---

yaml
---
r: 258331
b: refs/heads/master
c: aceb487
h: refs/heads/master
i:
  258329: 04bbeb3
  258327: 7facc1b
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 856bc356394a28edb8c388e31212f6ceb0a04ce6
+refs/heads/master: aceb487ab2ea0dca43f5131e456f45bc9f8c1bed

trunk/arch/arm/kernel/kprobes.c

@@ -34,10 +34,10 @@
 	min((unsigned long)MAX_STACK_SIZE,		\
 	    (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
 
-#define flush_insns(addr, cnt) 				\
+#define flush_insns(addr, size)				\
 	flush_icache_range((unsigned long)(addr),	\
 			   (unsigned long)(addr) +	\
-			   sizeof(kprobe_opcode_t) * (cnt))
+			   (size))
 
 /* Used as a marker in ARM_pc to note when we're in a jprobe. */
 #define JPROBE_MAGIC_ADDR		0xffffffff
@@ -86,7 +86,8 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 			return -ENOMEM;
 		for (is = 0; is < MAX_INSN_SIZE; ++is)
 			p->ainsn.insn[is] = tmp_insn[is];
-		flush_insns(p->ainsn.insn, MAX_INSN_SIZE);
+		flush_insns(p->ainsn.insn,
+				sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
 		break;
 
 	case INSN_GOOD_NO_SLOT:	/* instruction doesn't need insn slot */
@@ -97,24 +98,82 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 	return 0;
 }
 
+#ifdef CONFIG_THUMB2_KERNEL
+
+/*
+ * For a 32-bit Thumb breakpoint spanning two memory words we need to take
+ * special precautions to insert the breakpoint atomically, especially on SMP
+ * systems. This is achieved by calling this arming function using stop_machine.
+ */
+static int __kprobes set_t32_breakpoint(void *addr)
+{
+	((u16 *)addr)[0] = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION >> 16;
+	((u16 *)addr)[1] = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION & 0xffff;
+	flush_insns(addr, 2*sizeof(u16));
+	return 0;
+}
+
 void __kprobes arch_arm_kprobe(struct kprobe *p)
 {
-	*p->addr = KPROBE_BREAKPOINT_INSTRUCTION;
-	flush_insns(p->addr, 1);
+	uintptr_t addr = (uintptr_t)p->addr & ~1; /* Remove any Thumb flag */
+
+	if (!is_wide_instruction(p->opcode)) {
+		*(u16 *)addr = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
+		flush_insns(addr, sizeof(u16));
+	} else if (addr & 2) {
+		/* A 32-bit instruction spanning two words needs special care */
+		stop_machine(set_t32_breakpoint, (void *)addr, &cpu_online_map);
+	} else {
+		/* Word aligned 32-bit instruction can be written atomically */
+		u32 bkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
+#ifndef __ARMEB__ /* Swap halfwords for little-endian */
+		bkp = (bkp >> 16) | (bkp << 16);
+#endif
+		*(u32 *)addr = bkp;
+		flush_insns(addr, sizeof(u32));
+	}
 }
 
+#else /* !CONFIG_THUMB2_KERNEL */
+
+void __kprobes arch_arm_kprobe(struct kprobe *p)
+{
+	*p->addr = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
+	flush_insns(p->addr, sizeof(p->addr[0]));
+}
+
+#endif /* !CONFIG_THUMB2_KERNEL */
+
 /*
  * The actual disarming is done here on each CPU and synchronized using
  * stop_machine. This synchronization is necessary on SMP to avoid removing
  * a probe between the moment the 'Undefined Instruction' exception is raised
  * and the moment the exception handler reads the faulting instruction from
- * memory.
+ * memory. It is also needed to atomically set the two half-words of a 32-bit
+ * Thumb breakpoint.
  */
 int __kprobes __arch_disarm_kprobe(void *p)
 {
 	struct kprobe *kp = p;
+#ifdef CONFIG_THUMB2_KERNEL
+	u16 *addr = (u16 *)((uintptr_t)kp->addr & ~1);
+	kprobe_opcode_t insn = kp->opcode;
+	unsigned int len;
+
+	if (is_wide_instruction(insn)) {
+		((u16 *)addr)[0] = insn>>16;
+		((u16 *)addr)[1] = insn;
+		len = 2*sizeof(u16);
+	} else {
+		((u16 *)addr)[0] = insn;
+		len = sizeof(u16);
+	}
+	flush_insns(addr, len);
+
+#else /* !CONFIG_THUMB2_KERNEL */
 	*kp->addr = kp->opcode;
-	flush_insns(kp->addr, 1);
+	flush_insns(kp->addr, sizeof(kp->addr[0]));
+#endif
 	return 0;
 }
 
@@ -167,11 +226,23 @@ void __kprobes kprobe_handler(struct pt_regs *regs)
 {
 	struct kprobe *p, *cur;
 	struct kprobe_ctlblk *kcb;
-	kprobe_opcode_t	*addr = (kprobe_opcode_t *)regs->ARM_pc;
 
 	kcb = get_kprobe_ctlblk();
 	cur = kprobe_running();
-	p = get_kprobe(addr);
+
+#ifdef CONFIG_THUMB2_KERNEL
+	/*
+	 * First look for a probe which was registered using an address with
+	 * bit 0 set, this is the usual situation for pointers to Thumb code.
+	 * If not found, fallback to looking for one with bit 0 clear.
+	 */
+	p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
+	if (!p)
+		p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
+
+#else /* ! CONFIG_THUMB2_KERNEL */
+	p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
+#endif
 
 	if (p) {
 		if (cur) {
@@ -511,17 +582,44 @@ int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 	return 0;
 }
 
-static struct undef_hook kprobes_break_hook = {
+#ifdef CONFIG_THUMB2_KERNEL
+
+static struct undef_hook kprobes_thumb16_break_hook = {
+	.instr_mask	= 0xffff,
+	.instr_val	= KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
+	.cpsr_mask	= MODE_MASK,
+	.cpsr_val	= SVC_MODE,
+	.fn		= kprobe_trap_handler,
+};
+
+static struct undef_hook kprobes_thumb32_break_hook = {
+	.instr_mask	= 0xffffffff,
+	.instr_val	= KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
+	.cpsr_mask	= MODE_MASK,
+	.cpsr_val	= SVC_MODE,
+	.fn		= kprobe_trap_handler,
+};
+
+#else  /* !CONFIG_THUMB2_KERNEL */
+
+static struct undef_hook kprobes_arm_break_hook = {
 	.instr_mask	= 0xffffffff,
-	.instr_val	= KPROBE_BREAKPOINT_INSTRUCTION,
+	.instr_val	= KPROBE_ARM_BREAKPOINT_INSTRUCTION,
 	.cpsr_mask	= MODE_MASK,
 	.cpsr_val	= SVC_MODE,
 	.fn		= kprobe_trap_handler,
 };
 
+#endif /* !CONFIG_THUMB2_KERNEL */
+
 int __init arch_init_kprobes()
 {
 	arm_kprobe_decode_init();
-	register_undef_hook(&kprobes_break_hook);
+#ifdef CONFIG_THUMB2_KERNEL
+	register_undef_hook(&kprobes_thumb16_break_hook);
+	register_undef_hook(&kprobes_thumb32_break_hook);
+#else
+	register_undef_hook(&kprobes_arm_break_hook);
+#endif
 	return 0;
 }

trunk/arch/arm/kernel/kprobes.h

@@ -18,10 +18,13 @@
 #define _ARM_KERNEL_KPROBES_H
 
 /*
- * This undefined instruction must be unique and
+ * These undefined instructions must be unique and
  * reserved solely for kprobes' use.
  */
-#define KPROBE_BREAKPOINT_INSTRUCTION	0xe7f001f8
+#define KPROBE_ARM_BREAKPOINT_INSTRUCTION	0xe7f001f8
+#define KPROBE_THUMB16_BREAKPOINT_INSTRUCTION	0xde18
+#define KPROBE_THUMB32_BREAKPOINT_INSTRUCTION	0xf7f0a018
+
 
 enum kprobe_insn {
 	INSN_REJECTED,