// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Module strict rwx
 *
 * Copyright (C) 2015 Rusty Russell
 */

#include <linux/module.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <linux/set_memory.h>
#include <linux/execmem.h>
#include "internal.h"

static int module_set_memory(const struct module *mod, enum mod_mem_type type,
                             int (*set_memory)(unsigned long start, int num_pages))
{
        const struct module_memory *mod_mem = &mod->mem[type];

        if (!mod_mem->base)
                return 0;

        set_vm_flush_reset_perms(mod_mem->base);
        return set_memory((unsigned long)mod_mem->base, mod_mem->size >> PAGE_SHIFT);
}

/*
 * Since some arches are moving towards PAGE_KERNEL module allocations instead
 * of PAGE_KERNEL_EXEC, keep module_enable_x() independent of
 * CONFIG_STRICT_MODULE_RWX because they are needed regardless of whether we
 * are strict.
 */
int module_enable_text_rox(const struct module *mod)
{
        for_class_mod_mem_type(type, text) {
                const struct module_memory *mem = &mod->mem[type];
                int ret;

                if (mem->is_rox)
                        ret = execmem_restore_rox(mem->base, mem->size);
                else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
                        ret = module_set_memory(mod, type, set_memory_rox);
                else
                        ret = module_set_memory(mod, type, set_memory_x);
                if (ret)
                        return ret;
        }
        return 0;
}

int module_enable_rodata_ro(const struct module *mod)
{
        int ret;

        if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX) || !rodata_enabled)
                return 0;

        ret = module_set_memory(mod, MOD_RODATA, set_memory_ro);
        if (ret)
                return ret;
        ret = module_set_memory(mod, MOD_INIT_RODATA, set_memory_ro);
        if (ret)
                return ret;

        return 0;
}

int module_enable_rodata_ro_after_init(const struct module *mod)
{
        if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX) || !rodata_enabled)
                return 0;

        return module_set_memory(mod, MOD_RO_AFTER_INIT, set_memory_ro);
}

int module_enable_data_nx(const struct module *mod)
{
        if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
                return 0;

        for_class_mod_mem_type(type, data) {
                int ret = module_set_memory(mod, type, set_memory_nx);

                if (ret)
                        return ret;
        }
        return 0;
}

int module_enforce_rwx_sections(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
                                const char *secstrings,
                                const struct module *mod)
{
        const unsigned long shf_wx = SHF_WRITE | SHF_EXECINSTR;
        int i;

        if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
                return 0;

        for (i = 0; i < hdr->e_shnum; i++) {
                if ((sechdrs[i].sh_flags & shf_wx) == shf_wx) {
                        pr_err("%s: section %s (index %d) has invalid WRITE|EXEC flags\n",
                               mod->name, secstrings + sechdrs[i].sh_name, i);
                        return -ENOEXEC;
                }
        }

        return 0;
}

static const char *const ro_after_init[] = {
        /*
         * Section .data..ro_after_init holds data explicitly annotated by
         * __ro_after_init.
         */
        ".data..ro_after_init",

        /*
         * Section __jump_table holds data structures that are never modified,
         * with the exception of entries that refer to code in the __init
         * section, which are marked as such at module load time.
         */
        "__jump_table",

#ifdef CONFIG_HAVE_STATIC_CALL_INLINE
        /*
         * Section .static_call_sites holds data structures that need to be
         * sorted and processed at module load time but are never modified
         * afterwards.
         */
        ".static_call_sites",
#endif
};

void module_mark_ro_after_init(const Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
                               const char *secstrings)
{
        int i, j;

        for (i = 1; i < hdr->e_shnum; i++) {
                Elf_Shdr *shdr = &sechdrs[i];

                for (j = 0; j < ARRAY_SIZE(ro_after_init); j++) {
                        if (strcmp(secstrings + shdr->sh_name,
                                   ro_after_init[j]) == 0) {
                                shdr->sh_flags |= SHF_RO_AFTER_INIT;
                                break;
                        }
                }
        }
}