309 lines
8.3 KiB
C
309 lines
8.3 KiB
C
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// SPDX-License-Identifier: GPL-2.0-or-later
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/* Kernel module help for PPC.
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Copyright (C) 2001 Rusty Russell.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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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/ftrace.h>
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#include <linux/cache.h>
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#include <linux/bug.h>
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#include <linux/sort.h>
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#include <asm/setup.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 24-bit relocs, others don't need stubs */
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if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
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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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#ifdef CONFIG_DYNAMIC_FTRACE
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_count_relocs++; /* add one for ftrace_caller */
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#endif
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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"))
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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 ppc_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.init_plt_section].sh_size
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= get_plt_size(hdr, sechdrs, secstrings, 1);
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return 0;
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}
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static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
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{
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if (entry->jump[0] != (PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val)))
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return 0;
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if (entry->jump[1] != (PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) |
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PPC_LO(val)))
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return 0;
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return 1;
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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,
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Elf32_Addr val,
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const Elf32_Shdr *sechdrs,
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struct module *mod)
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{
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struct ppc_plt_entry *entry;
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pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
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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->jump[0]) {
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if (entry_matches(entry, val)) return (uint32_t)entry;
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entry++;
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}
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/*
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* lis r12, sym@ha
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* addi r12, r12, sym@l
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* mtctr r12
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* bctr
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*/
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entry->jump[0] = PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val);
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entry->jump[1] = PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) | PPC_LO(val);
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entry->jump[2] = PPC_INST_MTCTR | __PPC_RS(R12);
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entry->jump[3] = PPC_INST_BCTR;
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pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
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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 *module)
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{
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unsigned int i;
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Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
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Elf32_Sym *sym;
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uint32_t *location;
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uint32_t value;
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pr_debug("Applying ADD 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(*rela); 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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+ rela[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(rela[i].r_info);
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/* `Everything is relative'. */
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value = sym->st_value + rela[i].r_addend;
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switch (ELF32_R_TYPE(rela[i].r_info)) {
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case R_PPC_ADDR32:
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/* Simply set it */
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*(uint32_t *)location = value;
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break;
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case R_PPC_ADDR16_LO:
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/* Low half of the symbol */
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*(uint16_t *)location = value;
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break;
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case R_PPC_ADDR16_HI:
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/* Higher half of the symbol */
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*(uint16_t *)location = (value >> 16);
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break;
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case R_PPC_ADDR16_HA:
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/* Sign-adjusted lower 16 bits: PPC ELF ABI says:
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(((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
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This is the same, only sane.
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*/
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*(uint16_t *)location = (value + 0x8000) >> 16;
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break;
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case R_PPC_REL24:
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if ((int)(value - (uint32_t)location) < -0x02000000
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|| (int)(value - (uint32_t)location) >= 0x02000000)
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value = do_plt_call(location, value,
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sechdrs, module);
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/* Only replace bits 2 through 26 */
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pr_debug("REL24 value = %08X. location = %08X\n",
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value, (uint32_t)location);
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pr_debug("Location before: %08X.\n",
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*(uint32_t *)location);
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*(uint32_t *)location
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= (*(uint32_t *)location & ~0x03fffffc)
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| ((value - (uint32_t)location)
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& 0x03fffffc);
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pr_debug("Location after: %08X.\n",
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*(uint32_t *)location);
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pr_debug("ie. jump to %08X+%08X = %08X\n",
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*(uint32_t *)location & 0x03fffffc,
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(uint32_t)location,
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(*(uint32_t *)location & 0x03fffffc)
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+ (uint32_t)location);
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break;
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case R_PPC_REL32:
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/* 32-bit relative jump. */
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*(uint32_t *)location = value - (uint32_t)location;
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break;
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default:
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pr_err("%s: unknown ADD relocation: %u\n",
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module->name,
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ELF32_R_TYPE(rela[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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#ifdef CONFIG_DYNAMIC_FTRACE
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int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
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{
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module->arch.tramp = do_plt_call(module->core_layout.base,
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(unsigned long)ftrace_caller,
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sechdrs, module);
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if (!module->arch.tramp)
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return -ENOENT;
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return 0;
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}
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#endif
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