85 lines
2.9 KiB
Diff
85 lines
2.9 KiB
Diff
From 9273b2d0e93e7355656cad3be3a1ca76489df483 Mon Sep 17 00:00:00 2001
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From: Aurelien Jarno <aurelien@aurel32.net>
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Date: Mon, 10 Oct 2022 00:39:33 +0200
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Subject: [PATCH 64/81] Avoid undefined behaviour in ibm128 implementation of
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llroundl (BZ #29488)
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Detecting an overflow edge case depended on signed overflow of a long
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long. Replace the additions and the overflow checks by
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__builtin_add_overflow().
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Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
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(cherry picked from commit 2b5478569e72ee4820a6e163d306690c9c0eaf5e)
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---
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NEWS | 2 ++
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sysdeps/ieee754/ldbl-128ibm/s_llroundl.c | 21 +++++++++------------
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2 files changed, 11 insertions(+), 12 deletions(-)
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diff --git a/NEWS b/NEWS
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index a6da588c85..8c60d3dc8d 100644
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--- a/NEWS
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+++ b/NEWS
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@@ -33,6 +33,8 @@ The following bugs are resolved with this release:
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[29485] Linux: Terminate subprocess on late failure in tst-pidfd
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[29490] alpha: New __brk_call implementation is broken
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[29463] math/test-float128-y1 fails on x86_64
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+ [29488] test-ibm128-llround fails on ppc64el when built with gcc-12 and -O2
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+ or higher
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[29528] elf: Call __libc_early_init for reused namespaces
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[29537] libc: [2.34 regression]: Alignment issue on m68k when using
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[29539] libc: LD_TRACE_LOADED_OBJECTS changed how vDSO library are
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diff --git a/sysdeps/ieee754/ldbl-128ibm/s_llroundl.c b/sysdeps/ieee754/ldbl-128ibm/s_llroundl.c
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index d85154e73a..d8c0de1faf 100644
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--- a/sysdeps/ieee754/ldbl-128ibm/s_llroundl.c
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+++ b/sysdeps/ieee754/ldbl-128ibm/s_llroundl.c
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@@ -66,38 +66,35 @@ __llroundl (long double x)
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/* Peg at max/min values, assuming that the above conversions do so.
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Strictly speaking, we can return anything for values that overflow,
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but this is more useful. */
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- res = hi + lo;
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-
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- /* This is just sign(hi) == sign(lo) && sign(res) != sign(hi). */
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- if (__glibc_unlikely (((~(hi ^ lo) & (res ^ hi)) < 0)))
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+ if (__glibc_unlikely (__builtin_add_overflow (hi, lo, &res)))
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goto overflow;
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xh -= lo;
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ldbl_canonicalize (&xh, &xl);
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- hi = res;
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if (xh > 0.5)
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{
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- res += 1;
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+ if (__glibc_unlikely (__builtin_add_overflow (res, 1, &res)))
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+ goto overflow;
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}
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else if (xh == 0.5)
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{
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if (xl > 0.0 || (xl == 0.0 && res >= 0))
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- res += 1;
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+ if (__glibc_unlikely (__builtin_add_overflow (res, 1, &res)))
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+ goto overflow;
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}
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else if (-xh > 0.5)
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{
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- res -= 1;
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+ if (__glibc_unlikely (__builtin_add_overflow (res, -1, &res)))
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+ goto overflow;
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}
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else if (-xh == 0.5)
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{
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if (xl < 0.0 || (xl == 0.0 && res <= 0))
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- res -= 1;
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+ if (__glibc_unlikely (__builtin_add_overflow (res, -1, &res)))
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+ goto overflow;
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}
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- if (__glibc_unlikely (((~(hi ^ (res - hi)) & (res ^ hi)) < 0)))
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- goto overflow;
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-
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return res;
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}
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else
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--
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2.19.1.6.gb485710b
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