// SPDX-License-Identifier: GPL-2.0-or-later
/*  Kernel module help for PPC.
    Copyright (C) 2001 Rusty Russell.

*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#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/ftrace.h>
#include <linux/cache.h>
#include <linux/bug.h>
#include <linux/sort.h>
#include <asm/setup.h>

/* Count how many different relocations (different symbol, different
   addend) */
static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
{
        unsigned int i, r_info, r_addend, _count_relocs;

        _count_relocs = 0;
        r_info = 0;
        r_addend = 0;
        for (i = 0; i < num; i++)
                /* Only count 24-bit relocs, others don't need stubs */
                if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
                    (r_info != ELF32_R_SYM(rela[i].r_info) ||
                     r_addend != rela[i].r_addend)) {
                        _count_relocs++;
                        r_info = ELF32_R_SYM(rela[i].r_info);
                        r_addend = rela[i].r_addend;
                }

#ifdef CONFIG_DYNAMIC_FTRACE
        _count_relocs++;        /* add one for ftrace_caller */
#endif
        return _count_relocs;
}

static int relacmp(const void *_x, const void *_y)
{
        const Elf32_Rela *x, *y;

        y = (Elf32_Rela *)_x;
        x = (Elf32_Rela *)_y;

        /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
         * make the comparison cheaper/faster. It won't affect the sorting or
         * the counting algorithms' performance
         */
        if (x->r_info < y->r_info)
                return -1;
        else if (x->r_info > y->r_info)
                return 1;
        else if (x->r_addend < y->r_addend)
                return -1;
        else if (x->r_addend > y->r_addend)
                return 1;
        else
                return 0;
}

static void relaswap(void *_x, void *_y, int size)
{
        uint32_t *x, *y, tmp;
        int i;

        y = (uint32_t *)_x;
        x = (uint32_t *)_y;

        for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
                tmp = x[i];
                x[i] = y[i];
                y[i] = tmp;
        }
}

/* Get the potential trampolines size required of the init and
   non-init sections */
static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
                                  const Elf32_Shdr *sechdrs,
                                  const char *secstrings,
                                  int is_init)
{
        unsigned long ret = 0;
        unsigned i;

        /* Everything marked ALLOC (this includes the exported
           symbols) */
        for (i = 1; i < hdr->e_shnum; i++) {
                /* If it's called *.init*, and we're not init, we're
                   not interested */
                if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL)
                    != is_init)
                        continue;

                /* We don't want to look at debug sections. */
                if (strstr(secstrings + sechdrs[i].sh_name, ".debug"))
                        continue;

                if (sechdrs[i].sh_type == SHT_RELA) {
                        pr_debug("Found relocations in section %u\n", i);
                        pr_debug("Ptr: %p.  Number: %u\n",
                               (void *)hdr + sechdrs[i].sh_offset,
                               sechdrs[i].sh_size / sizeof(Elf32_Rela));

                        /* Sort the relocation information based on a symbol and
                         * addend key. This is a stable O(n*log n) complexity
                         * alogrithm but it will reduce the complexity of
                         * count_relocs() to linear complexity O(n)
                         */
                        sort((void *)hdr + sechdrs[i].sh_offset,
                             sechdrs[i].sh_size / sizeof(Elf32_Rela),
                             sizeof(Elf32_Rela), relacmp, relaswap);

                        ret += count_relocs((void *)hdr
                                             + sechdrs[i].sh_offset,
                                             sechdrs[i].sh_size
                                             / sizeof(Elf32_Rela))
                                * sizeof(struct ppc_plt_entry);
                }
        }

        return ret;
}

int module_frob_arch_sections(Elf32_Ehdr *hdr,
                              Elf32_Shdr *sechdrs,
                              char *secstrings,
                              struct module *me)
{
        unsigned int i;

        /* Find .plt and .init.plt sections */
        for (i = 0; i < hdr->e_shnum; i++) {
                if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
                        me->arch.init_plt_section = i;
                else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
                        me->arch.core_plt_section = i;
        }
        if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
                pr_err("Module doesn't contain .plt or .init.plt sections.\n");
                return -ENOEXEC;
        }

        /* Override their sizes */
        sechdrs[me->arch.core_plt_section].sh_size
                = get_plt_size(hdr, sechdrs, secstrings, 0);
        sechdrs[me->arch.init_plt_section].sh_size
                = get_plt_size(hdr, sechdrs, secstrings, 1);
        return 0;
}

static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
{
        if (entry->jump[0] != (PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val)))
                return 0;
        if (entry->jump[1] != (PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) |
                               PPC_LO(val)))
                return 0;
        return 1;
}

/* Set up a trampoline in the PLT to bounce us to the distant function */
static uint32_t do_plt_call(void *location,
                            Elf32_Addr val,
                            const Elf32_Shdr *sechdrs,
                            struct module *mod)
{
        struct ppc_plt_entry *entry;

        pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
        /* Init, or core PLT? */
        if (location >= mod->core_layout.base
            && location < mod->core_layout.base + mod->core_layout.size)
                entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
        else
                entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;

        /* Find this entry, or if that fails, the next avail. entry */
        while (entry->jump[0]) {
                if (entry_matches(entry, val)) return (uint32_t)entry;
                entry++;
        }

        /*
         * lis r12, sym@ha
         * addi r12, r12, sym@l
         * mtctr r12
         * bctr
         */
        entry->jump[0] = PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val);
        entry->jump[1] = PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) | PPC_LO(val);
        entry->jump[2] = PPC_INST_MTCTR | __PPC_RS(R12);
        entry->jump[3] = PPC_INST_BCTR;

        pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
        return (uint32_t)entry;
}

int apply_relocate_add(Elf32_Shdr *sechdrs,
                       const char *strtab,
                       unsigned int symindex,
                       unsigned int relsec,
                       struct module *module)
{
        unsigned int i;
        Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
        Elf32_Sym *sym;
        uint32_t *location;
        uint32_t value;

        pr_debug("Applying ADD relocate section %u to %u\n", relsec,
               sechdrs[relsec].sh_info);
        for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
                /* This is where to make the change */
                location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
                        + rela[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(rela[i].r_info);
                /* `Everything is relative'. */
                value = sym->st_value + rela[i].r_addend;

                switch (ELF32_R_TYPE(rela[i].r_info)) {
                case R_PPC_ADDR32:
                        /* Simply set it */
                        *(uint32_t *)location = value;
                        break;

                case R_PPC_ADDR16_LO:
                        /* Low half of the symbol */
                        *(uint16_t *)location = value;
                        break;

                case R_PPC_ADDR16_HI:
                        /* Higher half of the symbol */
                        *(uint16_t *)location = (value >> 16);
                        break;

                case R_PPC_ADDR16_HA:
                        /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
                           (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
                           This is the same, only sane.
                         */
                        *(uint16_t *)location = (value + 0x8000) >> 16;
                        break;

                case R_PPC_REL24:
                        if ((int)(value - (uint32_t)location) < -0x02000000
                            || (int)(value - (uint32_t)location) >= 0x02000000)
                                value = do_plt_call(location, value,
                                                    sechdrs, module);

                        /* Only replace bits 2 through 26 */
                        pr_debug("REL24 value = %08X. location = %08X\n",
                               value, (uint32_t)location);
                        pr_debug("Location before: %08X.\n",
                               *(uint32_t *)location);
                        *(uint32_t *)location
                                = (*(uint32_t *)location & ~0x03fffffc)
                                | ((value - (uint32_t)location)
                                   & 0x03fffffc);
                        pr_debug("Location after: %08X.\n",
                               *(uint32_t *)location);
                        pr_debug("ie. jump to %08X+%08X = %08X\n",
                               *(uint32_t *)location & 0x03fffffc,
                               (uint32_t)location,
                               (*(uint32_t *)location & 0x03fffffc)
                               + (uint32_t)location);
                        break;

                case R_PPC_REL32:
                        /* 32-bit relative jump. */
                        *(uint32_t *)location = value - (uint32_t)location;
                        break;

                default:
                        pr_err("%s: unknown ADD relocation: %u\n",
                               module->name,
                               ELF32_R_TYPE(rela[i].r_info));
                        return -ENOEXEC;
                }
        }

        return 0;
}

#ifdef CONFIG_DYNAMIC_FTRACE
int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
{
        module->arch.tramp = do_plt_call(module->core_layout.base,
                                         (unsigned long)ftrace_caller,
                                         sechdrs, module);
        if (!module->arch.tramp)
                return -ENOENT;

        return 0;
}
#endif