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114 lines
4.9 KiB
114 lines
4.9 KiB
9 months ago
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commit 9333498794cde1d5cca518badf79533a24114b6f
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Author: Joseph Myers <joseph@codesourcery.com>
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Date: Wed Feb 12 23:31:56 2020 +0000
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Avoid ldbl-96 stack corruption from range reduction of pseudo-zero (bug 25487).
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Bug 25487 reports stack corruption in ldbl-96 sinl on a pseudo-zero
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argument (an representation where all the significand bits, including
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the explicit high bit, are zero, but the exponent is not zero, which
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is not a valid representation for the long double type).
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Although this is not a valid long double representation, existing
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practice in this area (see bug 4586, originally marked invalid but
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subsequently fixed) is that we still seek to avoid invalid memory
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accesses as a result, in case of programs that treat arbitrary binary
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data as long double representations, although the invalid
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representations of the ldbl-96 format do not need to be consistently
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handled the same as any particular valid representation.
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This patch makes the range reduction detect pseudo-zero and unnormal
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representations that would otherwise go to __kernel_rem_pio2, and
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returns a NaN for them instead of continuing with the range reduction
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process. (Pseudo-zero and unnormal representations whose unbiased
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exponent is less than -1 have already been safely returned from the
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function before this point without going through the rest of range
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reduction.) Pseudo-zero representations would previously result in
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the value passed to __kernel_rem_pio2 being all-zero, which is
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definitely unsafe; unnormal representations would previously result in
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a value passed whose high bit is zero, which might well be unsafe
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since that is not a form of input expected by __kernel_rem_pio2.
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Tested for x86_64.
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Revised for RHEL 8.3.0.
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diff -Nrup a/sysdeps/ieee754/ldbl-96/e_rem_pio2l.c b/sysdeps/ieee754/ldbl-96/e_rem_pio2l.c
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--- a/sysdeps/ieee754/ldbl-96/e_rem_pio2l.c 2018-08-01 01:10:47.000000000 -0400
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+++ b/sysdeps/ieee754/ldbl-96/e_rem_pio2l.c 2020-04-03 13:05:02.609844427 -0400
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@@ -209,6 +209,18 @@ __ieee754_rem_pio2l (long double x, long
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y[1] = y[0];
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return 0;
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}
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+
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+ if ((i0 & 0x80000000) == 0)
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+ {
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+ /* Pseudo-zero and unnormal representations are not valid
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+ representations of long double. We need to avoid stack
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+ corruption in __kernel_rem_pio2, which expects input in a
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+ particular normal form, but those representations do not need
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+ to be consistently handled like any particular floating-point
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+ value. */
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+ y[1] = y[0] = __builtin_nanl ("");
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+ return 0;
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+ }
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/* Split the 64 bits of the mantissa into three 24-bit integers
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stored in a double array. */
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diff -Nrup a/sysdeps/ieee754/ldbl-96/Makefile b/sysdeps/ieee754/ldbl-96/Makefile
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--- a/sysdeps/ieee754/ldbl-96/Makefile 2018-08-01 01:10:47.000000000 -0400
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+++ b/sysdeps/ieee754/ldbl-96/Makefile 2020-04-03 13:03:20.233546734 -0400
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@@ -17,5 +17,6 @@
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# <http://www.gnu.org/licenses/>.
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ifeq ($(subdir),math)
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-tests += test-canonical-ldbl-96 test-totalorderl-ldbl-96
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+tests += test-canonical-ldbl-96 test-totalorderl-ldbl-96 test-sinl-pseudo
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+CFLAGS-test-sinl-pseudo.c += -fstack-protector-all
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endif
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diff -Nrup a/sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c b/sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c
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--- a/sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c 1969-12-31 19:00:00.000000000 -0500
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+++ b/sysdeps/ieee754/ldbl-96/test-sinl-pseudo.c 2020-04-03 13:05:37.857952212 -0400
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@@ -0,0 +1,41 @@
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+/* Test sinl for pseudo-zeros and unnormals for ldbl-96 (bug 25487).
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+ Copyright (C) 2020 Free Software Foundation, Inc.
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+ This file is part of the GNU C Library.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, see
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+ <https://www.gnu.org/licenses/>. */
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+
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+#include <math.h>
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+#include <math_ldbl.h>
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+#include <stdint.h>
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+
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+static int
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+do_test (void)
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+{
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+ for (int i = 0; i < 64; i++)
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+ {
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+ uint64_t sig = i == 63 ? 0 : 1ULL << i;
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+ long double ld;
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+ SET_LDOUBLE_WORDS (ld, 0x4141,
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+ sig >> 32, sig & 0xffffffffULL);
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+ /* The requirement is that no stack overflow occurs when the
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+ pseudo-zero or unnormal goes through range reduction. */
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+ volatile long double ldr;
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+ ldr = sinl (ld);
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+ (void) ldr;
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+ }
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+ return 0;
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+}
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+
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+#include <support/test-driver.c>
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