[coreboot-gerrit] New patch to review for coreboot: 6a8bd0d libpayload: provide basic 64bit division implementation
Patrick Georgi (pgeorgi@google.com)
gerrit at coreboot.org
Wed Mar 18 13:05:45 CET 2015
Patrick Georgi (pgeorgi at google.com) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/8742
-gerrit
commit 6a8bd0d726b5bb0956ba7a371bfc4dc415454cad
Author: Vadim Bendebury <vbendeb at chromium.org>
Date: Thu Nov 27 18:50:14 2014 -0800
libpayload: provide basic 64bit division implementation
These functions are usually provided by gcc lib, which is not supposed
to be included on embedded platforms. This patch adds a no thrills C
implementation.
Other than MIPS platforms are happy using the gcc library provided
implementation, but in case of Chrome OS MIPS toolchain the libraries
are compiled with the small GOT, such that the entire data segment
does not fit.
With this implementation mips, arm and x86 targets build fine.
BRANCH=none
BUG=chrome-os-partner:31438
TEST=checked the logic by incorporating this code into a C file and
running a loop continuously comparing random inputs' division and
left and right shift results.
The test ran for extended periods of time without failure.
Change-Id: I468acd2fdbcdd493a76758a394e79cad35f9535a
Signed-off-by: Patrick Georgi <pgeorgi at chromium.org>
Original-Commit-Id: 2cc5f8668dd2609408af8da5a74c5a3d063fc0d3
Original-Change-Id: Ib46616d7eb0b2b497199270057514f730bb1cb0b
Original-Signed-off-by: Vadim Bendebury <vbendeb at chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/232232
Original-Reviewed-by: Aaron Durbin <adurbin at chromium.org>
---
payloads/libpayload/include/stdlib.h | 5 ++
payloads/libpayload/libc/64bit_div.c | 141 ++++++++++++++++++++++++++++++++++
payloads/libpayload/libc/Makefile.inc | 4 +
3 files changed, 150 insertions(+)
diff --git a/payloads/libpayload/include/stdlib.h b/payloads/libpayload/include/stdlib.h
index 04acec5..0d00d52 100644
--- a/payloads/libpayload/include/stdlib.h
+++ b/payloads/libpayload/include/stdlib.h
@@ -211,4 +211,9 @@ void exit(int status) __attribute__ ((noreturn));
void qsort(void *aa, size_t n, size_t es, int (*cmp)(const void *, const void *));
char *getenv(const char*);
+uint64_t __umoddi3(uint64_t num, uint64_t den);
+uint64_t __udivdi3(uint64_t num, uint64_t den);
+uint64_t __ashldi3(uint64_t num, unsigned shift);
+uint64_t __lshrdi3(uint64_t num, unsigned shift);
+
#endif
diff --git a/payloads/libpayload/libc/64bit_div.c b/payloads/libpayload/libc/64bit_div.c
new file mode 100644
index 0000000..615a2d8
--- /dev/null
+++ b/payloads/libpayload/libc/64bit_div.c
@@ -0,0 +1,141 @@
+/*
+ * This file is part of the libpayload project.
+ *
+ * Copyright 2014 Google Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <libpayload-config.h>
+#include <stdlib.h>
+
+#ifndef CONFIG_LP_LITTLE_ENDIAN
+#error this code is for little endian only
+#endif
+
+union overlay64 {
+ uint64_t longw;
+ struct {
+ uint32_t lower;
+ uint32_t higher;
+ } words;
+};
+
+
+uint64_t __ashldi3(uint64_t num, unsigned shift)
+{
+ union overlay64 output;
+
+ output.longw = num;
+ if (shift >= 32) {
+ output.words.higher = output.words.lower << (shift - 32);
+ output.words.lower = 0;
+ } else {
+ if (!shift)
+ return num;
+ output.words.higher = (output.words.higher << shift) |
+ (output.words.lower >> (32 - shift));
+ output.words.lower = output.words.lower << shift;
+ }
+ return output.longw;
+}
+
+uint64_t __lshrdi3(uint64_t num, unsigned shift)
+{
+ union overlay64 output;
+
+ output.longw = num;
+ if (shift >= 32) {
+ output.words.lower = output.words.higher >> (shift - 32);
+ output.words.higher = 0;
+ } else {
+ if (!shift)
+ return num;
+ output.words.lower = output.words.lower >> shift |
+ (output.words.higher << (32 - shift));
+ output.words.higher = output.words.higher >> shift;
+ }
+ return output.longw;
+}
+
+#define MAX_32BIT_UINT ((((uint64_t)1) << 32) - 1)
+
+static uint64_t _64bit_divide(uint64_t dividend,
+ uint64_t divider, uint64_t *rem_p)
+{
+ uint64_t result = 0;
+
+ /*
+ * If divider is zero - let the rest of the system care about the
+ * exception.
+ */
+ if (!divider)
+ return 1/(uint32_t)divider;
+
+ /* As an optimization, let's not use 64 bit division unless we must. */
+ if (dividend <= MAX_32BIT_UINT) {
+ if (divider > MAX_32BIT_UINT) {
+ result = 0;
+ if (rem_p)
+ *rem_p = divider;
+ } else {
+ result = (uint32_t) dividend / (uint32_t) divider;
+ if (rem_p)
+ *rem_p = (uint32_t) dividend %
+ (uint32_t) divider;
+ }
+ return result;
+ }
+
+ while (divider <= dividend) {
+ uint64_t locald = divider;
+ uint64_t limit = __lshrdi3(dividend, 1);
+ int shifts = 0;
+
+ while (locald <= limit) {
+ shifts++;
+ locald = locald + locald;
+ }
+ result |= __ashldi3(1, shifts);
+ dividend -= locald;
+ }
+
+ if (rem_p)
+ *rem_p = dividend;
+
+ return result;
+}
+
+uint64_t __udivdi3(uint64_t num, uint64_t den)
+{
+ return _64bit_divide(num, den, NULL);
+}
+
+uint64_t __umoddi3(uint64_t num, uint64_t den)
+{
+ uint64_t v = 0;
+
+ _64bit_divide(num, den, &v);
+ return v;
+}
diff --git a/payloads/libpayload/libc/Makefile.inc b/payloads/libpayload/libc/Makefile.inc
index e2eee15..4d43ccc 100644
--- a/payloads/libpayload/libc/Makefile.inc
+++ b/payloads/libpayload/libc/Makefile.inc
@@ -40,3 +40,7 @@ libc-$(CONFIG_LP_LIBC) += die.c
# should be moved to coreboot directory
libc-$(CONFIG_LP_LAR) += lar.c
+
+ifeq ($(CONFIG_LP_ARCH_MIPS),y)
+libc-$(CONFIG_LP_LIBC) += 64bit_div.c
+endif
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