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objtool: Rewrite alt->skip_orig

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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: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Peter Zijlstra authored and Ingo Molnar committed 2019-04-03 11:02:24 +02:00
1 parent 7697eee3dd
commit 764eef4b10
1 file changed
+10 -6
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tools/objtool/check.c
+10 -6
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@@ -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) {