Messages in this thread Patch in this message | | | Date | Wed, 13 Aug 2008 11:38:14 -0700 | From | Suresh Siddha <> | Subject | [patch 2/3] x86, xsave: clear the user buffer before doing fxsave/xsave |
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fxsave/xsave instructions will not touch all the bytes in the fxsave/xsave frame. Clear the user buffer before doing fxsave/xsave directly to user buffer during the sigcontext setup.
This is essentially needed in the context of xsave(for example, some of the fields in the xsave header are not touched by the xsave and defined as must be zero).
This will also present uniform and clean context to the user (from which user can safely do fxrstor/xrstor).
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> ---
Index: tip/arch/x86/kernel/xsave.c =================================================================== --- tip.orig/arch/x86/kernel/xsave.c 2008-08-11 15:26:47.000000000 -0700 +++ tip/arch/x86/kernel/xsave.c 2008-08-11 15:44:33.000000000 -0700 @@ -92,6 +92,12 @@ return 0; clear_used_math(); /* trigger finit */ if (task_thread_info(tsk)->status & TS_USEDFPU) { + /* + * Start with clearing the user buffer. This will present a + * clean context for the bytes not touched by the fxsave/xsave. + */ + __clear_user(buf, sig_xstate_size); + if (task_thread_info(tsk)->status & TS_XSAVE) err = xsave_user(buf); else --
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