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parisc: Add lightweight spinlock checks

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Add a lightweight spinlock check which uses only two instructions
per spinlock call. It detects if a spinlock has been trashed by
some memory corruption and then halts the kernel. It will not detect
uninitialized spinlocks, for which CONFIG_DEBUG_SPINLOCK needs to
be enabled.

This lightweight spinlock check shouldn't influence runtime, so it's
safe to enable it by default.

The __ARCH_SPIN_LOCK_UNLOCKED_VAL constant has been choosen small enough
to be able to be loaded by one LDI assembler statement.

Signed-off-by: Helge Deller <deller@gmx.de>
This commit is contained in:
Helge Deller 2023-05-22 15:11:16 +02:00
parent b6405f0829
commit 15e64ef652
4 changed files with 61 additions and 7 deletions
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11
arch/parisc/Kconfig.debug
View File

@ -1 +1,12 @@
# SPDX-License-Identifier: GPL-2.0
#
config LIGHTWEIGHT_SPINLOCK_CHECK
bool "Enable lightweight spinlock checks"
depends on SMP && !DEBUG_SPINLOCK
default y
help
Add checks with low performance impact to the spinlock functions
to catch memory overwrites at runtime. For more advanced
spinlock debugging you should choose the DEBUG_SPINLOCK option
which will detect unitialized spinlocks too.
If unsure say Y here.

39
arch/parisc/include/asm/spinlock.h
View File

@ -7,10 +7,26 @@
#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))
asm volatile( "andcm,= %0,%1,%%r0\n"
".word %2\n"
: : "r" (lock_val), "r" (__ARCH_SPIN_LOCK_UNLOCKED_VAL),
"i" (SPINLOCK_BREAK_INSN));
}
static inline int arch_spin_is_locked(arch_spinlock_t *x)
{
volatile unsigned int *a = __ldcw_align(x);
return READ_ONCE(*a) == 0;
volatile unsigned int *a;
int lock_val;
a = __ldcw_align(x);
lock_val = READ_ONCE(*a);
arch_spin_val_check(lock_val);
return (lock_val == 0);
}
static inline void arch_spin_lock(arch_spinlock_t *x)
@ -18,9 +34,18 @@ static inline void arch_spin_lock(arch_spinlock_t *x)
volatile unsigned int *a;
a = __ldcw_align(x);
while (__ldcw(a) == 0)
do {
int lock_val_old;
lock_val_old = __ldcw(a);
arch_spin_val_check(lock_val_old);
if (lock_val_old)
return; /* got lock */
/* wait until we should try to get lock again */
while (*a == 0)
continue;
} while (1);
}
static inline void arch_spin_unlock(arch_spinlock_t *x)
@ -29,15 +54,19 @@ static inline void arch_spin_unlock(arch_spinlock_t *x)
a = __ldcw_align(x);
/* Release with ordered store. */
__asm__ __volatile__("stw,ma %0,0(%1)" : : "r"(1), "r"(a) : "memory");
__asm__ __volatile__("stw,ma %0,0(%1)"
: : "r"(__ARCH_SPIN_LOCK_UNLOCKED_VAL), "r"(a) : "memory");
}
static inline int arch_spin_trylock(arch_spinlock_t *x)
{
volatile unsigned int *a;
int lock_val;
a = __ldcw_align(x);
return __ldcw(a) != 0;
lock_val = __ldcw(a);
arch_spin_val_check(lock_val);
return lock_val != 0;
}
/*

8
arch/parisc/include/asm/spinlock_types.h
View File

@ -2,13 +2,17 @@
#ifndef __ASM_SPINLOCK_TYPES_H
#define __ASM_SPINLOCK_TYPES_H
#define __ARCH_SPIN_LOCK_UNLOCKED_VAL 0x1a46
typedef struct {
#ifdef CONFIG_PA20
volatile unsigned int slock;
# define __ARCH_SPIN_LOCK_UNLOCKED { 1 }
# define __ARCH_SPIN_LOCK_UNLOCKED { __ARCH_SPIN_LOCK_UNLOCKED_VAL }
#else
volatile unsigned int lock[4];
# define __ARCH_SPIN_LOCK_UNLOCKED { { 1, 1, 1, 1 } }
# define __ARCH_SPIN_LOCK_UNLOCKED \
{ { __ARCH_SPIN_LOCK_UNLOCKED_VAL, __ARCH_SPIN_LOCK_UNLOCKED_VAL, \
__ARCH_SPIN_LOCK_UNLOCKED_VAL, __ARCH_SPIN_LOCK_UNLOCKED_VAL } }
#endif
} arch_spinlock_t;

10
arch/parisc/kernel/traps.c
View File

@ -47,6 +47,10 @@
#include <linux/kgdb.h>
#include <linux/kprobes.h>
#if defined(CONFIG_LIGHTWEIGHT_SPINLOCK_CHECK)
#include <asm/spinlock.h>
#endif
#include "../math-emu/math-emu.h" /* for handle_fpe() */
static void parisc_show_stack(struct task_struct *task,
@ -309,6 +313,12 @@ static void handle_break(struct pt_regs *regs)
}
#endif
#ifdef CONFIG_LIGHTWEIGHT_SPINLOCK_CHECK
if ((iir == SPINLOCK_BREAK_INSN) && !user_mode(regs)) {
die_if_kernel("Spinlock was trashed", regs, 1);
}
#endif
if (unlikely(iir != GDB_BREAK_INSN))
parisc_printk_ratelimited(0, regs,
KERN_DEBUG "break %d,%d: pid=%d command='%s'\n",