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Commit f718d426 authored by Matt Brown's avatar Matt Brown Committed by Michael Ellerman
Browse files

powerpc/lib/xor_vmx: Ensure no altivec code executes before enable_kernel_altivec() 



The xor_vmx.c file is used for the RAID5 xor operations. In these functions
altivec is enabled to run the operation and then disabled.

The code uses enable_kernel_altivec() around the core of the algorithm, however
the whole file is built with -maltivec, so the compiler is within its rights to
generate altivec code anywhere. This has been seen at least once in the wild:

  0:mon> di $xor_altivec_2
  c0000000000b97d0  3c4c01d9	addis   r2,r12,473
  c0000000000b97d4  3842db30	addi    r2,r2,-9424
  c0000000000b97d8  7c0802a6	mflr    r0
  c0000000000b97dc  f8010010	std     r0,16(r1)
  c0000000000b97e0  60000000	nop
  c0000000000b97e4  7c0802a6	mflr    r0
  c0000000000b97e8  faa1ffa8	std     r21,-88(r1)
  ...
  c0000000000b981c  f821ff41	stdu    r1,-192(r1)
  c0000000000b9820  7f8101ce	stvx    v28,r1,r0		<-- POP
  c0000000000b9824  38000030	li      r0,48
  c0000000000b9828  7fa101ce	stvx    v29,r1,r0
  ...
  c0000000000b984c  4bf6a06d	bl      c0000000000238b8 # enable_kernel_altivec

This patch splits the non-altivec code into xor_vmx_glue.c which calls the
altivec functions in xor_vmx.c. By compiling xor_vmx_glue.c without
-maltivec we can guarantee that altivec instruction will not be executed
outside of the enable/disable block.

Signed-off-by: default avatarMatt Brown <matthew.brown.dev@gmail.com>
[mpe: Rework change log and include disassembly]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 48a316e3

arch/powerpc/lib/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -37,7 +37,7 @@ obj-$(CONFIG_PPC_LIB_RHEAP) += rheap.o 


obj-$(CONFIG_FTR_FIXUP_SELFTEST) += feature-fixups-test.o



obj-$(CONFIG_ALTIVEC)	+= xor_vmx.o

obj-$(CONFIG_ALTIVEC)	+= xor_vmx.o xor_vmx_glue.o

CFLAGS_xor_vmx.o += -maltivec $(call cc-option,-mabi=altivec)



obj-$(CONFIG_PPC64) += $(obj64-y)

arch/powerpc/lib/xor_vmx.c

+11 −42
Original line number Diff line number Diff line
@@ -29,10 +29,7 @@ 
#define vector __attribute__((vector_size(16)))

#endif



#include <linux/preempt.h>

#include <linux/export.h>

#include <linux/sched.h>

#include <asm/switch_to.h>

#include "xor_vmx.h"



typedef vector signed char unative_t;
@@ -64,16 +61,13 @@ typedef vector signed char unative_t; 
		V1##_3 = vec_xor(V1##_3, V2##_3);	\

	} while (0)



void xor_altivec_2(unsigned long bytes, unsigned long *v1_in,

void __xor_altivec_2(unsigned long bytes, unsigned long *v1_in,

		     unsigned long *v2_in)

{

	DEFINE(v1);

	DEFINE(v2);

	unsigned long lines = bytes / (sizeof(unative_t)) / 4;



	preempt_disable();

	enable_kernel_altivec();



	do {

		LOAD(v1);

		LOAD(v2);
@@ -83,13 +77,9 @@ void xor_altivec_2(unsigned long bytes, unsigned long *v1_in, 
		v1 += 4;

		v2 += 4;

	} while (--lines > 0);



	disable_kernel_altivec();

	preempt_enable();

}

EXPORT_SYMBOL(xor_altivec_2);



void xor_altivec_3(unsigned long bytes, unsigned long *v1_in,

void __xor_altivec_3(unsigned long bytes, unsigned long *v1_in,

		     unsigned long *v2_in, unsigned long *v3_in)

{

	DEFINE(v1);
@@ -97,9 +87,6 @@ void xor_altivec_3(unsigned long bytes, unsigned long *v1_in, 
	DEFINE(v3);

	unsigned long lines = bytes / (sizeof(unative_t)) / 4;



	preempt_disable();

	enable_kernel_altivec();



	do {

		LOAD(v1);

		LOAD(v2);
@@ -112,13 +99,9 @@ void xor_altivec_3(unsigned long bytes, unsigned long *v1_in, 
		v2 += 4;

		v3 += 4;

	} while (--lines > 0);



	disable_kernel_altivec();

	preempt_enable();

}

EXPORT_SYMBOL(xor_altivec_3);



void xor_altivec_4(unsigned long bytes, unsigned long *v1_in,

void __xor_altivec_4(unsigned long bytes, unsigned long *v1_in,

		     unsigned long *v2_in, unsigned long *v3_in,

		     unsigned long *v4_in)

{
@@ -128,9 +111,6 @@ void xor_altivec_4(unsigned long bytes, unsigned long *v1_in, 
	DEFINE(v4);

	unsigned long lines = bytes / (sizeof(unative_t)) / 4;



	preempt_disable();

	enable_kernel_altivec();



	do {

		LOAD(v1);

		LOAD(v2);
@@ -146,13 +126,9 @@ void xor_altivec_4(unsigned long bytes, unsigned long *v1_in, 
		v3 += 4;

		v4 += 4;

	} while (--lines > 0);



	disable_kernel_altivec();

	preempt_enable();

}

EXPORT_SYMBOL(xor_altivec_4);



void xor_altivec_5(unsigned long bytes, unsigned long *v1_in,

void __xor_altivec_5(unsigned long bytes, unsigned long *v1_in,

		     unsigned long *v2_in, unsigned long *v3_in,

		     unsigned long *v4_in, unsigned long *v5_in)

{
@@ -163,9 +139,6 @@ void xor_altivec_5(unsigned long bytes, unsigned long *v1_in, 
	DEFINE(v5);

	unsigned long lines = bytes / (sizeof(unative_t)) / 4;



	preempt_disable();

	enable_kernel_altivec();



	do {

		LOAD(v1);

		LOAD(v2);
@@ -184,8 +157,4 @@ void xor_altivec_5(unsigned long bytes, unsigned long *v1_in, 
		v4 += 4;

		v5 += 4;

	} while (--lines > 0);



	disable_kernel_altivec();

	preempt_enable();

}
 
EXPORT_SYMBOL(xor_altivec_5);

arch/powerpc/lib/xor_vmx.h

0 → 100644
+20 −0
Original line number Diff line number Diff line 
/*

 * Simple interface to link xor_vmx.c and xor_vmx_glue.c

 *

 * Separating these file ensures that no altivec instructions are run

 * outside of the enable/disable altivec block.

 */



void __xor_altivec_2(unsigned long bytes, unsigned long *v1_in,

			     unsigned long *v2_in);



void __xor_altivec_3(unsigned long bytes, unsigned long *v1_in,

			     unsigned long *v2_in, unsigned long *v3_in);



void __xor_altivec_4(unsigned long bytes, unsigned long *v1_in,

			     unsigned long *v2_in, unsigned long *v3_in,

			     unsigned long *v4_in);



void __xor_altivec_5(unsigned long bytes, unsigned long *v1_in,

			     unsigned long *v2_in, unsigned long *v3_in,

			     unsigned long *v4_in, unsigned long *v5_in);

arch/powerpc/lib/xor_vmx_glue.c

0 → 100644
+62 −0
Original line number Diff line number Diff line 
/*

 * Altivec XOR operations

 *

 * Copyright 2017 IBM Corp.

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version

 * 2 of the License, or (at your option) any later version.

 */



#include <linux/preempt.h>

#include <linux/export.h>

#include <linux/sched.h>

#include <asm/switch_to.h>

#include "xor_vmx.h"



void xor_altivec_2(unsigned long bytes, unsigned long *v1_in,

		   unsigned long *v2_in)

{

	preempt_disable();

	enable_kernel_altivec();

	__xor_altivec_2(bytes, v1_in, v2_in);

	disable_kernel_altivec();

	preempt_enable();

}

EXPORT_SYMBOL(xor_altivec_2);



void xor_altivec_3(unsigned long bytes,  unsigned long *v1_in,

		   unsigned long *v2_in, unsigned long *v3_in)

{

	preempt_disable();

	enable_kernel_altivec();

	__xor_altivec_3(bytes, v1_in, v2_in, v3_in);

	disable_kernel_altivec();

	preempt_enable();

}

EXPORT_SYMBOL(xor_altivec_3);



void xor_altivec_4(unsigned long bytes,  unsigned long *v1_in,

		   unsigned long *v2_in, unsigned long *v3_in,

		   unsigned long *v4_in)

{

	preempt_disable();

	enable_kernel_altivec();

	__xor_altivec_4(bytes, v1_in, v2_in, v3_in, v4_in);

	disable_kernel_altivec();

	preempt_enable();

}

EXPORT_SYMBOL(xor_altivec_4);



void xor_altivec_5(unsigned long bytes,  unsigned long *v1_in,

		   unsigned long *v2_in, unsigned long *v3_in,

		   unsigned long *v4_in, unsigned long *v5_in)

{

	preempt_disable();

	enable_kernel_altivec();

	__xor_altivec_5(bytes, v1_in, v2_in, v3_in, v4_in, v5_in);

	disable_kernel_altivec();

	preempt_enable();

}

EXPORT_SYMBOL(xor_altivec_5);