/* ;* Copyright (C) 2014 Google, Inc. * * 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; version 2 of the License. * * 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. */ #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include "elfparsing.h" #include "rmodule.h" #include <commonlib/rmodule-defs.h> /* * Architecture specific support operations. */ static int valid_reloc_386(Elf64_Rela *rel) { int type; type = ELF64_R_TYPE(rel->r_info); /* Only these 2 relocations are expected to be found. */ return (type == R_386_32 || type == R_386_PC32); } static int should_emit_386(Elf64_Rela *rel) { int type; type = ELF64_R_TYPE(rel->r_info); /* R_386_32 relocations are absolute. Must emit these. */ return (type == R_386_32); } static int valid_reloc_arm(Elf64_Rela *rel) { int type; type = ELF64_R_TYPE(rel->r_info); /* Only these 6 relocations are expected to be found. */ return (type == R_ARM_ABS32 || type == R_ARM_THM_PC22 || type == R_ARM_THM_JUMP24 || type == R_ARM_V4BX || type == R_ARM_CALL || type == R_ARM_JUMP24); } static int should_emit_arm(Elf64_Rela *rel) { int type; type = ELF64_R_TYPE(rel->r_info); /* R_ARM_ABS32 relocations are absolute. Must emit these. */ return (type == R_ARM_ABS32); } static int valid_reloc_aarch64(Elf64_Rela *rel) { int type; type = ELF64_R_TYPE(rel->r_info); return (type == R_AARCH64_ADR_PREL_PG_HI21 || type == R_AARCH64_ADD_ABS_LO12_NC || type == R_AARCH64_LDST8_ABS_LO12_NC || type == R_AARCH64_CONDBR19 || type == R_AARCH64_JUMP26 || type == R_AARCH64_LDST32_ABS_LO12_NC || type == R_AARCH64_LDST64_ABS_LO12_NC || type == R_AARCH64_CALL26 || type == R_AARCH64_ABS64 || type == R_AARCH64_LD_PREL_LO19 || type == R_AARCH64_ADR_PREL_LO21); } static int should_emit_aarch64(Elf64_Rela *rel) { int type; type = ELF64_R_TYPE(rel->r_info); return (type == R_AARCH64_ABS64); } static const struct arch_ops reloc_ops[] = { { .arch = EM_386, .valid_type = valid_reloc_386, .should_emit = should_emit_386, }, { .arch = EM_ARM, .valid_type = valid_reloc_arm, .should_emit = should_emit_arm, }, { .arch = EM_AARCH64, .valid_type = valid_reloc_aarch64, .should_emit = should_emit_aarch64, }, }; /* * Relocation processing loops. */ static int for_each_reloc(struct rmod_context *ctx, struct reloc_filter *f, int do_emit) { Elf64_Half i; struct parsed_elf *pelf = &ctx->pelf; for (i = 0; i < pelf->ehdr.e_shnum; i++) { Elf64_Shdr *shdr; Elf64_Rela *relocs; Elf64_Xword nrelocs; Elf64_Xword j; relocs = pelf->relocs[i]; /* No relocations in this section. */ if (relocs == NULL) continue; shdr = &pelf->shdr[i]; nrelocs = shdr->sh_size / shdr->sh_entsize; for (j = 0; j < nrelocs; j++) { int filter_emit = 1; Elf64_Rela *r = &relocs[j]; if (!ctx->ops->valid_type(r)) { ERROR("Invalid reloc type: %u\n", (unsigned int)ELF64_R_TYPE(r->r_info)); return -1; } /* Allow the provided filter to have precedence. */ if (f != NULL) { filter_emit = f->filter(f, r); if (filter_emit < 0) return filter_emit; } if (filter_emit && ctx->ops->should_emit(r)) { int n = ctx->nrelocs; if (do_emit) ctx->emitted_relocs[n] = r->r_offset; ctx->nrelocs++; } } } return 0; } static int find_program_segment(struct rmod_context *ctx) { int i; int nsegments; struct parsed_elf *pelf; Elf64_Phdr *phdr = NULL; pelf = &ctx->pelf; /* There should only be a single loadable segment. */ nsegments = 0; for (i = 0; i < pelf->ehdr.e_phnum; i++) { if (pelf->phdr[i].p_type != PT_LOAD) continue; phdr = &pelf->phdr[i]; nsegments++; } if (nsegments != 1) { ERROR("Unexepcted number of loadable segments: %d.\n", nsegments); return -1; } INFO("Segment at 0x%0llx, file size 0x%0llx, mem size 0x%0llx.\n", (long long)phdr->p_vaddr, (long long)phdr->p_filesz, (long long)phdr->p_memsz); ctx->phdr = phdr; return 0; } static int filter_relocation_sections(struct rmod_context *ctx) { int i; const char *shstrtab; struct parsed_elf *pelf; const Elf64_Phdr *phdr; pelf = &ctx->pelf; phdr = ctx->phdr; shstrtab = buffer_get(pelf->strtabs[pelf->ehdr.e_shstrndx]); /* * Find all relocation sections that contain relocation entries * for sections that fall within the bounds of the segment. For * easier processing the pointer to the relocation array for the * sections that don't fall within the loadable program are NULL'd * out. */ for (i = 0; i < pelf->ehdr.e_shnum; i++) { Elf64_Shdr *shdr; Elf64_Word sh_info; const char *section_name; shdr = &pelf->shdr[i]; /* Ignore non-relocation sections. */ if (shdr->sh_type != SHT_RELA && shdr->sh_type != SHT_REL) continue; /* Obtain section which relocations apply. */ sh_info = shdr->sh_info; shdr = &pelf->shdr[sh_info]; section_name = &shstrtab[shdr->sh_name]; DEBUG("Relocation section found for '%s' section.\n", section_name); /* Do not process relocations for debug sections. */ if (strstr(section_name, ".debug") != NULL) { pelf->relocs[i] = NULL; continue; } /* * If relocations apply to a non program section ignore the * relocations for future processing. */ if (shdr->sh_type != SHT_PROGBITS) { pelf->relocs[i] = NULL; continue; } if (shdr->sh_addr < phdr->p_vaddr || ((shdr->sh_addr + shdr->sh_size) > (phdr->p_vaddr + phdr->p_memsz))) { ERROR("Relocations being applied to section %d not " "within segment region.\n", sh_info); return -1; } } return 0; } static int vaddr_cmp(const void *a, const void *b) { const Elf64_Addr *pa = a; const Elf64_Addr *pb = b; if (*pa < *pb) return -1; if (*pa > *pb) return 1; return 0; } int rmodule_collect_relocations(struct rmod_context *ctx, struct reloc_filter *f) { Elf64_Xword nrelocs; /* * The relocs array in the pelf should only contain relocations that * apply to the program. Count the number relocations. Then collect * them into the allocated buffer. */ if (for_each_reloc(ctx, f, 0)) return -1; nrelocs = ctx->nrelocs; INFO("%" PRIu64 " relocations to be emitted.\n", nrelocs); if (!nrelocs) return 0; /* Reset the counter for indexing into the array. */ ctx->nrelocs = 0; ctx->emitted_relocs = calloc(nrelocs, sizeof(Elf64_Addr)); /* Write out the relocations into the emitted_relocs array. */ if (for_each_reloc(ctx, f, 1)) return -1; if (ctx->nrelocs != nrelocs) { ERROR("Mismatch counted and emitted relocations: %zu vs %zu.\n", (size_t)nrelocs, (size_t)ctx->nrelocs); return -1; } /* Sort the relocations by their address. */ qsort(ctx->emitted_relocs, nrelocs, sizeof(Elf64_Addr), vaddr_cmp); return 0; } static int populate_sym(struct rmod_context *ctx, const char *sym_name, Elf64_Addr *addr, int nsyms, const char *strtab, int optional) { int i; Elf64_Sym *syms; syms = ctx->pelf.syms; for (i = 0; i < nsyms; i++) { if (syms[i].st_name == 0) continue; if (strcmp(sym_name, &strtab[syms[i].st_name])) continue; DEBUG("%s -> 0x%llx\n", sym_name, (long long)syms[i].st_value); *addr = syms[i].st_value; return 0; } if (optional) { DEBUG("optional symbol '%s' not found.\n", sym_name); *addr = 0; return 0; } ERROR("symbol '%s' not found.\n", sym_name); return -1; } static int populate_rmodule_info(struct rmod_context *ctx) { int i; const char *strtab; struct parsed_elf *pelf; Elf64_Ehdr *ehdr; int nsyms; pelf = &ctx->pelf; ehdr = &pelf->ehdr; /* Obtain the string table. */ strtab = NULL; for (i = 0; i < ehdr->e_shnum; i++) { if (ctx->pelf.strtabs[i] == NULL) continue; /* Don't use the section headers' string table. */ if (i == ehdr->e_shstrndx) continue; strtab = buffer_get(ctx->pelf.strtabs[i]); break; } if (strtab == NULL) { ERROR("No string table found.\n"); return -1; } /* Determine number of symbols. */ nsyms = 0; for (i = 0; i < ehdr->e_shnum; i++) { if (pelf->shdr[i].sh_type != SHT_SYMTAB) continue; nsyms = pelf->shdr[i].sh_size / pelf->shdr[i].sh_entsize; break; } if (populate_sym(ctx, "_rmodule_params", &ctx->parameters_begin, nsyms, strtab, 1)) return -1; if (populate_sym(ctx, "_ermodule_params", &ctx->parameters_end, nsyms, strtab, 1)) return -1; if (populate_sym(ctx, "_bss", &ctx->bss_begin, nsyms, strtab, 0)) return -1; if (populate_sym(ctx, "_ebss", &ctx->bss_end, nsyms, strtab, 0)) return -1; return 0; } static int add_section(struct elf_writer *ew, struct buffer *data, const char *name, Elf64_Addr addr, Elf64_Word size) { Elf64_Shdr shdr; int ret; memset(&shdr, 0, sizeof(shdr)); if (data != NULL) { shdr.sh_type = SHT_PROGBITS; shdr.sh_flags = SHF_ALLOC | SHF_WRITE | SHF_EXECINSTR; } else { shdr.sh_type = SHT_NOBITS; shdr.sh_flags = SHF_ALLOC; } shdr.sh_addr = addr; shdr.sh_offset = addr; shdr.sh_size = size; ret = elf_writer_add_section(ew, &shdr, data, name); if (ret) ERROR("Could not add '%s' section.\n", name); return ret; } static int write_elf(const struct rmod_context *ctx, const struct buffer *in, struct buffer *out) { int ret; int bit64; size_t loc; size_t rmod_data_size; struct elf_writer *ew; struct buffer rmod_data; struct buffer rmod_header; struct buffer program; struct buffer relocs; Elf64_Xword total_size; Elf64_Addr addr; Elf64_Ehdr ehdr; bit64 = ctx->pelf.ehdr.e_ident[EI_CLASS] == ELFCLASS64; /* * 3 sections will be added to the ELF file. * +------------------+ * | rmodule header | * +------------------+ * | program | * +------------------+ * | relocations | * +------------------+ */ /* Create buffer for header and relocations. */ rmod_data_size = sizeof(struct rmodule_header); if (bit64) rmod_data_size += ctx->nrelocs * sizeof(Elf64_Addr); else rmod_data_size += ctx->nrelocs * sizeof(Elf32_Addr); if (buffer_create(&rmod_data, rmod_data_size, "rmod")) return -1; buffer_splice(&rmod_header, &rmod_data, 0, sizeof(struct rmodule_header)); buffer_clone(&relocs, &rmod_data); buffer_seek(&relocs, sizeof(struct rmodule_header)); /* Reset current location. */ buffer_set_size(&rmod_header, 0); buffer_set_size(&relocs, 0); /* Program contents. */ buffer_splice(&program, in, ctx->phdr->p_offset, ctx->phdr->p_filesz); /* Create ELF writer with modified entry point. */ memcpy(&ehdr, &ctx->pelf.ehdr, sizeof(ehdr)); ew = elf_writer_init(&ehdr); if (ew == NULL) { ERROR("Failed to create ELF writer.\n"); buffer_delete(&rmod_data); return -1; } /* Write out rmodule_header. */ ctx->xdr->put16(&rmod_header, RMODULE_MAGIC); ctx->xdr->put8(&rmod_header, RMODULE_VERSION_1); ctx->xdr->put8(&rmod_header, 0); /* payload_begin_offset */ loc = sizeof(struct rmodule_header); ctx->xdr->put32(&rmod_header, loc); /* payload_end_offset */ loc += ctx->phdr->p_filesz; ctx->xdr->put32(&rmod_header, loc); /* relocations_begin_offset */ ctx->xdr->put32(&rmod_header, loc); /* relocations_end_offset */ if (bit64) loc += ctx->nrelocs * sizeof(Elf64_Addr); else loc += ctx->nrelocs * sizeof(Elf32_Addr); ctx->xdr->put32(&rmod_header, loc); /* module_link_start_address */ ctx->xdr->put32(&rmod_header, ctx->phdr->p_vaddr); /* module_program_size */ ctx->xdr->put32(&rmod_header, ctx->phdr->p_memsz); /* module_entry_point */ ctx->xdr->put32(&rmod_header, ctx->pelf.ehdr.e_entry); /* parameters_begin */ ctx->xdr->put32(&rmod_header, ctx->parameters_begin); /* parameters_end */ ctx->xdr->put32(&rmod_header, ctx->parameters_end); /* bss_begin */ ctx->xdr->put32(&rmod_header, ctx->bss_begin); /* bss_end */ ctx->xdr->put32(&rmod_header, ctx->bss_end); /* padding[4] */ ctx->xdr->put32(&rmod_header, 0); ctx->xdr->put32(&rmod_header, 0); ctx->xdr->put32(&rmod_header, 0); ctx->xdr->put32(&rmod_header, 0); /* Write the relocations. */ for (unsigned i = 0; i < ctx->nrelocs; i++) { if (bit64) ctx->xdr->put64(&relocs, ctx->emitted_relocs[i]); else ctx->xdr->put32(&relocs, ctx->emitted_relocs[i]); } total_size = 0; addr = 0; /* * There are 2 cases to deal with. The program has a large NOBITS * section and the relocations can fit entirely within occupied memory * region for the program. The other is that the relocations increase * the memory footprint of the program if it was loaded directly into * the region it would run. The rmdoule header is a fixed cost that * is considered a part of the program. */ total_size += buffer_size(&rmod_header); if (buffer_size(&relocs) + ctx->phdr->p_filesz > ctx->phdr->p_memsz) { total_size += buffer_size(&relocs); total_size += ctx->phdr->p_filesz; } else { total_size += ctx->phdr->p_memsz; } ret = add_section(ew, &rmod_header, ".header", addr, buffer_size(&rmod_header)); if (ret < 0) goto out; addr += buffer_size(&rmod_header); ret = add_section(ew, &program, ".program", addr, ctx->phdr->p_filesz); if (ret < 0) goto out; addr += ctx->phdr->p_filesz; if (ctx->nrelocs) { ret = add_section(ew, &relocs, ".relocs", addr, buffer_size(&relocs)); if (ret < 0) goto out; addr += buffer_size(&relocs); } if (total_size != addr) { ret = add_section(ew, NULL, ".empty", addr, total_size - addr); if (ret < 0) goto out; } /* * Ensure last section has a memory usage that meets the required * total size of the program in memory. */ ret = elf_writer_serialize(ew, out); if (ret < 0) ERROR("Failed to serialize ELF to buffer.\n"); out: buffer_delete(&rmod_data); elf_writer_destroy(ew); return ret; } int rmodule_init(struct rmod_context *ctx, const struct buffer *elfin) { struct parsed_elf *pelf; size_t i; int ret; ret = -1; memset(ctx, 0, sizeof(*ctx)); pelf = &ctx->pelf; if (parse_elf(elfin, pelf, ELF_PARSE_ALL)) { ERROR("Couldn't parse ELF!\n"); return -1; } /* Only allow executables to be turned into rmodules. */ if (pelf->ehdr.e_type != ET_EXEC) { ERROR("ELF is not an executable: %u.\n", pelf->ehdr.e_type); goto out; } /* Determine if architecture is supported. */ for (i = 0; i < ARRAY_SIZE(reloc_ops); i++) { if (reloc_ops[i].arch == pelf->ehdr.e_machine) { ctx->ops = &reloc_ops[i]; break; } } if (ctx->ops == NULL) { ERROR("ELF is unsupported arch: %u.\n", pelf->ehdr.e_machine); goto out; } /* Set the endian ops. */ if (ctx->pelf.ehdr.e_ident[EI_DATA] == ELFDATA2MSB) ctx->xdr = &xdr_be; else ctx->xdr = &xdr_le; if (find_program_segment(ctx)) goto out; if (filter_relocation_sections(ctx)) goto out; ret = 0; out: return ret; } void rmodule_cleanup(struct rmod_context *ctx) { free(ctx->emitted_relocs); parsed_elf_destroy(&ctx->pelf); } int rmodule_create(const struct buffer *elfin, struct buffer *elfout) { struct rmod_context ctx; int ret = -1; if (rmodule_init(&ctx, elfin)) goto out; if (rmodule_collect_relocations(&ctx, NULL)) goto out; if (populate_rmodule_info(&ctx)) goto out; if (write_elf(&ctx, elfin, elfout)) goto out; ret = 0; out: rmodule_cleanup(&ctx); return ret; } static void rmod_deserialize(struct rmodule_header *rmod, struct buffer *buff, struct xdr *xdr) { rmod->magic = xdr->get16(buff); rmod->version = xdr->get8(buff); rmod->type = xdr->get8(buff); rmod->payload_begin_offset = xdr->get32(buff); rmod->payload_end_offset = xdr->get32(buff); rmod->relocations_begin_offset = xdr->get32(buff); rmod->relocations_end_offset = xdr->get32(buff); rmod->module_link_start_address = xdr->get32(buff); rmod->module_program_size = xdr->get32(buff); rmod->module_entry_point = xdr->get32(buff); rmod->parameters_begin = xdr->get32(buff); rmod->parameters_end = xdr->get32(buff); rmod->bss_begin = xdr->get32(buff); rmod->bss_end = xdr->get32(buff); rmod->padding[0] = xdr->get32(buff); rmod->padding[1] = xdr->get32(buff); rmod->padding[2] = xdr->get32(buff); rmod->padding[3] = xdr->get32(buff); } int rmodule_stage_to_elf(Elf64_Ehdr *ehdr, struct buffer *buff) { struct buffer reader; struct buffer elf_out; struct rmodule_header rmod; struct xdr *xdr; struct elf_writer *ew; Elf64_Shdr shdr; int bit64; size_t payload_sz; const char *section_name = ".program"; const size_t input_sz = buffer_size(buff); buffer_clone(&reader, buff); xdr = (ehdr->e_ident[EI_DATA] == ELFDATA2MSB) ? &xdr_be : &xdr_le; bit64 = ehdr->e_ident[EI_CLASS] == ELFCLASS64; rmod_deserialize(&rmod, &reader, xdr); /* Indicate that file is not an rmodule if initial checks fail. */ if (rmod.magic != RMODULE_MAGIC) return 1; if (rmod.version != RMODULE_VERSION_1) return 1; if (rmod.payload_begin_offset > input_sz || rmod.payload_end_offset > input_sz || rmod.relocations_begin_offset > input_sz || rmod.relocations_end_offset > input_sz) { ERROR("Rmodule fields out of bounds.\n"); return -1; } ehdr->e_entry = rmod.module_entry_point; ew = elf_writer_init(ehdr); if (ew == NULL) return -1; payload_sz = rmod.payload_end_offset - rmod.payload_begin_offset; memset(&shdr, 0, sizeof(shdr)); shdr.sh_type = SHT_PROGBITS; shdr.sh_flags = SHF_WRITE | SHF_ALLOC | SHF_EXECINSTR; shdr.sh_addr = rmod.module_link_start_address; shdr.sh_size = payload_sz; buffer_splice(&reader, buff, rmod.payload_begin_offset, payload_sz); if (elf_writer_add_section(ew, &shdr, &reader, section_name)) { ERROR("Unable to add ELF section: %s\n", section_name); elf_writer_destroy(ew); return -1; } if (payload_sz != rmod.module_program_size) { struct buffer b; buffer_init(&b, NULL, NULL, 0); memset(&shdr, 0, sizeof(shdr)); shdr.sh_type = SHT_NOBITS; shdr.sh_flags = SHF_WRITE | SHF_ALLOC; shdr.sh_addr = rmod.module_link_start_address + payload_sz; shdr.sh_size = rmod.module_program_size - payload_sz; if (elf_writer_add_section(ew, &shdr, &b, ".empty")) { ERROR("Unable to add ELF section: .empty\n"); elf_writer_destroy(ew); return -1; } } /* Provide a section symbol so the relcoations can reference that. */ if (elf_writer_add_symbol(ew, section_name, section_name, shdr.sh_addr, 0, STB_LOCAL, STT_SECTION)) { ERROR("Unable to add section symbol to ELF.\n"); elf_writer_destroy(ew); return -1; } /* Add symbols for the parameters if they are non-zero. */ if (rmod.parameters_begin != rmod.parameters_end) { int ret = 0; ret |= elf_writer_add_symbol(ew, "_rmodule_params", section_name, rmod.parameters_begin, 0, STB_GLOBAL, STT_NOTYPE); ret |= elf_writer_add_symbol(ew, "_ermodule_params", section_name, rmod.parameters_end, 0, STB_GLOBAL, STT_NOTYPE); if (ret != 0) { ERROR("Unable to add module params symbols to ELF\n"); elf_writer_destroy(ew); return -1; } } if (elf_writer_add_symbol(ew, "_bss", section_name, rmod.bss_begin, 0, STB_GLOBAL, STT_NOTYPE) || elf_writer_add_symbol(ew, "_ebss", section_name, rmod.bss_end, 0, STB_GLOBAL, STT_NOTYPE)) { ERROR("Unable to add bss symbols to ELF\n"); elf_writer_destroy(ew); return -1; } ssize_t relocs_sz = rmod.relocations_end_offset; relocs_sz -= rmod.relocations_begin_offset; buffer_splice(&reader, buff, rmod.relocations_begin_offset, relocs_sz); while (relocs_sz > 0) { Elf64_Addr addr; if (bit64) { relocs_sz -= sizeof(Elf64_Addr); addr = xdr->get64(&reader); } else { relocs_sz -= sizeof(Elf32_Addr); addr = xdr->get32(&reader); } /* Skip any relocations that are below the link address. */ if (addr < rmod.module_link_start_address) continue; if (elf_writer_add_rel(ew, section_name, addr)) { ERROR("Relocation addition failure.\n"); elf_writer_destroy(ew); return -1; } } if (elf_writer_serialize(ew, &elf_out)) { ERROR("ELF writer serialize failure.\n"); elf_writer_destroy(ew); return -1; } elf_writer_destroy(ew); /* Flip buffer with the created ELF one. */ buffer_delete(buff); *buff = elf_out; return 0; }