When compiling with CONFIG_LTO_CLANG_THIN, vmlinux.o has
__irf_[start|end] before the first FILE entry:
$ readelf -sW vmlinux.o
Symbol table '.symtab' contains 597706 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 NOTYPE LOCAL DEFAULT 18 __irf_start
2: 0000000000000200 0 NOTYPE LOCAL DEFAULT 18 __irf_end
3: 0000000000000000 0 SECTION LOCAL DEFAULT 17 .text
4: 0000000000000000 0 SECTION LOCAL DEFAULT 18 .init.ramfs
This causes klp-build warnings like:
vmlinux.o: warning: objtool: no correlation: __irf_start
vmlinux.o: warning: objtool: no correlation: __irf_end
The problem is that Clang LTO is stripping the initramfs_data.o FILE
symbol, causing those two symbols to be orphaned and not noticed by
klp-diff's correlation logic. Add a loop to correlate any symbols found
before the first FILE symbol.
Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing
object files")
Reported-by: Song Liu <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>
---
tools/objtool/klp-diff.c | 39 ++++++++++++++++++++++++++++++++++-----
1 file changed, 34 insertions(+), 5 deletions(-)
diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
index 1e649a3eb4cd..9f1f4011eb9c 100644
--- a/tools/objtool/klp-diff.c
+++ b/tools/objtool/klp-diff.c
@@ -364,11 +364,40 @@ static int correlate_symbols(struct elfs *e)
struct symbol *file1_sym, *file2_sym;
struct symbol *sym1, *sym2;
- /* Correlate locals */
- for (file1_sym = first_file_symbol(e->orig),
- file2_sym = first_file_symbol(e->patched); ;
- file1_sym = next_file_symbol(e->orig, file1_sym),
- file2_sym = next_file_symbol(e->patched, file2_sym)) {
+ file1_sym = first_file_symbol(e->orig);
+ file2_sym = first_file_symbol(e->patched);
+
+ /*
+ * Correlate any locals before the first FILE symbol. This has been
+ * seen when LTO inexplicably strips the initramfs_data.o FILE symbol
+ * due to the file only containing data and no code.
+ */
+ for_each_sym(e->orig, sym1) {
+ if (sym1 == file1_sym || !is_local_sym(sym1))
+ break;
+
+ if (dont_correlate(sym1))
+ continue;
+
+ for_each_sym(e->patched, sym2) {
+ if (sym2 == file2_sym || !is_local_sym(sym2))
+ break;
+
+ if (sym2->twin || dont_correlate(sym2))
+ continue;
+
+ if (strcmp(sym1->demangled_name, sym2->demangled_name))
+ continue;
+
+ sym1->twin = sym2;
+ sym2->twin = sym1;
+ break;
+ }
+ }
+
+ /* Correlate locals after the first FILE symbol */
+ for (; ; file1_sym = next_file_symbol(e->orig, file1_sym),
+ file2_sym = next_file_symbol(e->patched, file2_sym)) {
if (!file1_sym && file2_sym) {
ERROR("FILE symbol mismatch: NULL != %s",
file2_sym->name);
--
2.52.0
