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

Masahiro Yamada
2022-05-12T04:38:03Z

On Mon, May 9, 2022 at 4:09 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> 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>
> ---

Applied to linux-kbuild.

>
> 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
>
> --
> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20220508190631.2386038-3-masahiroy%40kernel.org.

--
Best Regards
Masahiro Yamada