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Re: R_X86_64_COPY bug
- From: Florian Weimer <fweimer at redhat dot com>
- To: Fredrick Prashanth John Berchmans <fredrickprashanth at gmail dot com>
- Cc: gcc-help at gcc dot gnu dot org, Suresh Siddha <sbsiddha at gmail dot com>, binutils at sourceware dot org, hjl dot tools at gmail dot com, nasuku at yahoo dot com, Alexander Ivchenko <aivchenk at gmail dot com>
- Date: Sun, 07 Apr 2013 12:46:51 +0200
- Subject: Re: R_X86_64_COPY bug
- References: <CACwgvgW5SNsXL2vND_qhgqO7RRsHwKyk+N-q5sTakeC9vwV0BA at mail dot gmail dot com> <20130406071305 dot GD3208 at bubble dot grove dot modra dot org> <CALmL7E92MjbsXbou8T3w895G9ahtd1tvC2JwREwV9EzT4Px20Q at mail dot gmail dot com> <CACysShj5aH4pWZHjxj74-B7z8a8d_NTKUyEcN8DFJXxaCa5=6g at mail dot gmail dot com> <CACwgvgXgjfwK9+HNRwyJMO-uJWM+WU9idj5gdBxJWr538rQRWQ at mail dot gmail dot com> <CACwgvgU9Gs0HUMU+Q2Hojx-y4s+FLzWarBEPHq+DCWfvTBa34A at mail dot gmail dot com>
On 04/07/2013 03:48 AM, Fredrick Prashanth John Berchmans wrote:
A struct with zero length array is defined in a shared library as a global data.
A binary links with this shared library and accesses the struct.
Because of copy relocation semantics, the binary linking with that
library sees(correctly) only the portion of the struct without the
zero length array.
We understand that it is due to the wrong or apparent size calculation
of the struct by GCC and using copy relocation semantics to resolve this
shared symbol is causing this problem.
This seems to be a bug in GCC:
.type test_dynamic, @object
.size test_dynamic, 4
The .size directive is wrong. I couldn't find anything matching in
Bugzilla, so you probably should file a new bug.
As a workaround, you could declare the struct object in question as
static. This should disable copy relocation.
Florian Weimer / Red Hat Product Security Team