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authorbde <bde@FreeBSD.org>2005-11-23 02:06:06 +0000
committerbde <bde@FreeBSD.org>2005-11-23 02:06:06 +0000
commit67ff03dd57510489a17d08d9df09e320ed2309f7 (patch)
tree3510fd47624abadaff84c1a5270580b9a8a158b4 /lib/msun
parent862650830c23569e3ff203af1d09a47fe4d2c830 (diff)
downloadFreeBSD-src-67ff03dd57510489a17d08d9df09e320ed2309f7.zip
FreeBSD-src-67ff03dd57510489a17d08d9df09e320ed2309f7.tar.gz
Quick fix for stack buffer overrun in rev.1.13. Oops. The prec == 1
arg to __kernel_rem_pio2() gives 53-bit (double) precision, not single precision and/or the array dimension like I thought. prec == 2 is used in e_rem_pio2.c for double precision although it is documented to be for 64-bit (extended) precision, and I just reduced it by 1 thinking that this would give the value suitable for 24-bit (float) precision. Reducing it 1 more to the documented value for float precision doesn't actually work (it gives errors of ~0.75 ulps in the reduced arg, but errors of much less than 0.5 ulps are needed; the bug seems to be in kernel_rem_pio2.c). Keep using a value 1 larger than the documented value but supply an array large enough hold the extra unused result from this. The bug can also be fixed quickly by increasing init_jk[0] in k_rem_pio2.c from 2 to 3. This gives behaviour identical to using prec == 1 except it doesn't create the extra result. It isn't clear how the precision bug affects higher precisions. 113-bit (quad) is the largest precision, so there is no way to use a large precision to fix it.
Diffstat (limited to 'lib/msun')
-rw-r--r--lib/msun/src/e_rem_pio2f.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/lib/msun/src/e_rem_pio2f.c b/lib/msun/src/e_rem_pio2f.c
index 6e939c1..c93ebd3 100644
--- a/lib/msun/src/e_rem_pio2f.c
+++ b/lib/msun/src/e_rem_pio2f.c
@@ -62,7 +62,7 @@ pio2_1t = 6.07710050650619224932e-11; /* 0x3DD0B461, 0x1A626331 */
int32_t __ieee754_rem_pio2f(float x, float *y)
{
double z,w,t,r,fn;
- double tx[3];
+ double tx[3],ty[2];
int32_t e0,i,nx,n,ix,hx;
GET_FLOAT_WORD(hx,x);
@@ -98,9 +98,9 @@ pio2_1t = 6.07710050650619224932e-11; /* 0x3DD0B461, 0x1A626331 */
tx[2] = z;
nx = 3;
while(tx[nx-1]==zero) nx--; /* skip zero term */
- n = __kernel_rem_pio2(tx,&z,e0,nx,1,two_over_pi);
- y[0] = z;
- y[1] = z - y[0];
+ n = __kernel_rem_pio2(tx,ty,e0,nx,1,two_over_pi);
+ y[0] = ty[0];
+ y[1] = ty[0] - y[0];
if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;}
return n;
}
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