x86, relocs: Add manual debug mode

Improve the debuggability of relocations output. When trying to compare
the output between different linkers, it's handy to be able to see the
section names in output.

Signed-off-by: Michael Davidson <md@google.com>
Link: http://lkml.kernel.org/r/20140121203223.GA12649@www.outflux.net
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/tools/relocs.c

@@ -1015,14 +1015,38 @@ static void emit_relocs(int as_text, int use_real_mode)
 	}
 }
 
+/*
+ * As an aid to debugging problems with different linkers
+ * print summary information about the relocs.
+ * Since different linkers tend to emit the sections in
+ * different orders we use the section names in the output.
+ */
+static int do_reloc_info(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
+				const char *symname)
+{
+	printf("%s\t%s\t%s\t%s\n",
+		sec_name(sec->shdr.sh_info),
+		rel_type(ELF_R_TYPE(rel->r_info)),
+		symname,
+		sec_name(sym->st_shndx));
+	return 0;
+}
+
+static void print_reloc_info(void)
+{
+	printf("reloc section\treloc type\tsymbol\tsymbol section\n");
+	walk_relocs(do_reloc_info);
+}
+
 #if ELF_BITS == 64
 # define process process_64
 #else
 # define process process_32
 #endif
 
 void process(FILE *fp, int use_real_mode, int as_text,
-	     int show_absolute_syms, int show_absolute_relocs)
+	     int show_absolute_syms, int show_absolute_relocs,
+	     int show_reloc_info)
 {
 	regex_init(use_real_mode);
 	read_ehdr(fp);
@@ -1040,5 +1064,9 @@ void process(FILE *fp, int use_real_mode, int as_text,
 		print_absolute_relocs();
 		return;
 	}
+	if (show_reloc_info) {
+		print_reloc_info();
+		return;
+	}
 	emit_relocs(as_text, use_real_mode);
 }

arch/x86/tools/relocs.h

@@ -29,8 +29,9 @@ enum symtype {
 };
 
 void process_32(FILE *fp, int use_real_mode, int as_text,
-		int show_absolute_syms, int show_absolute_relocs);
+		int show_absolute_syms, int show_absolute_relocs,
+		int show_reloc_info);
 void process_64(FILE *fp, int use_real_mode, int as_text,
-		int show_absolute_syms, int show_absolute_relocs);
-
+		int show_absolute_syms, int show_absolute_relocs,
+		int show_reloc_info);
 #endif /* RELOCS_H */

arch/x86/tools/relocs_common.c

@@ -11,12 +11,13 @@ void die(char *fmt, ...)
 
 static void usage(void)
 {
-	die("relocs [--abs-syms|--abs-relocs|--text|--realmode] vmlinux\n");
+	die("relocs [--abs-syms|--abs-relocs|--reloc-info|--text|--realmode]" \
+	    " vmlinux\n");
 }
 
 int main(int argc, char **argv)
 {
-	int show_absolute_syms, show_absolute_relocs;
+	int show_absolute_syms, show_absolute_relocs, show_reloc_info;
 	int as_text, use_real_mode;
 	const char *fname;
 	FILE *fp;
@@ -25,6 +26,7 @@ int main(int argc, char **argv)
 
 	show_absolute_syms = 0;
 	show_absolute_relocs = 0;
+	show_reloc_info = 0;
 	as_text = 0;
 	use_real_mode = 0;
 	fname = NULL;
@@ -39,6 +41,10 @@ int main(int argc, char **argv)
 				show_absolute_relocs = 1;
 				continue;
 			}
+			if (strcmp(arg, "--reloc-info") == 0) {
+				show_reloc_info = 1;
+				continue;
+			}
 			if (strcmp(arg, "--text") == 0) {
 				as_text = 1;
 				continue;
@@ -67,10 +73,12 @@ int main(int argc, char **argv)
 	rewind(fp);
 	if (e_ident[EI_CLASS] == ELFCLASS64)
 		process_64(fp, use_real_mode, as_text,
-			   show_absolute_syms, show_absolute_relocs);
+			   show_absolute_syms, show_absolute_relocs,
+			   show_reloc_info);
 	else
 		process_32(fp, use_real_mode, as_text,
-			   show_absolute_syms, show_absolute_relocs);
+			   show_absolute_syms, show_absolute_relocs,
+			   show_reloc_info);
 	fclose(fp);
 	return 0;
 }