// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 *  Copyright (C) 2001 Rusty Russell.
 *  Copyright (C) 2003, 2004 Ralf Baechle (ralf@linux-mips.org)
 *  Copyright (C) 2005 Thiemo Seufer
 */

#undef DEBUG

#include <linux/extable.h>
#include <linux/moduleloader.h>
#include <linux/elf.h>
#include <linux/mm.h>
#include <linux/numa.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/jump_label.h>
#include <asm/jump_label.h>

struct mips_hi16 {
        struct mips_hi16 *next;
        Elf_Addr *addr;
        Elf_Addr value;
};

static LIST_HEAD(dbe_list);
static DEFINE_SPINLOCK(dbe_lock);

static void apply_r_mips_32(u32 *location, u32 base, Elf_Addr v)
{
        *location = base + v;
}

static int apply_r_mips_26(struct module *me, u32 *location, u32 base,
                           Elf_Addr v)
{
        if (v % 4) {
                pr_err("module %s: dangerous R_MIPS_26 relocation\n",
                       me->name);
                return -ENOEXEC;
        }

        if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
                pr_err("module %s: relocation overflow\n",
                       me->name);
                return -ENOEXEC;
        }

        *location = (*location & ~0x03ffffff) |
                    ((base + (v >> 2)) & 0x03ffffff);

        return 0;
}

static int apply_r_mips_hi16(struct module *me, u32 *location, Elf_Addr v,
                             bool rela)
{
        struct mips_hi16 *n;

        if (rela) {
                *location = (*location & 0xffff0000) |
                            ((((long long) v + 0x8000LL) >> 16) & 0xffff);
                return 0;
        }

        /*
         * We cannot relocate this one now because we don't know the value of
         * the carry we need to add.  Save the information, and let LO16 do the
         * actual relocation.
         */
        n = kmalloc_obj(*n);
        if (!n)
                return -ENOMEM;

        n->addr = (Elf_Addr *)location;
        n->value = v;
        n->next = me->arch.r_mips_hi16_list;
        me->arch.r_mips_hi16_list = n;

        return 0;
}

static void free_relocation_chain(struct mips_hi16 *l)
{
        struct mips_hi16 *next;

        while (l) {
                next = l->next;
                kfree(l);
                l = next;
        }
}

static int apply_r_mips_lo16(struct module *me, u32 *location,
                             u32 base, Elf_Addr v, bool rela)
{
        unsigned long insnlo = base;
        struct mips_hi16 *l;
        Elf_Addr val, vallo;

        if (rela) {
                *location = (*location & 0xffff0000) | (v & 0xffff);
                return 0;
        }

        /* Sign extend the addend we extract from the lo insn.  */
        vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;

        if (me->arch.r_mips_hi16_list != NULL) {
                l = me->arch.r_mips_hi16_list;
                while (l != NULL) {
                        struct mips_hi16 *next;
                        unsigned long insn;

                        /*
                         * The value for the HI16 had best be the same.
                         */
                        if (v != l->value)
                                goto out_danger;

                        /*
                         * Do the HI16 relocation.  Note that we actually don't
                         * need to know anything about the LO16 itself, except
                         * where to find the low 16 bits of the addend needed
                         * by the LO16.
                         */
                        insn = *l->addr;
                        val = ((insn & 0xffff) << 16) + vallo;
                        val += v;

                        /*
                         * Account for the sign extension that will happen in
                         * the low bits.
                         */
                        val = ((val >> 16) + ((val & 0x8000) != 0)) & 0xffff;

                        insn = (insn & ~0xffff) | val;
                        *l->addr = insn;

                        next = l->next;
                        kfree(l);
                        l = next;
                }

                me->arch.r_mips_hi16_list = NULL;
        }

        /*
         * Ok, we're done with the HI16 relocs.  Now deal with the LO16.
         */
        val = v + vallo;
        insnlo = (insnlo & ~0xffff) | (val & 0xffff);
        *location = insnlo;

        return 0;

out_danger:
        free_relocation_chain(l);
        me->arch.r_mips_hi16_list = NULL;

        pr_err("module %s: dangerous R_MIPS_LO16 relocation\n", me->name);

        return -ENOEXEC;
}

static int apply_r_mips_pc(struct module *me, u32 *location, u32 base,
                           Elf_Addr v, unsigned int bits)
{
        unsigned long mask = GENMASK(bits - 1, 0);
        unsigned long se_bits;
        long offset;

        if (v % 4) {
                pr_err("module %s: dangerous R_MIPS_PC%u relocation\n",
                       me->name, bits);
                return -ENOEXEC;
        }

        /* retrieve & sign extend implicit addend if any */
        offset = base & mask;
        offset |= (offset & BIT(bits - 1)) ? ~mask : 0;

        offset += ((long)v - (long)location) >> 2;

        /* check the sign bit onwards are identical - ie. we didn't overflow */
        se_bits = (offset & BIT(bits - 1)) ? ~0ul : 0;
        if ((offset & ~mask) != (se_bits & ~mask)) {
                pr_err("module %s: relocation overflow\n", me->name);
                return -ENOEXEC;
        }

        *location = (*location & ~mask) | (offset & mask);

        return 0;
}

static int apply_r_mips_pc16(struct module *me, u32 *location, u32 base,
                             Elf_Addr v)
{
        return apply_r_mips_pc(me, location, base, v, 16);
}

static int apply_r_mips_pc21(struct module *me, u32 *location, u32 base,
                             Elf_Addr v)
{
        return apply_r_mips_pc(me, location, base, v, 21);
}

static int apply_r_mips_pc26(struct module *me, u32 *location, u32 base,
                             Elf_Addr v)
{
        return apply_r_mips_pc(me, location, base, v, 26);
}

static int apply_r_mips_64(u32 *location, Elf_Addr v, bool rela)
{
        if (WARN_ON(!rela))
                return -EINVAL;

        *(Elf_Addr *)location = v;

        return 0;
}

static int apply_r_mips_higher(u32 *location, Elf_Addr v, bool rela)
{
        if (WARN_ON(!rela))
                return -EINVAL;

        *location = (*location & 0xffff0000) |
                    ((((long long)v + 0x80008000LL) >> 32) & 0xffff);

        return 0;
}

static int apply_r_mips_highest(u32 *location, Elf_Addr v, bool rela)
{
        if (WARN_ON(!rela))
                return -EINVAL;

        *location = (*location & 0xffff0000) |
                    ((((long long)v + 0x800080008000LL) >> 48) & 0xffff);

        return 0;
}

/**
 * reloc_handler() - Apply a particular relocation to a module
 * @type: type of the relocation to apply
 * @me: the module to apply the reloc to
 * @location: the address at which the reloc is to be applied
 * @base: the existing value at location for REL-style; 0 for RELA-style
 * @v: the value of the reloc, with addend for RELA-style
 * @rela: indication of is this a RELA (true) or REL (false) relocation
 *
 * Each implemented relocation function applies a particular type of
 * relocation to the module @me. Relocs that may be found in either REL or RELA
 * variants can be handled by making use of the @base & @v parameters which are
 * set to values which abstract the difference away from the particular reloc
 * implementations.
 *
 * Return: 0 upon success, else -ERRNO
 */
static int reloc_handler(u32 type, struct module *me, u32 *location, u32 base,
                         Elf_Addr v, bool rela)
{
        switch (type) {
        case R_MIPS_NONE:
                break;
        case R_MIPS_32:
                apply_r_mips_32(location, base, v);
                break;
        case R_MIPS_26:
                return apply_r_mips_26(me, location, base, v);
        case R_MIPS_HI16:
                return apply_r_mips_hi16(me, location, v, rela);
        case R_MIPS_LO16:
                return apply_r_mips_lo16(me, location, base, v, rela);
        case R_MIPS_PC16:
                return apply_r_mips_pc16(me, location, base, v);
        case R_MIPS_PC21_S2:
                return apply_r_mips_pc21(me, location, base, v);
        case R_MIPS_PC26_S2:
                return apply_r_mips_pc26(me, location, base, v);
        case R_MIPS_64:
                return apply_r_mips_64(location, v, rela);
        case R_MIPS_HIGHER:
                return apply_r_mips_higher(location, v, rela);
        case R_MIPS_HIGHEST:
                return apply_r_mips_highest(location, v, rela);
        default:
                pr_err("%s: Unknown relocation type %u\n", me->name, type);
                return -EINVAL;
        }

        return 0;
}

static int __apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
                            unsigned int symindex, unsigned int relsec,
                            struct module *me, bool rela)
{
        union {
                Elf_Mips_Rel *rel;
                Elf_Mips_Rela *rela;
        } r;
        Elf_Sym *sym;
        u32 *location, base;
        unsigned int i, type;
        Elf_Addr v;
        int err = 0;
        size_t reloc_sz;

        pr_debug("Applying relocate section %u to %u\n", relsec,
               sechdrs[relsec].sh_info);

        r.rel = (void *)sechdrs[relsec].sh_addr;
        reloc_sz = rela ? sizeof(*r.rela) : sizeof(*r.rel);
        me->arch.r_mips_hi16_list = NULL;
        for (i = 0; i < sechdrs[relsec].sh_size / reloc_sz; i++) {
                /* This is where to make the change */
                location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
                        + r.rel->r_offset;
                /* This is the symbol it is referring to */
                sym = (Elf_Sym *)sechdrs[symindex].sh_addr
                        + ELF_MIPS_R_SYM(*r.rel);
                if (sym->st_value >= -MAX_ERRNO) {
                        /* Ignore unresolved weak symbol */
                        if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
                                continue;
                        pr_warn("%s: Unknown symbol %s\n",
                                me->name, strtab + sym->st_name);
                        err = -ENOENT;
                        goto out;
                }

                type = ELF_MIPS_R_TYPE(*r.rel);

                if (rela) {
                        v = sym->st_value + r.rela->r_addend;
                        base = 0;
                        r.rela = &r.rela[1];
                } else {
                        v = sym->st_value;
                        base = *location;
                        r.rel = &r.rel[1];
                }

                err = reloc_handler(type, me, location, base, v, rela);
                if (err)
                        goto out;
        }

out:
        /*
         * Normally the hi16 list should be deallocated at this point. A
         * malformed binary however could contain a series of R_MIPS_HI16
         * relocations not followed by a R_MIPS_LO16 relocation, or if we hit
         * an error processing a reloc we might have gotten here before
         * reaching the R_MIPS_LO16. In either case, free up the list and
         * return an error.
         */
        if (me->arch.r_mips_hi16_list) {
                free_relocation_chain(me->arch.r_mips_hi16_list);
                me->arch.r_mips_hi16_list = NULL;
                err = err ?: -ENOEXEC;
        }

        return err;
}

int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
                   unsigned int symindex, unsigned int relsec,
                   struct module *me)
{
        return __apply_relocate(sechdrs, strtab, symindex, relsec, me, false);
}

#ifdef CONFIG_MODULES_USE_ELF_RELA
int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
                       unsigned int symindex, unsigned int relsec,
                       struct module *me)
{
        return __apply_relocate(sechdrs, strtab, symindex, relsec, me, true);
}
#endif /* CONFIG_MODULES_USE_ELF_RELA */

/* Given an address, look for it in the module exception tables. */
const struct exception_table_entry *search_module_dbetables(unsigned long addr)
{
        unsigned long flags;
        const struct exception_table_entry *e = NULL;
        struct mod_arch_specific *dbe;

        spin_lock_irqsave(&dbe_lock, flags);
        list_for_each_entry(dbe, &dbe_list, dbe_list) {
                e = search_extable(dbe->dbe_start,
                                   dbe->dbe_end - dbe->dbe_start, addr);
                if (e)
                        break;
        }
        spin_unlock_irqrestore(&dbe_lock, flags);

        /* Now, if we found one, we are running inside it now, hence
           we cannot unload the module, hence no refcnt needed. */
        return e;
}

/* Put in dbe list if necessary. */
int module_finalize(const Elf_Ehdr *hdr,
                    const Elf_Shdr *sechdrs,
                    struct module *me)
{
        const Elf_Shdr *s;
        char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;

        if (IS_ENABLED(CONFIG_JUMP_LABEL))
                jump_label_apply_nops(me);

        INIT_LIST_HEAD(&me->arch.dbe_list);
        for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
                if (strcmp("__dbe_table", secstrings + s->sh_name) != 0)
                        continue;
                me->arch.dbe_start = (void *)s->sh_addr;
                me->arch.dbe_end = (void *)s->sh_addr + s->sh_size;
                spin_lock_irq(&dbe_lock);
                list_add(&me->arch.dbe_list, &dbe_list);
                spin_unlock_irq(&dbe_lock);
        }
        return 0;
}

void module_arch_cleanup(struct module *mod)
{
        spin_lock_irq(&dbe_lock);
        list_del(&mod->arch.dbe_list);
        spin_unlock_irq(&dbe_lock);
}