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/lex.l b/scripts/genksyms/lex.l
index c125d06..e4ddd49 100644
--- a/scripts/genksyms/lex.l
+++ b/scripts/genksyms/lex.l
@@ -99,12 +99,23 @@
/* 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 @@
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 @@
++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;
