x86/alternatives: Add and use text_gen_insn() helper

Provide a simple helper function to create common instruction
encodings.

Tested-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191111132457.703538332@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 11 insertions, 20 deletions

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index cf8c847c7b5d..9c4498ea0b3c 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -16,15 +16,7 @@
 #include <asm/alternative.h>
 #include <asm/text-patching.h>
 
-union jump_code_union {
-	char code[JUMP_LABEL_NOP_SIZE];
-	struct {
-		char jump;
-		int offset;
-	} __attribute__((packed));
-};
-
-static void bug_at(unsigned char *ip, int line)
+static void bug_at(const void *ip, int line)
 {
 	/*
 	 * The location is not an op that we were expecting.
@@ -38,33 +30,32 @@ static void bug_at(unsigned char *ip, int line)
 static const void *
 __jump_label_set_jump_code(struct jump_entry *entry, enum jump_label_type type, int init)
 {
-	static union jump_code_union code; /* relies on text_mutex */
 	const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
 	const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
-	const void *expect;
+	const void *expect, *code;
+	const void *addr, *dest;
 	int line;
 
-	lockdep_assert_held(&text_mutex);
+	addr = (void *)jump_entry_code(entry);
+	dest = (void *)jump_entry_target(entry);
 
-	code.jump = JMP32_INSN_OPCODE;
-	code.offset = jump_entry_target(entry) -
-		       (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
+	code = text_gen_insn(JMP32_INSN_OPCODE, addr, dest);
 
 	if (init) {
 		expect = default_nop; line = __LINE__;
 	} else if (type == JUMP_LABEL_JMP) {
 		expect = ideal_nop; line = __LINE__;
 	} else {
-		expect = code.code; line = __LINE__;
+		expect = code; line = __LINE__;
 	}
 
-	if (memcmp((void *)jump_entry_code(entry), expect, JUMP_LABEL_NOP_SIZE))
-		bug_at((void *)jump_entry_code(entry), line);
+	if (memcmp(addr, expect, JUMP_LABEL_NOP_SIZE))
+		bug_at(addr, line);
 
 	if (type == JUMP_LABEL_NOP)
-		memcpy(&code, ideal_nop, JUMP_LABEL_NOP_SIZE);
+		code = ideal_nop;
 
-	return &code;
+	return code;
 }
 
 static void inline __jump_label_transform(struct jump_entry *entry,