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2024-05-10 37f49e37ab4cb5d0bc4c60eb5c6d4dd57db767bb

 kernel/arch/x86/kernel/jump_label.c
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..
@@ -16,15 +16,7 @@
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 #include <asm/alternative.h>
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 #include <asm/text-patching.h>
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18
 
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-union jump_code_union {
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-	char code[JUMP_LABEL_NOP_SIZE];
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-	struct {
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-		char jump;
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-		int offset;
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-	} __attribute__((packed));
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-};
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-
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-static void bug_at(unsigned char *ip, int line)
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+static void bug_at(const void *ip, int line)
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 {
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 	/*
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 	 * The location is not an op that we were expecting.
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@@ -35,80 +27,103 @@
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 	BUG();
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 }
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29
 
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-static void __ref __jump_label_transform(struct jump_entry *entry,
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-					 enum jump_label_type type,
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-					 void *(*poker)(void *, const void *, size_t),
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-					 int init)
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+static const void *
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+__jump_label_set_jump_code(struct jump_entry *entry, enum jump_label_type type, int init)
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 {
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-	union jump_code_union code;
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 	const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
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 	const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
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+	const void *expect, *code;
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+	const void *addr, *dest;
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+	int line;
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-	if (early_boot_irqs_disabled)
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-		poker = text_poke_early;
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+	addr = (void *)jump_entry_code(entry);
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+	dest = (void *)jump_entry_target(entry);
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-	if (type == JUMP_LABEL_JMP) {
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-		if (init) {
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-			/*
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-			 * Jump label is enabled for the first time.
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-			 * So we expect a default_nop...
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-			 */
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-			if (unlikely(memcmp((void *)entry->code, default_nop, 5)
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-				     != 0))
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-				bug_at((void *)entry->code, __LINE__);
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-		} else {
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-			/*
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-			 * ...otherwise expect an ideal_nop. Otherwise
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-			 * something went horribly wrong.
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-			 */
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-			if (unlikely(memcmp((void *)entry->code, ideal_nop, 5)
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-				     != 0))
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-				bug_at((void *)entry->code, __LINE__);
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-		}
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+	code = text_gen_insn(JMP32_INSN_OPCODE, addr, dest);
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43
 
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-		code.jump = 0xe9;
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-		code.offset = entry->target -
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-				(entry->code + JUMP_LABEL_NOP_SIZE);
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+	if (init) {
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+		expect = default_nop; line = __LINE__;
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+	} else if (type == JUMP_LABEL_JMP) {
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+		expect = ideal_nop; line = __LINE__;
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 	} else {
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-		/*
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-		 * We are disabling this jump label. If it is not what
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-		 * we think it is, then something must have gone wrong.
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-		 * If this is the first initialization call, then we
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-		 * are converting the default nop to the ideal nop.
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-		 */
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-		if (init) {
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-			if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))
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-				bug_at((void *)entry->code, __LINE__);
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-		} else {
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-			code.jump = 0xe9;
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-			code.offset = entry->target -
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-				(entry->code + JUMP_LABEL_NOP_SIZE);
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-			if (unlikely(memcmp((void *)entry->code, &code, 5) != 0))
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-				bug_at((void *)entry->code, __LINE__);
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-		}
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-		memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
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+		expect = code; line = __LINE__;
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 	}
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+	if (memcmp(addr, expect, JUMP_LABEL_NOP_SIZE))
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+		bug_at(addr, line);
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+
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+	if (type == JUMP_LABEL_NOP)
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+		code = ideal_nop;
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+
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+	return code;
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+}
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+
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+static inline void __jump_label_transform(struct jump_entry *entry,
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+					  enum jump_label_type type,
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+					  int init)
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+{
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+	const void *opcode = __jump_label_set_jump_code(entry, type, init);
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+
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 	/*
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-	 * Make text_poke_bp() a default fallback poker.
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+	 * As long as only a single processor is running and the code is still
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+	 * not marked as RO, text_poke_early() can be used; Checking that
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+	 * system_state is SYSTEM_BOOTING guarantees it. It will be set to
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+	 * SYSTEM_SCHEDULING before other cores are awaken and before the
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+	 * code is write-protected.
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 	 *
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 	 * At the time the change is being done, just ignore whether we
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 	 * are doing nop -> jump or jump -> nop transition, and assume
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 	 * always nop being the 'currently valid' instruction
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-	 *
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 	 */
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-	if (poker)
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-		(*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
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-	else
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-		text_poke_bp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE,
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-			     (void *)entry->code + JUMP_LABEL_NOP_SIZE);
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+	if (init || system_state == SYSTEM_BOOTING) {
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+		text_poke_early((void *)jump_entry_code(entry), opcode,
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+				JUMP_LABEL_NOP_SIZE);
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+		return;
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+	}
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+
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+	text_poke_bp((void *)jump_entry_code(entry), opcode, JUMP_LABEL_NOP_SIZE, NULL);
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+}
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+
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+static void __ref jump_label_transform(struct jump_entry *entry,
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+				       enum jump_label_type type,
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+				       int init)
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+{
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+	mutex_lock(&text_mutex);
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+	__jump_label_transform(entry, type, init);
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+	mutex_unlock(&text_mutex);
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 }
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95
 
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 void arch_jump_label_transform(struct jump_entry *entry,
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97
 			       enum jump_label_type type)
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 {
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+	jump_label_transform(entry, type, 0);
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+}
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+
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+bool arch_jump_label_transform_queue(struct jump_entry *entry,
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+				     enum jump_label_type type)
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+{
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+	const void *opcode;
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+
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+	if (system_state == SYSTEM_BOOTING) {
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+		/*
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+		 * Fallback to the non-batching mode.
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+		 */
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+		arch_jump_label_transform(entry, type);
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+		return true;
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+	}
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+
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 	mutex_lock(&text_mutex);
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-	__jump_label_transform(entry, type, NULL, 0);
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+	opcode = __jump_label_set_jump_code(entry, type, 0);
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+	text_poke_queue((void *)jump_entry_code(entry),
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+			opcode, JUMP_LABEL_NOP_SIZE, NULL);
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+	mutex_unlock(&text_mutex);
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+	return true;
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+}
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+
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+void arch_jump_label_transform_apply(void)
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+{
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+	mutex_lock(&text_mutex);
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+	text_poke_finish();
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 	mutex_unlock(&text_mutex);
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 }
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..
..
@@ -138,5 +153,5 @@
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 			jlstate = JL_STATE_NO_UPDATE;
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 	}
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 	if (jlstate == JL_STATE_UPDATE)
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-		__jump_label_transform(entry, type, text_poke_early, 1);
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+		jump_label_transform(entry, type, 1);
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 }