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Commit 99aa22d0 authored by Yu-cheng Yu's avatar Yu-cheng Yu Committed by Ingo Molnar
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x86/fpu/xstate: Copy xstate registers directly to the signal frame when compacted format is in use 



XSAVES is a kernel instruction and uses a compacted format. When working
with user space, the kernel should provide standard-format, non-supervisor
state data. We cannot do __copy_to_user() from a compacted-format kernel
xstate area to a signal frame.

Dave Hansen proposes this method to simplify copy xstate directly to user.

This patch is based on an earlier patch from Fenghua Yu <fenghua.yu@intel.com>

Originally-from: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: default avatarYu-cheng Yu <yu-cheng.yu@intel.com>
Reviewed-by: default avatarDave Hansen <dave.hansen@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/c36f419d525517d04209a28dd8e1e5af9000036e.1463760376.git.yu-cheng.yu@intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 7d937060

arch/x86/include/asm/fpu/xstate.h

+1 −0
Original line number Diff line number Diff line
@@ -47,5 +47,6 @@ extern void update_regset_xstate_info(unsigned int size, u64 xstate_mask); 
void fpu__xstate_clear_all_cpu_caps(void);

void *get_xsave_addr(struct xregs_state *xsave, int xstate);

const void *get_xsave_field_ptr(int xstate_field);

int using_compacted_format(void);



#endif

arch/x86/kernel/fpu/signal.c

+2 −1
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
#include <asm/fpu/internal.h>

#include <asm/fpu/signal.h>

#include <asm/fpu/regset.h>

#include <asm/fpu/xstate.h>



#include <asm/sigframe.h>

#include <asm/trace/fpu.h>
@@ -169,7 +170,7 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) 
			sizeof(struct user_i387_ia32_struct), NULL,

			(struct _fpstate_32 __user *) buf) ? -1 : 1;



	if (fpregs_active()) {

	if (fpregs_active() || using_compacted_format()) {

		/* Save the live register state to the user directly. */

		if (copy_fpregs_to_sigframe(buf_fx))

			return -1;

arch/x86/kernel/fpu/xstate.c

+1 −1
Original line number Diff line number Diff line
@@ -420,7 +420,7 @@ static int xfeature_size(int xfeature_nr) 
 * that it is obvious which aspect of 'XSAVES' is being handled

 * by the calling code.

 */

static int using_compacted_format(void)

int using_compacted_format(void)

{

	return boot_cpu_has(X86_FEATURE_XSAVES);

}