75 lines
2.6 KiB
Diff
75 lines
2.6 KiB
Diff
Extracted from glibc upstream git repository. Changes to the ChangeLog have
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been removed. This patch is needed to fix spurious segmentation faults on
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i686.
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From 3abeeec5f46ff036bd9df60bb096e20314ccd078 Mon Sep 17 00:00:00 2001
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From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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Date: Tue, 14 Mar 2017 14:16:13 -0300
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Subject: [PATCH] Fix i686 memchr overflow calculation (BZ#21182)
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This patch fixes the regression added by 23d2770 for final address
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overflow calculation. The subtraction of the considered size (16)
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at line 120 is at wrong place, for sizes less than 16 subsequent
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overflow check will not take in consideration an invalid size (since
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the subtraction will be negative). Also, the lea instruction also
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does not raise the carry flag (CF) that is used in subsequent jbe
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to check for overflow.
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The fix is to follow x86_64 logic from 3daef2c where the overflow
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is first check and a sub instruction is issued. In case of resulting
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negative size, CF will be set by the sub instruction and a NULL
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result will be returned. The patch also add similar tests reported
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in bug report.
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Checked on i686-linux-gnu and x86_64-linux-gnu.
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* string/test-memchr.c (do_test): Add BZ#21182 checks for address
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near end of a page.
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* sysdeps/i386/i686/multiarch/memchr-sse2.S (__memchr): Fix
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overflow calculation.
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---
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string/test-memchr.c | 6 ++++++
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sysdeps/i386/i686/multiarch/memchr-sse2.S | 2 +-
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3 files changed, 15 insertions(+), 1 deletion(-)
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diff --git a/string/test-memchr.c b/string/test-memchr.c
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index 2403c9242b..669e092e7d 100644
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--- a/string/test-memchr.c
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+++ b/string/test-memchr.c
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@@ -210,6 +210,12 @@ test_main (void)
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do_test (0, i, i + 1, i + 1, 0);
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}
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+ /* BZ#21182 - wrong overflow calculation for i686 implementation
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+ with address near end of the page. */
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+ for (i = 2; i < 16; ++i)
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+ /* page_size is in fact getpagesize() * 2. */
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+ do_test (page_size / 2 - i, i, i, 1, 0x9B);
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+
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do_random_tests ();
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return ret;
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}
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diff --git a/sysdeps/i386/i686/multiarch/memchr-sse2.S b/sysdeps/i386/i686/multiarch/memchr-sse2.S
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index 910679cfc0..e41f324a77 100644
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--- a/sysdeps/i386/i686/multiarch/memchr-sse2.S
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+++ b/sysdeps/i386/i686/multiarch/memchr-sse2.S
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@@ -117,7 +117,6 @@ L(crosscache):
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# ifndef USE_AS_RAWMEMCHR
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jnz L(match_case2_prolog1)
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- lea -16(%edx), %edx
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/* Calculate the last acceptable address and check for possible
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addition overflow by using satured math:
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edx = ecx + edx
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@@ -125,6 +124,7 @@ L(crosscache):
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add %ecx, %edx
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sbb %eax, %eax
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or %eax, %edx
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+ sub $16, %edx
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jbe L(return_null)
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lea 16(%edi), %edi
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# else
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--
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2.12.2
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