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objtool: Rework ASM_REACHABLE 

Currently ASM_REACHABLE only works for UD2 instructions; reorder
things to also allow over-riding dead_end_function().

To that end:

 - Mark INSN_BUG instructions in decode_instructions(), this saves
   having to iterate all instructions yet again.

 - Have add_call_destinations() set insn->dead_end for
   dead_end_function() calls.

 - Move add_dead_ends() *after* add_call_destinations() such that
   ASM_REACHABLE can clear the ->dead_end mark.

 - have validate_branch() only check ->dead_end.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154319.410010807@infradead.org
This commit is contained in:
Peter Zijlstra 2022-03-08 16:30:49 +01:00
parent 105cd68596
commit 0e5b613b4d
1 changed files with 20 additions and 13 deletions
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33
tools/objtool/check.c
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@ -395,6 +395,14 @@ static int decode_instructions(struct objtool_file *file)
if (ret)
goto err;
/*
* By default, "ud2" is a dead end unless otherwise
* annotated, because GCC 7 inserts it for certain
* divide-by-zero cases.
*/
if (insn->type == INSN_BUG)
insn->dead_end = true;
hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
list_add_tail(&insn->list, &file->insn_list);
nr_insns++;
@ -523,14 +531,6 @@ static int add_dead_ends(struct objtool_file *file)
struct reloc *reloc;
struct instruction *insn;
/*
* By default, "ud2" is a dead end unless otherwise annotated, because
* GCC 7 inserts it for certain divide-by-zero cases.
*/
for_each_insn(file, insn)
if (insn->type == INSN_BUG)
insn->dead_end = true;
/*
* Check for manually annotated dead ends.
*/
@ -1114,6 +1114,9 @@ static void annotate_call_site(struct objtool_file *file,
list_add_tail(&insn->call_node, &file->mcount_loc_list);
return;
}
if (!sibling && dead_end_function(file, sym))
insn->dead_end = true;
}
static void add_call_dest(struct objtool_file *file, struct instruction *insn,
@ -2089,10 +2092,6 @@ static int decode_sections(struct objtool_file *file)
if (ret)
return ret;
ret = add_dead_ends(file);
if (ret)
return ret;
add_ignores(file);
add_uaccess_safe(file);
@ -2131,6 +2130,14 @@ static int decode_sections(struct objtool_file *file)
if (ret)
return ret;
/*
* Must be after add_call_destinations() such that it can override
* dead_end_function() marks.
*/
ret = add_dead_ends(file);
if (ret)
return ret;
ret = add_jump_table_alts(file);
if (ret)
return ret;
@ -3138,7 +3145,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
return 1;
}
if (dead_end_function(file, insn->call_dest))
if (insn->dead_end)
return 0;
break;