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MIPS MSA sigcontext changes in 3.15
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: <linux-mips at linux-mips dot org>, <libc-alpha at sourceware dot org>, <linux-api at vger dot kernel dot org>
- Date: Tue, 17 Jun 2014 15:03:15 +0000
- Subject: MIPS MSA sigcontext changes in 3.15
- Authentication-results: sourceware.org; auth=none
Reviewing changes in Linux 3.15 for anything for which glibc changes would
be appropriate, I don't see how the MSA sigcontext changes are supposed to
work with existing binaries.
The sigcontext structure isn't used on its own - it's part of ucontext,
which is passed to signal handlers, and it's not at the end of ucontext,
but followed by the signal mask. So existing binaries will expect the
signal mask at a particular offset in the ucontext. As far as I can see,
extending sigcontext requires a new sigaction flag that could be used to
opt in, for a particular signal handler, to receiving the new-layout
ucontext (so new symbol versions of sigaction in glibc could then pass
that flag to the kernel, but existing binaries would continue to get
old-layout ucontext from the kernel), or else putting the new data at the
end of ucontext rather than in the main sigcontext structure (though I
don't know if that would have other issues).
Joseph S. Myers