/*  Kernel module help for Alpha.
    Copyright (C) 2002 Richard Henderson.

    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
*/
#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/slab.h>

#if 0
#define DEBUGP printk
#else
#define DEBUGP(fmt...)
#endif

/* Allocate the GOT at the end of the core sections.  */

struct got_entry {
        struct got_entry *next;
        Elf64_Sxword r_addend;
        int got_offset;
};

static inline void
process_reloc_for_got(Elf64_Rela *rela,
                      struct got_entry *chains, Elf64_Xword *poffset)
{
        unsigned long r_sym = ELF64_R_SYM (rela->r_info);
        unsigned long r_type = ELF64_R_TYPE (rela->r_info);
        Elf64_Sxword r_addend = rela->r_addend;
        struct got_entry *g;

        if (r_type != R_ALPHA_LITERAL)
                return;

        for (g = chains + r_sym; g ; g = g->next)
                if (g->r_addend == r_addend) {
                        if (g->got_offset == 0) {
                                g->got_offset = *poffset;
                                *poffset += 8;
                        }
                        goto found_entry;
                }

        g = kmalloc (sizeof (*g), GFP_KERNEL);
        g->next = chains[r_sym].next;
        g->r_addend = r_addend;
        g->got_offset = *poffset;
        *poffset += 8;
        chains[r_sym].next = g;

 found_entry:
        /* Trick: most of the ELF64_R_TYPE field is unused.  There are
           42 valid relocation types, and a 32-bit field.  Co-opt the
           bits above 256 to store the got offset for this reloc.  */
        rela->r_info |= g->got_offset << 8;
}

int
module_frob_arch_sections(Elf64_Ehdr *hdr, Elf64_Shdr *sechdrs,
                          char *secstrings, struct module *me)
{
        struct got_entry *chains;
        Elf64_Rela *rela;
        Elf64_Shdr *esechdrs, *symtab, *s, *got;
        unsigned long nsyms, nrela, i;

        esechdrs = sechdrs + hdr->e_shnum;
        symtab = got = NULL;

        /* Find out how large the symbol table is.  Allocate one got_entry
           head per symbol.  Normally this will be enough, but not always.
           We'll chain different offsets for the symbol down each head.  */
        for (s = sechdrs; s < esechdrs; ++s)
                if (s->sh_type == SHT_SYMTAB)
                        symtab = s;
                else if (!strcmp(".got", secstrings + s->sh_name)) {
                        got = s;
                        me->arch.gotsecindex = s - sechdrs;
                }

        if (!symtab) {
                printk(KERN_ERR "module %s: no symbol table\n", me->name);
                return -ENOEXEC;
        }
        if (!got) {
                printk(KERN_ERR "module %s: no got section\n", me->name);
                return -ENOEXEC;
        }

        nsyms = symtab->sh_size / sizeof(Elf64_Sym);
        chains = kcalloc(nsyms, sizeof(struct got_entry), GFP_KERNEL);
        if (!chains) {
                printk(KERN_ERR
                       "module %s: no memory for symbol chain buffer\n",
                       me->name);
                return -ENOMEM;
        }

        got->sh_size = 0;
        got->sh_addralign = 8;
        got->sh_type = SHT_NOBITS;

        /* Examine all LITERAL relocations to find out what GOT entries
           are required.  This sizes the GOT section as well.  */
        for (s = sechdrs; s < esechdrs; ++s)
                if (s->sh_type == SHT_RELA) {
                        nrela = s->sh_size / sizeof(Elf64_Rela);
                        rela = (void *)hdr + s->sh_offset;
                        for (i = 0; i < nrela; ++i)
                                process_reloc_for_got(rela+i, chains,
                                                      &got->sh_size);
                }

        /* Free the memory we allocated.  */
        for (i = 0; i < nsyms; ++i) {
                struct got_entry *g, *n;
                for (g = chains[i].next; g ; g = n) {
                        n = g->next;
                        kfree(g);
                }
        }
        kfree(chains);

        return 0;
}

int
apply_relocate_add(Elf64_Shdr *sechdrs, const char *strtab,
                   unsigned int symindex, unsigned int relsec,
                   struct module *me)
{
        Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr;
        unsigned long i, n = sechdrs[relsec].sh_size / sizeof(*rela);
        Elf64_Sym *symtab, *sym;
        void *base, *location;
        unsigned long got, gp;

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

        base = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr;
        symtab = (Elf64_Sym *)sechdrs[symindex].sh_addr;

        /* The small sections were sorted to the end of the segment.
           The following should definitely cover them.  */
        gp = (u64)me->module_core + me->core_size - 0x8000;
        got = sechdrs[me->arch.gotsecindex].sh_addr;

        for (i = 0; i < n; i++) {
                unsigned long r_sym = ELF64_R_SYM (rela[i].r_info);
                unsigned long r_type = ELF64_R_TYPE (rela[i].r_info);
                unsigned long r_got_offset = r_type >> 8;
                unsigned long value, hi, lo;
                r_type &= 0xff;

                /* This is where to make the change.  */
                location = base + rela[i].r_offset;

                /* This is the symbol it is referring to.  Note that all
                   unresolved symbols have been resolved.  */
                sym = symtab + r_sym;
                value = sym->st_value + rela[i].r_addend;

                switch (r_type) {
                case R_ALPHA_NONE:
                        break;
                case R_ALPHA_REFQUAD:
                        /* BUG() can produce misaligned relocations. */
                        ((u32 *)location)[0] = value;
                        ((u32 *)location)[1] = value >> 32;
                        break;
                case R_ALPHA_GPREL32:
                        value -= gp;
                        if ((int)value != value)
                                goto reloc_overflow;
                        *(u32 *)location = value;
                        break;
                case R_ALPHA_LITERAL:
                        hi = got + r_got_offset;
                        lo = hi - gp;
                        if ((short)lo != lo)
                                goto reloc_overflow;
                        *(u16 *)location = lo;
                        *(u64 *)hi = value;
                        break;
                case R_ALPHA_LITUSE:
                        break;
                case R_ALPHA_GPDISP:
                        value = gp - (u64)location;
                        lo = (short)value;
                        hi = (int)(value - lo);
                        if (hi + lo != value)
                                goto reloc_overflow;
                        *(u16 *)location = hi >> 16;
                        *(u16 *)(location + rela[i].r_addend) = lo;
                        break;
                case R_ALPHA_BRSGP:
                        /* BRSGP is only allowed to bind to local symbols.
                           If the section is undef, this means that the
                           value was resolved from somewhere else.  */
                        if (sym->st_shndx == SHN_UNDEF)
                                goto reloc_overflow;
                        if ((sym->st_other & STO_ALPHA_STD_GPLOAD) ==
                            STO_ALPHA_STD_GPLOAD)
                                /* Omit the prologue. */
                                value += 8;
                        /* FALLTHRU */
                case R_ALPHA_BRADDR:
                        value -= (u64)location + 4;
                        if (value & 3)
                                goto reloc_overflow;
                        value = (long)value >> 2;
                        if (value + (1<<21) >= 1<<22)
                                goto reloc_overflow;
                        value &= 0x1fffff;
                        value |= *(u32 *)location & ~0x1fffff;
                        *(u32 *)location = value;
                        break;
                case R_ALPHA_HINT:
                        break;
                case R_ALPHA_SREL32:
                        value -= (u64)location;
                        if ((int)value != value)
                                goto reloc_overflow;
                        *(u32 *)location = value;
                        break;
                case R_ALPHA_SREL64:
                        value -= (u64)location;
                        *(u64 *)location = value;
                        break;
                case R_ALPHA_GPRELHIGH:
                        value = (long)(value - gp + 0x8000) >> 16;
                        if ((short) value != value)
                                goto reloc_overflow;
                        *(u16 *)location = value;
                        break;
                case R_ALPHA_GPRELLOW:
                        value -= gp;
                        *(u16 *)location = value;
                        break;
                case R_ALPHA_GPREL16:
                        value -= gp;
                        if ((short) value != value)
                                goto reloc_overflow;
                        *(u16 *)location = value;
                        break;
                default:
                        printk(KERN_ERR "module %s: Unknown relocation: %lu\n",
                               me->name, r_type);
                        return -ENOEXEC;
                reloc_overflow:
                        if (ELF64_ST_TYPE (sym->st_info) == STT_SECTION)
                          printk(KERN_ERR
                                 "module %s: Relocation (type %lu) overflow vs section %d\n",
                                 me->name, r_type, sym->st_shndx);
                        else
                          printk(KERN_ERR
                                 "module %s: Relocation (type %lu) overflow vs %s\n",
                                 me->name, r_type, strtab + sym->st_name);
                        return -ENOEXEC;
                }
        }

        return 0;
}