linux-kernel - [PATCH -v5 09/17] x86/alternative: Remove text_poke

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Date:   Mon, 11 Nov 2019 14:13:01 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        rostedt@...dmis.org, mhiramat@...nel.org, bristot@...hat.com,
        jbaron@...mai.com, torvalds@...ux-foundation.org,
        tglx@...utronix.de, mingo@...nel.org, namit@...are.com,
        hpa@...or.com, luto@...nel.org, ard.biesheuvel@...aro.org,
        jpoimboe@...hat.com, jeyu@...nel.org, alexei.starovoitov@...il.com
Subject: [PATCH -v5 09/17] x86/alternative: Remove text_poke_loc::len

Per the BUG_ON(len != insn.length) in text_poke_loc_init(), tp->len
must indeed be the same as text_opcode_size(tp->opcode). Use this to
remove this field from the structure.

Sadly, due to 8 byte alignment, this only increases the structure
padding.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/kernel/alternative.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -938,7 +938,6 @@ static void do_sync_core(void *info)
 
 struct text_poke_loc {
 	void *addr;
-	int len;
 	s32 rel32;
 	u8 opcode;
 	const u8 text[POKE_MAX_OPCODE_SIZE];
@@ -965,6 +964,7 @@ int notrace poke_int3_handler(struct pt_
 {
 	struct text_poke_loc *tp;
 	void *ip;
+	int len;
 
 	/*
 	 * Having observed our INT3 instruction, we now must observe
@@ -1004,7 +1004,8 @@ int notrace poke_int3_handler(struct pt_
 			return 0;
 	}
 
-	ip += tp->len;
+	len = text_opcode_size(tp->opcode);
+	ip += len;
 
 	switch (tp->opcode) {
 	case INT3_INSN_OPCODE:
@@ -1085,10 +1086,12 @@ static void text_poke_bp_batch(struct te
 	 * Second step: update all but the first byte of the patched range.
 	 */
 	for (do_sync = 0, i = 0; i < nr_entries; i++) {
-		if (tp[i].len - sizeof(int3) > 0) {
+		int len = text_opcode_size(tp[i].opcode);
+
+		if (len - sizeof(int3) > 0) {
 			text_poke((char *)tp[i].addr + sizeof(int3),
 				  (const char *)tp[i].text + sizeof(int3),
-				  tp[i].len - sizeof(int3));
+				  len - sizeof(int3));
 			do_sync++;
 		}
 	}
@@ -1141,7 +1144,6 @@ void text_poke_loc_init(struct text_poke
 	BUG_ON(len != insn.length);
 
 	tp->addr = addr;
-	tp->len = len;
 	tp->opcode = insn.opcode.bytes[0];
 
 	switch (tp->opcode) {