Import gcrypt public-key cryptography and implement signature checking.

grub-core/lib/libgcrypt/mpi/power/mpih-mul1.S

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+/* IBM POWER  mul_1 -- Multiply a limb vector with a limb and store
+ *                     the result in a second limb vector.
+ *
+ *      Copyright (C) 1992, 1994, 1999, 2002 Free Software Foundation, Inc.
+ *
+ * This file is part of Libgcrypt.
+ *
+ * Libgcrypt is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * Libgcrypt 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+
+#include "sysdep.h"
+#include "asm-syntax.h"
+
+/*
+# INPUT PARAMETERS
+# res_ptr	r3
+# s1_ptr	r4
+# size		r5
+# s2_limb	r6
+
+# The RS/6000 has no unsigned 32x32->64 bit multiplication instruction.  To
+# obtain that operation, we have to use the 32x32->64 signed multiplication
+# instruction, and add the appropriate compensation to the high limb of the
+# result.  We add the multiplicand if the multiplier has its most significant
+# bit set, and we add the multiplier if the multiplicand has its most
+# significant bit set.	We need to preserve the carry flag between each
+# iteration, so we have to compute the compensation carefully (the natural,
+# srai+and doesn't work).  Since the POWER architecture has a branch unit
+# we can branch in zero cycles, so that's how we perform the additions.
+ */
+
+	.toc
+	.csect ._gcry_mpih_mul_1[PR]
+	.align 2
+	.globl _gcry_mpih_mul_1
+	.globl ._gcry_mpih_mul_1
+	.csect _gcry_mpih_mul_1[DS]
+_gcry_mpih_mul_1:
+	.long ._gcry_mpih_mul_1[PR], TOC[tc0], 0
+	.csect ._gcry_mpih_mul_1[PR]
+._gcry_mpih_mul_1:
+
+	cal	3,-4(3)
+	l	0,0(4)
+	cmpi	0,6,0
+	mtctr	5
+	mul	9,0,6
+	srai	7,0,31
+	and	7,7,6
+	mfmq	8
+	ai	0,0,0		# reset carry
+	cax	9,9,7
+	blt	Lneg
+Lpos:	bdz	Lend
+Lploop: lu	0,4(4)
+	stu	8,4(3)
+	cmpi	0,0,0
+	mul	10,0,6
+	mfmq	0
+	ae	8,0,9
+	bge	Lp0
+	cax	10,10,6 	# adjust high limb for negative limb from s1
+Lp0:	bdz	Lend0
+	lu	0,4(4)
+	stu	8,4(3)
+	cmpi	0,0,0
+	mul	9,0,6
+	mfmq	0
+	ae	8,0,10
+	bge	Lp1
+	cax	9,9,6		# adjust high limb for negative limb from s1
+Lp1:	bdn	Lploop
+	b	Lend
+
+Lneg:	cax	9,9,0
+	bdz	Lend
+Lnloop: lu	0,4(4)
+	stu	8,4(3)
+	cmpi	0,0,0
+	mul	10,0,6
+	cax	10,10,0 	# adjust high limb for negative s2_limb
+	mfmq	0
+	ae	8,0,9
+	bge	Ln0
+	cax	10,10,6 	# adjust high limb for negative limb from s1
+Ln0:	bdz	Lend0
+	lu	0,4(4)
+	stu	8,4(3)
+	cmpi	0,0,0
+	mul	9,0,6
+	cax	9,9,0		# adjust high limb for negative s2_limb
+	mfmq	0
+	ae	8,0,10
+	bge	Ln1
+	cax	9,9,6		# adjust high limb for negative limb from s1
+Ln1:	bdn	Lnloop
+	b	Lend
+
+Lend0:	cal	9,0(10)
+Lend:	st	8,4(3)
+	aze	3,9
+	br
+