| // 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> |
| #include <asm/code-patching.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; |
| } |
| |
| /* 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 |
| * algorithm 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, NULL); |
| |
| 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_RAW_LIS(_R12, PPC_HA(val))) |
| return 0; |
| if (entry->jump[1] != PPC_RAW_ADDI(_R12, _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++; |
| } |
| |
| if (patch_instruction(&entry->jump[0], ppc_inst(PPC_RAW_LIS(_R12, PPC_HA(val))))) |
| return 0; |
| if (patch_instruction(&entry->jump[1], ppc_inst(PPC_RAW_ADDI(_R12, _R12, PPC_LO(val))))) |
| return 0; |
| if (patch_instruction(&entry->jump[2], ppc_inst(PPC_RAW_MTCTR(_R12)))) |
| return 0; |
| if (patch_instruction(&entry->jump[3], ppc_inst(PPC_RAW_BCTR()))) |
| return 0; |
| |
| pr_debug("Initialized plt for 0x%x at %p\n", val, entry); |
| return (uint32_t)entry; |
| } |
| |
| static int patch_location_16(uint32_t *loc, u16 value) |
| { |
| loc = PTR_ALIGN_DOWN(loc, sizeof(u32)); |
| return patch_instruction(loc, ppc_inst((*loc & 0xffff0000) | value)); |
| } |
| |
| 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 */ |
| if (patch_location_16(location, PPC_LO(value))) |
| return -EFAULT; |
| break; |
| |
| case R_PPC_ADDR16_HI: |
| /* Higher half of the symbol */ |
| if (patch_location_16(location, PPC_HI(value))) |
| return -EFAULT; |
| break; |
| |
| case R_PPC_ADDR16_HA: |
| if (patch_location_16(location, PPC_HA(value))) |
| return -EFAULT; |
| 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); |
| if (!value) |
| return -EFAULT; |
| } |
| |
| /* 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); |
| value = (*(uint32_t *)location & ~PPC_LI_MASK) | |
| PPC_LI(value - (uint32_t)location); |
| |
| if (patch_instruction(location, ppc_inst(value))) |
| return -EFAULT; |
| |
| pr_debug("Location after: %08X.\n", |
| *(uint32_t *)location); |
| pr_debug("ie. jump to %08X+%08X = %08X\n", |
| *(uint32_t *)PPC_LI((uint32_t)location), (uint32_t)location, |
| (*(uint32_t *)PPC_LI((uint32_t)location)) + (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 |
| notrace int module_trampoline_target(struct module *mod, unsigned long addr, |
| unsigned long *target) |
| { |
| ppc_inst_t jmp[4]; |
| |
| /* Find where the trampoline jumps to */ |
| if (copy_inst_from_kernel_nofault(jmp, (void *)addr)) |
| return -EFAULT; |
| if (__copy_inst_from_kernel_nofault(jmp + 1, (void *)addr + 4)) |
| return -EFAULT; |
| if (__copy_inst_from_kernel_nofault(jmp + 2, (void *)addr + 8)) |
| return -EFAULT; |
| if (__copy_inst_from_kernel_nofault(jmp + 3, (void *)addr + 12)) |
| return -EFAULT; |
| |
| /* verify that this is what we expect it to be */ |
| if ((ppc_inst_val(jmp[0]) & 0xffff0000) != PPC_RAW_LIS(_R12, 0)) |
| return -EINVAL; |
| if ((ppc_inst_val(jmp[1]) & 0xffff0000) != PPC_RAW_ADDI(_R12, _R12, 0)) |
| return -EINVAL; |
| if (ppc_inst_val(jmp[2]) != PPC_RAW_MTCTR(_R12)) |
| return -EINVAL; |
| if (ppc_inst_val(jmp[3]) != PPC_RAW_BCTR()) |
| return -EINVAL; |
| |
| addr = (ppc_inst_val(jmp[1]) & 0xffff) | ((ppc_inst_val(jmp[0]) & 0xffff) << 16); |
| if (addr & 0x8000) |
| addr -= 0x10000; |
| |
| *target = addr; |
| |
| return 0; |
| } |
| |
| 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; |
| |
| #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS |
| module->arch.tramp_regs = do_plt_call(module->core_layout.base, |
| (unsigned long)ftrace_regs_caller, |
| sechdrs, module); |
| if (!module->arch.tramp_regs) |
| return -ENOENT; |
| #endif |
| |
| return 0; |
| } |
| #endif |