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![Andrey Abramov](/assets/img/avatar_default.png)
Replace relaswap with built-in one, because relaswap does a simple byte to byte swap. Since Spectre mitigations have made indirect function calls more expensive, and the default simple byte copies swap is implemented without them, an "optimized" custom swap function is now a waste of time as well as code. Signed-off-by: Andrey Abramov <st5pub@yandex.ru> Reviewed-by: George Spelvin <lkml@sdf.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/994931554238042@iva8-b333b7f98ab0.qloud-c.yandex.net
293 lines
8 KiB
C
293 lines
8 KiB
C
// 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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/* 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, NULL);
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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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