kallsyms: expand symbol name into comment for debugging

The assembler output of kallsyms.c is not meant for people to understand,
and is generally not helpful when debugging "Inconsistent kallsyms data"
warnings. I have previously struggled with these, but found it helpful
to list which symbols changed between the first and second pass in the
.tmp_vmlinux.kallsyms*.S files.

As this file is preprocessed, it's possible to add a C-style multiline
comment with the full type/name tuple.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Author: arndb

scripts/kallsyms.c

@@ -525,7 +525,8 @@ static void write_src(void)
 					table[i]->addr);
 				exit(EXIT_FAILURE);
 			}
-			printf("\t.long\t%#x\n", (int)offset);
+			expand_symbol(table[i]->sym, table[i]->len, buf);
+			printf("\t.long\t%#x	/* %s */\n", (int)offset, buf);
 		} else if (!symbol_absolute(table[i])) {
 			output_address(table[i]->addr);
 		} else {