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Message-ID: <20161118114234.GB1197@leverpostej>
Date: Fri, 18 Nov 2016 11:42:35 +0000
From: Mark Rutland <mark.rutland@....com>
To: Kees Cook <keescook@...omium.org>
Cc: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: patches for __write_rarely section
On Fri, Nov 18, 2016 at 11:10:59AM +0000, Mark Rutland wrote:
> With something like the below (assuming all helpers are inlined):
>
> #define rare_write(__var, __val) ({ \
> typeof(var) *__rw_var; \
... iwith s/var/__var/ here...
> __some_typecheck_perhaps(__var, __val); \
> \
> __rw_var = __rare_rw_ptr(&(__var)); \
> \
> __rare_rw_map(); \
> *__rw_var = (__val); \
> __rare_rw_unmap(); \
> \
> __clobber_var_so_gcc_knows(__var); \
> })
... and with explicit clobber gone, since __rare_rw_unmap would
presumably have to have a memory clobber anyway, just like the fixmap
code.
Thanks,
Mark.
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