1 files changed, 311 insertions, 188 deletions

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index de7353c0ce9..703130f469e 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1,18 +1,21 @@
+#define pr_fmt(fmt) "SMP alternatives: " fmt
+
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/mutex.h>
 #include <linux/list.h>
 #include <linux/stringify.h>
-#include <linux/kprobes.h>
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
 #include <linux/memory.h>
+#include <linux/stop_machine.h>
+#include <linux/slab.h>
+#include <linux/kdebug.h>
 #include <asm/alternative.h>
 #include <asm/sections.h>
 #include <asm/pgtable.h>
 #include <asm/mce.h>
 #include <asm/nmi.h>
-#include <asm/vsyscall.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 #include <asm/io.h>
@@ -20,19 +23,6 @@
 
 #define MAX_PATCH_LEN (255-1)
 
-#ifdef CONFIG_HOTPLUG_CPU
-static int smp_alt_once;
-
-static int __init bootonly(char *str)
-{
-	smp_alt_once = 1;
-	return 1;
-}
-__setup("smp-alt-boot", bootonly);
-#else
-#define smp_alt_once 1
-#endif
-
 static int __initdata_or_module debug_alternative;
 
 static int __init debug_alt(char *str)
@@ -62,20 +52,36 @@ static int __init setup_noreplace_paravirt(char *str)
 __setup("noreplace-paravirt", setup_noreplace_paravirt);
 #endif
 
-#define DPRINTK(fmt, args...) if (debug_alternative) \
-	printk(KERN_DEBUG fmt, args)
-
+#define DPRINTK(fmt, ...)				\
+do {							\
+	if (debug_alternative)				\
+		printk(KERN_DEBUG fmt, ##__VA_ARGS__);	\
+} while (0)
+
+/*
+ * Each GENERIC_NOPX is of X bytes, and defined as an array of bytes
+ * that correspond to that nop. Getting from one nop to the next, we
+ * add to the array the offset that is equal to the sum of all sizes of
+ * nops preceding the one we are after.
+ *
+ * Note: The GENERIC_NOP5_ATOMIC is at the end, as it breaks the
+ * nice symmetry of sizes of the previous nops.
+ */
 #if defined(GENERIC_NOP1) && !defined(CONFIG_X86_64)
-/* Use inline assembly to define this because the nops are defined
-   as inline assembly strings in the include files and we cannot
-   get them easily into strings. */
-asm("\t" __stringify(__INITRODATA_OR_MODULE) "\nintelnops: "
-	GENERIC_NOP1 GENERIC_NOP2 GENERIC_NOP3 GENERIC_NOP4 GENERIC_NOP5 GENERIC_NOP6
-	GENERIC_NOP7 GENERIC_NOP8
-    "\t.previous");
-extern const unsigned char intelnops[];
-static const unsigned char *const __initconst_or_module
-intel_nops[ASM_NOP_MAX+1] = {
+static const unsigned char intelnops[] =
+{
+	GENERIC_NOP1,
+	GENERIC_NOP2,
+	GENERIC_NOP3,
+	GENERIC_NOP4,
+	GENERIC_NOP5,
+	GENERIC_NOP6,
+	GENERIC_NOP7,
+	GENERIC_NOP8,
+	GENERIC_NOP5_ATOMIC
+};
+static const unsigned char * const intel_nops[ASM_NOP_MAX+2] =
+{
 	NULL,
 	intelnops,
 	intelnops + 1,
@@ -85,17 +91,25 @@ intel_nops[ASM_NOP_MAX+1] = {
 	intelnops + 1 + 2 + 3 + 4 + 5,
 	intelnops + 1 + 2 + 3 + 4 + 5 + 6,
 	intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
+	intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
 };
 #endif
 
 #ifdef K8_NOP1
-asm("\t" __stringify(__INITRODATA_OR_MODULE) "\nk8nops: "
-	K8_NOP1 K8_NOP2 K8_NOP3 K8_NOP4 K8_NOP5 K8_NOP6
-	K8_NOP7 K8_NOP8
-    "\t.previous");
-extern const unsigned char k8nops[];
-static const unsigned char *const __initconst_or_module
-k8_nops[ASM_NOP_MAX+1] = {
+static const unsigned char k8nops[] =
+{
+	K8_NOP1,
+	K8_NOP2,
+	K8_NOP3,
+	K8_NOP4,
+	K8_NOP5,
+	K8_NOP6,
+	K8_NOP7,
+	K8_NOP8,
+	K8_NOP5_ATOMIC
+};
+static const unsigned char * const k8_nops[ASM_NOP_MAX+2] =
+{
 	NULL,
 	k8nops,
 	k8nops + 1,
@@ -105,17 +119,25 @@ k8_nops[ASM_NOP_MAX+1] = {
 	k8nops + 1 + 2 + 3 + 4 + 5,
 	k8nops + 1 + 2 + 3 + 4 + 5 + 6,
 	k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
+	k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
 };
 #endif
 
 #if defined(K7_NOP1) && !defined(CONFIG_X86_64)
-asm("\t" __stringify(__INITRODATA_OR_MODULE) "\nk7nops: "
-	K7_NOP1 K7_NOP2 K7_NOP3 K7_NOP4 K7_NOP5 K7_NOP6
-	K7_NOP7 K7_NOP8
-    "\t.previous");
-extern const unsigned char k7nops[];
-static const unsigned char *const __initconst_or_module
-k7_nops[ASM_NOP_MAX+1] = {
+static const unsigned char k7nops[] =
+{
+	K7_NOP1,
+	K7_NOP2,
+	K7_NOP3,
+	K7_NOP4,
+	K7_NOP5,
+	K7_NOP6,
+	K7_NOP7,
+	K7_NOP8,
+	K7_NOP5_ATOMIC
+};
+static const unsigned char * const k7_nops[ASM_NOP_MAX+2] =
+{
 	NULL,
 	k7nops,
 	k7nops + 1,
@@ -125,17 +147,25 @@ k7_nops[ASM_NOP_MAX+1] = {
 	k7nops + 1 + 2 + 3 + 4 + 5,
 	k7nops + 1 + 2 + 3 + 4 + 5 + 6,
 	k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
+	k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
 };
 #endif
 
 #ifdef P6_NOP1
-asm("\t" __stringify(__INITRODATA_OR_MODULE) "\np6nops: "
-	P6_NOP1 P6_NOP2 P6_NOP3 P6_NOP4 P6_NOP5 P6_NOP6
-	P6_NOP7 P6_NOP8
-    "\t.previous");
-extern const unsigned char p6nops[];
-static const unsigned char *const __initconst_or_module
-p6_nops[ASM_NOP_MAX+1] = {
+static const unsigned char p6nops[] =
+{
+	P6_NOP1,
+	P6_NOP2,
+	P6_NOP3,
+	P6_NOP4,
+	P6_NOP5,
+	P6_NOP6,
+	P6_NOP7,
+	P6_NOP8,
+	P6_NOP5_ATOMIC
+};
+static const unsigned char * const p6_nops[ASM_NOP_MAX+2] =
+{
 	NULL,
 	p6nops,
 	p6nops + 1,
@@ -145,59 +175,77 @@ p6_nops[ASM_NOP_MAX+1] = {
 	p6nops + 1 + 2 + 3 + 4 + 5,
 	p6nops + 1 + 2 + 3 + 4 + 5 + 6,
 	p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
+	p6nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
 };
 #endif
 
+/* Initialize these to a safe default */
 #ifdef CONFIG_X86_64
+const unsigned char * const *ideal_nops = p6_nops;
+#else
+const unsigned char * const *ideal_nops = intel_nops;
+#endif
 
-extern char __vsyscall_0;
-static const unsigned char *const *__init_or_module find_nop_table(void)
-{
-	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
-	    boot_cpu_has(X86_FEATURE_NOPL))
-		return p6_nops;
-	else
-		return k8_nops;
-}
-
-#else /* CONFIG_X86_64 */
-
-static const unsigned char *const *__init_or_module find_nop_table(void)
+void __init arch_init_ideal_nops(void)
 {
-	if (boot_cpu_has(X86_FEATURE_K8))
-		return k8_nops;
-	else if (boot_cpu_has(X86_FEATURE_K7))
-		return k7_nops;
-	else if (boot_cpu_has(X86_FEATURE_NOPL))
-		return p6_nops;
-	else
-		return intel_nops;
+	switch (boot_cpu_data.x86_vendor) {
+	case X86_VENDOR_INTEL:
+		/*
+		 * Due to a decoder implementation quirk, some
+		 * specific Intel CPUs actually perform better with
+		 * the "k8_nops" than with the SDM-recommended NOPs.
+		 */
+		if (boot_cpu_data.x86 == 6 &&
+		    boot_cpu_data.x86_model >= 0x0f &&
+		    boot_cpu_data.x86_model != 0x1c &&
+		    boot_cpu_data.x86_model != 0x26 &&
+		    boot_cpu_data.x86_model != 0x27 &&
+		    boot_cpu_data.x86_model < 0x30) {
+			ideal_nops = k8_nops;
+		} else if (boot_cpu_has(X86_FEATURE_NOPL)) {
+			   ideal_nops = p6_nops;
+		} else {
+#ifdef CONFIG_X86_64
+			ideal_nops = k8_nops;
+#else
+			ideal_nops = intel_nops;
+#endif
+		}
+		break;
+	default:
+#ifdef CONFIG_X86_64
+		ideal_nops = k8_nops;
+#else
+		if (boot_cpu_has(X86_FEATURE_K8))
+			ideal_nops = k8_nops;
+		else if (boot_cpu_has(X86_FEATURE_K7))
+			ideal_nops = k7_nops;
+		else
+			ideal_nops = intel_nops;
+#endif
+	}
 }
 
-#endif /* CONFIG_X86_64 */
-
 /* Use this to add nops to a buffer, then text_poke the whole buffer. */
 static void __init_or_module add_nops(void *insns, unsigned int len)
 {
-	const unsigned char *const *noptable = find_nop_table();
-
 	while (len > 0) {
 		unsigned int noplen = len;
 		if (noplen > ASM_NOP_MAX)
 			noplen = ASM_NOP_MAX;
-		memcpy(insns, noptable[noplen], noplen);
+		memcpy(insns, ideal_nops[noplen], noplen);
 		insns += noplen;
 		len -= noplen;
 	}
 }
 
 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
-extern u8 *__smp_locks[], *__smp_locks_end[];
-static void *text_poke_early(void *addr, const void *opcode, size_t len);
+extern s32 __smp_locks[], __smp_locks_end[];
+void *text_poke_early(void *addr, const void *opcode, size_t len);
 
 /* Replace instructions with better alternatives for this CPU type.
    This runs before SMP is initialized to avoid SMP problems with
-   self modifying code. This implies that assymetric systems where
+   self modifying code. This implies that asymmetric systems where
    APs have less capabilities than the boot processor are not handled.
    Tough. Make sure you disable such features by hand. */
 
@@ -205,64 +253,76 @@ void __init_or_module apply_alternatives(struct alt_instr *start,
 					 struct alt_instr *end)
 {
 	struct alt_instr *a;
-	char insnbuf[MAX_PATCH_LEN];
+	u8 *instr, *replacement;
+	u8 insnbuf[MAX_PATCH_LEN];
 
 	DPRINTK("%s: alt table %p -> %p\n", __func__, start, end);
+	/*
+	 * The scan order should be from start to end. A later scanned
+	 * alternative code can overwrite a previous scanned alternative code.
+	 * Some kernel functions (e.g. memcpy, memset, etc) use this order to
+	 * patch code.
+	 *
+	 * So be careful if you want to change the scan order to any other
+	 * order.
+	 */
 	for (a = start; a < end; a++) {
-		u8 *instr = a->instr;
+		instr = (u8 *)&a->instr_offset + a->instr_offset;
+		replacement = (u8 *)&a->repl_offset + a->repl_offset;
 		BUG_ON(a->replacementlen > a->instrlen);
 		BUG_ON(a->instrlen > sizeof(insnbuf));
+		BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
 		if (!boot_cpu_has(a->cpuid))
 			continue;
-#ifdef CONFIG_X86_64
-		/* vsyscall code is not mapped yet. resolve it manually. */
-		if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) {
-			instr = __va(instr - (u8*)VSYSCALL_START + (u8*)__pa_symbol(&__vsyscall_0));
-			DPRINTK("%s: vsyscall fixup: %p => %p\n",
-				__func__, a->instr, instr);
-		}
-#endif
-		memcpy(insnbuf, a->replacement, a->replacementlen);
+
+		memcpy(insnbuf, replacement, a->replacementlen);
+
+		/* 0xe8 is a relative jump; fix the offset. */
+		if (*insnbuf == 0xe8 && a->replacementlen == 5)
+		    *(s32 *)(insnbuf + 1) += replacement - instr;
+
 		add_nops(insnbuf + a->replacementlen,
 			 a->instrlen - a->replacementlen);
+
 		text_poke_early(instr, insnbuf, a->instrlen);
 	}
 }
 
 #ifdef CONFIG_SMP
 
-static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end)
+static void alternatives_smp_lock(const s32 *start, const s32 *end,
+				  u8 *text, u8 *text_end)
 {
-	u8 **ptr;
+	const s32 *poff;
 
 	mutex_lock(&text_mutex);
-	for (ptr = start; ptr < end; ptr++) {
-		if (*ptr < text)
-			continue;
-		if (*ptr > text_end)
+	for (poff = start; poff < end; poff++) {
+		u8 *ptr = (u8 *)poff + *poff;
+
+		if (!*poff || ptr < text || ptr >= text_end)
 			continue;
 		/* turn DS segment override prefix into lock prefix */
-		text_poke(*ptr, ((unsigned char []){0xf0}), 1);
-	};
+		if (*ptr == 0x3e)
+			text_poke(ptr, ((unsigned char []){0xf0}), 1);
+	}
 	mutex_unlock(&text_mutex);
 }
 
-static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end)
+static void alternatives_smp_unlock(const s32 *start, const s32 *end,
+				    u8 *text, u8 *text_end)
 {
-	u8 **ptr;
-
-	if (noreplace_smp)
-		return;
+	const s32 *poff;
 
 	mutex_lock(&text_mutex);
-	for (ptr = start; ptr < end; ptr++) {
-		if (*ptr < text)
-			continue;
-		if (*ptr > text_end)
+	for (poff = start; poff < end; poff++) {
+		u8 *ptr = (u8 *)poff + *poff;
+
+		if (!*poff || ptr < text || ptr >= text_end)
 			continue;
 		/* turn lock prefix into DS segment override prefix */
-		text_poke(*ptr, ((unsigned char []){0x3E}), 1);
-	};
+		if (*ptr == 0xf0)
+			text_poke(ptr, ((unsigned char []){0x3E}), 1);
+	}
 	mutex_unlock(&text_mutex);
 }
 
@@ -272,8 +332,8 @@ struct smp_alt_module {
 	char		*name;
 
 	/* ptrs to lock prefixes */
-	u8		**locks;
-	u8		**locks_end;
+	const s32	*locks;
+	const s32	*locks_end;
 
 	/* .text segment, needed to avoid patching init code ;) */
 	u8		*text;
@@ -283,7 +343,7 @@ struct smp_alt_module {
 };
 static LIST_HEAD(smp_alt_modules);
 static DEFINE_MUTEX(smp_alt);
-static int smp_mode = 1;	/* protected by smp_alt */
+static bool uniproc_patched = false;	/* protected by smp_alt */
 
 void __init_or_module alternatives_smp_module_add(struct module *mod,
 						  char *name,
@@ -292,19 +352,18 @@ void __init_or_module alternatives_smp_module_add(struct module *mod,
 {
 	struct smp_alt_module *smp;
 
-	if (noreplace_smp)
-		return;
+	mutex_lock(&smp_alt);
+	if (!uniproc_patched)
+		goto unlock;
 
-	if (smp_alt_once) {
-		if (boot_cpu_has(X86_FEATURE_UP))
-			alternatives_smp_unlock(locks, locks_end,
-						text, text_end);
-		return;
-	}
+	if (num_possible_cpus() == 1)
+		/* Don't bother remembering, we'll never have to undo it. */
+		goto smp_unlock;
 
 	smp = kzalloc(sizeof(*smp), GFP_KERNEL);
 	if (NULL == smp)
-		return; /* we'll run the (safe but slow) SMP code then ... */
+		/* we'll run the (safe but slow) SMP code then ... */
+		goto unlock;
 
 	smp->mod	= mod;
 	smp->name	= name;
@@ -316,11 +375,10 @@ void __init_or_module alternatives_smp_module_add(struct module *mod,
 		__func__, smp->locks, smp->locks_end,
 		smp->text, smp->text_end, smp->name);
 
-	mutex_lock(&smp_alt);
 	list_add_tail(&smp->next, &smp_alt_modules);
-	if (boot_cpu_has(X86_FEATURE_UP))
-		alternatives_smp_unlock(smp->locks, smp->locks_end,
-					smp->text, smp->text_end);
+smp_unlock:
+	alternatives_smp_unlock(locks, locks_end, text, text_end);
+unlock:
 	mutex_unlock(&smp_alt);
 }
 
@@ -328,68 +386,60 @@ void __init_or_module alternatives_smp_module_del(struct module *mod)
 {
 	struct smp_alt_module *item;
 
-	if (smp_alt_once || noreplace_smp)
-		return;
-
 	mutex_lock(&smp_alt);
 	list_for_each_entry(item, &smp_alt_modules, next) {
 		if (mod != item->mod)
 			continue;
 		list_del(&item->next);
-		mutex_unlock(&smp_alt);
-		DPRINTK("%s: %s\n", __func__, item->name);
 		kfree(item);
-		return;
+		break;
 	}
 	mutex_unlock(&smp_alt);
 }
 
-void alternatives_smp_switch(int smp)
+void alternatives_enable_smp(void)
 {
 	struct smp_alt_module *mod;
 
-#ifdef CONFIG_LOCKDEP
-	/*
-	 * Older binutils section handling bug prevented
-	 * alternatives-replacement from working reliably.
-	 *
-	 * If this still occurs then you should see a hang
-	 * or crash shortly after this line:
-	 */
-	printk("lockdep: fixing up alternatives.\n");
-#endif
-
-	if (noreplace_smp || smp_alt_once)
-		return;
-	BUG_ON(!smp && (num_online_cpus() > 1));
+	/* Why bother if there are no other CPUs? */
+	BUG_ON(num_possible_cpus() == 1);
 
 	mutex_lock(&smp_alt);
 
-	/*
-	 * Avoid unnecessary switches because it forces JIT based VMs to
-	 * throw away all cached translations, which can be quite costly.
-	 */
-	if (smp == smp_mode) {
-		/* nothing */
-	} else if (smp) {
-		printk(KERN_INFO "SMP alternatives: switching to SMP code\n");
+	if (uniproc_patched) {
+		pr_info("switching to SMP code\n");
+		BUG_ON(num_online_cpus() != 1);
 		clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
 		clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
 		list_for_each_entry(mod, &smp_alt_modules, next)
 			alternatives_smp_lock(mod->locks, mod->locks_end,
 					      mod->text, mod->text_end);
-	} else {
-		printk(KERN_INFO "SMP alternatives: switching to UP code\n");
-		set_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
-		set_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
-		list_for_each_entry(mod, &smp_alt_modules, next)
-			alternatives_smp_unlock(mod->locks, mod->locks_end,
-						mod->text, mod->text_end);
+		uniproc_patched = false;
 	}
-	smp_mode = smp;
 	mutex_unlock(&smp_alt);
 }
 
+/* Return 1 if the address range is reserved for smp-alternatives */
+int alternatives_text_reserved(void *start, void *end)
+{
+	struct smp_alt_module *mod;
+	const s32 *poff;
+	u8 *text_start = start;
+	u8 *text_end = end;
+
+	list_for_each_entry(mod, &smp_alt_modules, next) {
+		if (mod->text > text_end || mod->text_end < text_start)
+			continue;
+		for (poff = mod->locks; poff < mod->locks_end; poff++) {
+			const u8 *ptr = (const u8 *)poff + *poff;
+
+			if (text_start <= ptr && text_end > ptr)
+				return 1;
+		}
+	}
+
+	return 0;
+}
 #endif
 
 #ifdef CONFIG_PARAVIRT
@@ -442,40 +492,22 @@ void __init alternative_instructions(void)
 
 	apply_alternatives(__alt_instructions, __alt_instructions_end);
 
-	/* switch to patch-once-at-boottime-only mode and free the
-	 * tables in case we know the number of CPUs will never ever
-	 * change */
-#ifdef CONFIG_HOTPLUG_CPU
-	if (num_possible_cpus() < 2)
-		smp_alt_once = 1;
-#endif
-
 #ifdef CONFIG_SMP
-	if (smp_alt_once) {
-		if (1 == num_possible_cpus()) {
-			printk(KERN_INFO "SMP alternatives: switching to UP code\n");
-			set_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
-			set_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
-
-			alternatives_smp_unlock(__smp_locks, __smp_locks_end,
-						_text, _etext);
-		}
-	} else {
+	/* Patch to UP if other cpus not imminent. */
+	if (!noreplace_smp && (num_present_cpus() == 1 || setup_max_cpus <= 1)) {
+		uniproc_patched = true;
 		alternatives_smp_module_add(NULL, "core kernel",
 					    __smp_locks, __smp_locks_end,
 					    _text, _etext);
-
-		/* Only switch to UP mode if we don't immediately boot others */
-		if (num_present_cpus() == 1 || setup_max_cpus <= 1)
-			alternatives_smp_switch(0);
 	}
-#endif
- 	apply_paravirt(__parainstructions, __parainstructions_end);
 
-	if (smp_alt_once)
+	if (!uniproc_patched || num_possible_cpus() == 1)
 		free_init_pages("SMP alternatives",
 				(unsigned long)__smp_locks,
 				(unsigned long)__smp_locks_end);
+#endif
+
+	apply_paravirt(__parainstructions, __parainstructions_end);
 
 	restart_nmi();
 }
@@ -492,7 +524,7 @@ void __init alternative_instructions(void)
  * instructions. And on the local CPU you need to be protected again NMI or MCE
  * handlers seeing an inconsistent instruction while you patch.
  */
-static void *__init_or_module text_poke_early(void *addr, const void *opcode,
+void *__init_or_module text_poke_early(void *addr, const void *opcode,
 					      size_t len)
 {
 	unsigned long flags;
@@ -518,7 +550,7 @@ static void *__init_or_module text_poke_early(void *addr, const void *opcode,
  *
  * Note: Must be called under text_mutex.
  */
-void *__kprobes text_poke(void *addr, const void *opcode, size_t len)
+void *text_poke(void *addr, const void *opcode, size_t len)
 {
 	unsigned long flags;
 	char *vaddr;
@@ -552,3 +584,94 @@ void *__kprobes text_poke(void *addr, const void *opcode, size_t len)
 	local_irq_restore(flags);
 	return addr;
 }
+
+static void do_sync_core(void *info)
+{
+	sync_core();
+}
+
+static bool bp_patching_in_progress;
+static void *bp_int3_handler, *bp_int3_addr;
+
+int poke_int3_handler(struct pt_regs *regs)
+{
+	/* bp_patching_in_progress */
+	smp_rmb();
+
+	if (likely(!bp_patching_in_progress))
+		return 0;
+
+	if (user_mode_vm(regs) || regs->ip != (unsigned long)bp_int3_addr)
+		return 0;
+
+	/* set up the specified breakpoint handler */
+	regs->ip = (unsigned long) bp_int3_handler;
+
+	return 1;
+
+}
+
+/**
+ * text_poke_bp() -- update instructions on live kernel on SMP
+ * @addr:	address to patch
+ * @opcode:	opcode of new instruction
+ * @len:	length to copy
+ * @handler:	address to jump to when the temporary breakpoint is hit
+ *
+ * Modify multi-byte instruction by using int3 breakpoint on SMP.
+ * We completely avoid stop_machine() here, and achieve the
+ * synchronization using int3 breakpoint.
+ *
+ * The way it is done:
+ *	- add a int3 trap to the address that will be patched
+ *	- sync cores
+ *	- update all but the first byte of the patched range
+ *	- sync cores
+ *	- replace the first byte (int3) by the first byte of
+ *	  replacing opcode
+ *	- sync cores
+ *
+ * Note: must be called under text_mutex.
+ */
+void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
+{
+	unsigned char int3 = 0xcc;
+
+	bp_int3_handler = handler;
+	bp_int3_addr = (u8 *)addr + sizeof(int3);
+	bp_patching_in_progress = true;
+	/*
+	 * Corresponding read barrier in int3 notifier for
+	 * making sure the in_progress flags is correctly ordered wrt.
+	 * patching
+	 */
+	smp_wmb();
+
+	text_poke(addr, &int3, sizeof(int3));
+
+	on_each_cpu(do_sync_core, NULL, 1);
+
+	if (len - sizeof(int3) > 0) {
+		/* patch all but the first byte */
+		text_poke((char *)addr + sizeof(int3),
+			  (const char *) opcode + sizeof(int3),
+			  len - sizeof(int3));
+		/*
+		 * According to Intel, this core syncing is very likely
+		 * not necessary and we'd be safe even without it. But
+		 * better safe than sorry (plus there's not only Intel).
+		 */
+		on_each_cpu(do_sync_core, NULL, 1);
+	}
+
+	/* patch the first byte */
+	text_poke(addr, opcode, sizeof(int3));
+
+	on_each_cpu(do_sync_core, NULL, 1);
+
+	bp_patching_in_progress = false;
+	smp_wmb();
+
+	return addr;
+}
+