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Message-ID: <20200226052448.GA2769@voyager>
Date: Wed, 26 Feb 2020 06:24:48 +0100
From: Markus Wichmann <nullplan@....net>
To: musl@...ts.openwall.com
Subject: [PATCH] Add REL_COPY size change detection
Hi all,
I was recently reading the Oracle docs about the ELF, and I came across
their chapter about the COPY relocation. They discuraged its use, since
with those relocations, a binding exists between importing and exporting
module. If the semantics of the imported object changes, then this is an
ABI mismatch.
So I looked at the musl source code and noticed that COPY relocations
are simply processed, and an ABI mismatch is simply accepted. So, since
I am of the opinion that detectable errors should be detected, rather
than left to fester and spring a hard-to-explain bug on you, usually
five minutes before deadline, I wrote the attached patch to add
detection for at least a changed size. This won't detect all changes to
ABI regarding COPY relocation (e.g.int-->float, or in an array of
structs, a change to the struct size and to the array size cancelling
each other out), but it should find most of them.
Also, I wondered whether COPY relocations are even still in use. But on
my system (currently some Ubuntu version) I found over 15000 of the
things. Mostly for stdout and stderr, though.
Ciao,
Markus
View attachment "0001-Add-detection-for-changed-size-of-a-COPY-relocation.patch" of type "text/x-diff" (1591 bytes)
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