285 lines
7.8 KiB
C
285 lines
7.8 KiB
C
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/* Kernel module help for Meta.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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*/
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#include <linux/moduleloader.h>
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#include <linux/elf.h>
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#include <linux/vmalloc.h>
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#include <linux/fs.h>
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#include <linux/string.h>
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#include <linux/kernel.h>
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#include <linux/sort.h>
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#include <asm/unaligned.h>
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/* Count how many different relocations (different symbol, different
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addend) */
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static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
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{
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unsigned int i, r_info, r_addend, _count_relocs;
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_count_relocs = 0;
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r_info = 0;
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r_addend = 0;
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for (i = 0; i < num; i++)
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/* Only count relbranch relocs, others don't need stubs */
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if (ELF32_R_TYPE(rela[i].r_info) == R_METAG_RELBRANCH &&
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(r_info != ELF32_R_SYM(rela[i].r_info) ||
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r_addend != rela[i].r_addend)) {
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_count_relocs++;
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r_info = ELF32_R_SYM(rela[i].r_info);
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r_addend = rela[i].r_addend;
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}
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return _count_relocs;
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}
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static int relacmp(const void *_x, const void *_y)
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{
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const Elf32_Rela *x, *y;
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y = (Elf32_Rela *)_x;
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x = (Elf32_Rela *)_y;
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/* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
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* make the comparison cheaper/faster. It won't affect the sorting or
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* the counting algorithms' performance
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*/
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if (x->r_info < y->r_info)
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return -1;
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else if (x->r_info > y->r_info)
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return 1;
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else if (x->r_addend < y->r_addend)
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return -1;
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else if (x->r_addend > y->r_addend)
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return 1;
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else
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return 0;
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}
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static void relaswap(void *_x, void *_y, int size)
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{
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uint32_t *x, *y, tmp;
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int i;
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y = (uint32_t *)_x;
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x = (uint32_t *)_y;
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for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
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tmp = x[i];
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x[i] = y[i];
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y[i] = tmp;
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}
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}
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/* Get the potential trampolines size required of the init and
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non-init sections */
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static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
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const Elf32_Shdr *sechdrs,
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const char *secstrings,
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int is_init)
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{
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unsigned long ret = 0;
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unsigned i;
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/* Everything marked ALLOC (this includes the exported
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symbols) */
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for (i = 1; i < hdr->e_shnum; i++) {
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/* If it's called *.init*, and we're not init, we're
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not interested */
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if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL)
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!= is_init)
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continue;
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/* We don't want to look at debug sections. */
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if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != NULL)
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continue;
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if (sechdrs[i].sh_type == SHT_RELA) {
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pr_debug("Found relocations in section %u\n", i);
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pr_debug("Ptr: %p. Number: %u\n",
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(void *)hdr + sechdrs[i].sh_offset,
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sechdrs[i].sh_size / sizeof(Elf32_Rela));
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/* Sort the relocation information based on a symbol and
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* addend key. This is a stable O(n*log n) complexity
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* alogrithm but it will reduce the complexity of
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* count_relocs() to linear complexity O(n)
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*/
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sort((void *)hdr + sechdrs[i].sh_offset,
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sechdrs[i].sh_size / sizeof(Elf32_Rela),
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sizeof(Elf32_Rela), relacmp, relaswap);
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ret += count_relocs((void *)hdr
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+ sechdrs[i].sh_offset,
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sechdrs[i].sh_size
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/ sizeof(Elf32_Rela))
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* sizeof(struct metag_plt_entry);
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}
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}
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return ret;
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}
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int module_frob_arch_sections(Elf32_Ehdr *hdr,
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Elf32_Shdr *sechdrs,
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char *secstrings,
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struct module *me)
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{
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unsigned int i;
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/* Find .plt and .init.plt sections */
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for (i = 0; i < hdr->e_shnum; i++) {
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if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
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me->arch.init_plt_section = i;
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else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
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me->arch.core_plt_section = i;
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}
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if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
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pr_err("Module doesn't contain .plt or .init.plt sections.\n");
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return -ENOEXEC;
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}
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/* Override their sizes */
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sechdrs[me->arch.core_plt_section].sh_size
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= get_plt_size(hdr, sechdrs, secstrings, 0);
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sechdrs[me->arch.core_plt_section].sh_type = SHT_NOBITS;
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sechdrs[me->arch.init_plt_section].sh_size
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= get_plt_size(hdr, sechdrs, secstrings, 1);
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sechdrs[me->arch.init_plt_section].sh_type = SHT_NOBITS;
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return 0;
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}
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/* Set up a trampoline in the PLT to bounce us to the distant function */
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static uint32_t do_plt_call(void *location, Elf32_Addr val,
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Elf32_Shdr *sechdrs, struct module *mod)
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{
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struct metag_plt_entry *entry;
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/* Instructions used to do the indirect jump. */
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uint32_t tramp[2];
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/* We have to trash a register, so we assume that any control
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transfer more than 21-bits away must be a function call
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(so we can use a call-clobbered register). */
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/* MOVT D0Re0,#HI(v) */
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tramp[0] = 0x02000005 | (((val & 0xffff0000) >> 16) << 3);
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/* JUMP D0Re0,#LO(v) */
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tramp[1] = 0xac000001 | ((val & 0x0000ffff) << 3);
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/* Init, or core PLT? */
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if (location >= mod->core_layout.base
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&& location < mod->core_layout.base + mod->core_layout.size)
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entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
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else
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entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
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/* Find this entry, or if that fails, the next avail. entry */
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while (entry->tramp[0])
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if (entry->tramp[0] == tramp[0] && entry->tramp[1] == tramp[1])
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return (uint32_t)entry;
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else
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entry++;
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entry->tramp[0] = tramp[0];
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entry->tramp[1] = tramp[1];
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return (uint32_t)entry;
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}
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int apply_relocate_add(Elf32_Shdr *sechdrs,
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const char *strtab,
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unsigned int symindex,
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unsigned int relsec,
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struct module *me)
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{
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unsigned int i;
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Elf32_Rela *rel = (void *)sechdrs[relsec].sh_addr;
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Elf32_Sym *sym;
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Elf32_Addr relocation;
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uint32_t *location;
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int32_t value;
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pr_debug("Applying relocate section %u to %u\n", relsec,
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sechdrs[relsec].sh_info);
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for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
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/* This is where to make the change */
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location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
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+ rel[i].r_offset;
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/* This is the symbol it is referring to. Note that all
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undefined symbols have been resolved. */
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sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
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+ ELF32_R_SYM(rel[i].r_info);
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relocation = sym->st_value + rel[i].r_addend;
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switch (ELF32_R_TYPE(rel[i].r_info)) {
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case R_METAG_NONE:
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break;
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case R_METAG_HIADDR16:
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relocation >>= 16;
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case R_METAG_LOADDR16:
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*location = (*location & 0xfff80007) |
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((relocation & 0xffff) << 3);
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break;
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case R_METAG_ADDR32:
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/*
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* Packed data structures may cause a misaligned
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* R_METAG_ADDR32 to be emitted.
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*/
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put_unaligned(relocation, location);
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break;
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case R_METAG_GETSETOFF:
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*location += ((relocation & 0xfff) << 7);
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break;
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case R_METAG_RELBRANCH:
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if (*location & (0x7ffff << 5)) {
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pr_err("bad relbranch relocation\n");
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break;
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}
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/* This jump is too big for the offset slot. Build
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* a PLT to jump through to get to where we want to go.
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* NB: 21bit check - not scaled to 19bit yet
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*/
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if (((int32_t)(relocation -
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(uint32_t)location) > 0xfffff) ||
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((int32_t)(relocation -
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(uint32_t)location) < -0xfffff)) {
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relocation = do_plt_call(location, relocation,
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sechdrs, me);
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}
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value = relocation - (uint32_t)location;
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/* branch instruction aligned */
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value /= 4;
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if ((value > 0x7ffff) || (value < -0x7ffff)) {
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/*
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* this should have been caught by the code
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* above!
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*/
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pr_err("overflow of relbranch reloc\n");
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}
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*location = (*location & (~(0x7ffff << 5))) |
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((value & 0x7ffff) << 5);
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break;
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default:
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pr_err("module %s: Unknown relocation: %u\n",
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me->name, ELF32_R_TYPE(rel[i].r_info));
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return -ENOEXEC;
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}
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}
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return 0;
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}
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