1 files changed, 197 insertions, 38 deletions

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 390596b761e3..c3468b5242fd 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -14,6 +14,7 @@
 #include <linux/kdebug.h>
 #include <linux/kprobes.h>
 #include <linux/mmu_context.h>
+#include <linux/bsearch.h>
 #include <asm/text-patching.h>
 #include <asm/alternative.h>
 #include <asm/sections.h>
@@ -615,11 +616,83 @@ extern struct paravirt_patch_site __start_parainstructions[],
 	__stop_parainstructions[];
 #endif	/* CONFIG_PARAVIRT */
 
+/*
+ * Self-test for the INT3 based CALL emulation code.
+ *
+ * This exercises int3_emulate_call() to make sure INT3 pt_regs are set up
+ * properly and that there is a stack gap between the INT3 frame and the
+ * previous context. Without this gap doing a virtual PUSH on the interrupted
+ * stack would corrupt the INT3 IRET frame.
+ *
+ * See entry_{32,64}.S for more details.
+ */
+static void __init int3_magic(unsigned int *ptr)
+{
+	*ptr = 1;
+}
+
+extern __initdata unsigned long int3_selftest_ip; /* defined in asm below */
+
+static int __init
+int3_exception_notify(struct notifier_block *self, unsigned long val, void *data)
+{
+	struct die_args *args = data;
+	struct pt_regs *regs = args->regs;
+
+	if (!regs || user_mode(regs))
+		return NOTIFY_DONE;
+
+	if (val != DIE_INT3)
+		return NOTIFY_DONE;
+
+	if (regs->ip - INT3_INSN_SIZE != int3_selftest_ip)
+		return NOTIFY_DONE;
+
+	int3_emulate_call(regs, (unsigned long)&int3_magic);
+	return NOTIFY_STOP;
+}
+
+static void __init int3_selftest(void)
+{
+	static __initdata struct notifier_block int3_exception_nb = {
+		.notifier_call	= int3_exception_notify,
+		.priority	= INT_MAX-1, /* last */
+	};
+	unsigned int val = 0;
+
+	BUG_ON(register_die_notifier(&int3_exception_nb));
+
+	/*
+	 * Basically: int3_magic(&val); but really complicated :-)
+	 *
+	 * Stick the address of the INT3 instruction into int3_selftest_ip,
+	 * then trigger the INT3, padded with NOPs to match a CALL instruction
+	 * length.
+	 */
+	asm volatile ("1: int3; nop; nop; nop; nop\n\t"
+		      ".pushsection .init.data,\"aw\"\n\t"
+		      ".align " __ASM_SEL(4, 8) "\n\t"
+		      ".type int3_selftest_ip, @object\n\t"
+		      ".size int3_selftest_ip, " __ASM_SEL(4, 8) "\n\t"
+		      "int3_selftest_ip:\n\t"
+		      __ASM_SEL(.long, .quad) " 1b\n\t"
+		      ".popsection\n\t"
+		      : : __ASM_SEL_RAW(a, D) (&val) : "memory");
+
+	BUG_ON(val != 1);
+
+	unregister_die_notifier(&int3_exception_nb);
+}
+
 void __init alternative_instructions(void)
 {
-	/* The patching is not fully atomic, so try to avoid local interruptions
-	   that might execute the to be patched code.
-	   Other CPUs are not running. */
+	int3_selftest();
+
+	/*
+	 * The patching is not fully atomic, so try to avoid local
+	 * interruptions that might execute the to be patched code.
+	 * Other CPUs are not running.
+	 */
 	stop_nmi();
 
 	/*
@@ -644,10 +717,11 @@ void __init alternative_instructions(void)
 					    _text, _etext);
 	}
 
-	if (!uniproc_patched || num_possible_cpus() == 1)
+	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);
@@ -848,81 +922,133 @@ static void do_sync_core(void *info)
 	sync_core();
 }
 
-static bool bp_patching_in_progress;
-static void *bp_int3_handler, *bp_int3_addr;
+static struct bp_patching_desc {
+	struct text_poke_loc *vec;
+	int nr_entries;
+} bp_patching;
+
+static int patch_cmp(const void *key, const void *elt)
+{
+	struct text_poke_loc *tp = (struct text_poke_loc *) elt;
+
+	if (key < tp->addr)
+		return -1;
+	if (key > tp->addr)
+		return 1;
+	return 0;
+}
+NOKPROBE_SYMBOL(patch_cmp);
 
 int poke_int3_handler(struct pt_regs *regs)
 {
+	struct text_poke_loc *tp;
+	unsigned char int3 = 0xcc;
+	void *ip;
+
 	/*
 	 * Having observed our INT3 instruction, we now must observe
-	 * bp_patching_in_progress.
+	 * bp_patching.nr_entries.
 	 *
-	 * 	in_progress = TRUE		INT3
+	 * 	nr_entries != 0			INT3
 	 * 	WMB				RMB
-	 * 	write INT3			if (in_progress)
+	 * 	write INT3			if (nr_entries)
 	 *
-	 * Idem for bp_int3_handler.
+	 * Idem for other elements in bp_patching.
 	 */
 	smp_rmb();
 
-	if (likely(!bp_patching_in_progress))
+	if (likely(!bp_patching.nr_entries))
 		return 0;
 
-	if (user_mode(regs) || regs->ip != (unsigned long)bp_int3_addr)
+	if (user_mode(regs))
 		return 0;
 
-	/* set up the specified breakpoint handler */
-	regs->ip = (unsigned long) bp_int3_handler;
+	/*
+	 * Discount the sizeof(int3). See text_poke_bp_batch().
+	 */
+	ip = (void *) regs->ip - sizeof(int3);
+
+	/*
+	 * Skip the binary search if there is a single member in the vector.
+	 */
+	if (unlikely(bp_patching.nr_entries > 1)) {
+		tp = bsearch(ip, bp_patching.vec, bp_patching.nr_entries,
+			     sizeof(struct text_poke_loc),
+			     patch_cmp);
+		if (!tp)
+			return 0;
+	} else {
+		tp = bp_patching.vec;
+		if (tp->addr != ip)
+			return 0;
+	}
+
+	/* set up the specified breakpoint detour */
+	regs->ip = (unsigned long) tp->detour;
 
 	return 1;
 }
 NOKPROBE_SYMBOL(poke_int3_handler);
 
 /**
- * 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
+ * text_poke_bp_batch() -- update instructions on live kernel on SMP
+ * @tp:			vector of instructions to patch
+ * @nr_entries:		number of entries in the vector
  *
  * 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
+ * 	- For each entry in the vector:
+ *		- add a int3 trap to the address that will be patched
  *	- sync cores
- *	- update all but the first byte of the patched range
+ *	- For each entry in the vector:
+ *		- update all but the first byte of the patched range
  *	- sync cores
- *	- replace the first byte (int3) by the first byte of
- *	  replacing opcode
+ *	- For each entry in the vector:
+ *		- replace the first byte (int3) by the first byte of
+ *		  replacing opcode
  *	- sync cores
  */
-void text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
+void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries)
 {
+	int patched_all_but_first = 0;
 	unsigned char int3 = 0xcc;
-
-	bp_int3_handler = handler;
-	bp_int3_addr = (u8 *)addr + sizeof(int3);
-	bp_patching_in_progress = true;
+	unsigned int i;
 
 	lockdep_assert_held(&text_mutex);
 
+	bp_patching.vec = tp;
+	bp_patching.nr_entries = nr_entries;
+
 	/*
 	 * Corresponding read barrier in int3 notifier for making sure the
-	 * in_progress and handler are correctly ordered wrt. patching.
+	 * nr_entries and handler are correctly ordered wrt. patching.
 	 */
 	smp_wmb();
 
-	text_poke(addr, &int3, sizeof(int3));
+	/*
+	 * First step: add a int3 trap to the address that will be patched.
+	 */
+	for (i = 0; i < nr_entries; i++)
+		text_poke(tp[i].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));
+	/*
+	 * Second step: update all but the first byte of the patched range.
+	 */
+	for (i = 0; i < nr_entries; i++) {
+		if (tp[i].len - sizeof(int3) > 0) {
+			text_poke((char *)tp[i].addr + sizeof(int3),
+				  (const char *)tp[i].opcode + sizeof(int3),
+				  tp[i].len - sizeof(int3));
+			patched_all_but_first++;
+		}
+	}
+
+	if (patched_all_but_first) {
 		/*
 		 * According to Intel, this core syncing is very likely
 		 * not necessary and we'd be safe even without it. But
@@ -931,14 +1057,47 @@ void text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
 		on_each_cpu(do_sync_core, NULL, 1);
 	}
 
-	/* patch the first byte */
-	text_poke(addr, opcode, sizeof(int3));
+	/*
+	 * Third step: replace the first byte (int3) by the first byte of
+	 * replacing opcode.
+	 */
+	for (i = 0; i < nr_entries; i++)
+		text_poke(tp[i].addr, tp[i].opcode, sizeof(int3));
 
 	on_each_cpu(do_sync_core, NULL, 1);
 	/*
 	 * sync_core() implies an smp_mb() and orders this store against
 	 * the writing of the new instruction.
 	 */
-	bp_patching_in_progress = false;
+	bp_patching.vec = NULL;
+	bp_patching.nr_entries = 0;
 }
 
+/**
+ * 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
+ *
+ * Update a single instruction with the vector in the stack, avoiding
+ * dynamically allocated memory. This function should be used when it is
+ * not possible to allocate memory.
+ */
+void text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
+{
+	struct text_poke_loc tp = {
+		.detour = handler,
+		.addr = addr,
+		.len = len,
+	};
+
+	if (len > POKE_MAX_OPCODE_SIZE) {
+		WARN_ONCE(1, "len is larger than %d\n", POKE_MAX_OPCODE_SIZE);
+		return;
+	}
+
+	memcpy((void *)tp.opcode, opcode, len);
+
+	text_poke_bp_batch(&tp, 1);
+}