[PATCH 6/8] objtool/klp: Match symbols based on demangled_name for global variables

[Song Liu <song@kernel.org>]

correlate_symbols will always try to match full name first. If there is no
match, try match only demangled_name.

In very rare cases, it is possible to have multiple foo.llvm.<hash> in
the same kernel. So this match is not guaranteed to be correct. Show
a warning here so that the user can double check.

Signed-off-by: Song Liu <song@kernel.org>
---
 tools/objtool/elf.c                 | 13 +++++++++++++
 tools/objtool/include/objtool/elf.h |  2 ++
 tools/objtool/klp-diff.c            | 23 +++++++++++++++++++++++
 3 files changed, 38 insertions(+)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index efb13ec0a89d..d26ee877e613 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -323,6 +323,19 @@ struct symbol *find_global_symbol_by_name(const struct elf *elf, const char *nam
 	return NULL;
 }
 
+struct symbol *find_global_symbol_by_demangled_name(const struct elf *elf,
+						    const char *demangled_name)
+{
+	struct symbol *sym;
+
+	elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash(demangled_name)) {
+		if (!strcmp(sym->demangled_name, demangled_name) && !is_local_sym(sym))
+			return sym;
+	}
+
+	return NULL;
+}
+
 struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec,
 				     unsigned long offset, unsigned int len)
 {
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index e12c516bd320..f757850b8ff1 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -186,6 +186,8 @@ struct symbol *find_func_by_offset(struct section *sec, unsigned long offset);
 struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
 struct symbol *find_symbol_by_name(const struct elf *elf, const char *name);
 struct symbol *find_global_symbol_by_name(const struct elf *elf, const char *name);
+struct symbol *find_global_symbol_by_demangled_name(const struct elf *elf,
+						    const char *demangled_name);
 struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset);
 int find_symbol_hole_containing(const struct section *sec, unsigned long offset);
 struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, unsigned long offset);
diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
index 57606bc3390a..cd82f674862a 100644
--- a/tools/objtool/klp-diff.c
+++ b/tools/objtool/klp-diff.c
@@ -453,6 +453,29 @@ static int correlate_symbols(struct elfs *e)
 			continue;
 
 		sym2 = find_global_symbol_by_name(e->patched, sym1->name);
+		if (!sym2) {
+			/*
+			 * No full name match, try match demangled_name.
+			 * This would match foo.llvm.123 and foo.llvm.456.
+			 *
+			 * Note that, in very rare cases, it is possible
+			 * to have multiple foo.llvm.<hash> in the same
+			 * kernel, e.g., foo.llvm.123 in the original
+			 * kernel, and both foo.llvm.456 and foo.llvm.789
+			 * in the patched kernel. The correlation is not
+			 * guaranteed to be correct in such cases.
+			 *
+			 * Show a warning to remind the user to double
+			 * check the correlation.
+			 */
+
+			sym2 = find_global_symbol_by_demangled_name(e->patched,
+								    sym1->demangled_name);
+			if (sym2) {
+				WARN("correlate %s (origial) to %s (patched)",
+				     sym1->name, sym2->name);
+			}
+		}
 
 		if (sym2 && !sym2->twin) {
 			sym1->twin = sym2;
-- 
2.47.3