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module: use kflagstab instead of *_gpl sections

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Read kflagstab section for vmlinux and modules to determine whether
kernel symbols are GPL only.

This patch eliminates the need for fragmenting the ksymtab for infering
the value of GPL-only symbol flag, henceforth stop populating *_gpl
versions of the ksymtab and kcrctab in modpost.

Signed-off-by: Siddharth Nayyar <sidnayyar@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
This commit is contained in:
Siddharth Nayyar
2026-03-26 21:25:05 +00:00
committed by Sami Tolvanen
parent 16d0e04f54
commit 55fcb926b6
5 changed files with 46 additions and 40 deletions
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1
kernel/module/internal.h
View File

@@ -57,6 +57,7 @@ extern const struct kernel_symbol __start___ksymtab_gpl[];
extern const struct kernel_symbol __stop___ksymtab_gpl[];
extern const u32 __start___kcrctab[];
extern const u32 __start___kcrctab_gpl[];
extern const u8 __start___kflagstab[];
#define KMOD_PATH_LEN 256
extern char modprobe_path[];

55
kernel/module/main.c
View File

@@ -11,6 +11,7 @@
#include <linux/extable.h>
#include <linux/moduleloader.h>
#include <linux/module_signature.h>
#include <linux/module_symbol.h>
#include <linux/trace_events.h>
#include <linux/init.h>
#include <linux/kallsyms.h>
@@ -87,7 +88,7 @@ struct mod_tree_root mod_tree __cacheline_aligned = {
struct symsearch {
const struct kernel_symbol *start, *stop;
const u32 *crcs;
enum mod_license license;
const u8 *flagstab;
};
/*
@@ -364,19 +365,21 @@ static bool find_exported_symbol_in_section(const struct symsearch *syms,
struct find_symbol_arg *fsa)
{
struct kernel_symbol *sym;
if (!fsa->gplok && syms->license == GPL_ONLY)
return false;
u8 sym_flags;
sym = bsearch(fsa->name, syms->start, syms->stop - syms->start,
sizeof(struct kernel_symbol), cmp_name);
if (!sym)
return false;
sym_flags = *(syms->flagstab + (sym - syms->start));
if (!fsa->gplok && (sym_flags & KSYM_FLAG_GPL_ONLY))
return false;
fsa->owner = owner;
fsa->crc = symversion(syms->crcs, sym - syms->start);
fsa->sym = sym;
fsa->license = syms->license;
fsa->license = (sym_flags & KSYM_FLAG_GPL_ONLY) ? GPL_ONLY : NOT_GPL_ONLY;
return true;
}
@@ -387,36 +390,31 @@ static bool find_exported_symbol_in_section(const struct symsearch *syms,
*/
bool find_symbol(struct find_symbol_arg *fsa)
{
static const struct symsearch arr[] = {
{ __start___ksymtab, __stop___ksymtab, __start___kcrctab,
NOT_GPL_ONLY },
{ __start___ksymtab_gpl, __stop___ksymtab_gpl,
__start___kcrctab_gpl,
GPL_ONLY },
const struct symsearch syms = {
.start = __start___ksymtab,
.stop = __stop___ksymtab,
.crcs = __start___kcrctab,
.flagstab = __start___kflagstab,
};
struct module *mod;
unsigned int i;
for (i = 0; i < ARRAY_SIZE(arr); i++)
if (find_exported_symbol_in_section(&arr[i], NULL, fsa))
return true;
if (find_exported_symbol_in_section(&syms, NULL, fsa))
return true;
list_for_each_entry_rcu(mod, &modules, list,
lockdep_is_held(&module_mutex)) {
struct symsearch arr[] = {
{ mod->syms, mod->syms + mod->num_syms, mod->crcs,
NOT_GPL_ONLY },
{ mod->gpl_syms, mod->gpl_syms + mod->num_gpl_syms,
mod->gpl_crcs,
GPL_ONLY },
const struct symsearch syms = {
.start = mod->syms,
.stop = mod->syms + mod->num_syms,
.crcs = mod->crcs,
.flagstab = mod->flagstab,
};
if (mod->state == MODULE_STATE_UNFORMED)
continue;
for (i = 0; i < ARRAY_SIZE(arr); i++)
if (find_exported_symbol_in_section(&arr[i], mod, fsa))
return true;
if (find_exported_symbol_in_section(&syms, mod, fsa))
return true;
}
pr_debug("Failed to find symbol %s\n", fsa->name);
@@ -2681,6 +2679,7 @@ static int find_module_sections(struct module *mod, struct load_info *info)
sizeof(*mod->gpl_syms),
&mod->num_gpl_syms);
mod->gpl_crcs = section_addr(info, "__kcrctab_gpl");
mod->flagstab = section_addr(info, "__kflagstab");
#ifdef CONFIG_CONSTRUCTORS
mod->ctors = section_objs(info, ".ctors",
@@ -2884,8 +2883,12 @@ out_err:
return ret;
}
static int check_export_symbol_versions(struct module *mod)
static int check_export_symbol_sections(struct module *mod)
{
if (mod->num_syms && !mod->flagstab) {
pr_err("%s: no flags for exported symbols\n", mod->name);
return -ENOEXEC;
}
#ifdef CONFIG_MODVERSIONS
if ((mod->num_syms && !mod->crcs) ||
(mod->num_gpl_syms && !mod->gpl_crcs)) {
@@ -3501,7 +3504,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
if (err)
goto free_unload;
err = check_export_symbol_versions(mod);
err = check_export_symbol_sections(mod);
if (err)
goto free_unload;