/*  Kernel module help for x86.
    Copyright (C) 2001 Rusty Russell.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/moduleloader.h>
#include <linux/elf.h>
#include <linux/vmalloc.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/bug.h>
#include <linux/mm.h>
#include <linux/gfp.h>
#include <linux/jump_label.h>
#include <linux/random.h>

#include <asm/page.h>
#include <asm/pgtable.h>

#if 0
#define DEBUGP(fmt, ...)                                \
        printk(KERN_DEBUG fmt, ##__VA_ARGS__)
#else
#define DEBUGP(fmt, ...)                                \
do {                                                    \
        if (0)                                          \
                printk(KERN_DEBUG fmt, ##__VA_ARGS__);  \
} while (0)
#endif

#ifdef CONFIG_RANDOMIZE_BASE
static unsigned long module_load_offset;
static int randomize_modules = 1;

/* Mutex protects the module_load_offset. */
static DEFINE_MUTEX(module_kaslr_mutex);

static int __init parse_nokaslr(char *p)
{
        randomize_modules = 0;
        return 0;
}
early_param("nokaslr", parse_nokaslr);

static unsigned long int get_module_load_offset(void)
{
        if (randomize_modules) {
                mutex_lock(&module_kaslr_mutex);
                /*
                 * Calculate the module_load_offset the first time this
                 * code is called. Once calculated it stays the same until
                 * reboot.
                 */
                if (module_load_offset == 0)
                        module_load_offset =
                                (get_random_int() % 1024 + 1) * PAGE_SIZE;
                mutex_unlock(&module_kaslr_mutex);
        }
        return module_load_offset;
}
#else
static unsigned long int get_module_load_offset(void)
{
        return 0;
}
#endif

void *module_alloc(unsigned long size)
{
        if (PAGE_ALIGN(size) > MODULES_LEN)
                return NULL;
        return __vmalloc_node_range(size, 1,
                                    MODULES_VADDR + get_module_load_offset(),
                                    MODULES_END, GFP_KERNEL | __GFP_HIGHMEM,
                                    PAGE_KERNEL_EXEC, NUMA_NO_NODE,
                                    __builtin_return_address(0));
}

#ifdef CONFIG_X86_32
int apply_relocate(Elf32_Shdr *sechdrs,
                   const char *strtab,
                   unsigned int symindex,
                   unsigned int relsec,
                   struct module *me)
{
        unsigned int i;
        Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
        Elf32_Sym *sym;
        uint32_t *location;

        DEBUGP("Applying relocate section %u to %u\n",
               relsec, sechdrs[relsec].sh_info);
        for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
                /* This is where to make the change */
                location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
                        + rel[i].r_offset;
                /* This is the symbol it is referring to.  Note that all
                   undefined symbols have been resolved.  */
                sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
                        + ELF32_R_SYM(rel[i].r_info);

                switch (ELF32_R_TYPE(rel[i].r_info)) {
                case R_386_32:
                        /* We add the value into the location given */
                        *location += sym->st_value;
                        break;
                case R_386_PC32:
                        /* Add the value, subtract its position */
                        *location += sym->st_value - (uint32_t)location;
                        break;
                default:
                        pr_err("%s: Unknown relocation: %u\n",
                               me->name, ELF32_R_TYPE(rel[i].r_info));
                        return -ENOEXEC;
                }
        }
        return 0;
}
#else /*X86_64*/
int apply_relocate_add(Elf64_Shdr *sechdrs,
                   const char *strtab,
                   unsigned int symindex,
                   unsigned int relsec,
                   struct module *me)
{
        unsigned int i;
        Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
        Elf64_Sym *sym;
        void *loc;
        u64 val;

        DEBUGP("Applying relocate section %u to %u\n",
               relsec, sechdrs[relsec].sh_info);
        for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
                /* This is where to make the change */
                loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
                        + rel[i].r_offset;

                /* This is the symbol it is referring to.  Note that all
                   undefined symbols have been resolved.  */
                sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
                        + ELF64_R_SYM(rel[i].r_info);

                DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
                       (int)ELF64_R_TYPE(rel[i].r_info),
                       sym->st_value, rel[i].r_addend, (u64)loc);

                val = sym->st_value + rel[i].r_addend;

                switch (ELF64_R_TYPE(rel[i].r_info)) {
                case R_X86_64_NONE:
                        break;
                case R_X86_64_64:
                        *(u64 *)loc = val;
                        break;
                case R_X86_64_32:
                        *(u32 *)loc = val;
                        if (val != *(u32 *)loc)
                                goto overflow;
                        break;
                case R_X86_64_32S:
                        *(s32 *)loc = val;
                        if ((s64)val != *(s32 *)loc)
                                goto overflow;
                        break;
                case R_X86_64_PC32:
                        val -= (u64)loc;
                        *(u32 *)loc = val;
#if 0
                        if ((s64)val != *(s32 *)loc)
                                goto overflow;
#endif
                        break;
                default:
                        pr_err("%s: Unknown rela relocation: %llu\n",
                               me->name, ELF64_R_TYPE(rel[i].r_info));
                        return -ENOEXEC;
                }
        }
        return 0;

overflow:
        pr_err("overflow in relocation type %d val %Lx\n",
               (int)ELF64_R_TYPE(rel[i].r_info), val);
        pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
               me->name);
        return -ENOEXEC;
}
#endif

int module_finalize(const Elf_Ehdr *hdr,
                    const Elf_Shdr *sechdrs,
                    struct module *me)
{
        const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
                *para = NULL;
        char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;

        for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
                if (!strcmp(".text", secstrings + s->sh_name))
                        text = s;
                if (!strcmp(".altinstructions", secstrings + s->sh_name))
                        alt = s;
                if (!strcmp(".smp_locks", secstrings + s->sh_name))
                        locks = s;
                if (!strcmp(".parainstructions", secstrings + s->sh_name))
                        para = s;
        }

        if (alt) {
                /* patch .altinstructions */
                void *aseg = (void *)alt->sh_addr;
                apply_alternatives(aseg, aseg + alt->sh_size);
        }
        if (locks && text) {
                void *lseg = (void *)locks->sh_addr;
                void *tseg = (void *)text->sh_addr;
                alternatives_smp_module_add(me, me->name,
                                            lseg, lseg + locks->sh_size,
                                            tseg, tseg + text->sh_size);
        }

        if (para) {
                void *pseg = (void *)para->sh_addr;
                apply_paravirt(pseg, pseg + para->sh_size);
        }

        /* make jump label nops */
        jump_label_apply_nops(me);

        return 0;
}

void module_arch_cleanup(struct module *mod)
{
        alternatives_smp_module_del(mod);
}