modpost: add strict white-listing when referencing sections.

Prints a warning when a section references a section outside a strict
white-list.  This will be useful to print a warning if __ex_table
references a non-executable section.
Signed-off-by: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

scripts/mod/modpost.c

@@ -925,7 +925,8 @@ enum mismatch {
 
 struct sectioncheck {
 	const char *fromsec[20];
-	const char *tosec[20];
+	const char *bad_tosec[20];
+	const char *good_tosec[20];
 	enum mismatch mismatch;
 	const char *symbol_white_list[20];
 };
@@ -936,19 +937,19 @@ static const struct sectioncheck sectioncheck[] = {
  */
 {
 	.fromsec = { TEXT_SECTIONS, NULL },
-	.tosec   = { ALL_INIT_SECTIONS, NULL },
+	.bad_tosec = { ALL_INIT_SECTIONS, NULL },
 	.mismatch = TEXT_TO_ANY_INIT,
 	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
 },
 {
 	.fromsec = { DATA_SECTIONS, NULL },
-	.tosec   = { ALL_XXXINIT_SECTIONS, NULL },
+	.bad_tosec = { ALL_XXXINIT_SECTIONS, NULL },
 	.mismatch = DATA_TO_ANY_INIT,
 	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
 },
 {
 	.fromsec = { DATA_SECTIONS, NULL },
-	.tosec   = { INIT_SECTIONS, NULL },
+	.bad_tosec = { INIT_SECTIONS, NULL },
 	.mismatch = DATA_TO_ANY_INIT,
 	.symbol_white_list = {
 		"*_template", "*_timer", "*_sht", "*_ops",
@@ -957,54 +958,54 @@ static const struct sectioncheck sectioncheck[] = {
 },
 {
 	.fromsec = { TEXT_SECTIONS, NULL },
-	.tosec   = { ALL_EXIT_SECTIONS, NULL },
+	.bad_tosec = { ALL_EXIT_SECTIONS, NULL },
 	.mismatch = TEXT_TO_ANY_EXIT,
 	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
 },
 {
 	.fromsec = { DATA_SECTIONS, NULL },
-	.tosec   = { ALL_EXIT_SECTIONS, NULL },
+	.bad_tosec = { ALL_EXIT_SECTIONS, NULL },
 	.mismatch = DATA_TO_ANY_EXIT,
 	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
 },
 /* Do not reference init code/data from meminit code/data */
 {
 	.fromsec = { ALL_XXXINIT_SECTIONS, NULL },
-	.tosec   = { INIT_SECTIONS, NULL },
+	.bad_tosec = { INIT_SECTIONS, NULL },
 	.mismatch = XXXINIT_TO_SOME_INIT,
 	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
 },
 /* Do not reference exit code/data from memexit code/data */
 {
 	.fromsec = { ALL_XXXEXIT_SECTIONS, NULL },
-	.tosec   = { EXIT_SECTIONS, NULL },
+	.bad_tosec = { EXIT_SECTIONS, NULL },
 	.mismatch = XXXEXIT_TO_SOME_EXIT,
 	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
 },
 /* Do not use exit code/data from init code */
 {
 	.fromsec = { ALL_INIT_SECTIONS, NULL },
-	.tosec   = { ALL_EXIT_SECTIONS, NULL },
+	.bad_tosec = { ALL_EXIT_SECTIONS, NULL },
 	.mismatch = ANY_INIT_TO_ANY_EXIT,
 	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
 },
 /* Do not use init code/data from exit code */
 {
 	.fromsec = { ALL_EXIT_SECTIONS, NULL },
-	.tosec   = { ALL_INIT_SECTIONS, NULL },
+	.bad_tosec = { ALL_INIT_SECTIONS, NULL },
 	.mismatch = ANY_EXIT_TO_ANY_INIT,
 	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
 },
 {
 	.fromsec = { ALL_PCI_INIT_SECTIONS, NULL },
-	.tosec   = { INIT_SECTIONS, NULL },
+	.bad_tosec = { INIT_SECTIONS, NULL },
 	.mismatch = ANY_INIT_TO_ANY_EXIT,
 	.symbol_white_list = { NULL },
 },
 /* Do not export init/exit functions or data */
 {
 	.fromsec = { "__ksymtab*", NULL },
-	.tosec   = { INIT_SECTIONS, EXIT_SECTIONS, NULL },
+	.bad_tosec = { INIT_SECTIONS, EXIT_SECTIONS, NULL },
 	.mismatch = EXPORT_TO_INIT_EXIT,
 	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
 }
@@ -1018,9 +1019,12 @@ static const struct sectioncheck *section_mismatch(
 	const struct sectioncheck *check = &sectioncheck[0];
 
 	for (i = 0; i < elems; i++) {
-		if (match(fromsec, check->fromsec) &&
-		    match(tosec, check->tosec))
-			return check;
+		if (match(fromsec, check->fromsec)) {
+			if (check->bad_tosec[0] && match(tosec, check->bad_tosec))
+				return check;
+			if (check->good_tosec[0] && !match(tosec, check->good_tosec))
+				return check;
+		}
 		check++;
 	}
 	return NULL;