x86/alternatives: Use INT3_INSN_SIZE

Use INT3_INSN_SIZE instead of sizeof(int3).

Suggested-by: Ingo Molnar <mingo@kernel.org>
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: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191111132458.460144656@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Author: Peter Zijlstra

arch/x86/kernel/alternative.c

@@ -1088,7 +1088,7 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries
 	 * First step: add a int3 trap to the address that will be patched.
 	 */
 	for (i = 0; i < nr_entries; i++)
-		text_poke(text_poke_addr(&tp[i]), &int3, sizeof(int3));
+		text_poke(text_poke_addr(&tp[i]), &int3, INT3_INSN_SIZE);
 
 	text_poke_sync();
 
@@ -1098,10 +1098,10 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries
 	for (do_sync = 0, i = 0; i < nr_entries; i++) {
 		int len = text_opcode_size(tp[i].opcode);
 
-		if (len - sizeof(int3) > 0) {
-			text_poke(text_poke_addr(&tp[i]) + sizeof(int3),
-				  (const char *)tp[i].text + sizeof(int3),
-				  len - sizeof(int3));
+		if (len - INT3_INSN_SIZE > 0) {
+			text_poke(text_poke_addr(&tp[i]) + INT3_INSN_SIZE,
+				  (const char *)tp[i].text + INT3_INSN_SIZE,
+				  len - INT3_INSN_SIZE);
 			do_sync++;
 		}
 	}
@@ -1123,7 +1123,7 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries
 		if (tp[i].text[0] == INT3_INSN_OPCODE)
 			continue;
 
-		text_poke(text_poke_addr(&tp[i]), tp[i].text, sizeof(int3));
+		text_poke(text_poke_addr(&tp[i]), tp[i].text, INT3_INSN_SIZE);
 		do_sync++;
 	}