3 files changed, 50 insertions, 16 deletions

diff --git a/arch/i386/kernel/alternative.c b/arch/i386/kernel/alternative.c
index 0695be538de..206ea2ca63c 100644
--- a/arch/i386/kernel/alternative.c
+++ b/arch/i386/kernel/alternative.c
@@ -2,8 +2,12 @@
 #include <linux/sched.h>
 #include <linux/spinlock.h>
 #include <linux/list.h>
+#include <linux/kprobes.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
 #include <asm/alternative.h>
 #include <asm/sections.h>
+#include <asm/pgtable.h>
 
 #ifdef CONFIG_HOTPLUG_CPU
 static int smp_alt_once;
@@ -150,7 +154,7 @@ static void nop_out(void *insns, unsigned int len)
 		unsigned int noplen = len;
 		if (noplen > ASM_NOP_MAX)
 			noplen = ASM_NOP_MAX;
-		memcpy(insns, noptable[noplen], noplen);
+		text_poke(insns, noptable[noplen], noplen);
 		insns += noplen;
 		len -= noplen;
 	}
@@ -202,7 +206,7 @@ static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end)
 			continue;
 		if (*ptr > text_end)
 			continue;
-		**ptr = 0xf0; /* lock prefix */
+		text_poke(*ptr, ((unsigned char []){0xf0}), 1); /* add lock prefix */
 	};
 }
 
@@ -360,10 +364,6 @@ void apply_paravirt(struct paravirt_patch_site *start,
 		/* Pad the rest with nops */
 		nop_out(p->instr + used, p->len - used);
 	}
-
-	/* Sync to be conservative, in case we patched following
-	 * instructions */
-	sync_core();
 }
 extern struct paravirt_patch_site __start_parainstructions[],
 	__stop_parainstructions[];
@@ -406,3 +406,31 @@ void __init alternative_instructions(void)
  	apply_paravirt(__parainstructions, __parainstructions_end);
 	local_irq_restore(flags);
 }
+
+/*
+ * Warning:
+ * When you use this code to patch more than one byte of an instruction
+ * you need to make sure that other CPUs cannot execute this code in parallel.
+ * Also no thread must be currently preempted in the middle of these instructions.
+ * And on the local CPU you need to be protected again NMI or MCE handlers
+ * seeing an inconsistent instruction while you patch.
+ */
+void __kprobes text_poke(void *oaddr, unsigned char *opcode, int len)
+{
+        u8 *addr = oaddr;
+	if (!pte_write(*lookup_address((unsigned long)addr))) {
+		struct page *p[2] = { virt_to_page(addr), virt_to_page(addr+PAGE_SIZE) };
+		addr = vmap(p, 2, VM_MAP, PAGE_KERNEL);
+		if (!addr)
+			return;
+		addr += ((unsigned long)oaddr) % PAGE_SIZE;
+	}
+	memcpy(addr, opcode, len);
+	sync_core();
+	/* Not strictly needed, but can speed CPU recovery up. Ignore cross cacheline
+	   case. */
+	if (cpu_has_clflush)
+		asm("clflush (%0) " :: "r" (oaddr) : "memory");
+	if (addr != oaddr)
+		vunmap(addr);
+}
diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index dde828a333c..448a50b1324 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -35,6 +35,7 @@
 #include <asm/cacheflush.h>
 #include <asm/desc.h>
 #include <asm/uaccess.h>
+#include <asm/alternative.h>
 
 void jprobe_return_end(void);
 
@@ -169,16 +170,12 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 
 void __kprobes arch_arm_kprobe(struct kprobe *p)
 {
-	*p->addr = BREAKPOINT_INSTRUCTION;
-	flush_icache_range((unsigned long) p->addr,
-			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
+	text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
 }
 
 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 {
-	*p->addr = p->opcode;
-	flush_icache_range((unsigned long) p->addr,
-			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
+	text_poke(p->addr, &p->opcode, 1);
 }
 
 void __kprobes arch_remove_kprobe(struct kprobe *p)
diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
index 53f07a8275e..79c167fcaee 100644
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -124,20 +124,28 @@ unsigned paravirt_patch_ignore(unsigned len)
 	return len;
 }
 
+struct branch {
+	unsigned char opcode;
+	u32 delta;
+} __attribute__((packed));
+
 unsigned paravirt_patch_call(void *target, u16 tgt_clobbers,
 			     void *site, u16 site_clobbers,
 			     unsigned len)
 {
 	unsigned char *call = site;
 	unsigned long delta = (unsigned long)target - (unsigned long)(call+5);
+	struct branch b;
 
 	if (tgt_clobbers & ~site_clobbers)
 		return len;	/* target would clobber too much for this site */
 	if (len < 5)
 		return len;	/* call too long for patch site */
 
-	*call++ = 0xe8;		/* call */
-	*(unsigned long *)call = delta;
+	b.opcode = 0xe8; /* call */
+	b.delta = delta;
+	BUILD_BUG_ON(sizeof(b) != 5);
+	text_poke(call, (unsigned char *)&b, 5);
 
 	return 5;
 }
@@ -150,8 +158,9 @@ unsigned paravirt_patch_jmp(void *target, void *site, unsigned len)
 	if (len < 5)
 		return len;	/* call too long for patch site */
 
-	*jmp++ = 0xe9;		/* jmp */
-	*(unsigned long *)jmp = delta;
+	b.opcode = 0xe9;	/* jmp */
+	b.delta = delta;
+	text_poke(call, (unsigned char *)&b, 5);
 
 	return 5;
 }