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BN_div bugfix. The q-- loop should not be entered in the n0==d0 case.

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This commit is contained in:
Ulf Möller 2000-02-06 00:25:39 +00:00
parent e290c7d4e0
commit 4a6222d71b
2 changed files with 74 additions and 75 deletions
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4
CHANGES
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@ -4,6 +4,10 @@
Changes between 0.9.4 and 0.9.5 [xx XXX 2000]
*) Bug fix for BN_div() when the first words of num and divsor are
equal (it gave wrong results if (rem=(n1-q*d0)&BN_MASK2) < d0).
[Ulf Möller]
*) Add support for various broken PKCS#8 formats, and command line
options to produce them.
[Steve Henson]

145
crypto/bn/bn_div.c
View file

@ -62,7 +62,7 @@
#include "bn_lcl.h"
/* The old slow way */
#if 1
#if 0
int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d,
BN_CTX *ctx)
{
@ -126,6 +126,32 @@ int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d,
#else
#if !defined(NO_ASM) && !defined(PEDANTIC) && !defined(BN_DIV3W)
# if defined(__GNUC__) && __GNUC__>=2
# if defined(__i386)
/*
* There were two reasons for implementing this template:
* - GNU C generates a call to a function (__udivdi3 to be exact)
* in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to
* understand why...);
* - divl doesn't only calculate quotient, but also leaves
* remainder in %edx which we can definitely use here:-)
*
* <appro@fy.chalmers.se>
*/
# define bn_div_words(n0,n1,d0) \
({ asm volatile ( \
"divl %4" \
: "=a"(q), "=d"(rem) \
: "a"(n1), "d"(n0), "g"(d0) \
: "cc"); \
q; \
})
# define REMAINDER_IS_ALREADY_CALCULATED
# endif /* __<cpu> */
# endif /* __GNUC__ */
#endif /* NO_ASM */
int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
BN_CTX *ctx)
{
@ -214,103 +240,72 @@ int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
#ifdef BN_DIV3W
q=bn_div_3_words(wnump,d1,d0);
#else
#if !defined(NO_ASM) && !defined(PEDANTIC)
# if defined(__GNUC__) && __GNUC__>=2
# if defined(__i386)
/*
* There were two reasons for implementing this template:
* - GNU C generates a call to a function (__udivdi3 to be exact)
* in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to
* understand why...);
* - divl doesn't only calculate quotient, but also leaves
* remainder in %edx which we can definitely use here:-)
*
* <appro@fy.chalmers.se>
*/
# define bn_div_words(n0,n1,d0) \
({ asm volatile ( \
"divl %4" \
: "=a"(q), "=d"(rem) \
: "a"(n1), "d"(n0), "g"(d0) \
: "cc"); \
q; \
})
# define REMAINDER_IS_ALREADY_CALCULATED
# endif /* __<cpu> */
# endif /* __GNUC__ */
#endif /* NO_ASM */
BN_ULONG n0,n1,rem=0;
n0=wnump[0];
n1=wnump[-1];
if (n0 == d0)
{
q=BN_MASK2;
#ifdef REMAINDER_IS_ALREADY_CALCULATED /* in this case it isn't */
rem=(n1-q*d0)&BN_MASK2;
#endif
}
else /* n0 < d0 */
else /* n0 < d0 */
{
#ifdef BN_LLONG
BN_ULLONG t2;
#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0);
#else
q=bn_div_words(n0,n1,d0);
#endif
{
#ifdef BN_LLONG
BN_ULLONG t2;
#ifndef REMAINDER_IS_ALREADY_CALCULATED
/*
* rem doesn't have to be BN_ULLONG. The least we
* know it's less that d0, isn't it?
*/
rem=(n1-q*d0)&BN_MASK2;
/*
* rem doesn't have to be BN_ULLONG. The least we
* know it's less that d0, isn't it?
*/
rem=(n1-q*d0)&BN_MASK2;
#endif
t2=(BN_ULLONG)d1*q;
t2=(BN_ULLONG)d1*q;
for (;;)
{
if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2]))
break;
q--;
rem += d0;
if (rem < d0) break; /* don't let rem overflow */
t2 -= d1;
}
#else
BN_ULONG t2l,t2h,ql,qh;
for (;;)
{
if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2]))
break;
q--;
rem += d0;
if (rem < d0) break; /* don't let rem overflow */
t2 -= d1;
}
#else /* !BN_LLONG */
BN_ULONG t2l,t2h,ql,qh;
q=bn_div_words(n0,n1,d0);
#ifndef REMAINDER_IS_ALREADY_CALCULATED
/*
* It's more than enough with the only multiplication.
* See the comment above in BN_LLONG section...
*/
rem=(n1-q*d0)&BN_MASK2;
rem=(n1-q*d0)&BN_MASK2;
#endif
#ifdef BN_UMULT_HIGH
t2l = d1 * q;
t2h = BN_UMULT_HIGH(d1,q);
t2l = d1 * q;
t2h = BN_UMULT_HIGH(d1,q);
#else
t2l=LBITS(d1); t2h=HBITS(d1);
ql =LBITS(q); qh =HBITS(q);
mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
t2l=LBITS(d1); t2h=HBITS(d1);
ql =LBITS(q); qh =HBITS(q);
mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
#endif
for (;;)
{
if ((t2h < rem) ||
((t2h == rem) && (t2l <= wnump[-2])))
break;
q--;
rem += d0;
if (rem < d0) break; /* don't let rem overflow */
if (t2l < d1) t2h--; t2l -= d1;
for (;;)
{
if ((t2h < rem) ||
((t2h == rem) && (t2l <= wnump[-2])))
break;
q--;
rem += d0;
if (rem < d0) break; /* don't let rem overflow */
if (t2l < d1) t2h--; t2l -= d1;
}
#endif /* !BN_LLONG */
}
#endif
}
#endif /* !BN_DIV3W */
l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
wnum.d--; wnum.top++;
tmp->d[div_n]=l0;
@ -341,7 +336,7 @@ int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
BN_CTX_end(ctx);
return(1);
err:
BN_CX_end(ctx);
BN_CTX_end(ctx);
return(0);
}