xref: /openbmc/linux/lib/crypto/mpi/mpi-inline.h (revision 2a598d0b)
1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /* mpi-inline.h  -  Internal to the Multi Precision Integers
3  *	Copyright (C) 1994, 1996, 1998, 1999 Free Software Foundation, Inc.
4  *
5  * This file is part of GnuPG.
6  *
7  * Note: This code is heavily based on the GNU MP Library.
8  *	 Actually it's the same code with only minor changes in the
9  *	 way the data is stored; this is to support the abstraction
10  *	 of an optional secure memory allocation which may be used
11  *	 to avoid revealing of sensitive data due to paging etc.
12  *	 The GNU MP Library itself is published under the LGPL;
13  *	 however I decided to publish this code under the plain GPL.
14  */
15 
16 #ifndef G10_MPI_INLINE_H
17 #define G10_MPI_INLINE_H
18 
19 #ifndef G10_MPI_INLINE_DECL
20 #define G10_MPI_INLINE_DECL  static inline
21 #endif
22 
23 G10_MPI_INLINE_DECL mpi_limb_t
mpihelp_add_1(mpi_ptr_t res_ptr,mpi_ptr_t s1_ptr,mpi_size_t s1_size,mpi_limb_t s2_limb)24 mpihelp_add_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
25 	      mpi_size_t s1_size, mpi_limb_t s2_limb)
26 {
27 	mpi_limb_t x;
28 
29 	x = *s1_ptr++;
30 	s2_limb += x;
31 	*res_ptr++ = s2_limb;
32 	if (s2_limb < x) {	/* sum is less than the left operand: handle carry */
33 		while (--s1_size) {
34 			x = *s1_ptr++ + 1;	/* add carry */
35 			*res_ptr++ = x;	/* and store */
36 			if (x)	/* not 0 (no overflow): we can stop */
37 				goto leave;
38 		}
39 		return 1;	/* return carry (size of s1 to small) */
40 	}
41 
42 leave:
43 	if (res_ptr != s1_ptr) {	/* not the same variable */
44 		mpi_size_t i;	/* copy the rest */
45 		for (i = 0; i < s1_size - 1; i++)
46 			res_ptr[i] = s1_ptr[i];
47 	}
48 	return 0;		/* no carry */
49 }
50 
51 G10_MPI_INLINE_DECL mpi_limb_t
mpihelp_add(mpi_ptr_t res_ptr,mpi_ptr_t s1_ptr,mpi_size_t s1_size,mpi_ptr_t s2_ptr,mpi_size_t s2_size)52 mpihelp_add(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
53 	    mpi_ptr_t s2_ptr, mpi_size_t s2_size)
54 {
55 	mpi_limb_t cy = 0;
56 
57 	if (s2_size)
58 		cy = mpihelp_add_n(res_ptr, s1_ptr, s2_ptr, s2_size);
59 
60 	if (s1_size - s2_size)
61 		cy = mpihelp_add_1(res_ptr + s2_size, s1_ptr + s2_size,
62 				   s1_size - s2_size, cy);
63 	return cy;
64 }
65 
66 G10_MPI_INLINE_DECL mpi_limb_t
mpihelp_sub_1(mpi_ptr_t res_ptr,mpi_ptr_t s1_ptr,mpi_size_t s1_size,mpi_limb_t s2_limb)67 mpihelp_sub_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
68 	      mpi_size_t s1_size, mpi_limb_t s2_limb)
69 {
70 	mpi_limb_t x;
71 
72 	x = *s1_ptr++;
73 	s2_limb = x - s2_limb;
74 	*res_ptr++ = s2_limb;
75 	if (s2_limb > x) {
76 		while (--s1_size) {
77 			x = *s1_ptr++;
78 			*res_ptr++ = x - 1;
79 			if (x)
80 				goto leave;
81 		}
82 		return 1;
83 	}
84 
85 leave:
86 	if (res_ptr != s1_ptr) {
87 		mpi_size_t i;
88 		for (i = 0; i < s1_size - 1; i++)
89 			res_ptr[i] = s1_ptr[i];
90 	}
91 	return 0;
92 }
93 
94 G10_MPI_INLINE_DECL mpi_limb_t
mpihelp_sub(mpi_ptr_t res_ptr,mpi_ptr_t s1_ptr,mpi_size_t s1_size,mpi_ptr_t s2_ptr,mpi_size_t s2_size)95 mpihelp_sub(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
96 	    mpi_ptr_t s2_ptr, mpi_size_t s2_size)
97 {
98 	mpi_limb_t cy = 0;
99 
100 	if (s2_size)
101 		cy = mpihelp_sub_n(res_ptr, s1_ptr, s2_ptr, s2_size);
102 
103 	if (s1_size - s2_size)
104 		cy = mpihelp_sub_1(res_ptr + s2_size, s1_ptr + s2_size,
105 				   s1_size - s2_size, cy);
106 	return cy;
107 }
108 
109 #endif /*G10_MPI_INLINE_H */
110