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authorHelge Deller <deller@gmx.de>2023-05-22 15:11:16 +0200
committerHelge Deller <deller@gmx.de>2023-05-24 14:23:07 +0200
commit15e64ef6520ea8702998db05b87fa5c3d3d40710 (patch)
treeb7f67430b55167a2aeae50fd95fd4d4c50e2d2f8 /arch
parentb6405f0829d7b1dd926ba3ca5f691cab835abfaa (diff)
parisc: Add lightweight spinlock checks
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/parisc/Kconfig.debug11
-rw-r--r--arch/parisc/include/asm/spinlock.h39
-rw-r--r--arch/parisc/include/asm/spinlock_types.h8
-rw-r--r--arch/parisc/kernel/traps.c10
4 files changed, 61 insertions, 7 deletions
diff --git a/arch/parisc/Kconfig.debug b/arch/parisc/Kconfig.debug
index f66554cd5c45..3a059cb5e112 100644
--- a/arch/parisc/Kconfig.debug
+++ b/arch/parisc/Kconfig.debug
@@ -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.
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/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/kernel/traps.c b/arch/parisc/kernel/traps.c
index f9696fbf646c..13df6169f9e2 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -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",