Date: Tue, 1 Sep 2015 17:51:44 -0700 From: Andy Lutomirski <luto@...capital.net> To: Kees Cook <keescook@...omium.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, libc-alpha <libc-alpha@...rceware.org>, "musl@...ts.openwall.com" <musl@...ts.openwall.com>, gcc@....gnu.org, Binutils <binutils@...rceware.org> Subject: RFC: adding Linux vsyscall-disable and similar backwards-incompatibility flags to ELF headers? Hi all- Linux has a handful of weird features that are only supported for backwards compatibility. The big one is the x86_64 vsyscall page, but uselib probably belongs on the list, too, and we might end up with more at some point. I'd like to add a way that new programs can turn these features off. In particular, I want the vsyscall page to be completely gone from the perspective of any new enough program. This is straightforward if we add a system call to ask for the vsyscall page to be disabled, but I'm wondering if we can come up with a non-syscall way to do it. I think that the ideal behavior would be that anything linked against a sufficiently new libc would be detected, but I don't see a good way to do that using existing toolchain features. Ideas? We could add a new phdr for this, but then we'd need to play linker script games, and I'm not sure that could be done in a clean, extensible way. --Andy
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