[PATCH v2 04/53] objtool/klp: Don't correlate absolute symbols

[Josh Poimboeuf]

Some arch/x86/crypto/*.S files define local .set/.equ constants that get
duplicated in vmlinux.o.  This causes klp-diff to fail with "Multiple
correlation candidates" errors since it can't uniquely match these
between orig and patched builds.

Skip ABS symbols in dont_correlate().  They're purely compile-time
assembly constants that are never referenced by relocations, so they
don't need correlation.

Acked-by: Song Liu <song@xxxxxxxxxx>
Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 tools/objtool/klp-diff.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
index 36753eeba58c..27ebe1b1f463 100644
--- a/tools/objtool/klp-diff.c
+++ b/tools/objtool/klp-diff.c
@@ -361,6 +361,15 @@ static bool is_addressable_sym(struct symbol *sym)
 	return !strcmp(sym->sec->name, ".discard.addressable");
 }
 
+/*
+ * ABS symbols are typically assembly .set/.equ constants which are never
+ * referenced by relocations.  (Exclude FILE symbols which are also SHN_ABS.)
+ */
+static bool is_abs_sym(struct symbol *sym)
+{
+	return sym->sym.st_shndx == SHN_ABS && !is_file_sym(sym);
+}
+
 /*
  * These symbols should never be correlated, so their local patched versions
  * are used instead of linking to the originals.
@@ -370,6 +379,7 @@ static bool dont_correlate(struct symbol *sym)
 	return is_file_sym(sym) ||
 	       is_null_sym(sym) ||
 	       is_sec_sym(sym) ||
+	       is_abs_sym(sym) ||
 	       is_prefix_func(sym) ||
 	       is_uncorrelated_static_local(sym) ||
 	       is_clang_tmp_label(sym) ||
-- 
2.53.0