[tip: core/kprobes] x86/alternative: Remove text_poke_loc::len

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the core/kprobes branch of tip:

Commit-ID:     97e6c977ccf128c3f34d6084ad53fc0021f90e03
Gitweb:        https://git.kernel.org/tip/97e6c977ccf128c3f34d6084ad53fc0021f90e03
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Wed, 09 Oct 2019 12:44:20 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Wed, 27 Nov 2019 07:44:24 +01:00

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.

Tested-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Tested-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20191111132457.989922744@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/alternative.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index cfcfadf..6e3ee73 100644
--- 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_regs *regs)
 {
 	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_regs *regs)
 			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 text_poke_loc *tp, unsigned int nr_entries
 	 * 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_loc *tp, void *addr,
 	BUG_ON(len != insn.length);
 
 	tp->addr = addr;
-	tp->len = len;
 	tp->opcode = insn.opcode.bytes[0];
 
 	switch (tp->opcode) {