The following commit has been merged into the objtool/core branch of tip:
Commit-ID: 760da44ec676ec67d855cbdda6b3b2a3ca1f4d99
Gitweb: https://git.kernel.org/tip/760da44ec676ec67d855cbdda6b3b2a3ca1f4d99
Author: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
AuthorDate: Tue, 21 Apr 2020 15:08:43 -07:00
Committer: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
CommitterDate: Tue, 21 Apr 2020 18:49:21 -05:00
objtool: Optimize add_dead_ends for split sections
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.
This makes processing a -ffunction-sections vmlinux.o faster.
Suggested-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
tools/objtool/check.c | 36 +++++++++++++++++-------------------
1 file changed, 17 insertions(+), 19 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 276bce3..f4254d4 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -303,6 +303,19 @@ err:
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.
*/
@@ -311,7 +324,6 @@ 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
@@ -337,15 +349,8 @@ 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;
@@ -379,15 +384,8 @@ reachable:
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;
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