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>

diff --git a/scripts/genksyms/genksyms.c b/scripts/genksyms/genksyms.c
index 4a35081..f9e7553 100644 (file)
--- 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 9fdafb6..7ec52ae 100644 (file)
--- 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 c125d06..e4ddd49 100644 (file)
--- 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 '}':
+         /* is this the last line of an enum declaration? */
+         if (count == 0)
+           {
+             /* Put back the token we just read so's we can find it again
+                after registering the expression.  */
+             unput(token);
+
+             lexstate = ST_NORMAL;
+             token = EXPRESSION_PHRASE;
+             break;
+           }
+         /* FALLTHRU */
+       case ')': case ']':
          --count;
          APP;
          goto repeat;

diff --git a/scripts/genksyms/parse.y b/scripts/genksyms/parse.y
index 09a265c..ba5c242 100644 (file)
--- a/scripts/genksyms/parse.y
+++ b/scripts/genksyms/parse.y
@@ -25,6 +25,7 @@
 
 #include <assert.h>
 #include <stdlib.h>
+#include <string.h>
 #include "genksyms.h"
 
 static int is_typedef;
@@ -227,16 +228,19 @@ type_specifier:
                  add_symbol(i->string, SYM_UNION, s, is_extern);
                  $$ = $3;
                }
-       | ENUM_KEYW IDENT BRACE_PHRASE
+       | ENUM_KEYW IDENT enum_body
                { struct string_list *s = *$3, *i = *$2, *r;
                  r = copy_node(i); r->tag = SYM_ENUM;
                  r->next = (*$1)->next; *$3 = r; (*$1)->next = NULL;
                  add_symbol(i->string, SYM_ENUM, s, is_extern);
                  $$ = $3;
                }
-
-       /* Anonymous s/u/e definitions.  Nothing needs doing.  */
-       | ENUM_KEYW BRACE_PHRASE                        { $$ = $2; }
+       /*
+        * Anonymous enum definition. Tell add_symbol() to restart its counter.
+        */
+       | ENUM_KEYW enum_body
+               { add_symbol(NULL, SYM_ENUM, NULL, 0); $$ = $2; }
+       /* Anonymous s/u definitions.  Nothing needs doing.  */
        | STRUCT_KEYW class_body                        { $$ = $2; }
        | UNION_KEYW class_body                         { $$ = $2; }
        ;
@@ -449,6 +453,28 @@ attribute_opt:
        | attribute_opt ATTRIBUTE_PHRASE
        ;
 
+enum_body:
+       '{' enumerator_list '}'                         { $$ = $3; }
+       | '{' enumerator_list ',' '}'                   { $$ = $4; }
+        ;
+
+enumerator_list:
+       enumerator
+       | enumerator_list ',' enumerator
+
+enumerator:
+       IDENT
+               {
+                       const char *name = strdup((*$1)->string);
+                       add_symbol(name, SYM_ENUM_CONST, NULL, 0);
+               }
+       | IDENT '=' EXPRESSION_PHRASE
+               {
+                       const char *name = strdup((*$1)->string);
+                       struct string_list *expr = copy_list_range(*$3, *$2);
+                       add_symbol(name, SYM_ENUM_CONST, expr, 0);
+               }
+
 asm_definition:
        ASM_PHRASE ';'                                  { $$ = $2; }
        ;