ARMv7: division support for missing __aeabi_*divmod

ARMv7-A architectures that do not support the Virtualization extensions
do not support instructions for the 32bit division. This change provides
a software implementation for 32bit division.

The division implementation is dumped from the OP-TEE project
http://github.com/OP-TEE/optee_os

. The code was slightly modified
to pass trusted firmware checkpatch requirements and copyright is
given to the ARM trusted firmware initiative and its contributors.

Change-Id: Idae0c7b80a0d75eac9bd41ae121921d4c5af3fa3
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>

lib/aarch32/arm32_aeabi_divmod.c

+/*
+ * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+/*
+ * Form ABI specifications:
+ *      int __aeabi_idiv(int numerator, int denominator);
+ *     unsigned __aeabi_uidiv(unsigned numerator, unsigned denominator);
+ *
+ *     typedef struct { int quot; int rem; } idiv_return;
+ *     typedef struct { unsigned quot; unsigned rem; } uidiv_return;
+ *
+ *     __value_in_regs idiv_return __aeabi_idivmod(int numerator,
+ *     int *denominator);
+ *     __value_in_regs uidiv_return __aeabi_uidivmod(unsigned *numerator,
+ *     unsigned denominator);
+ */
+
+/* struct qr - stores qutient/remainder to handle divmod EABI interfaces. */
+struct qr {
+	unsigned int q;		/* computed quotient */
+	unsigned int r;		/* computed remainder */
+	unsigned int q_n;	/* specficies if quotient shall be negative */
+	unsigned int r_n;	/* specficies if remainder shall be negative */
+};
+
+static void uint_div_qr(unsigned int numerator, unsigned int denominator,
+			struct qr *qr);
+
+/* returns in R0 and R1 by tail calling an asm function */
+unsigned int __aeabi_uidivmod(unsigned int numerator, unsigned int denominator);
+
+unsigned int __aeabi_uidiv(unsigned int numerator, unsigned int denominator);
+unsigned int __aeabi_uimod(unsigned int numerator, unsigned int denominator);
+
+/* returns in R0 and R1 by tail calling an asm function */
+signed int __aeabi_idivmod(signed int numerator, signed int denominator);
+
+signed int __aeabi_idiv(signed int numerator, signed int denominator);
+signed int __aeabi_imod(signed int numerator, signed int denominator);
+
+/*
+ * __ste_idivmod_ret_t __aeabi_idivmod(signed numerator, signed denominator)
+ * Numerator and Denominator are received in R0 and R1.
+ * Where __ste_idivmod_ret_t is returned in R0 and R1.
+ *
+ * __ste_uidivmod_ret_t __aeabi_uidivmod(unsigned numerator,
+ *                                       unsigned denominator)
+ * Numerator and Denominator are received in R0 and R1.
+ * Where __ste_uidivmod_ret_t is returned in R0 and R1.
+ */
+#ifdef __GNUC__
+signed int ret_idivmod_values(signed int quotient, signed int remainder);
+unsigned int ret_uidivmod_values(unsigned int quotient, unsigned int remainder);
+#else
+#error "Compiler not supported"
+#endif
+
+static void division_qr(unsigned int n, unsigned int p, struct qr *qr)
+{
+	unsigned int i = 1, q = 0;
+
+	if (p == 0) {
+		qr->r = 0xFFFFFFFF;	/* division by 0 */
+		return;
+	}
+
+	while ((p >> 31) == 0) {
+		i = i << 1;	/* count the max division steps */
+		p = p << 1;     /* increase p until it has maximum size*/
+	}
+
+	while (i > 0) {
+		q = q << 1;	/* write bit in q at index (size-1) */
+		if (n >= p) {
+			n -= p;
+			q++;
+		}
+		p = p >> 1;	/* decrease p */
+		i = i >> 1;	/* decrease remaining size in q */
+	}
+	qr->r = n;
+	qr->q = q;
+}
+
+static void uint_div_qr(unsigned int numerator, unsigned int denominator,
+			struct qr *qr)
+{
+	division_qr(numerator, denominator, qr);
+
+	/* negate quotient and/or remainder according to requester */
+	if (qr->q_n)
+		qr->q = -qr->q;
+	if (qr->r_n)
+		qr->r = -qr->r;
+}
+
+unsigned int __aeabi_uidiv(unsigned int numerator, unsigned int denominator)
+{
+	struct qr qr = { .q_n = 0, .r_n = 0 };
+
+	uint_div_qr(numerator, denominator, &qr);
+
+	return qr.q;
+}
+
+unsigned int __aeabi_uimod(unsigned int numerator, unsigned int denominator)
+{
+	struct qr qr = { .q_n = 0, .r_n = 0 };
+
+	uint_div_qr(numerator, denominator, &qr);
+
+	return qr.r;
+}
+
+unsigned int __aeabi_uidivmod(unsigned int numerator, unsigned int denominator)
+{
+	struct qr qr = { .q_n = 0, .r_n = 0 };
+
+	uint_div_qr(numerator, denominator, &qr);
+
+	return ret_uidivmod_values(qr.q, qr.r);
+}
+
+signed int __aeabi_idiv(signed int numerator, signed int denominator)
+{
+	struct qr qr = { .q_n = 0, .r_n = 0 };
+
+	if (((numerator < 0) && (denominator > 0)) ||
+	    ((numerator > 0) && (denominator < 0)))
+		qr.q_n = 1;	/* quotient shall be negate */
+
+	if (numerator < 0) {
+		numerator = -numerator;
+		qr.r_n = 1;	/* remainder shall be negate */
+	}
+
+	if (denominator < 0)
+		denominator = -denominator;
+
+	uint_div_qr(numerator, denominator, &qr);
+
+	return qr.q;
+}
+
+signed int __aeabi_imod(signed int numerator, signed int denominator)
+{
+	signed int s;
+	signed int i;
+	signed int j;
+	signed int h;
+	struct qr qr = { .q_n = 0, .r_n = 0 };
+
+	/* in case modulo of a power of 2 */
+	for (i = 0, j = 0, h = 0, s = denominator; (s != 0) || (h > 1); i++) {
+		if (s & 1) {
+			j = i;
+			h++;
+		}
+		s = s >> 1;
+	}
+	if (h == 1)
+		return numerator >> j;
+
+	if (((numerator < 0) && (denominator > 0)) ||
+	    ((numerator > 0) && (denominator < 0)))
+		qr.q_n = 1;	/* quotient shall be negate */
+
+	if (numerator < 0) {
+		numerator = -numerator;
+		qr.r_n = 1;	/* remainder shall be negate */
+	}
+
+	if (denominator < 0)
+		denominator = -denominator;
+
+	uint_div_qr(numerator, denominator, &qr);
+
+	return qr.r;
+}
+
+signed int __aeabi_idivmod(signed int numerator, signed int denominator)
+{
+	struct qr qr = { .q_n = 0, .r_n = 0 };
+
+	if (((numerator < 0) && (denominator > 0)) ||
+	    ((numerator > 0) && (denominator < 0)))
+		qr.q_n = 1;	/* quotient shall be negate */
+
+	if (numerator < 0) {
+		numerator = -numerator;
+		qr.r_n = 1;	/* remainder shall be negate */
+	}
+
+	if (denominator < 0)
+		denominator = -denominator;
+
+	uint_div_qr(numerator, denominator, &qr);
+
+	return ret_idivmod_values(qr.q, qr.r);
+}

lib/aarch32/arm32_aeabi_divmod_a32.S

+/*
+ * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <asm_macros.S>
+
+/*
+ * EABI wrappers from the udivmod and idivmod functions
+ */
+
+	.globl ret_uidivmod_values
+	.globl ret_idivmod_values
+
+/*
+ * signed ret_idivmod_values(signed quot, signed rem);
+ * return quotient and remaining the EABI way (regs r0,r1)
+ */
+func ret_idivmod_values
+        bx lr
+endfunc ret_idivmod_values
+
+/*
+ * unsigned ret_uidivmod_values(unsigned quot, unsigned rem);
+ * return quotient and remaining the EABI way (regs r0,r1)
+ */
+func ret_uidivmod_values
+        bx      lr
+endfunc ret_uidivmod_values