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Commit 764eef4b authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

objtool: Rewrite alt->skip_orig 



Really skip the original instruction flow, instead of letting it
continue with NOPs.

Since the alternative code flow already continues after the original
instructions, only the alt-original is skipped.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 7697eee3

tools/objtool/check.c

+10 −6
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ 
struct alternative {

	struct list_head list;

	struct instruction *insn;

	bool skip_orig;

};



const char *objname;
@@ -623,9 +624,6 @@ static int add_call_destinations(struct objtool_file *file) 
 *    conditionally jumps to the _end_ of the entry.  We have to modify these

 *    jumps' destinations to point back to .text rather than the end of the

 *    entry in .altinstr_replacement.

 *

 * 4. It has been requested that we don't validate the !POPCNT feature path

 *    which is a "very very small percentage of machines".

 */

static int handle_group_alt(struct objtool_file *file,

			    struct special_alt *special_alt,
@@ -641,9 +639,6 @@ static int handle_group_alt(struct objtool_file *file, 
		if (insn->offset >= special_alt->orig_off + special_alt->orig_len)

			break;



		if (special_alt->skip_orig)

			insn->type = INSN_NOP;



		insn->alt_group = true;

		last_orig_insn = insn;

	}
@@ -808,6 +803,7 @@ static int add_special_section_alts(struct objtool_file *file) 
		}



		alt->insn = new_insn;

		alt->skip_orig = special_alt->skip_orig;

		list_add_tail(&alt->list, &orig_insn->alts);



		list_del(&special_alt->list);
@@ -1883,7 +1879,12 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, 
		insn->visited = true;



		if (!insn->ignore_alts) {

			bool skip_orig = false;



			list_for_each_entry(alt, &insn->alts, list) {

				if (alt->skip_orig)

					skip_orig = true;



				ret = validate_branch(file, alt->insn, state);

				if (ret) {

					if (backtrace)
@@ -1891,6 +1892,9 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, 
					return ret;

				}

			}



			if (skip_orig)

				return 0;

		}



		switch (insn->type) {