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Commit 543f2a33 authored by Chuck Ebbert's avatar Chuck Ebbert Committed by Linus Torvalds
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[PATCH] i386: fix broken FP exception handling 



The FXSAVE information leak patch introduced a bug in FP exception
handling: it clears FP exceptions only when there are already
none outstanding.  Mikael Pettersson reported that causes problems
with the Erlang runtime and has tested this fix.

Signed-off-by: default avatarChuck Ebbert <76306.1226@compuserve.com>
Acked-by: default avatarMikael Pettersson <mikpe@it.uu.se>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 693f7d36

include/asm-i386/i387.h

+2 −2
Original line number Diff line number Diff line
@@ -58,13 +58,13 @@ static inline void __save_init_fpu( struct task_struct *tsk ) 
	alternative_input(

		"fnsave %[fx] ;fwait;" GENERIC_NOP8 GENERIC_NOP4,

		"fxsave %[fx]\n"

		"bt $7,%[fsw] ; jc 1f ; fnclex\n1:",

		"bt $7,%[fsw] ; jnc 1f ; fnclex\n1:",

		X86_FEATURE_FXSR,

		[fx] "m" (tsk->thread.i387.fxsave),

		[fsw] "m" (tsk->thread.i387.fxsave.swd) : "memory");

	/* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception

	   is pending.  Clear the x87 state here by setting it to fixed

   	   values. __per_cpu_offset[0] is a random variable that should be in L1 */

   	   values. safe_address is a random variable that should be in L1 */

	alternative_input(

		GENERIC_NOP8 GENERIC_NOP2,

		"emms\n\t"	  	/* clear stack tags */