FreeCalypso > hg > freecalypso-tools
view target-utils/libc/bzero.S @ 407:19e5a3e2f9c0
fcup-settime: moved time() retrieval a little closer to the output
A fundamental problem with all simple time transfer tools is that there is
always some delay between the time retrieval on the source system and that
transmitted time being set on the destination, and the resulting time
on the destination system is off by that delay amount. This delay cannot
be fully eliminated when working in a simple environment like ours,
but we should make our best effort to minimize it. In the present case,
moving the atinterf_init() call before the time() retrieval should make
a teensy-tiny improvement.
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Sat, 11 Aug 2018 21:52:17 +0000 |
| parents | bfed7a5c21a6 |
| children |
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/* * This ARM implementation of bzero() has been derived from: * * linux/arch/arm/lib/memzero.S * * Copyright (C) 1995-2000 Russell King * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ .text .code 32 .globl bzero /* * Align the pointer in r0. r3 contains the number of bytes that we are * mis-aligned by, and r1 is the number of bytes. If r1 < 4, then we * don't bother; we use byte stores instead. */ 1: subs r1, r1, #4 @ 1 do we have enough blt 5f @ 1 bytes to align with? cmp r3, #2 @ 1 strltb r2, [r0], #1 @ 1 strleb r2, [r0], #1 @ 1 strb r2, [r0], #1 @ 1 add r1, r1, r3 @ 1 (r1 = r1 - (4 - r3)) /* * The pointer is now aligned and the length is adjusted. Try doing the * bzero again. */ bzero: mov r2, #0 @ 1 ands r3, r0, #3 @ 1 unaligned? bne 1b @ 1 /* * r3 = 0, and we know that the pointer in r0 is aligned to a word boundary. */ 3: subs r1, r1, #4 strcs r2, [r0], #4 bhi 3b @ 1 bxeq lr @ 1/2 quick exit /* * No need to correct the count; we're only testing bits from now on * * When we get here, we've got less than 4 bytes to zero. We * may have an unaligned pointer as well. */ 5: tst r1, #2 @ 1 2 bytes or more? strneb r2, [r0], #1 @ 1 strneb r2, [r0], #1 @ 1 tst r1, #1 @ 1 a byte left over strneb r2, [r0], #1 @ 1 bx lr @ 1