero pre-aligned section */
+ __asm__ __volatile__ ( "j 2f\n\t"
+ "\n1:\n\t"
+ "sb zero, (%0)\n\t"
+ "addi %0, %0, 1\n\t"
+ "\n2:\n\t"
+ "bne %0, %1, 1b\n\t"
+ : "+r" ( dest )
+ : "r" ( dest + len_pre )
+ : "memory" );
+
+ /* Zero aligned section */
+ __asm__ __volatile__ ( "j 2f\n\t"
+ "\n1:\n\t"
+ STOREN " zero, (%0)\n\t"
+ "addi %0, %0, %2\n\t"
+ "\n2:\n\t"
+ "bne %0, %1, 1b\n\t"
+ : "+r" ( dest )
+ : "r" ( dest + len_mid ),
+ "i" ( sizeof ( unsigned long ) )
+ : "memory" );
+
+ /* Zero post-aligned section */
+ __asm__ __volatile__ ( "j 2f\n\t"
+ "\n1:\n\t"
+ "sb zero, (%0)\n\t"
+ "addi %0, %0, 1\n\t"
+ "\n2:\n\t"
+ "bne %0, %1, 1b\n\t"
+ : "+r" ( dest )
+ : "r" ( dest + len_post )
+ : "memory" );
+}
+
+/**
+ * Fill memory region
+ *
+ * @v dest Destination region
+ * @v len Length
+ * @v character Fill character
+ *
+ * The unusual parameter order is to allow for more efficient
+ * tail-calling to riscv_bzero() when zeroing a region.
+ */
+void riscv_memset ( void *dest, size_t len, int character ) {
+
+ /* Do nothing if length is zero */
+ if ( ! len )
+ return;
+
+ /* Use optimised zeroing code if applicable */
+ if ( character == 0 ) {
+ riscv_bzero ( dest, len );
+ return;
+ }
+
+ /* Fill one byte at a time. Calling memset() with a non-zero
+ * value is relatively rare and unlikely to be
+ * performance-critical.
+ */
+ __asm__ __volatile__ ( "\n1:\n\t"
+ "sb %2, (%0)\n\t"
+ "addi %0, %0, 1\n\t"
+ "bne %0, %1, 1b\n\t"
+ : "+r" ( dest )
+ : "r" ( dest + len ), "r" ( character )
+ : "memory" );
+}
+
+/**
+ * Copy (possibly overlapping) memory region
+ *
+ * @v dest Destination region
+ * @v src Source region
+ * @v len Length
+ */
+void riscv_memmove ( void *dest, const void *src, size_t len ) {
+ void *orig_dest = dest;
+ unsigned long discard_data;
+
+ /* Do nothing if length is zero */
+ if ( ! len )
+ return;
+
+ /* Use memcpy() if copy direction is forwards */
+ if ( dest <= src ) {
+ memcpy ( dest, src, len );
+ return;
+ }
+
+ /* Assume memmove() is not performance-critical, and perform a
+ * bytewise copy backwards for simplicity.
+ */
+ dest += len;
+ src += len;
+ __asm__ __volatile__ ( "\n1:\n\t"
+ "addi %1, %1, -1\n\t"
+ "addi %0, %0, -1\n\t"
+ "lb %2, (%1)\n\t"
+ "sb %2, (%0)\n\t"
+ "bne %0, %3, 1b\n\t"
+ : "+r" ( dest ), "+r" ( src ),
+ "=&r" ( discard_data )
+ : "r" ( orig_dest )
+ : "memory" );
+}
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