Commit a0f4b787 authored by Helge Deller's avatar Helge Deller
Browse files

parisc: Fix lightweight spinlock checks to not break futexes 



The lightweight spinlock checks verify that a spinlock has either value
0 (spinlock locked) and that not any other bits than in
__ARCH_SPIN_LOCK_UNLOCKED_VAL is set.

This breaks the current LWS code, which writes the address of the lock
into the lock word to unlock it, which was an optimization to save one
assembler instruction.

Fix it by making spinlock_types.h accessible for asm code, change the
LWS spinlock-unlocking code to write __ARCH_SPIN_LOCK_UNLOCKED_VAL into
the lock word, and add some missing lightweight spinlock checks to the
LWS path. Finally, make the spinlock checks dependend on DEBUG_KERNEL.

Noticed-by: default avatarJohn David Anglin <dave.anglin@bell.net>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Tested-by: default avatarJohn David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # v6.4+
Fixes: 15e64ef6 ("parisc: Add lightweight spinlock checks")
parent a027b2ec

arch/parisc/Kconfig.debug

+1 −1
Original line number Diff line number Diff line
@@ -2,7 +2,7 @@ 
#

config LIGHTWEIGHT_SPINLOCK_CHECK

	bool "Enable lightweight spinlock checks"

	depends on SMP && !DEBUG_SPINLOCK

	depends on DEBUG_KERNEL && SMP && !DEBUG_SPINLOCK

	default y

	help

	  Add checks with low performance impact to the spinlock functions

arch/parisc/include/asm/spinlock.h

+0 −2
Original line number Diff line number Diff line
@@ -7,8 +7,6 @@ 
#include <asm/processor.h>

#include <asm/spinlock_types.h>



#define SPINLOCK_BREAK_INSN	0x0000c006	/* break 6,6 */



static inline void arch_spin_val_check(int lock_val)

{

	if (IS_ENABLED(CONFIG_LIGHTWEIGHT_SPINLOCK_CHECK))

arch/parisc/include/asm/spinlock_types.h

+6 −0
Original line number Diff line number Diff line
@@ -4,6 +4,10 @@ 


#define __ARCH_SPIN_LOCK_UNLOCKED_VAL	0x1a46



#define SPINLOCK_BREAK_INSN	0x0000c006	/* break 6,6 */



#ifndef __ASSEMBLY__



typedef struct {

#ifdef CONFIG_PA20

	volatile unsigned int slock;
@@ -27,6 +31,8 @@ typedef struct { 
	volatile unsigned int	counter;

} arch_rwlock_t;



#endif /* __ASSEMBLY__ */



#define __ARCH_RW_LOCK_UNLOCKED__       0x01000000

#define __ARCH_RW_LOCK_UNLOCKED         { .lock_mutex = __ARCH_SPIN_LOCK_UNLOCKED, \

					.counter = __ARCH_RW_LOCK_UNLOCKED__ }

arch/parisc/kernel/syscall.S

+20 −3
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ registers). 
#include <asm/assembly.h>

#include <asm/processor.h>

#include <asm/cache.h>

#include <asm/spinlock_types.h>



#include <linux/linkage.h>
@@ -66,6 +67,16 @@ registers). 
	stw	\reg1, 0(%sr2,\reg2)

	.endm



	/* raise exception if spinlock content is not zero or

	 * __ARCH_SPIN_LOCK_UNLOCKED_VAL */

	.macro	spinlock_check spin_val,tmpreg

#ifdef CONFIG_LIGHTWEIGHT_SPINLOCK_CHECK

	ldi	__ARCH_SPIN_LOCK_UNLOCKED_VAL, \tmpreg

	andcm,=	\spin_val, \tmpreg, %r0

	.word	SPINLOCK_BREAK_INSN

#endif

	.endm



	.text



	.import syscall_exit,code
@@ -508,7 +519,8 @@ lws_start: 


lws_exit_noerror:

	lws_pagefault_enable	%r1,%r21

	stw,ma	%r20, 0(%sr2,%r20)

	ldi	__ARCH_SPIN_LOCK_UNLOCKED_VAL, %r21

	stw,ma	%r21, 0(%sr2,%r20)

	ssm	PSW_SM_I, %r0

	b	lws_exit

	copy	%r0, %r21
@@ -521,7 +533,8 @@ lws_wouldblock: 


lws_pagefault:

	lws_pagefault_enable	%r1,%r21

	stw,ma	%r20, 0(%sr2,%r20)

	ldi	__ARCH_SPIN_LOCK_UNLOCKED_VAL, %r21

	stw,ma	%r21, 0(%sr2,%r20)

	ssm	PSW_SM_I, %r0

	ldo	3(%r0),%r28

	b	lws_exit
@@ -619,6 +632,7 @@ lws_compare_and_swap: 


	/* Try to acquire the lock */

	LDCW	0(%sr2,%r20), %r28

	spinlock_check	%r28, %r21

	comclr,<>	%r0, %r28, %r0

	b,n	lws_wouldblock
@@ -772,6 +786,7 @@ cas2_lock_start: 


	/* Try to acquire the lock */

	LDCW	0(%sr2,%r20), %r28

	spinlock_check	%r28, %r21

	comclr,<>	%r0, %r28, %r0

	b,n	lws_wouldblock
@@ -1001,6 +1016,7 @@ atomic_xchg_start: 


	/* Try to acquire the lock */

	LDCW	0(%sr2,%r20), %r28

	spinlock_check	%r28, %r21

	comclr,<>	%r0, %r28, %r0

	b,n	lws_wouldblock
@@ -1199,6 +1215,7 @@ atomic_store_start: 


	/* Try to acquire the lock */

	LDCW	0(%sr2,%r20), %r28

	spinlock_check	%r28, %r21

	comclr,<>	%r0, %r28, %r0

	b,n	lws_wouldblock
@@ -1330,7 +1347,7 @@ ENTRY(lws_lock_start) 
	/* lws locks */

	.rept 256

	/* Keep locks aligned at 16-bytes */

	.word 1

	.word __ARCH_SPIN_LOCK_UNLOCKED_VAL

	.word 0 

	.word 0

	.word 0