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@xxxxxx>
diff --git a/arch/parisc/include/asm/spinlock_types.h b/arch/parisc/include/asm/spinlock_types.h
index ca39ee350c3f..d65934079ebd 100644
--- a/arch/parisc/include/asm/spinlock_types.h
+++ b/arch/parisc/include/asm/spinlock_types.h
@@ -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;
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index a98940e64243..f7018a564f1d 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -308,6 +308,14 @@ config TLB_PTLOCK
updated consistently on SMP machines at the expense of some
loss in performance.
+config LIGHTWEIGHT_SPINLOCK_CHECK
+ bool "Add lightweight spinlock checks"
+ default y
+ help
+ Add lightweight checks to the spinlock functions to catch
+ memory overwrites at runtime. Those checks will not detect
+ uninitialized spinlocks.
+
config HOTPLUG_CPU
bool
default y if SMP
diff --git a/arch/parisc/include/asm/spinlock.h b/arch/parisc/include/asm/spinlock.h
index a6e5d66a7656..edfcb9858bcb 100644
--- a/arch/parisc/include/asm/spinlock.h
+++ b/arch/parisc/include/asm/spinlock.h
@@ -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;
}
/*
diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index f9696fbf646c..861cb19eb12c 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -308,6 +308,11 @@ static void handle_break(struct pt_regs *regs)
return;
}
#endif
+ if (IS_ENABLED(CONFIG_LIGHTWEIGHT_SPINLOCK_CHECK) &&
+ (iir == SPINLOCK_BREAK_INSN) &&
+ !user_mode(regs)) {
+ die_if_kernel("Spinlock was trashed", regs, 1);
+ }
if (unlikely(iir != GDB_BREAK_INSN))
parisc_printk_ratelimited(0, regs,
