[PATCH v4 02/14] modpost: change the license of EXPORT_SYMBOL to bool type

Masahiro Yamada
2022-05-08T19:19:07Z

There were more EXPORT_SYMBOL types in the past. The following commits
removed unused ones.

- f1c3d73e973c ("module: remove EXPORT_SYMBOL_GPL_FUTURE")
- 367948220fce ("module: remove EXPORT_UNUSED_SYMBOL*")

There are 3 remaining in enum export, but export_unknown does not make
any sense because we never expect such a situation like "we do not know
how it was exported".

If the symbol name starts with "__ksymtab_", but the section name
does not start with "___ksymtab+" or "___ksymtab_gpl+", it is not an
exported symbol.

It occurs when a variable starting with "__ksymtab_" is directly defined:

int __ksymtab_foo;

Presumably, there is no practical issue for using such a weird variable
name (but there is no good reason for doing so, either).

Anyway, that is not an exported symbol. Setting export_unknown is not
the right thing to do. Do not call sym_add_exported() in this case.

With pointless export_unknown removed, the export type finally becomes
boolean (either EXPORT_SYMBOL or EXPORT_SYMBOL_GPL).

I renamed the field name to is_gpl_only. EXPORT_SYMBOL_GPL sets it true.
Only GPL-compatible modules can use it.

I removed the orphan comment, "How a symbol is exported", which is
unrelated to sec_mismatch_count. It is about enum export.
See commit bd5cbcedf446 ("kbuild: export-type enhancement to modpost.c")

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
---

Changes in v4:
- Rebase again because I dropped
https://patchwork.kernel.org/project/linux-kbuild/patch/20220501084032.1025918-11-masahiroy@kernel.org/
- Remove warning message because I plan to change this hunk again in a later commit
- Remove orphan comment

Changes in v3:
- New patch

scripts/mod/modpost.c | 108 ++++++++++++------------------------------
1 file changed, 30 insertions(+), 78 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index d9efbd5b31a6..a78b75f0eeb0 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -30,7 +30,7 @@ static bool all_versions;
static bool external_module;
/* Only warn about unresolved symbols */
static bool warn_unresolved;
-/* How a symbol is exported */
+
static int sec_mismatch_count;
static bool sec_mismatch_warn_only = true;
/* ignore missing files */
@@ -47,12 +47,6 @@ static bool error_occurred;
#define MAX_UNRESOLVED_REPORTS 10
static unsigned int nr_unresolved;

-enum export {
- export_plain,
- export_gpl,
- export_unknown
-};
-
/* In kernel, this size is defined in linux/module.h;
* here we use Elf_Addr instead of long for covering cross-compile
*/
@@ -219,7 +213,7 @@ struct symbol {
bool crc_valid;
bool weak;
bool is_static; /* true if symbol is not global */
- enum export export; /* Type of export */
+ bool is_gpl_only; /* exported by EXPORT_SYMBOL_GPL */
char name[];
};

@@ -316,34 +310,6 @@ static void add_namespace(struct list_head *head, const char *namespace)
}
}

-static const struct {
- const char *str;
- enum export export;
-} export_list[] = {
- { .str = "EXPORT_SYMBOL", .export = export_plain },
- { .str = "EXPORT_SYMBOL_GPL", .export = export_gpl },
- { .str = "(unknown)", .export = export_unknown },
-};
-
-
-static const char *export_str(enum export ex)
-{
- return export_list[ex].str;
-}
-
-static enum export export_no(const char *s)
-{
- int i;
-
- if (!s)
- return export_unknown;
- for (i = 0; export_list[i].export != export_unknown; i++) {
- if (strcmp(export_list[i].str, s) == 0)
- return export_list[i].export;
- }
- return export_unknown;
-}
-
static void *sym_get_data_by_offset(const struct elf_info *info,
unsigned int secindex, unsigned long offset)
{
@@ -374,18 +340,6 @@ static const char *sec_name(const struct elf_info *info, int secindex)

#define strstarts(str, prefix) (strncmp(str, prefix, strlen(prefix)) == 0)

-static enum export export_from_secname(struct elf_info *elf, unsigned int sec)
-{
- const char *secname = sec_name(elf, sec);
-
- if (strstarts(secname, "___ksymtab+"))
- return export_plain;
- else if (strstarts(secname, "___ksymtab_gpl+"))
- return export_gpl;
- else
- return export_unknown;
-}
-
static void sym_update_namespace(const char *symname, const char *namespace)
{
struct symbol *s = find_symbol(symname);
@@ -405,7 +359,7 @@ static void sym_update_namespace(const char *symname, const char *namespace)
}

static struct symbol *sym_add_exported(const char *name, struct module *mod,
- enum export export)
+ bool gpl_only)
{
struct symbol *s = find_symbol(name);

@@ -417,7 +371,7 @@ static struct symbol *sym_add_exported(const char *name, struct module *mod,

s = alloc_symbol(name);
s->module = mod;
- s->export = export;
+ s->is_gpl_only = gpl_only;
list_add_tail(&s->list, &mod->exported_symbols);
hash_add_symbol(s);

@@ -689,8 +643,6 @@ static void handle_modversion(const struct module *mod,
static void handle_symbol(struct module *mod, struct elf_info *info,
const Elf_Sym *sym, const char *symname)
{
- const char *name;
-
switch (sym->st_shndx) {
case SHN_COMMON:
if (strstarts(symname, "__gnu_lto_")) {
@@ -724,12 +676,15 @@ static void handle_symbol(struct module *mod, struct elf_info *info,
default:
/* All exported symbols */
if (strstarts(symname, "__ksymtab_")) {
- enum export export;
+ const char *name, *secname;

name = symname + strlen("__ksymtab_");
- export = export_from_secname(info,
- get_secindex(info, sym));
- sym_add_exported(name, mod, export);
+ secname = sec_name(info, get_secindex(info, sym));
+
+ if (strstarts(secname, "___ksymtab_gpl+"))
+ sym_add_exported(name, mod, true);
+ else if (strstarts(secname, "___ksymtab+"))
+ sym_add_exported(name, mod, false);
}
if (strcmp(symname, "init_module") == 0)
mod->has_init = true;
@@ -2140,20 +2095,6 @@ void buf_write(struct buffer *buf, const char *s, int len)
buf->pos += len;
}

-static void check_for_gpl_usage(enum export exp, const char *m, const char *s)
-{
- switch (exp) {
- case export_gpl:
- error("GPL-incompatible module %s.ko uses GPL-only symbol '%s'\n",
- m, s);
- break;
- case export_plain:
- case export_unknown:
- /* ignore */
- break;
- }
-}
-
static void check_exports(struct module *mod)
{
struct symbol *s, *exp;
@@ -2192,8 +2133,9 @@ static void check_exports(struct module *mod)
add_namespace(&mod->missing_namespaces, exp->namespace);
}

- if (!mod->is_gpl_compatible)
- check_for_gpl_usage(exp->export, basename, exp->name);
+ if (!mod->is_gpl_compatible && exp->is_gpl_only)
+ error("GPL-incompatible module %s.ko uses GPL-only symbol '%s'\n",
+ basename, exp->name);
}
}

@@ -2437,6 +2379,7 @@ static void read_dump(const char *fname)
unsigned int crc;
struct module *mod;
struct symbol *s;
+ bool gpl_only;

if (!(symname = strchr(line, '\t')))
goto fail;
@@ -2454,12 +2397,22 @@ static void read_dump(const char *fname)
crc = strtoul(line, &d, 16);
if (*symname == '\0' || *modname == '\0' || *d != '\0')
goto fail;
+
+ if (!strcmp(export, "EXPORT_SYMBOL_GPL")) {
+ gpl_only = true;
+ } else if (!strcmp(export, "EXPORT_SYMBOL")) {
+ gpl_only = false;
+ } else {
+ error("%s: unknown license %s. skip", symname, export);
+ continue;
+ }
+
mod = find_module(modname);
if (!mod) {
mod = new_module(modname);
mod->from_dump = true;
}
- s = sym_add_exported(symname, mod, export_no(export));
+ s = sym_add_exported(symname, mod, gpl_only);
s->is_static = false;
sym_set_crc(symname, crc);
sym_update_namespace(symname, namespace);
@@ -2481,9 +2434,9 @@ static void write_dump(const char *fname)
if (mod->from_dump)
continue;
list_for_each_entry(sym, &mod->exported_symbols, list) {
- buf_printf(&buf, "0x%08x\t%s\t%s\t%s\t%s\n",
+ buf_printf(&buf, "0x%08x\t%s\t%s\tEXPORT_SYMBOL%s\t%s\n",
sym->crc, sym->name, mod->name,
- export_str(sym->export),
+ sym->is_gpl_only ? "_GPL" : "",
sym->namespace ?: "");
}
}
@@ -2604,9 +2557,8 @@ int main(int argc, char **argv)

for (s = symbolhash[n]; s; s = s->next) {
if (s->is_static)
- error("\"%s\" [%s] is a static %s\n",
- s->name, s->module->name,
- export_str(s->export));
+ error("\"%s\" [%s] is a static EXPORT_SYMBOL\n",
+ s->name, s->module->name);
}
}

--
2.32.0