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@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: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191111132457.989922744@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index cfcfadf5cc80ff10da8f7a00ea87a4174e712369..6e3ee73775f6a24409d4fed9b5f1240d49cea4e4 100644 (file)
--- 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) {