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objtool: Fix sibling call detection in alternatives 

In add_jump_destinations(), sibling call detection requires 'insn->func'
to be valid.  But alternative instructions get their 'func' set in
handle_group_alt(), which runs *after* add_jump_destinations().  So
sibling calls in alternatives code don't get properly detected.

Fix that by changing the initialization order: call
add_special_section_alts() *before* add_jump_destinations().

This also means the special case for a missing 'jump_dest' in
add_jump_destinations() can be removed, as it has already been dealt
with.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/c02e0a0a2a4286b5f848d17c77fdcb7e0caf709c.1649718562.git.jpoimboe@redhat.com
This commit is contained in:
Josh Poimboeuf 2022-04-11 16:10:31 -07:00 committed by Peter Zijlstra
parent 26ff604102
commit 34c861e806
1 changed files with 17 additions and 19 deletions
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28
tools/objtool/check.c
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@ -1277,6 +1277,13 @@ static int add_jump_destinations(struct objtool_file *file)
unsigned long dest_off;
for_each_insn(file, insn) {
if (insn->jump_dest) {
/*
* handle_group_alt() may have previously set
* 'jump_dest' for some alternatives.
*/
continue;
}
if (!is_static_jump(insn))
continue;
@ -1308,15 +1315,6 @@ static int add_jump_destinations(struct objtool_file *file)
jump_dest = find_insn(file, dest_sec, dest_off);
if (!jump_dest) {
/*
* This is a special case where an alt instruction
* jumps past the end of the section. These are
* handled later in handle_group_alt().
*/
if (!strcmp(insn->sec->name, ".altinstr_replacement"))
continue;
WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
insn->sec, insn->offset, dest_sec->name,
dest_off);
@ -1549,15 +1547,15 @@ static int handle_group_alt(struct objtool_file *file,
continue;
dest_off = arch_jump_destination(insn);
if (dest_off == special_alt->new_off + special_alt->new_len)
if (dest_off == special_alt->new_off + special_alt->new_len) {
insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
if (!insn->jump_dest) {
WARN_FUNC("can't find alternative jump destination",
insn->sec, insn->offset);
return -1;
}
}
}
if (!last_new_insn) {
WARN_FUNC("can't find last new alternative instruction",
@ -2254,14 +2252,14 @@ static int decode_sections(struct objtool_file *file)
return ret;
/*
* Must be before add_special_section_alts() as that depends on
* jump_dest being set.
* Must be before add_jump_destinations(), which depends on 'func'
* being set for alternatives, to enable proper sibling call detection.
*/
ret = add_jump_destinations(file);
ret = add_special_section_alts(file);
if (ret)
return ret;
ret = add_special_section_alts(file);
ret = add_jump_destinations(file);
if (ret)
return ret;