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objtool: optimize add_dead_ends for split sections

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Instead of iterating through all instructions to find the last
instruction each time .rela.discard.(un)reachable points beyond the
section, use find_insn to locate the last instruction by looking at
the last bytes of the section instead.

Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200421220843.188260-3-samitolvanen@google.com
This commit is contained in:
Sami Tolvanen 2020-04-21 15:08:43 -07:00 committed by Peter Zijlstra
parent 28fe1d7bf8
commit 6b5dd716da
1 changed files with 17 additions and 19 deletions
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36
tools/objtool/check.c
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@ -322,6 +322,19 @@ static int decode_instructions(struct objtool_file *file)
return ret;
}
static struct instruction *find_last_insn(struct objtool_file *file,
struct section *sec)
{
struct instruction *insn = NULL;
unsigned int offset;
unsigned int end = (sec->len > 10) ? sec->len - 10 : 0;
for (offset = sec->len - 1; offset >= end && !insn; offset--)
insn = find_insn(file, sec, offset);
return insn;
}
/*
* Mark "ud2" instructions and manually annotated dead ends.
*/
@ -330,7 +343,6 @@ static int add_dead_ends(struct objtool_file *file)
struct section *sec;
struct rela *rela;
struct instruction *insn;
bool found;
/*
* By default, "ud2" is a dead end unless otherwise annotated, because
@ -356,15 +368,8 @@ static int add_dead_ends(struct objtool_file *file)
if (insn)
insn = list_prev_entry(insn, list);
else if (rela->addend == rela->sym->sec->len) {
found = false;
list_for_each_entry_reverse(insn, &file->insn_list, list) {
if (insn->sec == rela->sym->sec) {
found = true;
break;
}
}
if (!found) {
insn = find_last_insn(file, rela->sym->sec);
if (!insn) {
WARN("can't find unreachable insn at %s+0x%x",
rela->sym->sec->name, rela->addend);
return -1;
@ -398,15 +403,8 @@ static int add_dead_ends(struct objtool_file *file)
if (insn)
insn = list_prev_entry(insn, list);
else if (rela->addend == rela->sym->sec->len) {
found = false;
list_for_each_entry_reverse(insn, &file->insn_list, list) {
if (insn->sec == rela->sym->sec) {
found = true;
break;
}
}
if (!found) {
insn = find_last_insn(file, rela->sym->sec);
if (!insn) {
WARN("can't find reachable insn at %s+0x%x",
rela->sym->sec->name, rela->addend);
return -1;