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@chromium.org>
Original-Commit-Id: 2cc5f8668dd2609408af8da5a74c5a3d063fc0d3
Original-Change-Id: Ib46616d7eb0b2b497199270057514f730bb1cb0b
Original-Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/232232
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/8742
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

2 files changed, 145 insertions, 0 deletions

diff --git a/payloads/libpayload/libc/64bit_div.c b/payloads/libpayload/libc/64bit_div.c
new file mode 100644
index 0000000000..615a2d8fdd
--- /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 bd2a6f7595..b4f75a6cb5 100644
--- a/payloads/libpayload/libc/Makefile.inc
+++ b/payloads/libpayload/libc/Makefile.inc
@@ -41,3 +41,7 @@ libc-$(CONFIG_LP_LIBC) += coreboot.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