genksyms: Track changes to enum constants

Enum constants can be used as array sizes; if the enum itself does not
appear in the symbol expansion, a change in the enum constant will go
unnoticed. Example patch that changes the ABI but does not change the
checksum with current genksyms:

| enum e {
|	E1,
|	E2,
|+	E3,
|	E_MAX
| };
|
| struct s {
|	int a[E_MAX];
| }
|
| int f(struct s *s) { ... }
| EXPORT_SYMBOL(f)

Therefore, remember the value of each enum constant and
expand each occurence to <constant> <value>. The value is not actually
computed, but instead an expression in the form
(last explicitly assigned value) + N
is used. This avoids having to parse and semantically understand whole
of C.

Note: The changes won't take effect until the lexer and parser are
rebuilt by the next patch.

Signed-off-by: Michal Marek <mmarek@suse.cz>
Acked-by: Sam Ravnborg <sam@ravnborg.org>

4 files changed, 127 insertions, 13 deletions

diff --git a/scripts/genksyms/genksyms.c b/scripts/genksyms/genksyms.c
index 4a350816a9e..f9e75531ea0 100644
--- a/scripts/genksyms/genksyms.c
+++ b/scripts/genksyms/genksyms.c
@@ -62,6 +62,7 @@ static const struct {
         [SYM_ENUM]       = {'e', "enum"},
         [SYM_STRUCT]     = {'s', "struct"},
         [SYM_UNION]      = {'u', "union"},
+        [SYM_ENUM_CONST] = {'E', "enum constant"},
 };
 
 static int equal_list(struct string_list *a, struct string_list *b);
@@ -149,10 +150,16 @@ static unsigned long crc32(const char *s)
 
 static enum symbol_type map_to_ns(enum symbol_type t)
 {
-        if (t == SYM_TYPEDEF)
-                t = SYM_NORMAL;
-        else if (t == SYM_UNION)
-                t = SYM_STRUCT;
+        switch (t) {
+        case SYM_ENUM_CONST:
+        case SYM_NORMAL:
+        case SYM_TYPEDEF:
+                return SYM_NORMAL;
+        case SYM_ENUM:
+        case SYM_STRUCT:
+        case SYM_UNION:
+                return SYM_STRUCT;
+        }
         return t;
 }
 
@@ -191,10 +198,47 @@ static struct symbol *__add_symbol(const char *name, enum symbol_type type,
                             struct string_list *defn, int is_extern,
                             int is_reference)
 {
-        unsigned long h = crc32(name) % HASH_BUCKETS;
+        unsigned long h;
         struct symbol *sym;
         enum symbol_status status = STATUS_UNCHANGED;
+        /* The parser adds symbols in the order their declaration completes,
+         * so it is safe to store the value of the previous enum constant in
+         * a static variable.
+         */
+        static int enum_counter;
+        static struct string_list *last_enum_expr;
+
+        if (type == SYM_ENUM_CONST) {
+                if (defn) {
+                        free_list(last_enum_expr, NULL);
+                        last_enum_expr = copy_list_range(defn, NULL);
+                        enum_counter = 1;
+                } else {
+                        struct string_list *expr;
+                        char buf[20];
+
+                        snprintf(buf, sizeof(buf), "%d", enum_counter++);
+                        if (last_enum_expr) {
+                                expr = copy_list_range(last_enum_expr, NULL);
+                                defn = concat_list(mk_node("("),
+                                                   expr,
+                                                   mk_node(")"),
+                                                   mk_node("+"),
+                                                   mk_node(buf), NULL);
+                        } else {
+                                defn = mk_node(buf);
+                        }
+                }
+        } else if (type == SYM_ENUM) {
+                free_list(last_enum_expr, NULL);
+                last_enum_expr = NULL;
+                enum_counter = 0;
+                if (!name)
+                        /* Anonymous enum definition, nothing more to do */
+                        return NULL;
+        }
 
+        h = crc32(name) % HASH_BUCKETS;
         for (sym = symtab[h]; sym; sym = sym->hash_next) {
                 if (map_to_ns(sym->type) == map_to_ns(type) &&
                     strcmp(name, sym->name) == 0) {
@@ -343,6 +387,22 @@ struct string_list *copy_node(struct string_list *node)
         return newnode;
 }
 
+struct string_list *copy_list_range(struct string_list *start,
+                                    struct string_list *end)
+{
+        struct string_list *res, *n;
+
+        if (start == end)
+                return NULL;
+        n = res = copy_node(start);
+        for (start = start->next; start != end; start = start->next) {
+                n->next = copy_node(start);
+                n = n->next;
+        }
+        n->next = NULL;
+        return res;
+}
+
 static int equal_list(struct string_list *a, struct string_list *b)
 {
         while (a && b) {
@@ -512,6 +572,7 @@ static unsigned long expand_and_crc_sym(struct symbol *sym, unsigned long crc)
                         crc = partial_crc32_one(' ', crc);
                         break;
 
+                case SYM_ENUM_CONST:
                 case SYM_TYPEDEF:
                         subsym = find_symbol(cur->string, cur->tag, 0);
                         /* FIXME: Bad reference files can segfault here. */
diff --git a/scripts/genksyms/genksyms.h b/scripts/genksyms/genksyms.h
index 9fdafb667e7..7ec52ae3846 100644
--- a/scripts/genksyms/genksyms.h
+++ b/scripts/genksyms/genksyms.h
@@ -26,7 +26,8 @@
 #include <stdio.h>
 
 enum symbol_type {
-        SYM_NORMAL, SYM_TYPEDEF, SYM_ENUM, SYM_STRUCT, SYM_UNION
+        SYM_NORMAL, SYM_TYPEDEF, SYM_ENUM, SYM_STRUCT, SYM_UNION,
+        SYM_ENUM_CONST
 };
 
 enum symbol_status {
@@ -66,6 +67,8 @@ void export_symbol(const char *);
 void free_node(struct string_list *list);
 void free_list(struct string_list *s, struct string_list *e);
 struct string_list *copy_node(struct string_list *);
+struct string_list *copy_list_range(struct string_list *start,
+                                    struct string_list *end);
 
 int yylex(void);
 int yyparse(void);
diff --git a/scripts/genksyms/lex.l b/scripts/genksyms/lex.l
index c125d06fbd3..e4ddd493fec 100644
--- a/scripts/genksyms/lex.l
+++ b/scripts/genksyms/lex.l
@@ -99,12 +99,23 @@ MC_TOKEN		([~%^&*+=|<>/-]=)|(&&)|("||")|(->)|(<<)|(>>)
 
 /* Macros to append to our phrase collection list.  */
 
+/*
+ * We mark any token, that that equals to a known enumerator, as
+ * SYM_ENUM_CONST. The parser will change this for struct and union tags later,
+ * the only problem is struct and union members:
+ *    enum e { a, b }; struct s { int a, b; }
+ * but in this case, the only effect will be, that the ABI checksums become
+ * more volatile, which is acceptable. Also, such collisions are quite rare,
+ * so far it was only observed in include/linux/telephony.h.
+ */
 #define _APP(T,L)       do {                                               \
                           cur_node = next_node;                            \
                           next_node = xmalloc(sizeof(*next_node));         \
                           next_node->next = cur_node;                      \
                           cur_node->string = memcpy(xmalloc(L+1), T, L+1); \
-                          cur_node->tag = SYM_NORMAL;                      \
+                          cur_node->tag =                                  \
+                            find_symbol(cur_node->string, SYM_ENUM_CONST, 1)?\
+                            SYM_ENUM_CONST : SYM_NORMAL ;                  \
                         } while (0)
 
 #define APP             _APP(yytext, yyleng)
@@ -182,8 +193,8 @@ repeat:
 
                   case STRUCT_KEYW:
                   case UNION_KEYW:
-                    dont_want_brace_phrase = 3;
                   case ENUM_KEYW:
+                    dont_want_brace_phrase = 3;
                     suppress_type_lookup = 2;
                     goto fini;
 
@@ -312,7 +323,20 @@ repeat:
           ++count;
           APP;
           goto repeat;
-        case ')': case ']': case '}':
+        case '}':
+