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Subject[genksyms patch 3/4] Track symbol checksum changes
Sometimes it is preferable to avoid changes of exported symbol checksums (to
avoid breaking externally provided modules). When a checksum change occurs, it
can be hard to figure out what caused this change: underlying types may have
changed, or additional type information may simply have become available at the
point where a symbol is exported.

Add a new --reference option to genksyms which allows it to report why
checksums change, based on the type information dumps it creates with
the --dump-types flag. Genksyms will read in such a dump from a previous run,
and report which symbols have changed (and why).

The behavior can be controlled for an entire build as follows: If
KBUILD_SYMTYPES is set, genksyms uses --dump-types to produce *.symtypes dump
files. If any *.symref files exist, those will be used as the reference to
check against. If KBUILD_PRESERVE is set, checksum changes will fail the
build.

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>

---
scripts/Makefile.build | 16 ++
scripts/genksyms/genksyms.c | 236 +++++++++++++++++++++++++++++++++++++++++---
scripts/genksyms/genksyms.h | 6 +
3 files changed, 239 insertions(+), 19 deletions(-)
Index: b/scripts/genksyms/genksyms.c
===================================================================
--- a/scripts/genksyms/genksyms.c
+++ b/scripts/genksyms/genksyms.c
@@ -42,7 +42,8 @@ static FILE *debugfile;
int cur_line = 1;
char *cur_filename;

-static int flag_debug, flag_dump_defs, flag_dump_types, flag_warnings;
+static int flag_debug, flag_dump_defs, flag_reference, flag_dump_types,
+ flag_preserve, flag_warnings;
static const char *arch = "";
static const char *mod_prefix = "";

@@ -58,6 +59,8 @@ static const char *const symbol_type_nam

static int equal_list(struct string_list *a, struct string_list *b);
static void print_list(FILE * f, struct string_list *list);
+static void print_location(void);
+static void print_type_name(enum symbol_type type, const char *name);

/*----------------------------------------------------------------------*/

@@ -151,25 +154,66 @@ struct symbol *find_symbol(const char *n

for (sym = symtab[h]; sym; sym = sym->hash_next)
if (map_to_ns(sym->type) == map_to_ns(ns) &&
- strcmp(name, sym->name) == 0)
+ strcmp(name, sym->name) == 0 &&
+ sym->is_declared)
break;

return sym;
}

-struct symbol *add_symbol(const char *name, enum symbol_type type,
- struct string_list *defn, int is_extern)
+static int is_unknown_symbol(struct symbol *sym)
+{
+ struct string_list *defn;
+
+ return ((sym->type == SYM_STRUCT ||
+ sym->type == SYM_UNION ||
+ sym->type == SYM_ENUM) &&
+ (defn = sym->defn) && defn->tag == SYM_NORMAL &&
+ strcmp(defn->string, "}") == 0 &&
+ (defn = defn->next) && defn->tag == SYM_NORMAL &&
+ strcmp(defn->string, "UNKNOWN") == 0 &&
+ (defn = defn->next) && defn->tag == SYM_NORMAL &&
+ strcmp(defn->string, "{") == 0);
+}
+
+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;
struct symbol *sym;
+ enum symbol_status status = STATUS_UNCHANGED;

for (sym = symtab[h]; sym; sym = sym->hash_next) {
- if (map_to_ns(sym->type) == map_to_ns(type)
- && strcmp(name, sym->name) == 0) {
- if (!equal_list(sym->defn, defn))
+ if (map_to_ns(sym->type) == map_to_ns(type) &&
+ strcmp(name, sym->name) == 0) {
+ if (is_reference)
+ /* fall through */ ;
+ else if (sym->type == type &&
+ equal_list(sym->defn, defn)) {
+ sym->is_declared = 1;
+ return sym;
+ } else if (!sym->is_declared) {
+ status = is_unknown_symbol(sym) ?
+ STATUS_DEFINED : STATUS_MODIFIED;
+ } else {
error_with_pos("redefinition of %s", name);
- return sym;
+ return sym;
+ }
+ break;
+ }
+ }
+
+ if (sym) {
+ struct symbol **psym;
+
+ for (psym = &symtab[h]; *psym; psym = &(*psym)->hash_next) {
+ if (*psym == sym) {
+ *psym = sym->hash_next;
+ break;
+ }
}
+ --nsyms;
}

sym = xmalloc(sizeof(*sym));
@@ -183,6 +227,9 @@ struct symbol *add_symbol(const char *na
sym->hash_next = symtab[h];
symtab[h] = sym;

+ sym->is_declared = !is_reference;
+ sym->status = status;
+
if (flag_debug) {
fprintf(debugfile, "Defn for %s %s == <",
symbol_type_name[type], name);
@@ -196,6 +243,18 @@ struct symbol *add_symbol(const char *na
return sym;
}

+struct symbol *add_symbol(const char *name, enum symbol_type type,
+ struct string_list *defn, int is_extern)
+{
+ return __add_symbol(name, type, defn, is_extern, 0);
+}
+
+struct symbol *add_reference_symbol(const char *name, enum symbol_type type,
+ struct string_list *defn, int is_extern)
+{
+ return __add_symbol(name, type, defn, is_extern, 1);
+}
+
/*----------------------------------------------------------------------*/

void free_node(struct string_list *node)
@@ -236,6 +295,82 @@ static int equal_list(struct string_list
return !a && !b;
}

+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+
+struct string_list *read_node(FILE *f)
+{
+ char buffer[256];
+ struct string_list node = {
+ .string = buffer,
+ .tag = SYM_NORMAL };
+ int c;
+
+ while ((c = fgetc(f)) != EOF) {
+ if (c == ' ') {
+ if (node.string == buffer)
+ continue;
+ break;
+ } else if (c == '\n') {
+ if (node.string == buffer)
+ return NULL;
+ ungetc(c, f);
+ break;
+ }
+ if (node.string >= buffer + sizeof(buffer) - 1) {
+ fprintf(stderr, "Token too long\n");
+ exit(1);
+ }
+ *node.string++ = c;
+ }
+ if (node.string == buffer)
+ return NULL;
+ *node.string = 0;
+ node.string = buffer;
+
+ if (node.string[1] == '#') {
+ int n;
+
+ for (n = 0; n < ARRAY_SIZE(symbol_type_name); n++) {
+ if (node.string[0] == symbol_type_name[n][0]) {
+ node.tag = n;
+ node.string += 2;
+ return copy_node(&node);
+ }
+ }
+ fprintf(stderr, "Unknown type %c\n", node.string[0]);
+ exit(1);
+ }
+ return copy_node(&node);
+}
+
+static void read_reference(FILE *f)
+{
+ while (!feof(f)) {
+ struct string_list *defn = NULL;
+ struct string_list *sym, *def;
+ int is_extern = 0;
+
+ sym = read_node(f);
+ if (!sym)
+ continue;
+ def = read_node(f);
+ if (def && def->tag == SYM_NORMAL &&
+ !strcmp(def->string, "extern")) {
+ is_extern = 1;
+ free_node(def);
+ def = read_node(f);
+ }
+ while (def) {
+ def->next = defn;
+ defn = def;
+ def = read_node(f);
+ }
+ add_reference_symbol(xstrdup(sym->string), sym->tag,
+ defn, is_extern);
+ free_node(sym);
+ }
+}
+
static void print_node(FILE * f, struct string_list *list)
{
if (list->tag != SYM_NORMAL) {
@@ -311,6 +446,7 @@ static unsigned long expand_and_crc_sym(

case SYM_TYPEDEF:
subsym = find_symbol(cur->string, cur->tag);
+ /* FIXME: Bad reference files can segfault here. */
if (subsym->expansion_trail) {
if (flag_dump_defs)
fprintf(debugfile, "%s ", cur->string);
@@ -347,9 +483,22 @@ static unsigned long expand_and_crc_sym(
t = n;

n = xmalloc(sizeof(*n));
- n->string = xstrdup("{ UNKNOWN }");
+ n->string = xstrdup("{");
+ n->tag = SYM_NORMAL;
+ n->next = t;
+ t = n;
+
+ n = xmalloc(sizeof(*n));
+ n->string = xstrdup("UNKNOWN");
+ n->tag = SYM_NORMAL;
+ n->next = t;
+ t = n;
+
+ n = xmalloc(sizeof(*n));
+ n->string = xstrdup("}");
n->tag = SYM_NORMAL;
n->next = t;
+ t = n;

subsym =
add_symbol(cur->string, cur->tag, n, 0);
@@ -397,20 +546,42 @@ void export_symbol(const char *name)
error_with_pos("export undefined symbol %s", name);
else {
unsigned long crc;
+ int has_changed = 0;

if (flag_dump_defs)
fprintf(debugfile, "Export %s == <", name);

expansion_trail = (struct symbol *)-1L;

+ sym->expansion_trail = expansion_trail;
+ expansion_trail = sym;
crc = expand_and_crc_sym(sym, 0xffffffff) ^ 0xffffffff;

sym = expansion_trail;
while (sym != (struct symbol *)-1L) {
struct symbol *n = sym->expansion_trail;
+
+ if (sym->status != STATUS_UNCHANGED) {
+ if (!has_changed) {
+ print_location();
+ fprintf(stderr, "%s: %s: modversion "
+ "changed because of changes "
+ "in ", flag_preserve ? "error" :
+ "warning", name);
+ } else
+ fprintf(stderr, ", ");
+ print_type_name(sym->type, sym->name);
+ if (sym->status == STATUS_DEFINED)
+ fprintf(stderr, " (became defined)");
+ has_changed = 1;
+ if (flag_preserve)
+ errors++;
+ }
sym->expansion_trail = 0;
sym = n;
}
+ if (has_changed)
+ fprintf(stderr, "\n");

if (flag_dump_defs)
fputs(">\n", debugfile);
@@ -421,13 +592,26 @@ void export_symbol(const char *name)
}

/*----------------------------------------------------------------------*/
+
+static void print_location(void)
+{
+ fprintf(stderr, "%s:%d: ", cur_filename ? : "<stdin>", cur_line);
+}
+
+static void print_type_name(enum symbol_type type, const char *name)
+{
+ if (type != SYM_NORMAL)
+ fprintf(stderr, "%s %s", symbol_type_name[type], name);
+ else
+ fprintf(stderr, "%s", name);
+}
+
void error_with_pos(const char *fmt, ...)
{
va_list args;

if (flag_warnings) {
- fprintf(stderr, "%s:%d: ", cur_filename ? : "<stdin>",
- cur_line);
+ print_location();

va_start(args, fmt);
vfprintf(stderr, fmt, args);
@@ -445,7 +629,9 @@ static void genksyms_usage(void)
" -a, --arch Select architecture\n"
" -d, --debug Increment the debug level (repeatable)\n"
" -D, --dump Dump expanded symbol defs (for debugging only)\n"
- " -T, --dump-types file Dump expanded types into file (for debugging only)\n"
+ " -r, --reference file Read reference symbols from a file\n"
+ " -T, --dump-types file Dump expanded types into file\n"
+ " -p, --preserve Preserve reference modversions or fail\n"
" -w, --warnings Enable warnings\n"
" -q, --quiet Disable warnings (default)\n"
" -h, --help Print this message\n"
@@ -454,7 +640,9 @@ static void genksyms_usage(void)
" -a Select architecture\n"
" -d Increment the debug level (repeatable)\n"
" -D Dump expanded symbol defs (for debugging only)\n"
- " -T file Dump expanded types into file (for debugging only)\n"
+ " -r file Read reference symbols from a file\n"
+ " -T file Dump expanded types into file\n"
+ " -p Preserve reference modversions or fail\n"
" -w Enable warnings\n"
" -q Disable warnings (default)\n"
" -h Print this message\n"
@@ -465,7 +653,7 @@ static void genksyms_usage(void)

int main(int argc, char **argv)
{
- FILE *dumpfile = NULL;
+ FILE *dumpfile = NULL, *ref_file = NULL;
int o;

#ifdef __GNU_LIBRARY__
@@ -475,16 +663,18 @@ int main(int argc, char **argv)
{"warnings", 0, 0, 'w'},
{"quiet", 0, 0, 'q'},
{"dump", 0, 0, 'D'},
+ {"reference", 1, 0, 'r'},
{"dump-types", 1, 0, 'T'},
+ {"preserve", 0, 0, 'p'},
{"version", 0, 0, 'V'},
{"help", 0, 0, 'h'},
{0, 0, 0, 0}
};

- while ((o = getopt_long(argc, argv, "a:dwqVDT:h",
+ while ((o = getopt_long(argc, argv, "a:dwqVDr:T:ph",
&long_opts[0], NULL)) != EOF)
#else /* __GNU_LIBRARY__ */
- while ((o = getopt(argc, argv, "a:dwqVDT:h")) != EOF)
+ while ((o = getopt(argc, argv, "a:dwqVDr:T:ph")) != EOF)
#endif /* __GNU_LIBRARY__ */
switch (o) {
case 'a':
@@ -505,6 +695,14 @@ int main(int argc, char **argv)
case 'D':
flag_dump_defs = 1;
break;
+ case 'r':
+ flag_reference = 1;
+ ref_file = fopen(optarg, "r");
+ if (!ref_file) {
+ perror(optarg);
+ return 1;
+ }
+ break;
case 'T':
flag_dump_types = 1;
dumpfile = fopen(optarg, "w");
@@ -513,6 +711,9 @@ int main(int argc, char **argv)
return 1;
}
break;
+ case 'p':
+ flag_preserve = 1;
+ break;
case 'h':
genksyms_usage();
return 0;
@@ -534,6 +735,9 @@ int main(int argc, char **argv)
/* setlinebuf(debugfile); */
}

+ if (flag_reference)
+ read_reference(ref_file);
+
yyparse();

if (flag_dump_types && visited_symbols) {
Index: b/scripts/genksyms/genksyms.h
===================================================================
--- a/scripts/genksyms/genksyms.h
+++ b/scripts/genksyms/genksyms.h
@@ -29,6 +29,10 @@ enum symbol_type {
SYM_NORMAL, SYM_TYPEDEF, SYM_ENUM, SYM_STRUCT, SYM_UNION
};

+enum symbol_status {
+ STATUS_UNCHANGED, STATUS_DEFINED, STATUS_MODIFIED
+};
+
struct string_list {
struct string_list *next;
enum symbol_type tag;
@@ -43,6 +47,8 @@ struct symbol {
struct symbol *expansion_trail;
struct symbol *visited;
int is_extern;
+ int is_declared;
+ enum symbol_status status;
};

typedef struct string_list **yystype;
Index: b/scripts/Makefile.build
===================================================================
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -153,12 +153,18 @@ $(obj)/%.i: $(src)/%.c FORCE

quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
cmd_cc_symtypes_c = \
+ set -e; \
$(CPP) -D__GENKSYMS__ $(c_flags) $< \
- | $(GENKSYMS) -T $@ >/dev/null; \
+ | $(GENKSYMS) -T $@ \
+ -r $(firstword $(wildcard \
+ $(@:.symtypes=.symref) /dev/null)) \
+ $(if $(KBUILD_PRESERVE),-p) \
+ -a $(ARCH) \
+ >/dev/null; \
test -s $@ || rm -f $@

$(obj)/%.symtypes : $(src)/%.c FORCE
- $(call if_changed_dep,cc_symtypes_c)
+ $(call cmd,cc_symtypes_c)

# C (.c) files
# The C file is compiled and updated dependency information is generated.
@@ -187,7 +193,11 @@ cmd_modversions = \
if $(OBJDUMP) -h $(@D)/.tmp_$(@F) | grep -q __ksymtab; then \
$(CPP) -D__GENKSYMS__ $(c_flags) $< \
| $(GENKSYMS) $(if $(KBUILD_SYMTYPES), \
- -T $(@D)/$(@F:.o=.symtypes)) -a $(ARCH) \
+ -T $(@:.o=.symtypes)) \
+ -r $(firstword $(wildcard \
+ $(@:.o=.symref) /dev/null)) \
+ $(if $(KBUILD_PRESERVE),-p) \
+ -a $(ARCH) \
> $(@D)/.tmp_$(@F:.o=.ver); \
\
$(LD) $(LDFLAGS) -r -o $@ $(@D)/.tmp_$(@F) \



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